Impact of Land Use/ Land Cover Changes on Ecosystem Service Values in the Cherangany Hills Water Tower, Kenya

Abstract

Changes in Land Use/ Land Cover (LULC) due to anthropogenic and natural drivers alter the ecosystem structure and function, resulting in variations of the Ecosystem Service Values (ESVs). This study investigated the impacts of LULC Changes on ESVs over 37 years in the Cherangany Hills Water Tower (CHWT) of Kenya. Landsat images from 1985 and 2022 were used to examine historical land cover changes in the CHWT. Supervised classification was carried out using Random Forest (RF) classifier in R-Studio while ArcGIS desktop software (version 10.8) was used for mapping to evaluate the LULC changes. Accuracy assessments were also conducted for each reference year. The estimation of ESVs was done using the benefit transfer approach, employing modified local value coefficients. Six LULC types (Forest, Cropland, Grassland, Water features, Bareland, Built-up area) were successfully classified, with overall accuracies of more than 92.5% and Kappa coefficients greater than 0.91. Results showed an expansion in cropland areas by about 36.78% (35,082 hectares [ha]) 1whereas grassland and forest experienced a reduction of their land areas by 28.26% (-22,181ha) and 13.38% (-10,353ha) respectively between 1985 and 2022. Consequently, there was an increase in the ESV of cropland by 7.91 million United States Dollars (USD) while forest and grassland registered a decrease in their ESVs by 10.22 million USD and 6.50 million USD respectively. Overall, the total ESV of the CHWT declined by 7.16% (-8.68 million USD) from 121.22 million USD in the year 1985 to 112.54 million USD in 2022. As for the individual ESVs, 15 out of the 17 individual ESs registered negative changes in their ESVs. Food production and biological control were the two individual ESs with positive ESV changes over the study period. There is a need to curb the current drivers of LULC changes within the water tower, especially the expansion of croplands, to stop further ecosystem degradation for optimum delivery of ecosystem services.