Seasonal variation of carbon dioxide, rainfall, NDVI and it’s association to land degradation in Tanzania

Abstract

In recent years there has been global concern over extreme weather events like droughts and floods which are linked to climate change. This concern has arisen from both observed and modeling studies that have indicated a possible climate change. Carbon dioxide which is principally linked to climate change, is a green house gas that has been blamed to be the driving force. However extreme weather events have been observed to cause land degradation in different parts of the globe. While studies on global scale show a significant increase in CO2 resulting in global warming and hence climate change, few regional studies have been carried out to demonstrate changes at the regional level. In this study trends and variability of CO2, rainfall and NDVI over Tanzania were investigated to find out their association with land degradation. Results reveal that CO2 exhibits a bimodal distribution, with a maximum in March and December, while minimum values are observed in January and May. This pattern can be associated with the annual cycle of vegetation cover. During maximum CO2 season, the land is bare and thus subjected to land degradation. NDVI showed a maximum in May and January/December for areas with bimodal rainfall and March/April for areas with unimodal rainfall. NDVI showed a minimum in March and October for bimodal areas and September/October for unimodal areas. A decreasing trend in NDVI is evident in most stations in different seasons over the country. This is a signal for land degradation and should be arrested. Rainfall, a very important factor in environmental sustainability, has proved to be decreasing in different seasons over the country. As it decreases it leaves the land dry, hinders vegetation and other hydro related factors. Decreased rainfall results in dry soil, decreased vegetation and hence land degradation. Excessive rainfall also contributes to land degradation by washing away loose and exposed soil in some parts of the country by floods. There is a need to arrest this situation for better land use.