In Portugal’s Greater Côa Valley, a change in grazing management is helping to shape the recovery of Mediterranean montado shrubland habitats. At two rewilding sites, commercial cattle have been replaced with small groups of free-living Sorraia horses: a hardy domestic breed with Portuguese origins, well adapted to living in semi-wild conditions. This shift is part of a wider rewilding strategy led by Rewilding Portugal and supported by the Endangered Landscapes & Seascapes Programme.
Over a three-year period, researchers monitored how this transition affected vegetation across both sites. The results, now published in Frontiers in Ecology & Evolution, reveal that semi-wild horse grazing has reduced grass height, potentially helping both wildfire management and biodiversity in fire-prone Mediterranean landscapes.
The study was designed as part of one of the Programme’s restoration trials – experimental approaches embedded within each of the landscape and seascape restoration project funded by the Programme to generate new evidence that can be applied in future management decisions.
“We support projects not only to implement restoration, but also to learn how it can be made more effective” said Dr Nancy Ockendon, Science Manager at the Endangered Landscapes & Seascapes Programme. “This is a great example of how, by using carefully designed trials, Endangered Landscapes & Seascapes Programme projects are helping to build our understanding of the results of different restoration actions. This will ensure future restoration can be based on good evidence of what does and doesn’t work.”
By linking scientific monitoring with restoration practice, the findings offer valuable insight into how different grazing regimes shape ecological recovery – and where additional interventions, such as introducing a mix of herbivore species, may be needed to achieve long-term goals.
The importance of wild horses
Across several landscapes supported by the Endangered Landscapes & Seascapes Programme, the return of free-roaming herbivores is helping to bring back natural grazing. In the Greater Côa Valley, semi-wild Sorraia horses now graze areas once managed for cattle, while in the Iberian Highlands, the iconic Przewalski’s horse has been reintroduced to support steppe habitat restoration. These large herbivores are shaping vegetation, reducing the build-up of flammable grasses, and creating conditions that support a wider range of wildlife.
Through their natural grazing and interactions with the land, wild and semi-wild horses play an important ecological role. By breaking up dense grasslands, creating open patches, dispersing seeds and fertilising the soil, they contribute to more diverse, dynamic habitats. Their presence can also bring socio-economic benefits by increasing nature-based tourism.
Evaluating horse grazing in the Greater Côa Valley
The beneficial impact of natural grazing by semi-wild horses has been confirmed by new research carried out in the Greater Côa Valley rewilding landscape in Portugal, with the results presented in a new paper published in scientific journal Frontiers in Ecology & Evolution.
The researchers explored the impact of transitioning from extensive commercial cattle grazing to semi-wild horse grazing at two rewilding sites in the landscape – Vale Carapito and Ermo das Águias – over a three-year period. Both sites are now exclusively grazed by Sorraia horses – a native Portuguese breed adapted to living in wild or semi-wild conditions – which have been reintroduced by the Rewilding Portugal team. Plots in both sites were fenced off and used as ungrazed control sites.
Implications for managing fire risk
The findings of the study showed that horse grazing at the two rewilding sites reduced the risk of catastrophic wildfire outbreaks by reducing the height and quantity of grass. This impact is particularly relevant to rural landscapes across the Mediterranean region where wildfire outbreaks – which can be devastating to people, property and wild nature – are now increasingly common. Two underlying drivers of this trend are more extreme temperatures resulting from climate change, and a decline in agriculture and grazing by livestock, which is leading to the unregulated growth of grasses and shrubs.
The study also showed that while horses in the rewilding sites helped to control grasses through their grazing, they had little impact on woody vegetation, which is also easily combustible. From a management perspective, the co-authors of the study suggest that a combination of different herbivores – such as horses, deer, European bison, or extensively grazed cattle – may be even more effective at reducing fire risk at rewilding sites in Mediterranean landscapes, because different species graze on different types of vegetation, fostering greater ecosystem function and resilience. This aligns with the rewilding approach to boosting natural grazing, which aims to bring back different types of wild and semi-wild herbivore in the same landscapes to amplify their positive impact.
Boosting biodiversity
The benefits of reintroducing free-roaming herbivores such as semi-wild horses aren’t limited to reducing wildfire risk. The Greater Côa Valley study also showed that grazing by Sorraia horses increased the proportion of flowering plants in the landscape, which in turn could increase the amount of food available for pollinating insects such as bees and butterflies.
Natural grazing by the horses also increased the amount of organic matter in the soil – which is fundamental for enhancing soil biodiversity – and supported the growth of different native tree species. This second impact is particularly important at sites where wild nature is recovering from intense and recurrent wildfires, as is the case at Ermo das Águias.
The bigger picture
Today, socio-economic changes heighten the importance of returning wild and semi-wild horses and other free-roaming herbivores to European landscapes. Across Europe, millions of hectares of farmland are transitioning as people living in the countryside migrate to urban areas, agricultural economies evolve, and traditional small-scale farming becomes less viable – which, in turn, is leading to the disappearance of livestock. After millions of years of natural grazing and some 10,000 years of grazing by domesticated animals such as cows and sheep, large parts of Europe are now lacking this essential natural process. This is why reintroducing large herbivores to European landscapes is one of Rewilding Europe’s key activities, with the wild horse one of our focus species.
Early-stage assessments, such as the study carried out in the Greater Côa Valley, are essential as they show how vegetation changes when free-roaming wild and semi-wild herbivores are reintroduced at rewilding sites. The results can guide how natural grazing is used as a way of managing the risk of wildfire, as well as highlighting the other benefits that enhancing such grazing delivers. From the perspective of Rewilding Portugal and Rewilding Europe, the methodology and results of the study are informing future decisions about how to rewild the landscape.
This article was first published on the Rewilding Europe website.
The study was fully funded by the Endangered Landscapes & Seascapes Programme, while the organisations participating in the study comprised the Marine, Environment & Technology Centre (MARETEC) at the University of Lisbon, Rewilding Portugal, Rewilding Europe, and the Hill and Mountain Research Centre of Scotland’s Rural College.
