‘Life on land’: one large interconnected ecosystem of flora and fauna

The Botanic Gardens at Utrecht University are more than just a place where people can gawk at pretty plants and flowers; it is also a test garden for Utrecht’s scientists. In hundreds of containers behind the greenhouses, plant- and soil ecologists are replicating natural grasslands to study the effect that changing climate, combined with the loss of biodiversity, will have on the ecosystem. What are the consequences of changing precipitation patterns, with wetter winters, drier summers, more extreme weather, or a combination of all three? And what will be the long-term effects of the changing climate not only today, but over five, ten or 20 years?

Collaborative plants

The Utrecht University Biodiversity and Climate Variability Experiment (UU BioCliVE) is unique in the world in its scale and time frame. Within the project, Assistant Professor of Ecology and Biodiversity Yann Hautier studies how plants collaborate or compete with one another, and which influence human activity has on these interactions.

In natural grasslands, every plant species has its own unique niche. Some species grow better under drier conditions, while others grow better in damp or wet circumstances. As the climate changes, some species will not be able to adapt to the new circumstances, while others will thrive.

The theory is that grasslands with more diversity in plant species will be better able to adapt to climate change, as there will always be a few species that grow well under the new conditions. The positive effect that high levels of biodiversity has on buffering for climate change can even increase if the plants in the grasslands help one another to survive periods of extreme weather. The initial results after the dry summer of 2018 have already shown that this is the case.

It is more important than ever for us to limit nitrogen emissions so that we can maintain the diversity of plant species

Is it therefore the perfect natural solution? Unfortunately, no. Human activity, such as fertilising the land, increases the availability of nitrogen in the grassland, which in turn decreases plant diversity. That is cause for concern, according to Hautier. “If we wish to continue to benefit from all of the services that the ecosystems provide, then it is more important than ever for us to limit nitrogen emissions so that we can maintain the diversity of plant species.”

In the containers in the Botanic Gardens, he therefore studies how important a high level of biodiversity is for the provision of essential ecosystem services, such as crop yields, carbon sequestration and water retention.

Plants and animals

Professor of Plant Dispersal Ecology & Nature Preservation Merel Soons is also participating in an experiment in the Botanic Gardens. She studies how biodiversity develops and is maintained in ecosystems. Grasslands naturally have a high level of diversity, with up to 25 plant species per square meter, but in the current Dutch agricultural landscape many grassland species can only be found in nature reserves.

Those protected areas are also fragmented in the landscape, which presents the risk of population isolation and the disappearance of entire species. The dispersal of plant seeds is crucial for the maintenance of populations in nature reserves, but also for the colonisation of new areas after nature restoration measures and to enhance the biodiversity of existing grasslands.

Nature has some tools at its disposal in this area, such as the flight and feeding patterns of wild ducks. Ducks eat many plant seeds in the autumn and winter that are not digested in their stomachs, and they then spread these seeds over the nature reserves they visit, up to two to four areas per night. In so doing, wild ducks connect the fragmented nature reserves and the plant species that live in them. Soons explains that studying how this process works can provide knowledge for use in nature preservation and restoration, which can in turn be used to answer vital questions such as:

• How can we maintain the connections between natural areas?
• Which areas are most promising for nature restoration?
• How can we ensure that plants can move to adapt to a changing climate?

Soons not only studies dispersal of plant seeds via animals such as wild ducks, but also dispersal via the air and water. In the UU BioCLIVE project, she will also study how the dispersed seeds can take root in existing grassland vegetation and how this biodiversity changes the composition of the grassland.