The most immediate environmental problem in major regions of the world is probably the scarcity of fresh water for agriculture. Insufficiency and irregularity of rainfall require the use of stored water. Both major compartments for fresh water storage—glaciers and groundwater—are being depleted rapidly and at similar rates. Drawdown of groundwater is primarily the result of irrigation required to supply the food needs of large populations. Glacier melt is an effect of global warming chiefly caused by high levels of industrial production and transport. However, an important fraction of glacier melt is caused by food chain emissions (agricultural greenhouse gases and black carbon or cooking soot). In toto, the loss of water resulting from food and agriculture may be significantly greater than that resulting from industrial production and transport, the factors more commonly cited. This suggests that the role of population, closely linked to food and agriculture, is central to the depletion of fresh water.