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.
Highlights
Long term trend analysis of climatic elements of temperature and rainfall have shown that climate is changing (Warburton and Schulze, 2005; Dore, 2005; Kruger and Shongwe, 2004; New et al, 2006; Warburton et al, 2005)
Temperatures are increasing and rainfall amount declining in Mutirikwi sub-catchment, thereby affecting vegetative species richness
There is a significant increase in the inter-annual variability of the climatic elements that have been punctuated by extreme events in the form of droughts and floods
Summary
Long term trend analysis of climatic elements of temperature and rainfall have shown that climate is changing (Warburton and Schulze, 2005; Dore, 2005; Kruger and Shongwe, 2004; New et al, 2006; Warburton et al, 2005). Several studies (Lenihan et al, 2003; Perrings, 2010; Bellard et al; 2012; Michelle et al, 2012) have claimed that climate change affects biodiversity but without focusing on specific diversity indices This poses challenges when designing adaptive and mitigation strategies that are ecosystem and species specific. Regional climate models, dynamic and equilibrium vegetation models, species bioclimatic envelope models and site-specific sensitivity analysis are some of the tools that have been used to assess the impact of climate change on biodiversity (Sulzman et al, 1995). Each of these tools has its weaknesses ranging from oversimplification of reality to complexity. The study was developed and tested in the Mutirikwi sub-catchment of Masvingo province of Zimbabwe
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