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

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 in a 7-year time interval between 1988 and 2016 and performed a supervised Random Forest classification. For each time interval we calculated extent of the invasion, rates of spread and gains and losses of specific LULC classes. We further assessed the relative importance of Prosopis invasion on LULC changes and ultimately on the provision of ecosystem services rural people depend on. Overall accuracy and kappa coefficients of the LULC classifications ranged between 98.1 % and 98.5 %, and 0.93 and 0.96, respectively. We found that Prosopis coverage increased from 882 ha in 1988 to 18,792 ha in 2016. Highest negative change in LULC classes was found for grasslands (-6252 ha; -86 %), irrigated cropland (-849 ha; -57 %), Vachellia tortilis dominated vegetation (-3602 ha; -42 %), and rainfed cropland (-1432 ha; -37 %) – all of them important categories with regard to rural people’s livelihoods. 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. The observed rates of invasion are alarming and ask for urgent implementation of coordinated and sustainable Prosopis management in Baringo and other invaded areas in East Africa.