Increased grazing pressure threatens the most arid rangelands
Ranchers driving livestock in Patagonia (Argentina). (Picture: Sergio Velasco Ayuso.)
Using a standardized survey at 98 sites across six continents, the study shows that the impacts of increased grazing pressure on the delivery of fundamental ecosystem services depend on climate, soil, and biodiversity across drylands worldwide. Increasing grazing pressure reduced ecosystem service delivery in warmer and species-poor drylands, whereas positive effects of grazing were observed in colder and species-rich areas. (Picture: Cirenia Arias Baldrich)
Positive effects of grazing can turn to negative under warmer climate
Based on a media release of the University of Alicante
Grazing can have positive effects on ecosystem services, particularly in species-rich rangelands. However, these effects turn to negative under a warmer climate. This was found by a team of researchers led by the University of Alicante (UA) and with participation of the German Centre for Integrative Biodiversity Research (iDiv). The study, which was published in Science, reports results from the first-ever global field assessment of the ecological impacts of grazing in drylands.
Grazing is an essential land use that sustains the livelihood of billions of people and is tightly linked to many UN Sustainable Development Goals. Grazing is particularly important in drylands, which cover about 41% of the Earth's land surface, host one in three humans inhabiting our planet and over 50% of all livestock existing in our planet.
Despite the importance of grazing for humans and ecosystems, to date no previous study had attempted to characterize its impacts on the delivery of ecosystem services at the global scale using field data. For doing so, Prof Fernando T. Maestre, Distinguished Researcher at UA and former iDiv sabbatical, teamed up with more than 100 colleagues to carry out a unique global survey conducted in 326 drylands located in 25 countries from six continents.
“We used standardized protocols to assess the impacts of increasing grazing pressure on the capacity of drylands to deliver nine essential ecosystem services, including soil fertility and erosion, forage/wood production and climate regulation. Doing so allowed us to characterize how the impacts of grazing depend on local climatic, soil and local biodiversity conditions, and to gain additional insights on the role of biodiversity on the provision of ecosystem services essential to sustain human livelihoods”, says first author Fernando T. Maestre.
The researchers found that the relationships between climate, soil conditions, biodiversity and the ecosystem services measured varied with grazing pressure. As climate became warmer, carbon stocks decreased and soil erosion increased under high grazing pressure, an effect that was not observed under low grazing pressure. These results suggest that the response of drylands to ongoing climate change may depend on how they are managed locally.
The impacts of increasing grazing pressure shifted from mostly positive in colder drylands with a lower rainfall seasonality and higher plant species richness to negative in hotter drylands with lower plant diversity and higher rainfall seasonality. Thus, the effects of grazing, particularly overgrazing, vary across the globe.
The authors also observed that the diversity of both vascular plants and mammalian herbivores was positively linked to the provision of essential services such as carbon storage, which plays a fundamental role in climate regulation.
"This study does an excellent job of demonstrating that only by considering multiple influencing factors in concert can we make meaningful recommendations for the sustainable management of our ecosystems during changing climate”, says co-author Simone Cesarz, Head of Laboratory of iDiv’s Experimental Interaction Ecology group.
The findings of this study are of great relevance for achieving a more sustainable management of grazing, as well as for establishing effective management and restoration actions aimed at mitigating the effects of ongoing climate change and desertification across global drylands. “We have now reached a human population of 8 billion people and climate change increases the proportion of dry areas worldwide. The present results clearly highlight that we need to tackle the climate and biodiversity crises in concert and to manage ecosystems in a sustainable way to protect their integrity”, says co-author Nico Eisenhauer, head of Experimental Interaction Ecology at iDiv and professor at Leipzig University.
Original publication
(Researchers with iDiv affiliation are in bold)
Maestre, F.T., …, Simone Cesarz, Nico Eisenhauer, … Carlos A. Guerra et al. Grazing and ecosystem service delivery in global drylands. Science (2022), doi: 10.1126/science.abq4062
Contact:
Prof Fernando T. Maestre
University of Allicante
Email: ft.maestre@ua.es
Prof Dr Nico Eisenhauer
Head of the research group Experimental Interaction Ecology
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Leipzig University
Phone: +49 341 97 33167
Email: nico.eisenhauer@idiv.de
Web: www.idiv.de/en/groups_and_people/employees/details/eshow/eisenhauer_nico.html
Simone Cesarz
Experimental Interaction Ecology
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Leipzig University
Email: simone.cesarz@idiv.de
Kati Kietzmann
Media and Communications
German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig
Phone: +49 341 9739222
Email: kati.kietzmann@idiv.de
