Plant Diversity In Drylands Predicts Resistance To Grazing Pressure

New work by researchers at King Abdullah University of Science and Technology (KAUST) finds that the variety of plant species is a better guide to how dryland ecosystems cope with grazing pressure than climate, soil features or the kind of livestock. Areas with richer plant communities are more likely to keep their vegetation cover as grazing increases.

Drylands are critical for people and nature worldwide, and for Saudi Arabia in particular. These lands support close to a billion people, hold about half of global livestock production, and help maintain soil stability and carbon storage. In the Kingdom, grazing is the main land use across many dry regions, making rangeland degradation a central concern for sustainability and food security.

The research, published in Nature Ecology & Evolution, reports one of the largest field assessments of grazed dryland ecosystems so far. Scientists gathered data from 73 sites in 25 countries across six continents, using the same field protocols. They compared vegetation under low and high grazing pressure in grasslands, shrublands, steppes and savannas.

The team analysed how grazing pressure changed plant cover and how this related to climate, soils and vegetation type. Across most sites, heavier grazing reduced vegetation, with an average decline of 35 percent. The amount of loss, however, differed strongly between locations. When all drivers were assessed together, plant species richness emerged as the most important factor explaining resistance to grazing.

Across the world’s drylands, grazing pressure is increasing, yet its impact is inconsistent. In some landscapes, vegetation declines swiftly as pressure rises. In others, plant cover remains stable even when grazing continues for long periods. The KAUST results help explain these differences by linking them directly to levels of plant diversity.

Fernando Maestre, Professor at KAUST and senior author of the study, said that the findings help reframe how resilience in drylands is understood. He said, "Grazing pressure does not impact all landscapes uniformly. Where plant communities are biologically diverse, pressure is distributed across different ecological strategies. Where diversity has been eroded, the same level of use can lead to much faster decline."

The conclusions carry particular weight for Saudi Arabia, where large tracts of dryland are used as rangelands. Recognising plant diversity as a key part of ecosystem resistance gives stronger scientific support to land restoration and sustainable grazing programmes already planned or underway in the region. The study also underlines that managing for species richness can help keep productivity while limiting degradation.

The timing of the work aligns with global discussions on rangeland management. The United Nations has named 2026 as the International Year of Rangelands and Pastoralists, focusing attention on their ecological and economic roles. Evidence from the KAUST-led research offers guidance for policies aiming to protect dryland ecosystems under growing grazing pressure, both in Saudi Arabia and worldwide.

With inputs from SPA