An assessment of the impact of climate change on plant species richness through an analysis of the Normalised Difference Water Index (NDWI) in Mutirikwi Sub-catchment, Zimbabwe

Abstract

This study assesses the effects of climate change on vegetative species diversity exploring the usefulness of the Normalised Difference Water Index (NDWI) in predicting spatio-temporal diversity variations. The relationship between species richness and climatic variables of rainfall and temperature is explored based on species data collected from the field over a 3 year period and climate data collected from four local weather stations. Relationship between NDWI and species diversity indices is examined to confirm the usefulness of Remote Sensing in predicting vegetative diversity. The resultant predictive model was used to estimate changes in species richness over a 27 year period (1987-2014). The species diversity data was then regressed with climatic data for the same period. The results show a significant (P<0.05) correlation between species diversity and the two climatic variables. The results also indicate that there is a significant positive (P=0.0001; α=0.05; R²=0.565) relationship between species richness and NDWI. This implies that the NDWI is essential when assessing changes in species diversity over time. The Mann Kendall test revealed a decrease, though not statistically significant, in the rainfall received within the catchment over the period and significant variability. The minimum and maximum temperatures over the period were significantly increasing. These changes in climate variables were matched with a decrease in species richness. Some species tend to be succumbing to the environmental changes influenced by climate change resulting in their changes in phenology, abundance and distribution.