Spatial Evolution of Prosopis Invasion and its Effects on LULC and Livelihoods in Baringo, Kenya

Abstract

Woody alien plant species have been deliberately introduced globally in many arid and semi-arid regions, as they can provide services and goods to the rural poor. However, some of these alien trees and shrubs have become invasive over time, with important impacts on biodiversity, ecosystem services, and human well-being. Prosopis was introduced in Baringo County, Kenya, in the 1980s, but since then, it has spread rapidly from the original plantations to new areas. To assess land-use and land-cover (LULC) changes and dynamics in Baringo, we used a combination of dry and wet season Landsat satellite data acquired over a seven-year time interval between 1988–2016, and performed a supervised Random Forest classification. For each time interval, we calculated the extent of Prosopis invasion, rates of spread, gains and losses of specific LULC classes, and the relative importance of Prosopis invasion on LULC changes. The overall accuracy and kappa coefficients of the LULC classifications ranged between 98.1–98.5% and 0.93–0.96, respectively. We found that Prosopis coverage increased from 882 ha in 1988 to 18,792 ha in 2016. The highest negative changes in LULC classes were found for grasslands (−6252 ha; −86%), irrigated cropland (−849 ha; −57%), Vachellia tortilis-dominated vegetation (−3602 ha; −42%), and rainfed cropland (−1432 ha; −37%). Prosopis invasion alone directly accounted for over 30% of these negative changes, suggesting that Prosopis invasion is a key driver of the observed LULC changes in Baringo County. Although the management of Prosopis by utilization has been promoted in Baringo for 10–15 years, the spread of Prosopis has not stopped or slowed down. This suggests that Prosopis management in Baringo and other invaded areas in East Africa needs to be based on a more integrated approach.

Direct and indirect effects of invasive species: Biodiversity loss is a major mechanism by which an invasive tree affects ecosystem functioning

“…Prosopis was likely a driver of change in our study region because its effects on functioning were independent of our disturbance measures. Land degradation by humans and overgrazing are the most important disturbances in our study regions (Mbaabu et al, ); our disturbance index quantifies these two effects. In addition, Prosopis seeds are often spread by livestock (Van Klinken & Pichancourt, ).…”

Niche change analysis as a tool to inform management of two invasive species in Eastern Africa

“…To model the regional niches in Eastern Africa, we again reduced the number of bioclimatic variables, this time using the Eastern Africa presence points. In order to obtain a refined model for our study area, we added seven non-climatic variables that had previously been shown to influence the distribution of invasive species (Elith et al 2011, Mbaabu et al 2019, Shiferaw et al 2019. We additionally included two MODIS 16day NDVI products with a 250 m spatial resolution (Didan 2015) that had the highest model importance when running preliminary variable importance tests using only MODIS 16day NDVI products captured in 2014.…”

Towards sustainable charcoal production and trade in Baringo County

“…The major species used for charcoal production in Marigat Subcounty in Baringo is Prosopis juliflora (mathenge), an invasive tree species that was introduced in Baringo County in the 1980s to address desertification ( Figure 7). Since its introduction, mathenge has spread across the county at a rate of 640 hectares per year (Mbaabu et al 2019), leading to the degradation of pasture, woodlands and human settlements. Participatory mapping exercises during a stakeholder engagement workshop in October 2018 suggested a similar trend in the expansion of mathenge.…”