Abstract:
The study examined the role of anthropogenic disturbances, temperature, precipitation and evapotranspiration in the range shift of aquatic plants, fish and bird communities in six wetlands. It was conducted over a 2-year period. The dominance ratio approach was used to determine the range shift of plants. Ordination techniques were used to determine the influence of environmental factors on biological data-set. Of the 40 species of plants sampled, obligate species constituted 35%, while facultative wetland species and obligate upland species were 40% and 27.5% respectively. Animal dung assessment showed that 14 seedlings identified were the same species as those sampled among the 40 species. Plant diversity and evenness distribution did not differ significantly (F = 2.27, p>0.05) in the wet and dry seasons. Plant range shift was largely influenced by farming practices, bushfire and grazing. These variables correlated significantly (p<0.05) with axis I and axis II, and accounted for 61.29% of the total variance in species range shift. Field survey indicated the declining abundance of Pistia stratiotes and was attributed among others to sensitivity to environmental disturbances. Fish diversity and abundance was slightly higher in the dry season than in the wet season. Bird densities and diversity (F = 4.101, p<0.05) were significantly higher in the wet season than in the dry season. Influence of temperature on precipitation, over the last 50-years, was not significant (R2 = 0.354; p>0.05). Plant range shift and variations in fish and bird diversity may be attributed more to human-led activities than the impacts of climate change and variability.
