Precipitation and temperature drive woody vegetation dynamics in the grasslands of sub-Saharan Africa

Abstract

Identifying the drivers of ecosystem dynamics, and how responses vary spatially and temporally, is a critical challenge in the face of global change. Grasslands in sub-Saharan Africa are vital ecosystems supporting biodiversity, carbon storage, and livelihoods through grazing. However, despite their importance, the processes driving change in these systems remain poorly understood, as cross-scale interactions among drivers produce complex, context-dependent dynamics that vary across space and time. This is particularly relevant for woody vegetation dynamics, which are often linked to degradation processes (e.g., woody encroachment), with consequences for biodiversity, forage availability, and fire regimes. Here, we used satellite data and structural equation models to investigate the effects of rainfall, temperature, fire, and population density on woody vegetation dynamics in four African grassland regions (the Sahel grasslands, Greater Karoo and Kalahari drylands, Southeast African subtropical grasslands, and Madagascar) during 1997–2016. Across all regions, rainfall was consistently positively correlated with increased woody vegetation, while higher temperatures were associated with decreased woody vegetation, suggesting that water availability promotes woody plant growth, whereas rising aridity limits it. Unexpectedly, fire had a negative effect on woody cover only in the Greater Karoo and Kalahari drylands, while in Madagascar, higher temperatures and greater population density reduced fire; yet these relationships did not translate into significant indirect effects on woody vegetation. These findings illustrate the complex ways by which environmental and anthropogenic drivers shape woody vegetation dynamics in grasslands across sub-Saharan Africa. Compared to savannas, fire plays a weaker and more region-specific role in grasslands, where its feedback with woody cover is less consistent. The opposing effects of rainfall and temperature may currently constrain woody expansion, but climate change could disrupt this balance and further weaken fire's limited regulatory role. These differences highlight the need for management strategies tailored to the distinct climate–vegetation dynamics of grassland systems.

More information

Identifiers

ORCID for Francesco D'Adamo: orcid.org/0000-0003-4428-0713

ORCID for Rebecca Spake: orcid.org/0000-0003-4671-2225

ORCID for Booker Ogutu: orcid.org/0000-0002-1804-6205

ORCID for Jadunandan Dash: orcid.org/0000-0002-5444-2109

ORCID for Felix Eigenbrod: orcid.org/0000-0001-8982-824X

Catalogue record

Export record

Altmetrics