Spatio-temporal distribution and impacts of Prosopis juliflora: an application of remote sensing and experiential ecological knowledge in a semi-arid rangeland of Kenya

Abstract

Prosopis juliflora species was introduced in the Kenyan drylands as part of an afforestation program to rehabilitate rangelands and supply fuelwood in the 1980s. However, the species has since spread beyond areas of intervention, altering ecosystem integrity and threatening the livelihoods of pastoralists. This study analysed the spatial and temporal dynamics of P . juliflora in Cherab Ward, Isiolo County, to provide empirical evidence for the management and utilisation of this species. High-resolution satellite imagery was used to assess land-use and land-cover changes between 2017 and 2024, complemented by participatory socio-ecological approaches to elicit pastoralists’ local knowledge of the species' invasion patterns and impacts. The results show that P. juliflora cover increased by approximately 706.1 km 2 between 2017 and 2024. Equally, shrubland and crop land declined by approximately 414.9 km 2 and 122.8 km 2 , respectively. Bare land decreased by 397.4 km 2 , whereas built-up land increased slightly by 26.2 km 2 . These trends were corroborated by maps generated through participatory approaches with communities, which showed that P. juliflora invaded riverine and roadside areas, making it difficult for livestock to access pasture and water in the affected area. These results imply both ecological and socioeconomic consequences, with expected negative impacts on livestock production in the study area. The observed rate of spread of P. juliflora (103%) from 2017 to 2024 indicates that, if the invasion continues unabated, grazing resources in the area will diminish, leading to the loss of ecosystem services and, consequently, impacting pastoral livelihoods. These findings highlight the need for context-specific, co-developed management approaches that integrate spatial evidence with local knowledge to ensure the sustainable control and exploitation of the species, thereby maximising ecological and economic benefits.