A bull grazes on dry wheat husks(Phi) in Logan, Kansas, one of the regions hit by therecord drought that has affected more than half of the U. S. and is expected to drive up foodprices. 　　Leadinu water scientists have issued one of the sternest warnings yet about global foodsupplies, saying that the world's population may have to switch almost completely to avegetarian diet over the next 40 years to avoid catastrophic shortages. 　　Adopting a vegetarian diet is one option to increase the amount of water available to growmore food in an increasingly climate-unstable world, the scientists said. Animal protein-richfood consumes 5 to 10 times more water than a vegetarian diet. One third of the world'sarable(适于耕种的) land is used to grow crops to feed animals. Other options to feed peopleinclude eliminating waste and increasing trade between countries in food surplus and those indeficit. 　　"900 million people already go hungry and 2 billion people are malnourished in spite of thefact that per capita food production continues to increase," they said. "With 70% of allavailable water being in agriculture, growing more food to feed an additional 2 billion peopleby 2050 will place greater pressure on available water and land. " 　　The report is being released at the start of the annual world water conference inStockholm, Sweden, where 2,500 politicians, UN bodies, non-governmental groups andresearchers from 120 countries meet to address global water supply problems. 　　Competition for water between food production and other uses will intensify pressure onessential resources, the scientists said. "The UN predicts that we must increase foodproduction by 70% by mid-century. This will place additional pressure on our 'alreadystressed water resources, at a time when we also need to allocate more water to satisfy globalenergy demand--　which is expected to rise 60% over the coming 30 years--and to generateelectricity for the 1.3 billion people currently without it," said the report. 　　Overeating, undernourishment and waste are all on the rise and increased food productionmay face future constraints from water scarcity. 　　"We will need a new recipe to feed the world in the future," said the report's editor, AndersJagerskog. 　　A separate report from the International Water Management Institute (IWMI) said the bestway for countries to protect millions of farmers from food insecurity in sub-Saharan Africa andsouth Asia was to help them invest in small pumps and simple technology, rather than todevelop expensive, large-scale irrigation projects. 　　"Farmem across the developing world are increasingly relying on and benefiting from small-scale,locally-relevant water solutions. These techniques could increase yields up to 300% andadd tens of billions of U. S. dollars to household revenues across sub-Saharan Africa and southAsia. " said Dr. Colin Chartres, the director general. 　◆61. What can be inferred from the water scientists' warning?