Protected natural areas across Europe are changing. Climate change, with rising temperatures and heavy rainfall, is turbocharging the growth of shrubs and trees, choking the flowers and insects that need the light and heat of open spaces.
Traditionally, this scenario prompts nature managers to reach for chainsaws and brush cutters to keep the landscape open.
But researchers at Aarhus University and the Natural History Museum Aarhus, Denmark, can now show that horses and cattle represent a more effective method of nature management given adequate time to do their work.
The method is called 'trophic rewilding', and at the Mols Laboratory field station in Eastern Jutland researchers followed herds of up to 70 feral horses and cattle from 2017 to 2022. The animals live the autonomous lives of wild animals without supplementary feeding year-round, allowing researchers to gain a deeper understanding of how they use the area.
The five-year study, published in the scientific journal Ecological Applications, shows that the animals use all parts of the landscape, but with a general preference for open grassland areas over closed woodland.
Jeppe Aagaard Kristensen, assistant professor at the Department of Biology and lead author of the study, explains:
"Where traditional nature management often tries to freeze the landscape in a particular state, the animals at Mols make their own decisions and we see that they do not spread their efforts evenly. This means we cannot expect uniform development across the landscape. It is precisely this natural dynamic that shapes a varied landscape and forms the foundation of a healthy ecosystem."
Animals shape the landscape
In the new study, the researchers combine, for the first time, the massive amounts of GPS data from cattle and horses from this area with time series of vegetation data captured from satellites (NDVI). By analysing how the animals use the landscape over several years, the researchers can now understand with great confidence how the animals' preferences directly affect vegetation development and ecosystem resilience.
"When the animals favour certain open grassland areas, their presence has a direct effect: biomass is kept down in those areas, while trees and shrubs can more freely grow and spread in areas the animals visit less often. You should therefore not expect a uniform outcome from a rewilding project, but rather a nature shaped by the animals' active and dynamic choices in the landscape," explains Jeppe Aagaard Kristensen.
Horses and cattle make a good mix
Although horses and cattle are often regarded as similar, the GPS data shows they are different specialists.
In summer they agree on the best pastures, but during periods of resource scarcity, they move toward different areas and food sources. This diversity is valuable for biodiversity, as it ensures a more varied impact on vegetation than if only one species of large herbivore were present.
Jens-Christian Svenning, professor in biology and co-author of the study, explains that we may fool ourselves by perceiving horses and cattle as one homogeneous group of 'large grazers'.
"Their different use of the landscape during periods of resource scarcity aligns well with DNA studies of their food choices, and this functional variation can help create more dynamic and varied landscapes with greater biodiversity value," says Jens-Christian Svenning.
Animals build drought resilience
The study also examined the effects of the extreme pan-European drought of 2018. It found that the areas used most intensively by the animals were most sensitive to drought, but also the fastest to turn green again afterwards. This ability to 'bounce back' is called resilience, says Jeppe Aagaard Kristensen.
"As the climate becomes more extreme, the role of the animals becomes even more important. They create a dynamic that passive nature management – simple land abandonment – cannot match. By keeping small patches completely open while allowing others to grow, the animals create a patchwork of habitats with varying resilience to the extreme weather events that will occur more frequently in a warmer future."
A subsequent reduction of the herbivore population by around two thirds led to a general greening of the landscape, with no clear relationship to previous space-use intensity – underlining that the animals' positive effect depends on their continued presence.
A shelter as an unintended magnet
The most surprising finding in the study was the animals' attraction to man-made infrastructure. A wooden shelter in the area acted as a magnet, particularly for the horses. This insight is crucial for future nature projects, says Jeppe Aagaard Kristensen:
"It prompts careful consideration of how we design these areas, so we do not inadvertently end up controlling the development of nature. Our results show that the placement of a shelter or a water trough can unintentionally dictate where the animals spend most of their time. By moving infrastructure, you can control which parts of the landscape the animals keep open, rather than letting the animals' natural preferences guide them."
Senior researcher Kent Olsen, who leads the rewilding project at the Mols Laboratory and is a co-author of the study, adds that while water troughs are a necessity in areas without natural water sources, shelters are not a biological necessity for the animals' survival, even if they choose to use them:
"The animals at the Mols Laboratory belong to species that can handle most weather conditions. They find natural shelter under tree canopies and in hollows in the terrain. While our study indicate that they seek out shelters when the opportunity arises, it is important to emphasise that this is not a sign of distress, but a behaviour we need to take into account, so we do not alter their natural movement by erecting unnecessary infrastructure."
Welfare is a top priority
Although the goal of rewilding is to let nature take its course, this does not mean the animals are left entirely to their own devices, underlines Kent Olsen.
A central part of the experiment at the Mols Laboratory is precisely to combine wild behaviour with high animal welfare. Each individual animal is monitored daily, and if an animal is assessed as unlikely to survive the winter naturally, it is removed from the herd.
"It is important to understand that we aim to recreate natural dynamics in which the animal population fluctuates according to the landscape's resources. But this happens under controlled conditions, where there are never more animals on the land than the food base can support," explains Kent Olsen.
Study type:
The study used GPS data from 2 horses and 2 cattle and vegetation data from satellites (NDVI from Sentinel 2) to understand the animals' use of the landscape at the Mols Laboratory and the resulting impact on vegetation development in the period 2017–2022.
Ecological Applications
Content analysis
Animals
Space-use by feral cattle and horses shapes vegetation structure in a trophic rewilding area
4-Feb-2026