The Relationship Between Grazing Pressure and Environmental Factors Drives Vegetation Fragmentation Across Global Drylands

Aim

To evaluate how grazing pressure, a key land-use factor, interacts with climatic, vegetation, and soil variables to shape the fragmentation of perennial vegetation across drylands globally.

Location

171 plots across 25 countries on six continents.

Time Period

Field data: 2016–2019.

Major Taxa Studied

Perennial grasses, shrubs, and woody plants.

Methods

We conducted a standardised field survey across 171 45 m × 45 m plots to assess grazing pressure, vegetation, and soil properties. Vegetation fragmentation was quantified using three patch-based metrics derived from high-resolution satellite images. Linear mixed-effects models were used to relate fragmentation to climatic, vegetation, and soil variables. Predictor importance was assessed through multi-model inference and validated using a random forest approach.

Results

Vegetation fragmentation increased with aridity, and this effect was 4.7 times stronger under high grazing pressure than under low pressure. The most influential interactions involved grazing pressure with soil amelioration (49.7% importance) and with vegetation cover (44.6%). Soil amelioration—measured as the enrichment of soil organic carbon beneath vegetation—reduced fragmentation, especially under high grazing pressure. In contrast, the ability of vegetation cover to sustain large patches diminished as grazing intensity increased. Soil amelioration was strongly linked to the proportion of facilitated plant species (p < 0.01), whereas soil organic carbon alone—beneath vegetation (p = 0.37) or in bare areas (p = 0.94)—was not significantly related.

Main Conclusions

Grazing pressure and aridity interact to intensify vegetation fragmentation, potentially accelerating land degradation in drylands under future climate and land-use scenarios. Mitigating this fragmentation requires not only enhancing vegetation cover but also promoting plant–soil facilitation processes, especially under high grazing pressure. These findings underscore the critical role of plant-driven soil amelioration in maintaining ecosystem structure and resilience across global drylands.