December 2025: New publication on advancing grazing pressure assessment in semi-arid rangelands

Dryland grasslands cover vast areas of our planet and support millions of people who depend on livestock for their livelihoods. Yet these ecosystems are highly vulnerable: droughts and heavy grazing can degrade the land, reduce forage for animals, and threaten the long-term health of rangelands. A key challenge in rangeland research and management is accurately assessing grazing pressure. Most studies rely on simple proxies such as distance to the nearest water source, but grazing behaviour is far more complex. Cattle movements are affected by vegetation dynamics, fencing, terrain, and management practices, resulting in highly variable grazing pressure even over short distances.

In a new study led by PhD student Lisa-Maricia Schwarz, we developed composite grazing indices that combine several indicators of cattle activity, including grazing intensity, plant material left behind, and distance-based measures. These indices were tested in Namibian rangelands managed under different land-tenure systems, as part of the NamTip project. Our results show that the more detailed indices explained vegetation patterns – such as bare soil, perennial grass cover, and plant diversity – better than traditional distance-based metrics. This was especially true for plant diversity, which responded clearly to grazing pressure captures by the composite indices but not by distance alone.

Overall, our study demonstrates that composite grazing indices offer a more precise, fine-scale representation of grazing pressure in semi-arid rangelands. They offer a valuable tool for researchers seeking to quantify or approximate grazing impacts at the plot level, enabling more detailed investigations of vegetation dynamics and ecosystem responses to grazing.

The full paper, which was published on Ecological Indicators, can be found here.

Source: Schwarz et al. 2025

Fig. 1: Graphical abstract showing how composite grazing indices integrate multiple indicators of cattle activity to quantify grazing pressure at fine spatial scales in semi-arid rangelands. The indices combine long- and short-term grazing metrics (e.g. distance measures, grazing offtake) to capture spatial variability more accurately than the common 'distance from water point' metric. The variables were combined into indices by using principal component regression. The explanatory power of the new grazing proxies for grazing sensitive variables, such as bare soil, were tested via polynomial quantile regression. The illustration highlights the improved ability of the indices to explain vegetation responses in the two dominant Namibian rangeland tenure systems.