Bending the curve of biodiversity loss starts with insight into the causes
The Netherlands is unfortunately one of the world’s leaders in biodiversity loss. Scientists at Utrecht University are studying the causes of biodiversity loss, and the possibilities for bending the curve. Insight into effective measures is vital: greater biodiversity makes ecosystems more stable and can help mitigate the consequences of climate change.
Four main causes of biodiversity loss
Land use change resulting in the loss of habitat for plant and animal species is the main cause for the decrease in global biodiversity. Another cause is overexploitation, such as fishing, hunting and harvesting species at unsustainable levels. Pollution and climate change are also major causes behind the current decline in biodiversity. Researchers at Utrecht University address all these drivers of biodiversity loss.
Land use change is the biggest problem worldwide
Landscape ecologist Merel Soons conducts research into the survival of species in landscapes that are increasingly modified by humans. “Humans have changed landscapes all over the world, and that is the main cause of loss of diversity. Plant and animal habitat areas are becoming smaller and more fragmented, resulting in a higher chance of species extinctions. Our research on forest fragments around the world shows that the larger the fragment size, the more species survive in it.”
Her research also shows that nature conservation helps, especially in areas larger than 50 hectares. Protected areas contain higher numbers of species. Soons: “Threatened species especially benefit from conservation. And it is important to connect fragmented areas, so that plants and animals can disperse between remaining nature areas.”
High nitrogen pollution in the Netherlands
In the Netherlands, pollution also plays a major role in the loss of biodiversity. Soons: “The intensification of agriculture since World War Two has led to loss and fragmentation of nature on the one hand, and to pollution of the remaining nature areas through nitrogen and phosphate enrichment on the other.”
The more nitrogen is added to a natural ecosystem, the fewer plant species can survive.
Research conducted by Soons and an international group of colleagues indicates that especially nitrogen enrichment leads to a decline in natural biodiversity. She brought together studies from around the world to examine how vegetation changed as a result of added nitrogen. “The more nitrogen is added to a natural ecosystem, the fewer plant species can survive. Plus, part of the additional nitrogen accumulates over time, causing more species to disappear from the ecosystem. At this moment, the most important factor explaining how well a plant species can survive in our country, is how well it responds to large amounts of nitrogen.”
Per 1 February 2023, Merel Soons is appointed Professor of Land Use and Biodiversity at the Faculty of Geosciences. She will also remain involved in research at the Faculty of Science, where she has served as Professor of Plant Dispersal Ecology and Conservation since 2018.
Nature restoration needed
According to Soons, the Netherlands has passed the stage of nature conservation. “What we really need now is nature restoration. We’ve already lost many species, and remaining populations of many species are very small. A more robust nature requires restoration of plant and animal populations and their living conditions in natural areas as well as agricultural landscapes. The remaining populations are vital for restoration to succeed, because they act as the source of recovery.”
Soons explains that the restoration of Dutch nature will also help it become more resistant to invasive species and climate change. “A higher biodiversity is likely to be more resilient to climate change. In the UU-BioCliVE project, we investigate to what extent grassland biodiversity can mitigate the consequences of climate change.” Soons emphasises that it is also important for the future of natural areas that they are connected to one another, so that species can migrate to keep up with the changing climate.
Discovering and understanding patterns
The research conducted by Edwin Pos, Scientific Director of the Botanic Gardens at Utrecht University, can offer insight in the dynamics of biodiversity; how it changes over time and space and what is driving these dynamics. Pos recently formed the new research group Quantitative Biodiversity Dynamics (QBD) to address, among other things, the loss of biodiversity with fundamental understanding. QBD combines methods and expertise from the field of biology with those from mathematics, physics and computer science. “That makes us better able to study complex systems and work with large data sets, which are accumulating. This way, we aim to discover and understand patterns that tell us something about how biodiversity changes, from one place to the next but also over time. Using those methods, we can gain insight from looking at different snap-shots and learn about the rules of the game when it comes to biodiversity.”
With these methods, we can gain insight into the rules of the game for biodiversity.
Pos looks at ecosystems as if it was a network, with larger and smaller nodes and a variety of connections between the nodes. “In a network like that, for example, you have all kinds of different tree species, plants around and between the trees, insects on the plants and microorganisms on the roots of the plants. But how do you decipher the network as a whole? Step-by-step, Pos hopes to discover the rules behind such a system by comparing different ecosystems to one another, including the species and their characteristics and to use and develop net methods.
Dynamical toolbox
At virtually every scale, researchers observe a similar curve in biodiversity, Pos explains. “A number of species occur frequently, others are present in smaller numbers, and then there usually is a long tail of very rare species. When biodiversity is lost, it is often these rare species that disappear. But how can those species come back? And why are they the species that disappear? If we want to know whether it’s important for us to be concerned, or know what to do about it, then you need to know how biodiversity works from a fundamental principle.” According to Pos, he provides handles that can help to develop strategies for biodiversity conservation or restauration, methods to gain insight into a system so that others are better able to protect or restore natural systems. “A dynamical toolbox.”
Management in times of climate change
The tools in that box may hopefully be used for future policy measures for future-proof nature recovery in the Netherlands. Faculty of Geosciences paleoecologist Timme Donders has acquired knowledge about the composition of species in the distant past, and that has given him insight into the chances of survival for trees and plants in the future. “The Douglas firs that were introduced from North America and planted in the Veluwe since the late 19th century are starting to die off, but they don’t actually belong here. In today’s warmer climate, the species that disappeared here during the ice age should be able to grow here just fine. That’s because they are better adapted to deal with the new conditions over the long term.”
In the Netherlands, you will have to reintroduce old plant species that can survive here over the long term.
But Donders’ idea for re-introducing old species shouldn’t be left to chance. “Those species, like the wingnut and zelkova, are still present in the Caucasus, for example. And the sweetgum tree is present on a single island in Greece. So there’s absolutely no chance they’ll get here on their own. We’ll have to plant them.”
Choices for new landscape
According to Donders, it is also important for us to make choices at the level of the landscape as a whole. “You have to choose how you want to manage each area individually. For example; draining water, like we do in large areas of the west of the country, isn’t sustainable over the long term because the peat soil subsides, and eventually salt water will intrude into the water table. The Veluwe and Drenthe originally had poor, sandy soils. We should aim to keep them low in nutrients, and within those regions choose areas to keep wetter than we do today to restore the original acidic, low-nutrient peat environment where unique species can grow, like drosera. The original peat is gone now, which causes the soil to dry out and erode.”
Donders explains that it is entirely feasible to preserve the Netherlands’ biodiversity around the major rivers. “That area was never low in nutrients, thanks to the nutrient-rich water from the river. But it’s also a dynamic area, so it’s possible to maintain a high degree of biodiversity there.”