A three-year study in Portugal’s Greater Côa Valley has shown that grazing by free-roaming, semi-wild horses can help to reduce the risk of wildfire outbreaks and enhance biodiversity in Mediterranean landscapes. It has also highlighted the fact that when groups of different herbivores graze the same landscapes, this may be even more effective at reducing fire risk.
The importance of wild horses
Since its foundation in 2011, Rewilding Europe has reintroduced and reinforced populations of semi-wild horses in many of its landscapes – from Przewalski’s horses in the Iberian Highlands of Spain, to Konik and Karakachan horses in the Rhodope Mountains of Bulgaria.
Through their natural grazing and other interactions with landscapes and their wildlife, wild and semi-wild horses play an essential ecological role, which is why restoring populations across Europe is so important.
Free-roaming horses help to create a mosaic of diverse, nature-rich habitats by breaking up grasslands and creating wallowing areas, while they also contribute to the spread of plant species and act as natural fertilisers. In addition, large herbivores such as horses can deliver socio-economic benefits. By consuming flammable vegetation, they can reduce the amount of fuel available for catastrophic wildfires, while the presence of iconic horse breeds in landscapes can drive the growth of nature-based tourism, as Przewalski’s horses are doing in the Iberian Highlands.
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. – READ THE PAPER HERE
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 long-term impact monitoring plans in the Greater Côa Valley rewilding landscape.
Rewilding Europe published an updated report on rewilding horses in Europe in 2023. An authoritative guide to the reintroduction of wild horses in European landscapes, the publication is intended for all rewilding initiatives already working with wild horses, or thinking of working with them.
Study partners
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.