<Li> Dependence on rain - fed agricultural systems, especially in the arid / semi-arid tropics </Li> <Li> Shortening of growing seasons and increases in temperature beyond the extremes already experienced in some areas </Li> <Li> Projected decrease in crop yields at low latitudes in contrast to high latitudes </Li> <P> The fact that climate change and temperature increases are expected to negatively affect crop yields in the tropics could have troublesome implications for poverty and food security, mainly because populations in the area are so dependent on agriculture as their only means of survival . A 2008 study by the CGIAR Research Program on Climate Change, Agriculture and Food Security matched future climate change "hotspots" with regions that are already suffering from chronic poverty and food insecurity to pinpoint regions in the tropics that could be especially vulnerable to future changes in climate . These include regions such as West Africa which are already dependent on drought - and stress - resistant crop varieties and thus left with little room to manoeuvre when the climate becomes even drier . The study says that East and West Africa, India, parts of Mexico and Northeastern Brazil will experience a shortening of growing seasons by more than 5%, negatively impacting a number of important crop staples . </P>

The most important crop grown under irrigation in central asia is