River runoff and aquifer recharges will decrease in the Mediterranean, the Americas, Australia and southern Africa, it said.
Areas in Asia which depend on the melting of ice and mountain glaciers will also be affected, while areas with a lot of fluvial deltas are threatened by reduced water flow, increased salinity and rising sea levels, said the report entitled “Climate Change, Water and Food Security”.
The report also predicted an acceleration of the hydrologic cycle of the planet because high temperatures will raise the evaporation rate of the soil and sea.
“The rain will increase in the tropics and at higher altitudes, but it will decrease in areas that already have dry and semi-dry characters and are located inland on the big continents,” the report said.
Because of this, there will be a higher frequency of droughts and flooding, which will lead to an increased use of ground water and limit the water available for agriculture even more.
“The loss of glaciers, which sustain about 40 percent of the watering at world level, will finally affect the amount of available water on the surface for watering in the main producer basins,” it said.
The increase in temperature will prolong the growing season of crops in warmer regions, but reduce the harvest season elsewhere, adding to a higher rate of evaporation and a decrease in agricultural productivity, the report said.
Rural communities and the food security of the urban population are threatened, “but the poor people in rural areas are the most vulnerable, and they could be affected in a disproportionate way,” it said.