The world's population may have to switch almost completely to a vegetarian diet over the next 40 years to avoid catastrophic food shortages, leading water scientists have warned.
They say humans derive about 20 percent of their protein from animal-based products now, but this may need to drop to just 5 percent to feed the extra 2 billion people expected to be alive by 2050, according to the Guardian.
"There will not be enough water available on current croplands to produce food for the expected 9 billion population in 2050 if we follow current trends and changes towards diets common in western nations," the report by Malik Falkenmark and colleagues at the Stockholm International Water Institute (SIWI) said.
The scientists suggested adopting a vegetarian diet as one option to increase the amount of water available to grow more food in an increasingly climate-erratic world,
Animal protein-rich food consumes five to 10 times more water than a vegetarian diet. One third of the world's arable land is used to grow crops to feed animals.
Eliminating waste and increasing trade between countries in food surplus and those in deficit are other options suggested by them.
"Nine hundred million people already go hungry and 2 billion people are malnourished in spite of the fact that per capita food production continues to increase," they said.
"With 70 percent of all available water being in agriculture, growing more food to feed an additional 2 billion people by 2050 will place greater pressure on available water and land," they added.
The report is being released at the start of the annual world water conference in Stockholm, Sweden, where 2,500 politicians, UN bodies, non-governmental groups and researchers from 120 countries meet to address global water supply problems.