Environmental degradation is threatening the health and livelihoods of two billion people living in arid regions round the world, says an international team of researchers.
They say that desertification — the irreversible degradation of drylands due to climatic factors and human activities — is among the world's greatest environmental challenges.
The researchers published their findings yesterday (16 June) in a report of the Millennium Ecosystem Assessment, a US$22 million study by an international partnership of scientists, UN agencies, the World Bank and the World Conservation Union (IUCN) (see Healthy ecosystems 'critical in fight against poverty').
According to the report, desertification is spreading because of climate change and population growth, both of which have led to pressure on resources such as water for irrigating fields. It says that 43 per cent of the world's cultivated land is in drylands.
Half of the world's poor live in drylands, and the infant mortality rate in these areas is twice as high as that in other regions of developing countries, says the report.
"Desertification is not due to lack of knowledge and science, but to a lack of proper governance," says co-author Uriel Safriel, a professor at the Hebrew University of Jerusalem, Israel.
Safriel explains that the knowledge needed to generate sustainable incomes from drylands is available in the world's scientific and engineering communities, yet doesn't reach the people affected.
"The reason is either that their own governments are not very efficient or that the donor countries are not investing their systems in a proper way," he says.
Safriel and colleagues note in their study that desertification is a global problem, affecting not only drylands but also regions distant from them. Dust from the Gobi and Sahara deserts has, for instance, been linked to respiratory problems in North America and has affected coral reefs in the Caribbean Sea.
Nevertheless, the report says there are still "serious gaps in our knowledge of the seriousness of desertification".
The study suggests that 10-20 per cent of drylands are already degraded, with those in sub-Saharan Africa and Central Asia most vulnerable to further desertification.
It adds that the 'least dry drylands' are those most at risk. These areas are often identified as possible areas for growing crops to meet increasing demand for food. However, converting them to agriculture introduces stresses that can lead to irreversible damage and desertification.
The authors say policymakers need to consider what are the most appropriate and sustainable livelihoods for people living in drylands, which cover 40 per cent of the planet's land area.
They recommend taking steps to prevent future desertification rather than attempting to reverse it, a costly option that is prone to failure. Measures to protect soils from erosion, to manage water resources sustainably and to maintain vegetation can all help prevent desertification.
"The global population has to find better ways to use the good areas for agriculture, and use land less suited to agriculture for other livelihoods," says Safriel.
The transportation of goods between drylands and non-drylands would need to be improved so that people living in drylands can import agricultural goods from other areas.
The authors point out that agricultural land needs more water than urban environments, and that water used in cities could be recycled and used on crops.
Although the drylands do not have much water, they do have other natural resources that can be exploited.
"Drylands could generate solar energy for non-dryland areas," suggests Safriel.