Question

how deforestation will lead to decrease in rainfall. explain???

Answer 1

trees evaporate excess water in underground and make them to go above and form clouds. due to this rain is comming. if there is no tree no evaporation 
occurs and no rainfall

Answer 2

deforestation means less trees so when the trees are less even transpiration also less and which puts total pressure on evaporation for cloud formation if there is cloud then ultimately no rains thus deforesation willnlead to reducing or decrease in rains.