A new study published in Sciences Reports the findings of the first-ever global field assessment of the environmental impacts of dryland grazing. An international research team has found that grazing can have positive effects on ecosystem services, particularly on species-rich grasslands, but that these effects turn negative under a warmer climate.
Pastoralism is an essential land use that sustains the livelihoods of billions of people and is closely linked to many of the United Nations Sustainable Development Goals. Grazing is particularly important in the drylands, which cover about 41% of the Earth’s surface, and host one in three people that inhabit our planet and more than 50% of all livestock on the planet.
Despite the importance of grazing to humans and ecosystems, no previous study to date has attempted to describe its effects on the provision of ecosystem services on a global scale using field data. To do this, an international research team of more than 100 specialists, led by Dr. Fernando T. Maestri (University of Alicante, Spain), conducted a unique global survey conducted in 326 drylands located in 25 countries on six continents.
“We used standardized protocols to assess the effects of increased grazing pressure on the ability of drylands to provide nine essential ecosystem services, including soil fertility and erosion, forage/timber production and climate regulation. Doing so allowed us to quantify how the impact of grazing depends on local climate and soil conditions. and local biodiversity, and to gain additional insights into the role of biodiversity in providing ecosystem services essential to sustaining human livelihoods, says Dr. Maestri, Director of the Drylands Environment and Global Change Laboratory (Alicante, Spain).
The researchers found that the relationships between climate, soil conditions, biodiversity and measured ecosystem services varied with grazing pressure. “The effects of increased grazing pressure on ecosystem services were mostly negative in warmer, drylands. These results highlight the importance of managing grazing locally, to deal with ongoing climate change in drylands, an issue of particular concern in the Montados oak forests that We studied in Portugal were part of this work,” notes Dr Alice Nunes of the Center for Ecology, Evolution and Environmental Change (cE3c) in the Faculty of Sciences of the University of Lisbon (Ciências ULisboa) and co-author of the study.
The effects of increased grazing pressure shifted from a predominantly positive effect in cooler, drylands with lower rainfall seasonality and greater plant species richness to a negative effect in hotter, drylands with lower plant diversity and higher rainfall seasonality. says d. David Eldridge of the University of New South Wales (Australia) and co-author of the study.
The authors also found positive relationships between plant species richness and the provision of multiple ecosystem services such as soil carbon storage, erosion control, and forage quality and quantity, independent of grazing pressure. “Our findings highlight the importance of conserving and restoring diverse plant communities to prevent land degradation, ensure the provision of essential ecosystem services to humans, and mitigate climate change in grazing drylands,” says Ph.D. Student Melanie Kopel of cE3c at Ciências ULisboa and co-author of the study.
The results of this study are of great importance for achieving more sustainable management of grazing, as well as for establishing effective management and restoration measures aimed at mitigating the effects of ongoing climate change and desertification across the global drylands.
Fernando T. Maestri, Serving Grazing and Ecosystems in Global Drylands, Sciences (2022). DOI: 10.1126/science.abq4062. www.science.org/doi/10.1126/science.abq4062
Provided by the University of Lisbon
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