Pastoralism has existed since the beginning of agriculture; nomads domesticated sheep and goats before the first human settlements were built. A new study has assessed how grazing affects 326 arid ecosystems located in 25 countries across six continents, and it’s not always a good idea.
The study published in Science and led by researchers at Laboratory of Ecology of Arid Zones and Global Change at the University of Alicante (UA) presents the first assessment of the ecological impacts of grazing in the arid zones of the planet. The results indicate that grazing has positive effects on the provision of ecosystem services in the more diverse and colder rangelands, but becomes negative in the warmer and less diverse ones.
Pastoralism is a fundamental human activity that sustains hundreds of millions of people and is closely linked to the United Nations Sustainable Development Goals (SDGs). This activity is particularly important in the arid zones, which cover more than 40% of the Earth’s surface, and are home to one in three people who inhabit it and half of all the livestock on the planet. 🇧🇷
Despite the importance of rangeland for people and ecosystems, to date no studies have characterized their impacts on the provision of ecosystem services on a global scale using in situ data. To this end, UA scientists, led by distinguished researcher Fernando T. Maestre, joined an international team of more than a hundred collaborators to study 326 arid ecosystems located in 25 countries on six continents.
Impact on soil fertility, climate regulation or forage and wood production
“Using standardized protocols, we assessed how increased grazing pressure affects the ability of arid grasslands to provide critical ecosystem services to people, such as maintaining soil fertility, climate regulation or forage and timber production. This made it possible to characterize how the impacts of this increase depend on the climate, soil and local biodiversity and to obtain additional information about the role of biodiversity in providing these services”, explains Professor Maestre, who directs the Laboratory of Ecology of Drylands and Global Change from the University of Alicante.
The researchers found that the relationships between climate, soil condition, biodiversity and measured ecosystem services vary with pasture pressure. “Soil carbon stocks declined and soil erosion increased as the climate became warmer under high grazing pressure, something that was not observed when grazing pressure decreased. These results suggest that the response of drylands to ongoing climate change may depend on how we manage them locally,” says researcher Nicolas Gross, from the National Institute for Research in Agriculture, Food and the Environment (INRAe, France).
The impacts of increased grazing pressure shifted from positive in colder areas with greater plant species richness to negative in warmer locations with lower plant diversity and greater rainfall seasonality. “There is no single answer to dryland grazing. Any effects of grazing, particularly overgrazing, vary across the world, so it is important to take local conditions into account when managing domestic livestock and wild herbivores,” says David Eldridge of the University of New South Wales (Australia) and co-author of the study.
The authors also observed that the diversity of vascular plants and herbivores is positively related to the provision of ecosystem services, such as carbon storage, which play a key role in climate regulation. “Our results clearly highlight the importance of preserving the biodiversity of the world’s drylands as a whole, not only to conserve their ability to provide essential services to people, but also to mitigate climate change,” says Yoann Pinguet of the Center National Scientific Research Institute (CNRS, France) and co-author of the study.
The conclusions of this study are of great relevance to achieve a more sustainable management of grazing, as well as to establish effective management and restoration actions aimed at mitigating the effects of climate change and desertification in the arid zones of our planet.
BIODESERT project
This work was carried out within the scope of the project BIODESERT, Awarded by the Consolidator Grant program of the European Research Council (ERC) to Fernando T. Maestre. “I am very grateful to the ERC for supporting this global sampling, as it is a high-stakes project that would not have been possible without the generous funding and freedom that comes with this grant. And, of course, this would not have been possible without our network of international collaborators, who provided their expertise, resources and manpower to research sites in their respective study sites. This work is also a good example of the power that global and collaborative research networks have to carry out research at the frontier of knowledge”, highlights Maestre.