Decreasing river flows, rising saltiness of estuaries, loss of fish and aquatic plant species and reductions in coastal sediments are likely to intensify farmland losses, food insecurity and damage to fisheries, increasing malnutrition and disease around the world by 2020, according to a new United Nations report released today. Climate change is viewed as the overarching issue in the report – Challenges to International Waters: Regional Assessments in a Global Perspective – with specific concerns for fisheries and marine organisms. It considers climate variability the key controlling factor in fishing yields for about half of the world’s large marine ecosystems. “There are many important messages emerging from this pioneering study,” UN Environment Programme (UNEP) Executive Director Klaus Toepfer said. “One that rings loud and clear is the economic one – that our collective failure to value the goods and services provided by international waters, and to narrowly price the benefits in terms of the few rather than the many, is impoverishing us all.”Key findings of UNEP’s Global International Waters Assessment (GIWA) project, funded by the independent Global Environment Facility (GEF) and national governments, especially Nordic ones, include: Agriculture ranks highest as the key concern on the freshwater front with increased global demand for agricultural products and a trend towards more water-intensive food such as meat rather than vegetables and fruits rather than cereals. Irrigated agriculture accounts for 70 per cent of withdrawals with only 30 per cent returned to the environment – compared with industry and households which return up to 90 per cent.Knowledge gaps, especially with regard to aquifers, are an increasingly significant hindrance for effective water management, with many developing countries operating in the dark on the size of water resource and precise patterns of supply and demand.Market failures are important contributors to damage in both freshwaters and coastal zones, with most production inputs “under-priced compared with their full social and environmental costs,” including under-pricing of water, subsidies for pesticides and fishing and incentives for infrastructure, like dams and water transfer schemes.International waters are damaged by over-fishing and destructive fishing methods, such as excessive catches fuelled by $20 billion a year fishing subsidies, lax enforcement of fishing laws and practices like blast fishing on coral reefs. A $1-dollar investment in blast fishing can generate an immediate 200-fold return for local fishermen but leaves a devastated reef that takes 50 years to recover.Ecosystem service payments are one way of better valuing goods and services from natural features like coral reefs and wetlands. For example, wetlands in Mexico would be less vulnerable if landowners were paid for waste water treatment provided by these natural pollution filters.Climate change may have important impacts on fishing yields for about half of the world’s large marine ecosystems, including the East and West Greenland shelves, the Benguela Current off Southwest Africa, the Canary Current off Northwest Africa and the Humboldt Current off the west coast of South America.Dams, river diversions, water transfers, and other structures designed to supply water and energy have important knock-on effects, obstructing migration routes and reducing spawning habitats. The dams on the Volga River have reduced the spawning habitat of Caspian sturgeon, more than 90 per cent of water in Namibia’s Eastern National Water Carrier canal is lost through evaporation, and ecosystems in the Aral and Dead seas and the Volta River Basin and Lake Chad in Africa have been destroyed.