BARCELONA (AlertNet) - After falling for decades, the number of hungry people in the world is rising again, and melting glaciers and falling water tables in some of the world's biggest grain-producing nations threaten to dramatically worsen the problem, food security experts said on Monday.

Within 30 to 50 years, "there may well be places on the planet where water conservation is not sufficient and farming activities now taking place may no longer be viable," warned Saleemul Huq, a climate expert with the London-based International Institute for Environment and Development.

That could mean that "we may have to think about relocating populations," he said.

International negotiators are meeting this week in Barcelona in an attempt to hammer out details of a new global climate pact in time for world leaders to sign a deal at a much-touted climate gathering in Copenhagen in December.

Progress has been slow, however, and many observers now believe any deal that includes firm commitments of emissions reductions and funding to help developing nations cope with climate change may come only next year.

Meanwhile, climate-related concerns - including threats to food security - are continuing to grow, experts said, particularly with the world's population expected to rise from 6.7 billion people today to 9 billion by 2050.

THREAT TO HARVESTS

In Saudi Arabia, deep aquifers that have for years allowed the country to be self-sufficient in grain production are now running out, according to Saudi authorities. By 2016, the nation is expected to halt grain farming and become entirely dependent on grain imports to feed its population of 30 million, said Lester Brown, president of the Washington-based Earth Policy Institute, which focuses on sustainable development.

While Saudi Arabia accounts for only half a percent of the world's wheat harvest, similar problems are playing out in big producing countries like India, which relies on both disappearing groundwater and fast-melting glaciers for irrigation.

"Fifteen percent of India's people are fed on over-pumping, from wells that will be dry in the not-too-distant future," said Brown via telephone link from Washington.

Rising sea levels also threaten to inundate key rice producing zones. A one-meter hike in sea levels, which many climate models predict by the end of the century, would flood half the rice fields of Bangladesh and much of the Mekong Delta, where half of Vietnam's rice is produced, Brown added.

Such reductions in food supply would not only drive up prices around the world but lead to greater political instability and potentially failed states, he warned, saying this raised "some disturbing questions about our future."

REDUCE POPULATION GROWTH?

Dealing with the problem won't be easy. Agricultural productivity gains will be key to feeding an ever-larger world population, experts said. But productivity boosts in the past have generally come by planting only the most productive crops, rather than the less productive but more tolerant and diverse crops experts say are needed to ensure harvests in an era of more frequent droughts and other unpredictable weather.

International markets for grain also are likely to become more unpredictable, both in price and supply, as localized climate-driven crises ruin crops and push up demand.

"The world food market is a dangerous abstraction and we are learning that quite fast," said Roger Martin, of the UK Environment Agency. Britain, which is 70 percent self-sufficient in food, he said, is now itself struggling to figure out how to feed a rising population expected to grow from 61 million to 70 million over the next 20 years.

One solution may be to take a hard look at policies on population growth, Martin and others suggested.

"One of the best ways to reduce the amount of greenhouse gases and reduce the number of vulnerable people is to reduce the birth rate," said Paul Ehrlich, a population studies expert at Stanford University, who since the 1960s has predicted famines as a result of overpopulation. "We can't support 9 billion to 10 billion people on the planet, or even 4 billion to 5 billion, with the lifestyle most of us in this room enjoy."

One opportunity climate change offers, Huq said, is "to rethink the entire food system" in the same way the world's economic and energy systems are being debated as a result of climate change.

"We need to shift gear and think differently," added Carlo Scaramella, coordinator of climate change planning and strategy for the UN World Food Programme, but "we are not going to have easy solutions."

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