Rome, September 11 - The squandering of around a third of all the food the world produces each year has colossal economic and environmental costs, the United Nations Food and Agriculture Organization (FAO) said Wednesday. The Rome-based UN agency said that the waste of around 1.3 billion tonnes of food per year has a direct cost to producers of $750 billion annually, even without counting the fish and seafood sectors. But the economic cost is only part of the impact of chronic food losses. The FAO said food that is produced but not eaten consumes a volume of water equivalent to the annual flow of Russia's Volga River and is responsible for adding 3.3 billion tonnes of greenhouse gases to the planet's atmosphere. The waste is shocking in a world in which 870 million people do not have enough to eat, according to FAO estimates. The report said 54% of global food wastage occurs during production, post-harvest handling and storage, according to FAO's study. The rest happens at the processing, distribution and consumption stages. The later a food product is lost along the chain, the greater the environmental consequences, since the environmental costs incurred during processing, transport, storage and cooking must be added to the initial production costs. So the most costly form of waste is when consumers throw away cooked food. "We simply cannot allow one-third of all the food we produce to go to waste or be lost because of inappropriate practices, when 870 million people go hungry every day," said FAO Director-General José Graziano da Silva at the presentation of the report entitled Food Wastage Footprint: Impacts on Natural Resources. "All of us - farmers and fishers; food processors and supermarkets; local and national governments; individual consumers - must make changes at every link of the human food chain to prevent food wastage from happening in the first place, and re-use or recycle it when we can't". The FAO's drive to combat losses has been supported by Pope Francis, who earlier this year compared wasting food to stealing from the poor. The agency said the highest levels of food waste were in affluent societies. In part this is due to consumers failing to plan their shopping, overpurchasing, or over-reacting to best-before-dates. Another factor is that quality and aesthetic standards lead retailers to reject large amounts of perfectly edible food, the FAO said. In developing countries, post-harvest losses early in the supply chain are a key problem due to financial and structural limitations in harvesting techniques and storage and transport infrastructure and climatic conditions favorable to food spoilage. The FAO said measures to combat waste included better balancing of food production with demand. It said efforts should be made to find secondary markets for surplus food and, in some cases, to donate it to vulnerable members of society. Where re-use is not possible, recycling and recovery should be pursued to stop uneaten food rotting in landfills and producing methane, a particularly harmful greenhouse gas.