Prosopis Juliflora Invasion in Baringo, Kenya: Exploring Its Impacts on Lulc Dynamics, Vachellia Tortilis, Selected Ecosystem Services, Livelihoods and Potential Spread Under Climate Change

Abstract

Savanna grasslands are invaluable, but face threats from multiple stressors such as land degradation, woody encroachment and climate change. While it is expected that climatic changes will continue to exacerbate existing stressors, rapid invasion by woody plants such as Prosopis juliflora is now widely considered a key factor accelerating degradation in grasslands. This raises concerns about the functioning and sustainability of these ecosystems. In the savanna grasslands of Baringo County in Kenya, Prosopis juliflora (hereafter referred to as “Prosopis”) was introduced in 1982/83 to alleviate firewood shortage and mitigate desertification. However, it has become invasive and continues to disperse to new areas at exceptional rates, impacting on the environment, economies and people. This study utilized various datasets and methodologies to analyze the 1) spatio-temporal changes in Prosopis coverage in Baringo County since its introduction, 2) implications of these changes on other land-uses and land-cover, native Vachellia tortilis, livelihoods, biodiversity and selected ecosystem services (ES), and 3) impacts of current and predicted future climate change on suitable habitat of alien Prosopis and the dominant native Vachellia tortilis, which is currently highly threatened by Prosopis invasion. Prosopis spread at a rate of 640 ha / year between 1988 and 2016, replaced over 30% of other valuable land-uses/land-cover and caused significant livelihood losses. Further, grassland restoration is as effective as Prosopis invasion in replenishing soil organic carbon, and does not comprise the provisioning of other ES, while Prosopis limits fodder productivity and species diversity. Species distribution models revealed that climate warming will have profound effects on species geographic ranges of both alien and native species. Climate models predict both habit expansion and contraction. The adverse effects (habitat encroachment) of invasive plants on biodiversity will equally persist in the face of the envisaged climatic changes. Over 30% of the predicted future suitable habitat for Vachellia tortilis is also suitable for Prosopis, indicating possible invasion into these habitats in future. These findings suggest an integrated approach to Prosopis management to prevent further spread. Further, effects of climate change should be mainstreamed in policies addressing invasive species, land degradation and biodiversity loss.