The vast amounts of food lost to spoilage and insects in poor countries, and simply tossed in rich ones, also represent an enormous stream of wasted water, according to a new report that calls for big improvements in a world heading toward 9 billion hungry, thirsty mouths.

The report, “Saving Water: From Field to Fork — Curbing Losses and Wastage in the Food Chain,” was issued on Thursday by the Stockholm International Water Institute, Food and Agriculture Organization of the United Nations, and the International Water Management Institute (report pdf here). It outlines ways that governments could halve the amount of food lost between field and plate by 2025.

The amounts of waste are staggering. In the United States, nearly one-third of the food that is produced each year, worth about $48 billion, is discarded. The water it took to grow and process that wasted food amounts to about 10 trillion gallons, according to the analysis. Many European countries have similar losses, proportional to their size.

One reason for the waste is simply that in prospering countries, as food costs have become an ever smaller proportion of total household budgets, the amount of discarded food has ballooned, according to a recent article by Andrew Martin.

Losses in poorer countries most often occur in fields and storehouses, through spoilage and damage by pests. I wrote last year about efforts to devise low-tech methods to help preserve fruits and vegetables on the way to markets in hot climates. Years ago, in the context of the anthrax attacks, I learned about food irradiation, which developing countries increasingly are employing to cut spoilage rates; the technique has just been approved in the United States for spinach and lettuce.

One way or another, it’s clear that improved efficiency in food production and water use will be needed in a world of growing populations seeking decent lives. As the new report explains, more than a billion people now live in areas with insufficient water. Rising demand for agricultural products that require large amounts of water, particularly beef cattle and biofuel crops, is adding to shortages.

For a close-up look at food waste at the level of the household, you can check out Tara Parker-Pope’s interview earlier this year with the food-waste maven Jonathan Bloom.