Our lakes and rivers are subjected to various pressures that lead to an increase in nutrient levels of water. This promotes the excessive growth of free-floating microalgae the phytoplankton. A high abundance of algae reduces water transparency, and thus the depth where light is available for photosynthesis. As a result, overall oxygen production in water decreases.
Importantly, it is not only the quantity of phytoplankton that determines water quality, but also its composition. The extent of shading and changes in the water’s optical properties depend on the size and shape of the algal cells or colonies. While the size of algae can be determined through microscopic measurements and calculations, reliable estimates for comparing the light-absorbing capacity of algae with different shapes have been lacking until recently.
Thanks to research conducted at the HUN-REN Centre for Ecological Research’s Institute of Aquatic Ecology, we now have accurate data on these properties of microalgae. Members of the Functional Algology Research Group have created three-dimensional digital models of more than 800 algal species and developed mathematical and computational methods, that allow precise calculation of the shaded area of each species.
This database of species specific projected (shading) areas enables new interpretations of existing research findings and phytoplankton water quality data. It also supports the design of interventions aimed at improving water quality through the promotion of desirable phytoplankton community compositions.
Climate change cannot be fixed by simple measures such as planting trees. New research published in Nature Geoscience journal shows that restoring our natural terrestrial habitats can remove much smaller amount of the carbon from the air than previous models suggested. Focus needs to be on rapidly reducing emissions and ensuring that initiatives are equitable and focused on climate change adaptation.
Senior author Ákos Bede-Fazekas, research fellow at the HUN-REN Centre for Ecological Research outlines that policymakers should take a holistic approach when considering ecosystem restoration, with a focus on biodiversity and nature’s contribution to people, while reducing emphasis on carbon sequestration. In the last 10 years, habitat restoration has been increasingly used as a means for climate change mitigation, a key element in response to both the climate crisis and the biodiversity emergency. The recurring theme being that it could offset a substantial fraction of human carbon emissions. This view was supported by earlier modeling results – but these followed the principle of “plant trees everywhere possible!”. Ecosystem restoration is a more complex process that requires greater consideration than simply establishing seminatural forests or, worse, creating tree plantations.
The international group of scientists was led by Csaba Tölgyesi, of University of Szeged, who highlighted: “Carbon sequestration modeling necessitates a more inclusive approach, considering all possible natural ecosystem types. Forests will store carbon mostly in their biomass, grassland in the soil. All ecosystems are good where they belong.”
The available models and predictions still had some problematic assumptions and incorrect input data, which the researchers wanted to rectify to have a clearer view of the potential of ecosystem restoration in climate change mitigation. Hence, they made a model much more realistic than the previous ones had been. For example, their model does not force restoring forests in every location they are predicted to be suitable – including established grasslands with high carbon sequestration potential or productive agricultural lands. This led them not to a slight adjustment, but to a massive difference from previous carbon capture potentials. The scientists found that ecosystem restoration has a measurable but limited effect on atmospheric carbon concentrations if compared to previous predictions. In the greenest of all climate scenario, 17 percent of human emissions can be recaptured by 2100, while in the business-as-usual (most pessimistic) scenario, it is less than four per cent.
These model forecasts of climate change mitigation via ecosystem restorations suggest an urgent need for a change of direction in polices to transition to a low carbon economy.
Fellow author, Caroline Lehmann, of Royal Botanic Garden Edinburgh added: “With the limited likelihood of significantly mitigating climate change through global ecosystem restoration in the short or medium term, policies need to prioritize restoration activities in favor of vulnerable communities and biodiversity to support the resilience of nature and people with ongoing climate change.”
Historically, the burden for ecological restoration has been placed on the Global South with the offsetting and carbon sequestration agenda driven by the Global North. Not only is it unjust that the communities who did not create the problem of climate change bear the brunt of its solution, the study shows that a large number of potential priority regions for restoration for carbon gain are located across the Global North.
Villages, often separated from larger towns and cities, consist of clusters of households and a few public buildings. Despite their long history, the biodiversity of European villages has been understudied compared to urban areas, forests, grasslands, or agricultural fields. A new study reveals their biodiversity potential and how nearby landscapes influence biodiversity patterns and human well-being.
This research was led by an international team from the HUN-REN Centre for Ecological Research with 20 other institutes contributing from Hungary, Romania, Germany, and Italy. Published in Nature Sustainability, the study examines how landscape complexity and proximity to cities affect village biodiversity and socioeconomic conditions. The findings show higher biodiversity in villages within forest-dominated landscapes compared to agricultural settings, while city proximity boosts human well-being.
The researchers surveyed biodiversity in 64 villages around 16 mid-size cities in Hungary and Romania. Half of the villages were near cities, the other half farther away, and were either in agriculture- or forest-dominated landscapes. The team conducted botanical surveys, used pitfall traps for ground-dwelling arthropods, employed D-vac suction sampling for vegetation-dwelling arthropods, and set trap nests for cavity-nesting bees and wasps, as well as point counts for birds.
Project leader, Péter Batáry, working with D-vac insect suction sampler in the centre of village Salköveskút, Hungary. The samples revealed significantly higher vegetation-dwelling arthropod species richness at village edges compared to centres, especially in forest-dominated landscapes. Photo: Attila Torma
They documented 1,164 species across nine taxonomic groups. Multitrophic diversity, a measure of overall biodiversity, was 15% lower in villages surrounded by agricultural fields than by forests. Lead author Dr. Péter Batáry explains, “This underscores the importance of landscape-wide species pools in shaping village biodiversity. City proximity had little impact on species numbers and overall diversity, suggesting other factors have a greater influence.”
The team also collected socioeconomic data for Hungarian villages to calculate the Better Life Index, reflecting human well-being through living conditions and quality of life. The Better Life Index was 27% higher in villages in the agglomerations of cities and 14% higher in villages in forest-dominated landscapes than those in agricultural ones. Co-author Dr. Katalin Szitár notes, “Proximity to urban areas brings better access to services, while forested landscapes offer cleaner air and more green spaces, enhancing living standards and quality of life.”
Village edge of Botfa, a village embedded in a forested-dominated landscape near the city, Zalaegerszeg, Hungary. Proximity to the city was associated with higher human well-being without reducing biodiversity, despite increased human footprint. Photo: Tamás Lakatos
Using GIS, the researchers measured the Human Footprint Index (HFI) to assess environmental impact from infrastructure and land use. Villages with a higher Better Life Index also had a higher HFI, especially near cities, indicating that better living standards can increase environmental impacts. A higher HFI was linked to lower multitrophic diversity, revealing a trade-off between human development and biodiversity. However, forest-dominated landscapes maintained higher biodiversity despite increased human activity, suggesting complex landscapes can mitigate biodiversity loss. Dr. Edina Török notes, “Our findings highlight the delicate balance needed to enhance human well-being without compromising the ecological health of rural landscapes.”
To be effective, sustainable village management should integrate landscape context into development plans. For villages near cities, minimizing soil sealing and green infrastructure intensification can help protect biodiversity. In villages predominantly surrounded by forests, limiting agricultural expansion is crucial. Increasing the connectivity of villages centres with forests and upgrading green infrastructure in agricultural areas can boost biodiversity and well-being. Collaboration between residents, authorities, and landowners, combining policy-driven and community-driven actions, is vital. Dr. Péter Batáry emphasizes, “The EU Rural Development Strategy should prioritize biodiversity management to improve conservation and landscape quality in and around villages.”
Lead photo: Várda is an example of a village embedded in an agriculture-dominated landscape, where multitrophic diversity was 15% lower on average than in forested landscapes.
Land use change and the increased agrochemical use associated with agricultural intensification significantly alter farmland biodiversity and associated ecosystem services worldwide. Vineyards as ecologically, culturally, and economically important agroecosystems, are particularly vulnerable, facing numerous pests and diseases while only a small proportion adopt sustainable management practices. Nevertheless, under suitable conditions, vineyards can support diverse and abundant predator communities capable of delivering effective natural pest control services. Birds and bats, in particular, play a key role by consuming large quantities of insect pests. However, their contribution to biological control – especially in European permanent crops – remains understudied.
The collaborative study conducted by researchers from the HUN-REN Centre for Ecological Research and the University of Milan investigated the role of flying vertebrate predators – birds and bats – in vineyard natural pest control. Their findings, published in the Journal of Applied Ecology, demonstrate that these predators not only help regulate pest populations but also increase economic benefit to farmers.
Vineyard with integrated pest management near Káptalantóti, in the Balaton Uplands region (photo: Tamás Lakatos).
Using exclusion experiments in Hungarian vineyards with differing pest management regimes (organic farming vs. integrated pest management) and landscape contexts (forested vs. open, agricultural landscapes), the authors examined how birds and bats influence arthropod densities and related ecosystem functions. They recorded bird densities and bat activity, as well as the abundance of a key grape pest – the European grapevine moth (Lobesia botrana) – alongside phytophagous and predatory arthropods in the grapevine canopy. Additionally, they assessed fruit damage caused by moths, herbivory from canopy-dwelling arthropods, and associated predation pressure. Results showed that forested landscapes supported greater bird and bat activity in spring and were associated with reduced fruit damage, primarily due to the suppressive effect of increased bat activity on moth populations. While management practices had no measurable effect on birds and bats, organic vineyards hosted more canopy-dwelling arthropods and faced greater leaf herbivory, although also higher predation pressure on sentinel caterpillars. Most importantly, fruit damage and herbivory were consistently higher in exclusion treatments, underscoring the role of birds and bats in mitigating herbivory and enhancing crop yield.
Grapevines inside a cage used for the exclusion of birds and bats (photo: Dávid Korányi).Installed AudioMoth device in a waterproof case for bat sound recording (photo: Dávid Korányi).Grapevine moth (Lobesia botrana) specimens caught with a pheromone trap (photo: Dávid Korányi).
These results highlight the ecological and economic value of birds and bats as natural pest control agents. Dávid Korányi, lead researcher of the field experiment, explains: “The presence of these predators can be promoted by maintaining connected landscapes with native deciduous forest patches, hedgerows, and small groups of trees that offer abundant food sources and suitable nesting or roosting sites.” The study also underscores the importance of local vineyard management in pest control. The senior author of the research, Péter Batáry, adds: “Pest control services can be further enhanced through organic management, which avoids herbicides and synthetic insecticides, thereby facilitating the colonization of beneficial arthropods and strengthening pest predation pressure in vineyards.”
Publication:
Dávid Korányi, Sándor Zsebők, András Báldi, Mattia Brambilla, Máté Varga & Péter Batáry (2025). Forest cover enhances pest control by birds and bats independently of vineyard management intensity. Journal of Applied Ecology. https://doi.org/10.1111/1365-2664.70094
Requests for copies of the study and interviews can be sent to:
Dr. Dávid Korányi – HUN-REN Centre for Ecological Research: koranyi.david@ecolres.hu
Dr. Péter Batáry – HUN-REN Centre for Ecological Research: batary.peter@ecolres.hu
Niels Bohr, the Nobel laureate in Physics and father of the atomic model, is famously supposed to have said, “It is difficult to make predictions, especially about the future.” Our uncertainty about whether he actually said this or not, some attribute the quote of the legendary baseball player (and philosopher) Yogi Berra, highlights that making predictions about the past can be equally challenging. However, reconstructing the distant past and tracing how and when life adapted to new conditions, such as the rise of oxygen on Earth, requires making exactly such predictions.
“In a recent study published in Science, a multinational collaboration led by Gergely Szöllősi, senior research associate at HUN REN’s Institute of Evolution and the head of the Model-based Evolutionary Genomics Unit at the Okinawa Institute of Science and Technology (OIST), Tom Williams’ lab at the University of Bristol and Adrian Davin from Phil Hugenholtz’s group at the University of Queensland constructed a detailed timeline for bacterial evolution and oxygen adaptation, with a specific focus on how microorganisms responded to the Great Oxygenation Event (GOE) some 2.33 billion years ago. This event, triggered in large part by the innovation of oxygenic photosynthesis in cyanobacteria, fundamentally changed Earth’s atmosphere from mostly devoid of oxygen to one where oxygen became relatively abundant. Until now, establishing accurate timescales for how bacteria evolved before, during, and after this pivotal transition has been hampered by incomplete fossil evidence and the challenge of determining the maximum possible ages for microbial groups—given that the only credible maximum for the vast majority of lineages is the Moon-forming impact 4.52 billion years ago, which likely sterilised the planet.
The researchers addressed these gaps by turning to the geological and genomic records in tandem. Their key innovation was to use the GOE itself as a temporal constraint, assuming that most aerobic (oxygen-using) bacterial lineages are unlikely to be older than this event—unless fossil or genetic signals strongly suggest an earlier origin. They introduced a Bayesian approach that uses this assumption as a “soft” maximum, allowing for exceptions where the data warrant it. This approach, however, requires making predictions about which lineages were aerobic in the deep past. To do so, the team deployed machine-learning algorithms that aggregate signals across the entire genome, thereby robustly inferring oxygen tolerance from incomplete ancestral gene repertoires. To best leverage the fossil record, they incorporated genes from mitochondria (branching with Alphaproteobacteria) and chloroplasts (branching with Cyanobacteria), enabling additional fossil-based calibrations from the eukaryotic record and thereby improving dating accuracy.
Their results indicate that at least three aerobic lineages appeared prior to the GOE—by nearly 900 million years—suggesting that a capacity for using oxygen evolved well before its widespread accumulation in the atmosphere. Intriguingly, these findings also point to the possibility that aerobic metabolism may have predated the evolution of oxygenic photosynthesis. For instance, the earliest inferred aerobic transition occurred around 3.2 billion years ago in the common ancestor of two cyanobacterial groups, indicating that the ability to utilise trace oxygen may have facilitated the later emergence of genes central to oxygenic photosynthesis. Moreover, the study estimates the last common ancestor of all modern bacteria lived sometime between 4.4 and 3.9 billion years ago, in the Hadean or earliest Archaean era. Major bacterial phyla are placed in the Archaean and Proterozoic eras (2.5–1.8 billion years ago), while many families date back to 0.6–0.75 billion years ago, overlapping with the era when land plants and animal phyla originated.
Notably, once atmospheric oxygen levels rose during the GOE, aerobic lineages diversified more rapidly than their anaerobic counterparts, indicating that oxygen availability played a substantial role in shaping bacterial evolution. The researchers argue that this combined approach of using genomic data, fossils, and Earth’s geochemical history brings new clarity to evolutionary timelines, particularly for microbial groups that lack a straightforward fossil record. It also offers a powerful framework for exploring how other microbial traits arose and interacted with the planet’s shifting environment across geological time.
Photo: Banded Iron Formation (BIF): sedimentary rocks that record the rise of atmospheric oxygen during the Great Oxidation Event (GOE)
Predicting and mitigating the effects of climate change while preserving biodiversity is a top priority for both scientists and policymakers. As climate change intensifies, leading to more frequent and severe droughts, understanding the impact on natural ecosystems has become increasingly important. One of the main challenges is forecasting changes in species richness due to shifts in precipitation patterns. While it’s established that, on a broad geographic scale, regions with more water generally support greater plant diversity, results vary at smaller plot levels concerning how rainfall affects species richness. To improve predictions, it’s essential to explore the underlying mechanisms – particularly how intense droughts and long-term rainfall changes impact biodiversity. A new study shows that increased aridity at the plot level is indeed linked to a decrease in plant species richness, and this connection is even more pronounced following extreme droughts. However, this phenomenon is not easy to detect because in the absence of drought, dominant plant species can obscure this effect.
The study, carried out by the HUN-REN Centre for Ecological Research in Hungary, examines the intricate connections between long-term changes in rainfall, extreme drought conditions, the biomass of dominant plant species, and plant species diversity in a dryland ecosystem. Published in the Journal of Ecology, the research reveals that increased dryness leads to a reduction in plant species diversity in drylands and uncovers the mechanisms through which rising aridity contributes to biodiversity loss in these fragile ecosystems.
The experimental area in Fülöpháza, Central Hungary. Chronic precipitation treatments (along with decreasing aridity: severe drought, moderate drought, control and water addition) simulates changes in precipitation that have occurred several times historically. The image shows severe drought management, which excludes all rainfall from late June to late August. Prior to chronic treatments, half of the plots were exposed to an extreme treatment which simulated a drought unprecedented since the beginning of regional measurements.
Using data from a seven-year climate change field experiment, researchers conducted a path analysis to examine how precipitation influences species diversity, both directly and indirectly. The experiment simulated an extreme drought event followed by long-term variations in summer rainfall with the use of rainout shelters. Initial analysis showed a strong positive relationship between rainfall and species diversity after extreme drought treatment, but this effect was absent without drought. Interestingly, the path analysis uncovered another layer: in the absence of drought, increased rainfall boosted the biomass of dominant grass species, leading to a decrease in overall plant diversity. Nevertheless, the direct effect of rainfall remained positive, enhancing species richness even when dominant species exerted a suppressive impact. Additionally, the study revealed that past extreme droughts strengthened the link between rainfall and species diversity. Lead author Dr. Gábor Ónodi explains, “Extreme droughts decrease plant species richness and weaken dominant species. The reduction in the biomass of dominant species allows other plants to colonise, potentially altering the plant community.”
These findings have significant implications for predicting how natural ecosystems will respond to future climate change. Dr. György Kröel-Dulay, the lead researcher of the field experiment, notes “As global temperatures rise and precipitation patterns become more extreme, ecosystems may become increasingly sensitive to changes in water availability.” The study underscores the importance of considering both direct and indirect effects when evaluating the impact of climate change on biodiversity. Senior author Dr. Zoltán Botta-Dukát adds, “By deepening our understanding of these dynamics, we can better anticipate upcoming challenges and develop more effective strategies for conserving biodiversity in a world facing growing environmental uncertainties.”
Urbanisation is rapidly transforming landscapes worldwide, becoming a key driver of global biodiversity loss. It often impacts biodiversity negatively by creating selective environments that limit species diversity in urban compared to natural habitats. Amidst this challenge, understanding and enhancing urban blue-green infrastructure is critical. Garden ponds are small yet significant water features that are increasingly common in urban areas. They offer numerous ecosystem services, like aesthetic purposes, microclimate regulation, and habitats for ornamental species. However, their role in supporting biodiversity is still largely unknown.
A recent countrywide citizen science project called MyPond launched by researchers from the HUN-REN Centre for Ecological Research in Hungary highlights the potential of garden ponds as crucial contributors to urban biodiversity. The online survey gathered data from over 800 garden pond owners, uncovering insights into how these small water bodies support various animals, including amphibians and their tadpoles, odonates, and birds. The study also examined the impact of pond features, pond management practices, and urbanisation on the occurrence of these animals, shedding light on the role of pond management for wildlife.
“Our findings revealed that key pond features such as pond age, area, aquatic, and shoreline vegetation all have a strong influence on the occurrence of the studied animals. Amphibians and their tadpoles, odonates, and birds were less likely to be present in or at newly installed ponds (0-1 year), which can be due to the lack of vegetation and sediment that could offer hiding and breeding places. Aquatic vegetation was positively associated with the presence of tadpoles, odonates, and birds which indicates the habitat structuring role of aquatic vegetation that benefits biodiversity. Conversely, algaecide addition negatively affected the presence of amphibians and their tadpoles. Ponds in strongly urbanised areas had less sightings of adult amphibians and their tadpoles, while these types of ponds were visited by more odonates and birds. Despite these challenges, garden ponds emerged as vital refuges for wildlife, hosting a total of 13 amphibian species across the country, and providing critical secondary habitats within urban landscapes.” – explains Dr Zsuzsanna Márton, first author of the study.
Beyond biodiversity, the study also highlighted the ecological importance of garden ponds and provided actionable insights for urban biodiversity conservation, encouraging thoughtful pond management and design to maximize their benefits.
“Our study demonstrates that citizen science is a powerful tool for urban planning, as it can contribute to gathering valuable data on urban biodiversity and utilise it for more efficient conservation strategies. It could help urban planning by identifying hotspots of aquatic biodiversity or critical areas for the conservation of key groups like amphibians in urban environments. Garden ponds might provide important stepping stones, connecting other aquatic habitats in the landscape. Also, participants may become more conscious of environmental issues and their role in it which might lead to more active engagement in supporting blue-green infrastructure development.” – summarises Dr Zsófia Horváth, the senior author of the study and head of the Biodiversity and Metacommunity Ecology Research Group at Institute of Aquatic Ecology, HUN-REN Centre for Ecological Research.
Tropical forests, often referred to as the “lungs of the Earth,” are essential for sustaining life on our planet. They provide clean air, water, and unparalleled biodiversity. While deforestation due to slash-and-burn agriculture, mining, and logging remains the most recognized threat, less visible but equally dangerous forces are at work. A new study reveals that nutrient enrichment – driven by human activities such as agriculture and fossil fuel combustion – poses a significant risk to the delicate dynamics of tropical forests.
The research, conducted by an international team of scientists from the University of Kaiserlautern-Landau (RPTU), the University of Applied Sciences and Arts Goettingen, and the HUN-REN Centre for Ecological Research in Hungary, focuses on how nutrient deposition affects tropical tree seedlings’ growth and biomass accumulation. Their findings, published in Current Forestry Reports, show that this phenomenon can potentially disrupt forest composition and resilience, particularly in the face of global climate change.
By synthesizing data from 59 studies conducted across tropical regions worldwide, the researchers employed meta-analysis to uncover broad patterns of nutrient effects. Their analysis revealed that nutrient addition significantly boosted tree seedling growth, with shoot biomass increasing by an average of 26% and growth rates by 14%. Notably, the combination of nitrogen (N), phosphorus (P), and potassium (K) produced the most pronounced effects, driving growth rate increases of up to 27%. These impacts were particularly pronounced in seasonally dry sites, where growth rates surged by 38% and shoot biomass by an impressive 70%. Lead author Dr. Daisy Cárate Tandalla explains, “NPK are fundamental nutrients for plant growth. However, many tropical soils are nutrient-limited. Adding these nutrients disproportionately benefits fast-growing, competitive species, potentially shifting forest composition.”
The team, led by Daisy Cárate Tandalla (centre), working with tree seedlings for a transplantation experiment in the San Francisco Reserve, Ecuador, 2013.
Human activities are dramatically altering natural nutrient cycles. While volcanic activity and wildfires have historically contributed to nutrient deposition, agriculture and fossil fuel burning have intensified and expanded this process to even the most remote tropical regions. These nutrient inputs can give a competitive edge to certain tree species, leading to homogenized forests with fewer species – a trend that threatens biodiversity and ecosystem stability. Senior author Dr. Péter Batáry warns, “These changes may reduce species diversity across entire food chains and weaken forest resilience in the face of climate change. The loss of diversity also diminishes the forests’ ability to adapt to environmental stressors.”
The study also highlights the complexity of tropical forest research. Co-author Dr. Jürgen Homeier from the University of Applied Sciences and Arts Goettingen notes, “The studies we reviewed used a mix of methods – greenhouse pot experiments, transplantation trials, and in-situ fertilizer applications. Identifying seedlings to the species level remains a significant challenge due to the extraordinary diversity and similarity of young tropical trees.”
The dedicated effort of transplanting tree seedlings in the tropical montane forest.
The findings underscore the need for urgent attention to nutrient management in tropical regions. While nutrient deposition may seem like a localized issue, its impacts ripple through global ecosystems, affecting biodiversity, carbon storage, and the planet’s overall health. Tropical forests are a cornerstone of life on Earth, and preserving their complexity and resilience is crucial. This study is a timely reminder that even remote human activities can have far-reaching consequences for the natural world.
Researchers at the HUN-REN Centre for Ecological Research in Hungary applied an outdoor experimental setup of artificial ponds (mesocosms) to simulate habitat fragmentation and found that it significantly reduces microbial biodiversity, particularly among unicellular microeukaryotes. The study also highlights that fragmentation not only affects biodiversity but also disrupts essential food web interactions, underscoring the importance of maintaining connectivity among habitats to preserve biodiversity and ecosystem functioning.
In the midst of the ongoing global biodiversity crisis, even the smallest habitats like ponds demand our attention. Fragmentation of these habitats—driven by human activities like urbanization, agriculture, and land-use changes—poses a significant threat to biodiversity. Often overlooked in conservation efforts, ponds serve as vital ecological hotspots, supporting diverse species and sustaining essential ecosystem processes. These waterbodies are home to various microbial communities that, despite their tiny size play an indispensable role in ecosystem functioning, acting as primary producers, decomposers, and links in food webs. While the impacts of habitat fragmentation on large organisms like mammals and birds are well-documented, the effects on microscopic organisms, including bacteria, algae, and other unicellular eukaryotes remain poorly understood.
A recent study carried out by researchers from HUN-REN Centre for Ecological Research in Hungary explored the effects of connectivity loss within pond networks. Using an outdoor experimental setup of artificial ponds (mesocosms), the researchers simulated fragmentation by terminating the movement of water and organisms between habitats in half of the pond networks while maintaining dispersal in the other half. By controlling for factors like habitat size and environmental conditions, and focusing solely on connectivity loss, the study provided an insight into the direct impacts of fragmentation on biodiversity.
“Our findings were particularly striking for unicellular microeukaryotes. Connectivity loss led to significant declines in their diversity at both local and regional levels, highlighting that fragmentation can directly drive biodiversity loss, even under controlled circumstances. Both rare and abundant species were impacted, suggesting that fragmentation represents a widespread and severe threat to microbial biodiversity. In contrast, prokaryotes appeared more resilient, though we observed signs of a potential “extinction debt,” where biodiversity loss may emerge over longer timescales.” – explains Dr. Beáta Szabó, the first author of the study.
Beyond biodiversity, the study also highlighted how connectivity loss disrupts trophic interactions. Zooplankton grazers, which interact closely with microbial communities, experienced reduced biomass in fragmented habitats, further exacerbating the decline in diversity and community evenness of microeukaryotes. These findings highlight the interdependence of organism groups within ecosystems and the cascading impacts that habitat fragmentation can have on biodiversity and ecosystem functioning.
“Our study clearly demonstrates that habitat fragmentation—specifically the loss of connectivity—can have serious and far-reaching consequences for biodiversity. Even when habitat size or environmental conditions remain constant, simply disrupting the dispersal of individuals between habitats can trigger significant declines in microbial diversity. Conservation efforts must not only focus on preventing habitat destruction, particularly in vulnerable ecosystems like pond networks, but also prioritize maintaining and restoring connectivity between habitats to protect the ecosystems and species that rely on them. This is especially crucial for microbes, which, despite their small size, have enormous ecological significance.” – summarizes Dr Zsófia Horváth, the senior author of the study and head of the Biodiversity and Metacommunity Ecology Research Group at Institute of Aquatic Ecology, HUN-REN Centre for Ecological Research.
The invasive mosquito species, the tiger mosquito (Aedes albopictus), poses significant threats to human and animal health due to its ability to spread over large geographic areas and act as a vector for numerous pathogens. Understanding the ecological relationships this species establishes in different locations is crucial for assessing its worldwide dispersion success and its role in disease transmission. To uncover how invasiveness couples with the ability to adapt to various food sources László Zsolt Garamszegi from the Institute of Ecology and Botany, Centre for Ecological Research, Hungary performed a meta-analysis of published blood-meal surveys.
The analysis included data from 48 independent studies, providing a comprehensive overview of the mosquito’s feeding behavior across different regions and stages of invasion. The results indicate that the tiger mosquito exhibits significant variability in host selection depending on the geographic location and stage of invasion. Importantly, host diversity was greater in the invasive range than in the native range, but in newly invaded areas, the mosquito tends to have a narrower host range than in the long-established populations.
Literature survey and meta analysis of blood-feeding patterns in Aedes albopictus. Invasive Ae. albopictus has considerable ecological flexibility. The species’ ability to adapt to various food sources goes hand in hand with its successful worldwide dispersion, which has strong implications for its role in pathogen transmission.The results have strong implications for how the tiger mosquito mediates host-parasite dynamics in natural systems. Wider host diversity in the invasive range indicates that the chances for the species to act as a bridge vector between distantly related hosts such as humans and birds is higher than in the native distribution range, and this risk enhancing the spread of diseases further increases if the species has more time to adapt to the ecological conditions experienced in a given invaded region. Therefore, the obtained results can align with the ecological foundations that make this species a widespread disease vector worldwide.
The distribution of species and other ecological phenomena (e.g. vegetation types) may be affected by climate change. This impact is commonly investigated and predicted by predictive distribution models. The key components of these models are the so-called bioclimatic variables. The expected distributions predicted by the models depend on the values of bioclimatic variables (e.g. the temperature of the wettest quarter of the year). Meanwhile, the time period on which the variable is calculated (e.g. the wettest quarter) may shift within the year. This shift can easily be hidden, even though the ecological meaning of bioclimatic variables is highly dependent on the time period. For example, the wettest quarter may have been in May-June-July recently (this is true for a large part of Hungary), but this may shift to autumn or winter in the coming decades. It is not hard to see that this poses difficulties for distribution modeling. While in the recent past the bioclimatic variable describing the temperature of the wettest quarter characterized, in fact, the early summer period, in the future the same variable will describe the temperature of a completely different (in our example, much cooler) period of the year. However, to train the models that predict the future distribution (in our case, using autumn-winter temperatures), we have used the recent early summer temperatures.
Two researchers at the HUN-REN Centre for Ecological Research, Ákos Bede-Fazekas and Imelda Somodi, have already shown in a previous study that the so-called specific climate periods, such as the wettest quarter, used to calculate bioclimatic variables can not only theoretically shift by several months within the year, but that this can actually happen in the future in parts of Hungary according to climate models. The shift of the specific climatic periods reduces the reliability of the distribution models, so the modeler needs to recognize the problem and address it.
“Will Hungary be the only country in the future to be in a situation such unfortunate – from a modeling point of view? Or is the problem affecting the whole world, and perhaps some regions in particular? How far do the different global climate models agree on this issue? And the scenarios behind the climate models?,” lists Ákos Bede-Fazekas the research questions that have kept the two researchers busy.
“The questions we wanted to ask were given, as were the necessary climate data. We also knew that the results, whatever they would be, would not only be of interest to us, but would also provide important information to the large community of distribution modelers. The only thing left to do was to somehow synthesize the vast amount of data and the results that could be extracted from it, and present it to the scientific community in a form that would be accessible. I think that was the biggest challenge for us.”
Flowchart illustrating the main steps of the research, from input data to the calculation of specific climate periods and synthesizing analyses
In the end, the researchers succeeded, and their analysis of four climate models, four scenarios and four future time periods covering the whole Earth was published in the prestigious scientific journal Global Change Biology. The study highlights the areas most affected by the shift of specific climate periods.
In the map of intra-annual variability of precipitation (top) and temperature (bottom) blue polygons represent the areas that will be most exposed to shifts in the specific climate periods associated with precipitation and temperature
In addition to the map results, the two researchers from the HUN-REN Centre for Ecological Research also revealed which of the three important decisions that a distribution modeler must make when predicting the future distribution are the most and the least important ones. These decisions are the choice of the global climate model, the choice of the scenario, and the choice of the future period.
“We found that the modeler’s choice of the global climate model was the least important, while the choice of the future period was typically more important than the choice of the scenario,” reports Ákos Bede-Fazekas on the results. “The shift in specific climate periods becomes more pronounced over time and as more pessimistic scenarios are considered. However, global climate models could not be ranked in a clear order in this respect. From a modeling point of view, I find the result somewhat reassuring, as it is the choice of climate models that tends to cause the most difficulty for climate modelers, but this choice seems to be the least important.”
Unfortunately, from the point of view of ecology and the diversity of natural communities, the result is not nearly as reassuring. The researchers have found numerous examples of specific climate periods shifting by more than two months, and have also reported an expected shift of six months – the largest possible. Such a major shift in the within-year distribution of climatic features is something that is feared that many species will not be able to follow. To continue with our example, this means that plant and animal species that have adapted to the precipitation falling in the pleasant early summer heat over thousands of years, could face a major challenge if most of the precipitation falls in the autumn-winter months, when their life cycle makes it difficult for them to use this precipitation. This could lead to the migration or, in the worst case, the extinction of species.
“In the tropics, shifts in both temperature and precipitation related specific climate periods are expected in many areas. However, shifts related to the precipitation are also expected in many areas of the temperate and arctic zones,” summarizes Imelda Somodi the spatial analysis. “The combined shifts around the equator confirm the likelihood that a climate not known from elsewhere (non-analogue climate) will develop there in the future. Consequences of the development of such non-analogue climates are most difficult to grasp.”
In the conclusion of their study, the researchers from the HUN-REN Centre for Ecological Research point out that future predictive distribution models will need to take into account the shift of specific climate periods and incorporate this phenomenon into the modeling work if they are to provide reliable predictions.
The first pan-European study of its kind (Keith, H., Z. Kun, S. Hugh et al. 2024 – nature, communications earth & environment) calculated that Europe’s existing forests could sequester up to 309 megatons of carbon dioxide per year for 150 years if the use of these forests were abandoned and we let them continue to grow and re-grow.. This is equivalent to the CO2 reduction rate targeted in the European Green Deal for the LULUCF sector by 2030 (310 Mt/ha) and is greater than the current level of sequestration of managed forests in Europe (289 Mt/ha).
The authors calculated the amount of carbon stored in above-ground, below-ground and dead biomass from survey data on 288,262 trees in the remaining European primeval and old-growth forests in 27 countries, on 7,982 plots.
Surveyed primary and old-growth forest stands on Europe’s forest cover map
The carbon stocks and carbon sequestration capacities of naturally functioning primary and old-growth forest ecosystems composed of native trees are essential benchmarks. The authors calculated this benchmark forecological zones and forest types, ranging from low-productivity alpine birch forest in Sweden to the highest productivity mixed spruce-fir-beech forests in Bosnia-Herzegovina. Based on this, the predicted carbon carrying capacity of primary and old-growth forests is 22,449 MtC compared to 9,790 MtC in managed forests.
Aboveground carbon stock per hectare – Hungarian data are in the group of “Temperate continental forest – broadleaf” (case numbers are given in the columns)
The GlobBiomass and GeoCarbon projects have so far significantly underestimated forest carbon stocks in all forest types compared to data from primeval and old-growth forest.Therefore global models and parameters need to be developed and revised. Analysis of the tree density, diameter distribution and biomass of standing trees has shown that the thickest trees play the largest role in carbon storage, as half of all biomass is stored in trees thicker than 60 cm.
Tree density (light green) and carbon stock (dark green) of primary and old-growth forests by diameter class with the profile of cumulative biomass (red curve)
The protection and restoration of primary and old-growth forests are therefore not only of paramount importance for the conservation and maintenance of biodiversity, but also have an increasing role in mitigating climate change through their huge carbon sequestration and storage potential.
Researchers of the HUN-REN Centre for Ecological Research also contributed to the pan-European study with recent survey data of forest reserves representing the natural conditions of the Carpathian Basin.
The survey of forest reserves is supported by the public monitoring programme of HUN-REN Centre for Ecological Research and the Ministry of Agriculture.
Slide photo: Beech forest remnant in the Kékes Forest Reserve (Photo: Attila Bíró)
There is a lot of debate about how and why simple multicellularity emerged many times independently and what factors contributed to its prevalence. There are many theories why it was advantageous to be multicellular. Factors with direct advantage for aggregation (like avoiding predation) are evident but there are factors with indirect advantages, like spatiality and a changing environment. The latter can ensure the survival of the cooperative trait through group selection, without kin recognition or selection towards larger size (predation). Researchers of HUN-REN Centre for Ecological Research, Institute of Evolution and ELTE University investigated this hypothesis. They have modelled two types of cells in a temporally heterogenous, spatial environment. Cooperators can associate to form aggregates while cheaters cannot by themselves stick to others but can enjoy the benefits of the aggregate. In resource-rich environments, cooperators have a disadvantage due to slower growth, but only they can create propagules in resource-poor environments. Cheaters therefore need to piggyback propagule-forming cooperators to make it to the next rich habitat. The researchers have successfully demonstrated in their publication published in PLOS Computational Biology that cooperators can survive due to aggregation and group selection, enabled by spatiality in an alternating environment, without any further mechanism needed, like predation.
The evolution of multicellularity is one of the major transitions in evolution. It has occurred independently more than 25 times across different branches of life. Complex multicellular organisms, such as humans, achieve high complexity through related cells that remain together during division. In contrast, most single-celled organisms lack the regulatory mechanisms needed for this. For them, a simpler path is typically viable: forming multicellular structures temporarily, often under stressful conditions, like starvation. These aggregative multicellular species, such as the slime mold Dictyostelium, usually live as single-celled organisms. However, as their name suggests, the multicellular, slime-like form can move to a suitable habitat and grow a stalked fruiting body, which allows their spores to spread to nutrient-rich new locations.
The issue with this kind of multicellularity is that non-related individuals, or even those that don’t actively participate in cooperation (cheaters), can end up among the surviving cells. Since they don’t help, they can invest all their energy into feeding and reproduction—at the expense of the cooperative cells. This not only endangers the survival of the cooperative cells but ultimately the species itself, as too many cheaters would prevent the formation of the multicellular structure needed for reproduction. So, how can an aggregative multicellular species survive if cheaters always reproduce faster than cooperators? This is a particularly important question in the context of evolutionary transitions, where maintaining cooperation against cheaters is crucial.
Several hypotheses exist to explain why we see successful aggregative multicellular species nevertheless. One theory suggests that aggregation offers protection against predators: the more single cells stick together, the harder it is for a microbial predator to prey on them. Another hypothesis is that periodic starvation necessitates colonizing new habitats, which requires cooperative cells, thus even cheaters depend on them.
Researchers from the Institute of Evolution and ELTE University investigated these two hypotheses, examining the effects of aggregation and colonization under individual selection and group selection. They developed an individual-based, spatial computer model simulating the life cycle of a slime mold-like single-celled organism. In the model, cooperative cells produce the “glue” necessary for aggregation, while cheaters do not. The computer simulations clearly demonstrated that defense against predators is essential for the survival of cooperators in a continuously resource-rich environment. However, if resources periodically become scarce, predator-driven selection is not only insufficient but is also unnecessary for maintaining cooperation and multicellularity—it is a must to colonize new habitats.
Lifecycle of the slime mold Dictyostelium discoideum. (Source of insets: Wikimedia.) Single-celled slime molds usually start to aggregate when resources become scarce, and cells begin to starve. A secreted molecule (cAMP) coordinates movement to a tight aggregate that ultimately forms a slug. This motile form moves around to find a suitable spot for sporulation where it grows to a fruiting body with a stalk and spores in the head. Only the spores will survive to see the next habitat. The researchers have simplified this complex life cycle in their computer simulations, retaining only the crucial steps. Drawn by: István Zachar Photos: By Bruno in Columbus; by Usman Bashir (Copyright: CC BY-SA 4.0 Deed) and by Tyler Larsen (Copyright: CC BY-SA 4.0 Deed )
The researchers examined various colonization mechanisms (dispersal, fragmentation, aggregative spore formation, etc.) and found that only aggregative reproductive mechanisms can sustain cooperation long-term and robustly in such fluctuating environments. Thus, in a changing environment, group selection is more crucial than individual selection, in maintaining cooperation. The results suggest that these mechanisms played a key role in the evolutionary development of aggregative multicellularity.
In a nonchanging environment, predation, or any size-dependent selection, is enough to give a chance for cooperators to survive (top right). Without predation, however, cheaters will always win (top left). In a changing environment, when there is need to colonize new habitats, random dispersion decreases the chance of cooperators due to disrupting aggregations (middle). However, aggregation and aggregation-based colonization can effectively maintain cooperators against cheaters with or without predation (bottom left). Figure: István Zachar and István Oszoli
Dispersal is a crucial process in community ecology, through which individuals of a species can move into new and often different habitats. Species spread can happen actively, with individuals moving on their own, or passively, aided by dispersal agents. Understanding the dynamics and constraints of dispersal is a key to predict how species will adapt to changing environments, and can indirectly support biodiversity conservation and ecosystem stability.
The study of alien species dispersion is an important though relatively under-studied aspect of biological invasions. The colonisation of isolated wetlands and the introduction of pioneer and alien species are observable phenomena, but the underlying mechanisms are largely speculative. Researchers from the Institute of Aquatic Ecology at the HUN-REN Centre for Ecological Research have undertaken experiments on fish and plants to test hypotheses related to alien species dispersion. Previously, it was widely believed that waterbirds played an important role in the dispersal of fish in isolated water bodies, with fish eggs surviving passage through birds’ digestive tracts (i.e. endozoochory). Researchers at HUN-REN CER recently confirmed this hypothesis—the first such confirmation globally. However, questions persist regarding its prevalence among bony fishes and the variability in dispersal capacities across species.
In a series of feeding experiments with mallards, the researchers investigated the passive dispersal abilities of several common native (Wels Catfish, Common carp, Pike perch, Tench) and alien (Hybrid African catfish, Grass carp, Pumpkinseed, Amur sleeper, Stone moroko) fish species. In their paper, published in the journal Ecography, they reported the recovery of viable embryos of five fish taxa in the faeces of mallard, with successful hatching into larvae in one native (Tench) and one alien (Stone moroko) species. This result provide evidence that endozoochorous dispersal might be a widespread but likely rare phenomenon among bony fishes, with significant variability between species likely due to unique egg characteristics.
Herbivorous birds are known to play a significant role in seed dispersal, dietary studies from Europe showed that waterbirds can disperse hundreds of plant species, including many aliens. Moreover, passage through their digestive system can affect seeds’ germination rates. In a similar feeding experiment, researchers from HUN-REN CER compared the endozoochorous dispersal ability of six pairs of closely related (i.e. congeneric) alien and native wetland plant species. In their study, published in Freshwater Biology, they found that alien plant species can disperse more efficiently, with significantly higher seed passage rates.
However, these seeds germinated more slowly after gut passage compared to native species. Higher seed passage contributes to higher “propagule pressure” in new habitats, increasing the likelihood of establishing new populations of alien species. The delayed germination of aliens’ seeds also can offer a competitive edge to non-native species, particularly if they exhibit a fast growth rate and higher trait plasticity. Considering that mallards typically move several kilometres per day and even longer during migrations long-distance dispersal might be common and important for all studied plant species. Mallards also make shorter daily movements between wetlands, which might assist alien species to become fully established after their introduction to an area.
Pollinators are declining rapidly, largely due to land conversion and intensification of agriculture. To mitigate their crisis, low-disturbance habitats, such as sown wildflower plantings (commonly known forms are wildflower strips at the edges of arable fields), could promote pollinators by restoration of their resources (food, sheltering and nesting habitats). However, comprehensive knowledge is lacking on how landscape context, spatial configuration and age of wildflower plantings, seasonality and flower composition affect pollinator communities, especially from East-Central Europe.
To understand these effects, researchers from the HUN-REN Centre for Ecological Research established diverse native wildflower plantings within heterogeneous and homogeneous agricultural landscapes, by two spatial configurations: one large field or three smaller strips. Floral resources and wild pollinator insects (wild bees, hoverflies, butterflies) were sampled, in early and mid-summer, for two years after establishment (2020-21).
Flower resources of the sown plant species increased continuously, and were complemented at high rate by flowering plant species from the soil seed bank, especially in the first year. Both flower abundance and diversity increased the abundance of pollinators, highlighting the important role of using diverse seed mixtures. Wild bee abundance and species richness increased year by year and season by season, while butterfly abundance also demonstrated a yearly increase after establishment. Hoverfly abundance and species richness, however, showed an opposite trend, possibly due to the inter-annual variation. Wild bee and butterfly abundance was higher in the heterogeneous than in the homogeneous landscapes. Researchers did not observe any significant local effects of spatial configuration itself on pollinator populations.
Field-work photos from the transect walk method and the flower resources assessment from the four years of the study Photos: Borbála Bihaly (top left, buttom right) and Áron Bihaly (buttom left, middle and top right)
Our results emphasize that to support pollinators effectively, future wildflower plantings should be maintained for multiple years, in order to maximize floral diversity and ensure continuously available flower resources throughout the entire season.
Further results from the upcoming years and similar long-term and landscape-scale experimental studies are needed to understand all the benefits and ecological processes of diverse native wildflower plantings especially in understudied European regions.
The diverse floral resource of wildflower plantings in the second and third years and the pollinator insects visiting the flowers Photos: Viktor Szigeti (top left and middle left) and Borbála Bihaly (bottom row, top right and middle right)
Researchers at the HUN-REN Centre for Ecological Research (HUN-REN CER) are continuously studying the effects of changing environment on ecosystems, caused by human activity and climate change, and how animals respond to it. They recently showed that the increase of salinity of ponds can drive the evolution of planktonic organisms, and this process can be observed in the Daphnia (water flea) populations in the sodic water of World War II bomb craters in Hungary. The paper presenting their latest discoveries has been published in the flagship biological journal of the Royal Society, Proceedings of the Royal Society B.
Natural ecosystems are exposed to a multitude of stressors including climate change, urbanisation, or the rising salinity of aquatic habitats. These stressors change the environmental conditions, which determine the success of organisms. The emerging spatial variation in environmental factors is called a gradient. The Plankton Ecology Research Group at HUN-REN CER, led by research fellow Csaba Vad, studies the effects of environmental change on the functioning, species composition, and evolution of planktonic communities.
“Organisms have to adapt to environmental stress, otherwise they go extinct,” the researcher says. “Sensitive species can be replaced by other more stress-tolerant species, or the resident populations can also adapt to the changing environment. In other words, an evolutionary adaptation occurs in the population, and this provides an opportunity to survive in the habitat.”
Salinisation, the increasing salinity levels of aquatic ecosystems, is a global threat. The salinity of large lakes is rising as well, but the change can be much more dramatic in shallow temporary ponds. Salinisation is caused by many factors, but one of the most important drivers is increasing evaporation (as a result of warming). Meanwhile, pollution from mining or other industrial activities, or the environmental effects of urbanisation can also lead to salinisation.
Soda pan in the Seewinkel area, Austria (Oberer Stinkersee, photo: Horváth Zsófia)
Soda pans are naturally saline habitats in the lowlands of Carpathian Basin. The researchers studied the plankton communities and salinity of these soda pans and compared them to the communities of ~80-year-old sodic bomb crater ponds in the Great Plains of Hungary. Their exact origin is somewhat uncertain, but some sources suggest that during World War II, American bombers bombed the plains instead of the nearby airport, creating more than 100 explosion craters in an 800 m diameter circle. These craters were filled with sodic water and have since become very useful model systems for ecological research.
The salinity of the bomb crater ponds varies widely, so ecologists were able to compare their Daphnia populations and find out whether they are adapted to this environmental factor. Water fleas, such as the object of this study, Daphnia magna, are large-bodied zooplankton species, which are common model organisms in ecological and evolutionary research, because they play important roles in aquatic communities and can be kept easily in laboratories. “We wanted to find out whether the salinity tolerance of Daphnia originating from ponds with low and high salinity levels is different”, tells Csaba Vad. “We also studied soda pans, which are also sodic and hold similar zooplankton communities to the bomb craters. Both types of these habitats are naturally saline, and can be used as model systems, because their clusters consist of several ponds with different salinity levels in close proximity to each other.”
If local adaptation occurs, the salinity tolerance of the populations is matching with the salinity levels of their home ponds. This means that water fleas from more saline ponds will have a higher salinity tolerance compared to the Daphnia from less saline waters. In theory, local adaptation could be more prominent in more isolated habitats (in ponds more distant in space), because the mixing of their populations with others is less likely in the case of more distant habitats. The soda pans are kilometres apart, while bomb crater ponds are only a few metres away from each other. So, based on merely the position of ponds, more intense evolutionary patterns could be expected to be found in soda pans. But this was not the case.
Local adaptation (adaptation to the local salinity concentrations) was only found in the bomb crater ponds, which are very close to each other in space. There are some possible reasons underlying this observation. For example, salinity levels in soda pans are usually higher and more variable within and across years than in the bomb crater ponds. Soda pans are also shallower and larger, while bomb craters are deeper and smaller in diameter. When soda pans dry up, the resting eggs of water fleas can be easily blown to another pond by the wind. In contrast, bomb craters dry up more rarely (only in years with extreme weather conditions), their salinity level fluctuates less, and during the explosion, a prominent rim was created along their edges. Thus, Daphnia eggs cannot be as easily transported among the neighbouring ponds, and the more stable salinity levels allow for local adaptation to this stressor.
The researchers found adaptation to salinity in the soda pans as well, but this occurred on a regional level. Soda pans have a higher average salinity level than bomb craters, therefore the water flea populations from soda pans have higher overall salinity tolerance than those from the bomb crater ponds.
“Despite soda pans being more distant from each other, because of their more frequent drying-up, the gene flow among their Daphnia populations is more intense,” argues Csaba Vad. “Furthermore, many waterbirds visit soda pans, which transport several aquatic organisms from one pond to another. These circumstances overall reduce the possibility for local adaptation in this habitat type. In contrast, we found strong local adaptation in bomb crater ponds, which are sometimes only a few metres apart. Our results show that the response of aquatic communities to salinity may be influenced by several factors.”
Opening image: The model organism of the study, the water flea Daphnia magna Photo: Zsófia Horváth
Nowadays we hear a lot about climate change impacts in general, however, we still lack in-depth knowledge about how climate change might modify the processes determining the ecological status of lakes and the structure and functioning of aquatic communities. This is largely because these processes are intertwined in a complex manner, making any estimation regarding these changes challenging. In their latest study, researchers of the HUN-REN CER Institute of Aquatic Ecology used model simulations to analyse warming effects on phytoplankton dynamics based on field and experimental observations.
Although numerous lakes around the world have been showing an increase in annual mean temperature over the last few decades, it still remains difficult to assess long-term warming-related impacts in water bodies with various physical and chemical properties and diverse communities. Exploring these impacts is crucial not only for fishes, macroinvertebrates or aquatic macrophytes, but also for planktonic organisms, which form the basis of the aquatic food web and have a substantial influence on material cycles. Despite the broad range of sophisticated techniques developed to study this important group, elucidating how interrelated environmental factors drive plankton functioning is still a hard task due to the typically rapid dynamics of these communities. Monitoring based on regular field work is a crucial part of research on aquatic systems, but it is also time-consuming and lab-intensive, making any sampling effort limited in both space and time. In a sense, this is like following a streaming series with several seasons by only looking at a few snapshots from each episode, trying to guess what the actual story is.
We need complementary approaches to improve our ability to assess, estimate or forecast the ecological effects of climate change.Numerical models are promising candidates for this role, gradually gaining importance in ecological research. Generally speaking, such models describe fundamental relationships in the form of mathematical equations based on current data and scientific knowledge. Such relationships include e.g. species growth as a function of food item availability or the dependence of plant photosynthetic activity on light intensity. The strength of modelling lies in the possibility to create computer-generated simulations about changes in a population, community or ecosystem and their environment through space and/or time, helping to find causality behind natural phenomena. Thus, while field and experimental observations provide data about a series of temporary states and conditions, modelling aims at the processes that induce temporal change in those states and conditions.
In a Hungarian-Greek collaboration, Károly Pálffy, researcher of the institute’s Plankton Ecology Group, studied the dynamics of planktonic algae (phytoplankton, major primary producers of aquatic habitats) using an ecological modelling approach. While analysing a data series on Lake Balaton, Hungary in his previous study he found that the long-term rise in annual mean water temperature was accompanied by increasing seasonal fluctuations in phytoplankton composition (increasing seasonal variability), which might suggest a decline in ecosystem stability. He and his colleagues also managed to demonstrate something highly similar in a mesocosm experiment, raising the question of whether there is a more general connection between warming and the dynamics of planktonic algae.
A typical graphical output of a model simulation of one year run under different seasonal temperature scenarios (daily temperature values characteristic at present and increased with 1, 2 or 3˚C). Curves with different colours represent seasonal changes in the abundance of different species of algae. The modelling of temporal dynamics in multiple randomly assembled phytoplankton communities under different nutrient load and temperature combinations added up to more than 100,000 simulations. The study focussed on both short-term (one year) and long-term (30 years) changes and impacts.
The newly developed model made it possible to simulate changes in phytoplankton on the species level under various temperature scenarios. The output of the simulations was in agreement with the previous observations, elevated mean temperature caused more pronounced seasonal changes in phytoplankton composition, but the degree of this impact was also highly dependent on how the communities received inorganic nutrients essential for their growth. Accordingly, the ratio of the two most important ones, nitrogen and phosphorus as well as the temporal fluctuations in nutrient supply had significant influence on the effect of warming. This is in close agreement with recent studies that suggest the importance of considering nutrient load conditions (the so-called trophic state of a water body) when assessing the effect of climate change on aquatic ecosystems. Besides nutrients, initial species richness of the simulated communities also affected their response to warming. From a methodological point of view, this is an important finding, since it suggests that choosing an adequate number of species can be crucial in the planning of community-scale climate change experiments.
The recent paper published in Limnology and Oceanography also sheds light on what long-term consequences an increase in the seasonal variability of phytoplankton can have in terms of stability. At higher mean temperatures, seasonal extremes in community composition became more prominent, shifting the communities toward lower overall evenness. On a longer time scale, elevated temperatures also increased the probability of species loss, providing a mathematical explanation for the role of warming in reducing plankton community stability and thus modifying aquatic ecosystem functioning. The research group has plans for further extending the model, facilitating the simulation of climate change impacts in a spatial context as well as on the level of the planktonic food web.
Numerical models nowadays have an increasingly important role in the interpretation of field observations
The nature surrounding us, the living world, and the ecosystem provide us with the means to produce food. They play an essential role in regulating the climate by absorbing carbon dioxide, storing carbon, or protecting the soil from erosion. In recent decades, the concept of ecosystem services has gained ground. Its spread is due to the opportunity it offers to explore the complex interrelationships between the natural and socio-economic systems. It highlights how society and the economy are based on ecosystems and how human activities modify the natural environment. There is a clear link between the state of ecosystems and the well-being, health and happiness of people through ecosystem services.
Hungary’s current National Biodiversity Strategy to 2030 (3rd National Biodiversity Strategy) was adopted in August 2023. Its objectives are creating a coherent network of protected areas, improving the condition of different protected areas and restoring degraded ecosystems. The above objectives can only be achieved based on proper information and a thorough situation assessment. For this, we need a comprehensive understanding of the current state of our habitats.
Over the past five years, extensive cooperation has been established between sectoral experts and nearly 250 researchers and conservationists in a project coordinated by the Ministry of Agriculture (KEHOP-4.3.0.-VEKOP-15-2016-00001). One project element is the National Ecosystem Services Mapping and Assessment (MAES-HU), which aims to assess and map the extent of ecosystems, ecosystem condition and ecosystem services nationwide. The extensive collaboration resulted in several studies, which amounted to about 2,400 pages overall. The most important results are highlighted in a book titled ‘The Assessment and Mapping of Ecosystem services in Hungary’.
“One of the tasks was to assess ecosystem condition. However, what someone means by the condition of an area or habitat can be very varied,” says Eszter Tanács, one of the project researchers and a research fellow at the HUN-REN Ecological Research Centre. “Each stakeholder defines ‘good condition’ from their own perspective. They usually focus on factors that directly affect the state of the habitat or group of organisms that are especially important to them. For example, the health of plants (whether trees or crops of some kind) is an important indicator. If this is not in order, everyone pays attention. However, there may also be indirect links between condition and services that are more difficult to identify. For example, the diversity of wildlife in an area may be closely linked to its condition and thus indirectly to what services may be provided by the particular ecosystem type and in what quality.”
“To inform nationwide decisions, we need to produce maps that try to reflect the state of the environment and habitats nationally. This scale represents a particular challenge because the ‘goodness’ of large-scale maps depends to a large extent on the data we can base them on. However, how much detailed data we have for a given area is often arbitrary in space and time. Information on different types of habitat is not uniformly available. In the case of forests, where management means that we have to think in terms of decades or centuries, a lot of data are available at the national level. This is also true for agricultural land, partly due to the different subsidy schemes. For grasslands and wetlands, however, there is little information at the national level based on accurate measurements, although many sectors could make good use of such. Generally, more related information is available on very valuable protected areas, but these cover only a small part of the country’s territory,” said Eszter Tanács, explaining the difficulties of the task.
“Where there are insufficient sources of information, i.e. little measured data, the researchers have tried to indirectly estimate the extent of environmental pressures and mapped them. They have built on previous research and knowledge of responses to such pressures. Maps based on such relationships can also be used to estimate current condition and suitability for wildlife. Still, they have a relatively high degree of uncertainty because they represent risk. There are cases where only rough estimates can be provided through multi-step analyses – for example, flower abundance is estimated based on the presence of pollinators, and flower abundance is estimated based on what habitat is being discussed. The usefulness of such maps is more limited than those based on measured data. Therefore, an important element of our research is to investigate how well such maps reflect the condition according to more detailed, fine-scale data where they are available. This is a prerequisite for producing better and more accurate maps over time,” said Eszter Tanács.
The Ecosystem Map of Hungary, completed in 2019 (with a baseline year of 2015), was a major milestone in the implementation of the project. Although there were significant data gaps in some of the maps used for compiling it, a detailed, wall-to-wall land cover database has been developed. It is currently the best available for Hungary in terms of spatial and thematic resolution.
Proportion (%) of seminatural habitat types (based on the Ecosystem Map of Hungary) within a 300 m radius of each point
Researchers from the HUN-REN ÖK Lendület Ecosystem Services Research Group have reviewed European ecosystem services mapping projects using national experience in a recent prestigious international publication. The paper, published in the journal Ecosystem Services and first authored by Ágnes Vári, reviews the ecosystem mapping process in 13 European countries, presenting the results of a survey of project participants. The publication reviews the types of methods used, the ecosystem services assessed, the problems identified, and possible ways forward at the European level.
Publication:
Ágnes Vári, Cristian Mihai Adamescu, Mario Balzan, Kremena Gocheva, Martin Götzl, Karsten Grunewald, Miguel Inácio, Madli Linder, Grégory Obiang-Ndong, Paulo Pereira, Fernando Santos-Martin, Ina Sieber, Małgorzata Stępniewska, Eszter Tanács, Mette Termansen, Eric Tromeur, Davina Vačkářová, Bálint Czúcz: National mapping and assessment of ecosystem services projects in Europe – Participants’ experiences, state of the art and lessons learned Ecosystem Services, Vol.65, 2024, https://doi.org/10.1016/j.ecoser.2023.101592
Habitat fragmentation poses a growing global threat to our natural ecosystems, making it one of the greatest challenges in biodiversity conservation. Among the most vulnerable of these ecosystems are ponds, due to their small sizes and intricate networks. Ponds have experienced global declines in numbers and extent, making them a critical focus for conservation efforts. Once a pond loses its neighbors, it becomes isolated, which can lead to biodiversity decline. A new study, conducted in Hungary, sheds light on the importance of connectivity among ponds in these small-scaled habitat networks and its impact on the biodiversity of ponds.
Situated in the heart of the Pannonian Plain on the interfluve of the Danube and Tisza rivers, Hungary’s Kiskunság region is a diverse landscape, encompassing a variety of aquatic and terrestrial habitats. From shallow lakes, soda pans, and swamps to dry and wet meadows, semi-arid sand dunes, and grasslands, the region supports a unique array of flora and fauna, including numerous rare and endemic species. Large parts of the region belong to the Kiskunság National Park and are parts of a UNESCO Biosphere reserve, while a number of aquatic habitats are listed under the Ramsar Convention. Here, a cluster of 112 bomb crater ponds form a network with ponds differing in their distances, and therefore their relative connectivity to their neighbors. This so-called ‘pondscape’ was likely created during World War II by mistargeted bombing on a sodic meadow of the nearby airport.
Bomb craters may be scars on our Earth and reminders of devastating history but these ponds are thriving with life and providing habitat for a range of aquatic species today. They hold sodic water mostly dominated by sodium carbonates and hydrocarbonates and they vary in environmental and morphological characteristics. The ponds host a variety of species, including Pannonian endemic fairy shrimp (Chirocephalus carnuntanus), protected amphibians, pond turtles, and a range of invertebrates such as dragonflies, mayflies, aquatic beetles, and microcrustaceans. Beside its importance for conservation, the pondscape offers a unique setting for investigating scientific questions in a natural laboratory. The ponds are small and easy to sample and they form a well-delineated network far from other waterbodies. Therefore, they represent an excellent model system to understand how pond networks sustain biodiversity, and form a metacommunity, i.e., multiple separate habitat patches potentially connected through the dispersing organisms.
The ponds are not physically connected by waterways thus the dispersal of organisms is expected to occur mainly via wind or by the active movement of the organisms. The prevailing assumption has been that such small-scaled habitat networks lack structuring by spatial processes, i.e. we cannot observe diversity gradients in the network due to differential dispersal rates because all organisms could potentially spread to all habitats.
However, the findings of a study carried out by researchers from HUN-REN Centre for Ecological Research in Hungary challenge this notion. The researchteam investigated the influence of both space, i.e., the arrangement of the habitat patches and the local environmental variables (e.g. water nutrient content, depth, salinity) on species richness and community composition in an international collaboration led by Barbara Barta. These were tested in a range of organism groups including the tiniest microscopic creatures to ones as large as amphibians. They are expected to respond differently to the environmental conditions and connectivity.
“The findings showed that besides environmental conditions which certainly play a significant role in shaping community composition, the spatial position of ponds in the network is also important, particularly for passively dispersing organism groups. These are the organisms (e.g. microbes, plankton) that rely on dispersal agents, such as wind to move them across the landscape. For these species, it is better to be in the centre of the network where their pond is surrounded by many other ponds from which conspecifics can easily arrive. This leads to higher diversity of these groups in the centre of the pondscape.” explains Barbara Barta, the lead author of this study. This discovery highlights the importance of the central-peripheral connectivity gradient within pond networks.
“These findings underscore the significance of studying and conserving ponds as integral components of a network, rather than as isolated entities. It is crucial that the network as a whole is protected with all the connections which ensures that the biodiversity is sustained. Understanding the impact of connectivity on biodiversity in fragmented ecosystems like ponds is vital for the preservation of these unique habitats.” summarises Barbara Barta.
Photo: Horváth Zsófia
A network of bombcrater ponds on a meadow in Apaj, Central Hungary
One of the effects of climate change is shifting the habitats of species. For example, warming is pushing upward the forest boundary in high mountains. The question is whether the species’ speed of spreading is fast enough to follow the suitable habitats. Dr. Beáta Oborny, a researcher from the Institute of Evolution at the Centre for Ecological Research and the Institute of Biology at the Eötvös Loránd University, together with her colleagues have developed a new method to investigate this. Their paper co-authored with Dániel Zimmermann was the editor’s choice in Ecography. (The editor’s choice is a paper highlighted as the most exciting and novel paper in the monthly journal issue.)
As our planet undergoes significant transformations due to climate change, habitats are being altered, appearing, disappearing, or changing in quality. Understanding the impact of these changes on the geographic distributions of species is of great significance. The shrinking ranges of protected organisms and the expanding ranges of noxious species, such as pests and pathogens, highlight the urgent need to monitor range movements precisely. However, this task poses challenges as the available observation time is often short compared to the pace of underlying population processes, making it difficult to distinguish between directional shifts and random fluctuations.
Addressing this challenge, a research team led by Dr. Beáta Oborny from Loránd Eötvös University and the Centre for Ecological Research in Budapest has developed a novel method to monitor range shifts. The team aimed to precisely and consistently delineate range edges, allowing for comparisons between different years, geographic locations, and species.
Delineating range edges accurately is a non-trivial task as they often exhibit complex patterns. Occupied peninsulas are interspersed with unoccupied bays, and isolated occurrences dot the landscape. While traditional methods rely on the outermost occurrences of a species, Oborny and her colleagues propose a different approach. They suggest marking the range edge at the boundary between connected and fragmented occurrences, known as the “hull.” By marking the average position of the hull, the “connectivity limit,” over time, the researchers offer a statistically more reliable method. This region has a higher population density and exhibits smaller fluctuations, enhancing the robustness of the approach.
An upper limit of Dwarf mountain pine (Pinus mugo) in the low Tatra Mountains, Slovakia. The inset shows a snapshot from simulated population dynamics. Dark/light green shows the connected/fragmented occurrence of the species. The hull is marked by red. Photo: Courtesy of Konrád Lájer simulated image: Beáta Oborny
Oborny and her colleagues delved into the pattern-generating mechanisms using spatially explicit models. Unlike previous approaches based on general spatial statistical methods, their novel approach capitalizes on knowledge about the mechanisms governing the emergence of these patterns: birth, dispersal, and death within populations. Through computer simulations along environmental gradients (e.g., hillsides), the team explored the connectivity limits of different kinds of species. Remarkably, they discovered that the hull displayed a robust fractal structure with a dimension of 7/4. Further investigations conducted by Beáta Oborny and Dániel Zimmermann confirmed that this fractal structure remained consistent regardless of whether the range was rapidly advancing or retreating compared to the generation time. Notably, the method demonstrated particular robustness in the retreating (trailing) edge of species ranges. These findings highlight the applicability of the connectivity limit in tracking range shifts across diverse geographic scenarios, enabling a global perspective on these changes. For instance, the method allows for the comparison of treelines in different mountains, even when composed of different species, utilizing universal scaling laws.
The universal features uncovered in this study find their explanation in percolation theory, a field of research in statistical physics. This exemplifies the power of knowledge transfer between seemingly disparate scientific disciplines. The insights gained from these investigations deepen our understanding of the intricate relationship between environmental changes and species distributions. As scientists continue to refine and validate this method, it holds the potential to contribute to more robust assessments of biodiversity shifts and inform effective conservation strategies.
Image:An upper limit of Dwarf mountain pine (Pinus mugo) in the low Tatra Mountains, Slovakia. The inset shows a snapshot from simulated population dynamics. Dark/light green shows the connected/fragmented occurrence of the species. The hull is marked by red.
Photo: Courtesy of Konrád Lájer simulated image: Beáta Oborny
