Impact of land use/land cover changes on ecosystem service values in the cherangany hills water tower, Kenya

Abstract

Land Use/Land Cover (LULC) changes 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 LULC changes in the CHWT. Supervised classification was carried out using the Random Forest (RF) classifier in R-Studio while ArcGIS desktop software 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 (BTA), employing modified local value coefficients. Six LULC types (Forest, Cropland, Grassland, Water bodies, Bareland, and Built-up area) were successfully classified, with overall accuracies of more than 92.5% and Kappa coefficients greater than 0.91. Our study findings showed an expansion in built-up areas (201.63%), cropland (36.78%), and water bodies (40.05%) whereas grassland, forest, and bareland experienced a reduction in their land areas by 28.26%, 13.38%, and 24.15% respectively between 1985 and 2022 in the CHWT. Consequently, there was an increase in the ESV of cropland while forest and grassland registered a decrease in their ESVs. Overall, the total ESV of the CHWT declined by 7.16% from 121.22 million United States Dollars (USD) in the year 1985 to 112.54 million USD in 2022. As for the individual ESVs, 15 out of the 17 individual Ecosystem Services (ES) registered negative changes in their ESVs. Food production and biological control were the two individual ES 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 ES.