Effects of Anthropogenic Disturbance on the Biophysical Features of a Tropical Inland Valley Wetland

Abstract

Wetlands provide a wide range of ecosystem functions and services. However, anthropogenic activities in wetlands have led to changes in biophysical attributes that are rarely investigated, especially in the tropical inland valley wetlands (IVWs), likely due to their small sizes. The major objective of the study was to assess the effects of anthropogenic activities on Nalwekomba IVW (Uganda) biophysical features. This was achieved through the use of scores for impacts of three categories of human disturbances at 13 sites to obtain stress index scores and relative disturbance levels, in addition to measured environmental variables. Agriculture (denoted as AD) and grazing (denoted as GD) disturbances were the major contributing factors at 76.9% and 23.1%, respectively, of the sites. At > 10% impact rating, the relative disturbance level was higher for ADs in 39%, other human disturbances (31%), and least for GDs in 15.4% of the site. At ≥5% to < 10% impact rating, relative disturbance was high for GDs in 61.5% of the sites, ADs and ODs in 46% and 23% of the sites, respectively. Sites impacted by grazing and other human activities were significantly different (Kruskal-Wallis rank sum test, p<0.005). Mean values for surface-water- depth of 0.29±0.10m; DO-2.56 ± 1.12 mg/l; pH- 7.26±0.26 and Temperature-26.99± 4.81℃ did not reflect effects on water quality. The higher electro-conductivity values of 932.79± 300.53µS/cm and total dissolved solids-467.75± 149.70 mg/l may signify a high gradient of impact. Though the impact scores reveal low anthropogenic wetland disturbance (observed at 53.8% of the sites), strategic management is recommended to lessen the modification and ensure environmental integrity of the Nalwekomba inland valley wetland.