BioEd Online

Many of the world's dry regions, currently home to some 2.1 billion people, are in danger of becoming useless for growing food, according to the latest in a series of reports on the world's ecosystems. It blames climate change and human activities.

The report's authors estimate that 10-20% of these 'drylands' have already lost some plant life or economic use, and they say the situation is getting worse. Hundreds of thousands of people will be in need of new homes and lifestyles over the next 30 years, they estimate.

The report, titled Ecosystems and Human Well-Being: Desertification Synthesis¹, is the third in a series of seven detailing the findings of the Millennium Ecosystem Assessment, a four-year, US$22-million stocktake of the world's biological resources.

The assessment aims to compile all of the available data from previous studies to give the most accurate picture yet of the condition of the world's ecosystems. In the case of drylands it highlights the lack of knowledge about these regions, which cover 41% of the planet's land surface. They include everything from the 'dry-sub-humid' regions of eastern Mediterranean croplands, to full-blown 'hyper-arid' deserts such as the Sahara.

"There are serious gaps in our understanding of how big deserts are, and how they are growing," says Zafar Adeel, assistant director of the United Nations University International Network on Water, Environment and Health in Hamilton, Canada, and one of the report's main authors.

What is clear, however, is that deserts are getting bigger. "Desertification has emerged as an immense global problem that affects a lot of people," Adeel says. Dust storms from the Gobi Desert in Asia and the African Sahara are responsible for respiratory problems as far afield as North America, the report says.

Fields of dreams

Perhaps the biggest problem, however, is that as land dries up it becomes unsuitable for farming. The problem is worsened by the fact that many of the areas at greatest risk, such as central Asia and regions to the north and south of the Sahara, are home to the world's poorest people. "Without strong efforts to reverse desertification, some of the gains we've seen in development in these regions may be reversed," Adeel says.

The report's release comes ahead of the World Day to Combat Desertification on 17 June. This day marks the 11th birthday of a United Nations agreement, signed by 191 countries, to tackle the expansion of deserts. But, says Adeel, previous efforts have been hampered by ignorance of the scale of the problem.

Solutions should be tailored to individual countries' situations, the authors recommend. They hope that governments of countries at risk of drying up will promote 'alternative livelihoods' that protect dry regions.

This could involve investment in ecotourism rather than farming, Adeel suggests. Other possibilities involve embracing solar power, or farming fish rather than irrigating crops, which turns out to be a more efficient way of wringing food and money from a limited amount of water.

Walter Reid, director of the Millennium Ecosystem Assessment, estimates it might take US$100 billion to invest properly in dryland areas. "That's substantial. But relative to other areas where public money is spent it's not such a big deal," says Reid.