Restoring and rewilding ecosystems

For Geert de Snoo, director of NIOO and Professor of Conservation Biology, helping to counteract the biodiversity crisis is one important goal of the research carried out at the institute. “Bending the curve of biodiversity loss is how we researchers refer to it. Doing nothing is not an option.”

Increasing biodiversity

The question is how. De Snoo: “A lot of nature in the Netherlands is not part of the original landscape. Hay fields are cultural landscape but nevertheless have an important function in nature. And in 1906, a Dutch lake, the, Naardermeer, was established as the Netherlands’ first nature reserve to protect birds. However, you need to manage such areas, as otherwise they will eventually develop into woodland.” It is a constant and intensive process that you cannot let go of, but, says De Snoo: “Via this so-called ‘pattern management’, it is indeed possible to achieve the kind of nature you intend.”

An example of this management approach is the current practice of seeding the edges of fields with wild native plants to create more opportunities for insects. De Snoo: “NIOO investigates which areas of agricultural land should consist of natural elements to increase the biodiversity in these areas. Just an expansion of 3 to 7 percent of the surface area can already boost the percentage of butterfly species to be expected from 52 to 64 percent”

Creating the starting conditions

The counterpart of pattern management for developing nature is what De Snoo calls ‘process management’: instead of actively introducing species, nature restores itself. This approach is known as rewilding. Ecologist Liesbeth Bakker at NIOO is a specialist in this area and investigates such extensive ecosystem recovery. In this field, you do not examine specific species but the entire ecosystem and how that functions. Bakker: “It is a completely different way of working than the traditional restoration methods.”

It is all about the creation of the right starting conditions to give nature the chance to restore itself. Bakker: “The idea behind rewilding centres on the 3 Cs: cores, carnivores and corridors. Cores are the core areas and corridors are the connections between these areas. In the Netherlands, we do not focus on carnivores but mainly on large herbivores such as wild horses and cattle. This means that vital links in the food chain are still missing. If we were to introduce those, then this would result in more biodiversity.”

Absorbing excess water

Rewilding was introduced to the Netherlands in the mid-1990s with the well-known project Ruimte voor de rivier (Space for the river) in which water safety was increased by moving dikes inland so that the flood meadows came into existence that now absorb the excess water that annually flows into the Netherlands in great peaks from Germany. Bakker: “That made the land unsuitable for agriculture. Accordingly, climate policy actually provided an indirect opportunity for nature development.” Back then, people in the Netherlands wondered what would happen in those areas if you gave nature a free hand, says Bakker.

Nowadays, such water storage also exists in other areas. “A large marsh area to the south of Groningen will protect the city from flooding in the future. Wetlands were reintroduced there out of necessity, creating an opportunity for biodiversity.”

Good soil structure

Effective rewilding in wet areas requires a good soil structure with sufficient variation, such as channels. “A large part of the work does, in fact, boil down to engineering”, says Bakker. “A case in point is the dyke that runs alongside the artificial archipelago, the Marker Wadden, a large area that has so far been half rewilded.” In those initial interesting years, Bakker coordinated the ecological research into this newly constructed group of islands in Ijsselmeer (Lake IJssel).

A mix of pattern and process management often proves to be the solution. For example, the NIOO soil ecologist Ciska Veen and her colleagues examine how moving soil from a nature reserve to former farmland can contribute to the restoration of nature. The broadly shared point of departure for this is that the biodiversity of beneficial fungi, bacteria and animals in the soil is essential for nature above the ground. Veen: “Our question is whether these so-called soil transplantations kickstart the biodiversity, and whether the plant communities that grow there subsequently become more diverse. Ultimately, a healthy soil can even contribute to climate mitigation: counteracting climate change, namely by storing more carbon.”

Rewilding at a microscale

Colleague Jos Raaijmakers from the Microbial Ecology department is convinced that the right microorganisms are important for the success of a recovery programme. He published a review article in the journal Science about the rewilding of plant microbiomes in the soil. This concerns communities of microorganisms that live around plants and/or their roots.

Raaijmakers even sees possibilities to make agricultural crops more resilient to climate change by rewilding the soil microbiome. “Domestication of food crops was originally meant to make crops more attractive, less bitter, for instance. However, that selection was associated with a decrease in the genetic diversity of the plants and, as a consequence, a diminished relationship with protective microorganisms in the soil. We are developing a sort of probiotics for agricultural crops to make them more resilient to drought and increased salinity. At the same time, we aim to reduce the need to use artificial fertiliser and pesticides on these crops.”

People also need to change

Bakker is of the opinion that rewilding has yielded “an awful lot” so far. “That is particularly the case in areas where intensive agriculture used to be practised. Not only the soil and the plants benefit, but the birds too.”

Consequently, rewilding allows us to tackle both the biodiversity crisis and the climate crisis. However, that would require a lot from citizens. Bakker: “Traditionally, we feel that you need to manage nature. That is, for example, how our characteristic heathlands arose, and that is nature too.” ‘Therefore, to garner acceptance for the ecosystem approach, says Bakker, it would be wise not to allow too much rewilding of nature. “Many people find it difficult to accept rewilding, as they are used to dead trees being removed from the woods. Also, nature can bite and sting. In addition, we know that what people consider to be normal is how things were when they were young. So, in part, rewilding is also a matter of shifting baselines: rewilding will only be possible if we rewild ourselves.”