Abstract
Abstract. Trees of the genus Prosopis from the Americas, were introduced in Eastern Africa in the 1970s to mitigate land degradation and its associated disservices. However, over time these trees have spread and invaded valuable grasslands and croplands and consequently led to significant land use and land cover (LULC) changes and livelihood stress. Early detection of invasive species is essential for formulating effective management strategies to prevent further spread into non-invaded lands and for monitoring the outcome of management interventions. We mapped the spatio-temporal evolution and dynamics of Prosopis invasion, its impacts on LULC and livelihoods in Baringo, Kenya by applying a Random Forest classifier on Landsat satellite data over seven-year intervals from 1988 – 2016. We then linked the LULC changes to soil organic carbon (SOC) stocks that we had measured for the different LULCs and also to socio-economic data on annual costs of clearing Prosopis from farmlands. By 2016, Prosopis had invaded 18,792 ha of land, spreading at a rate of 640 ha/yr, while all other land uses and land cover declined, each by over 40% of its original coverage in 1988. Through LULC specific SOC measurements, and relating the changes to annual costs of clearing Prosopis, we found that Prosopis removal and restoration to grassland is more effective for climate change mitigation compared to Prosopis “cultivation” while also avoiding trade-offs with other ecosystem services and livelihoods. Therefore, future management of this species in Kenya and Eastern Africa should be based on a more collaborative and integrated approach.
Highlights
Grasslands are the dominant natural cover in terrestrial tropics and comprise about 20% of the global land area (Parr et al, 2014; Scholes & Archer, 1997)
Through land use and land cover (LULC) specific soil organic carbon (SOC) measurements, and relating the changes to annual costs of clearing Prosopis, we found that Prosopis removal and restoration to grassland is more effective for climate change mitigation compared to Prosopis ―cultivation‖ while avoiding trade-offs with other ecosystem services and livelihoods
Prosopis invasion alone directly contributed to over 30% of these negative changes, implying that Prosopis invasion is a key driver of the observed LULC changes in Baringo, which is severely affecting agro-pastoral livelihoods
Summary
Grasslands are the dominant natural cover in terrestrial tropics and comprise about 20% of the global land area (Parr et al, 2014; Scholes & Archer, 1997). They are home to a substantial diversity of plants and animals, directly support livelihoods of about one-fifth of the global population through provision of food, grazing, fuel wood and medicinal value plants They account for about 30% of global total terrestrial net primary productivity, provide other ecosystem services including forage for livestock, tourism and the regulation and storage of water flows (White et al, 2000). Prosopis spp. or mesquite, are perennial, nitrogen-fixing singlecanopy trees or multi-stemmed shrubs tolerant to arid conditions (Andersson, 2005) These species are among the most damaging invasive species, which has led to their inclusion in the World Conservation Unions list of 100 worst invasive alien species (Lowe et al, 2000). They are regarded as noxious invaders considerably impacting biodiversity, ecosystems services and economies, in their invasive ranges (Shackleton et al, 2014)
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