Publications by authors named "G P Hempson"
Fire and herbivory interact to alter ecosystems and carbon cycling. In savannas, herbivores can reduce fire activity by removing grass biomass, but the size of these effects and what regulates them remain uncertain. To examine grazing effects on fuels and fire regimes across African savannas, we combined data from herbivore exclosure experiments with remotely sensed data on fire activity and herbivore density.
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- In ecosystems with high herbivory pressure, plant species often develop dense branching and spines to protect themselves from mammalian herbivores.
- This research focuses on how these features evolved in the Combretaceae family during the period of mammalian radiation and diversified in tropical regions.
- The findings suggest that plant defenses developed in a stepwise manner: first, through dense branching under moderate herbivory, followed by spines in response to increased herbivore pressure, indicating that large mammals significantly influence woody plant architecture.
Sub-Saharan Africa is under-represented in global biodiversity datasets, particularly regarding the impact of land use on species' population abundances. Drawing on recent advances in expert elicitation to ensure data consistency, 200 experts were convened using a modified-Delphi process to estimate 'intactness scores': the remaining proportion of an 'intact' reference population of a species group in a particular land use, on a scale from 0 (no remaining individuals) to 1 (same abundance as the reference) and, in rare cases, to 2 (populations that thrive in human-modified landscapes). The resulting bii4africa dataset contains intactness scores representing terrestrial vertebrates (tetrapods: ±5,400 amphibians, reptiles, birds, mammals) and vascular plants (±45,000 forbs, graminoids, trees, shrubs) in sub-Saharan Africa across the region's major land uses (urban, cropland, rangeland, plantation, protected, etc.
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- - Frequent grazing can lead to the creation of high-quality grazing lawns that attract many grazers, but it can also result in overgrazed areas with poor grass quality and low grazers, making the outcome highly dependent on environmental conditions.
- - A study of 33 grass communities in eastern South Africa and Tanzania identified four types of grass growth forms, including two that are palatable and support grazing lawns, and two that are of low forage value and are avoided by grazers.
- - Grazing lawns are influenced by environmental factors, with certain grasses thriving in dry, sandy areas and others in wetter, clay-rich soils; monitoring these lawns is crucial to prevent overgrazing, especially since tufted grasses are more susceptible to degradation