- Deserts cover about a quarter of the world's land surface from the Sahara in Africa to the Atacama in Chile and degradation of soil in dryland areas, due mainly to a rising human population, is making them spread.

- Drylands, including many crop producing areas, cover 41 percent of the world's land surface. About 10-20 percent of drylands are already degraded.

- The total land area affected by desertification is estimated at 6-12 million sq kms (2.32-4.64 million sq miles), an area bigger than China or Canada. Each year an estimated 20 million hectares (49.4 million acres) of farmland becomes too degraded for crop production or is lost to urban sprawl.

- Asia and Africa are the continents worst affected by desertification. Land degradation causes an estimated loss of $42 billion a year from agricultural production.

- Experts say desertification can be muted by better management of crops, more careful irrigation and strategies to provide non-farming jobs.

- Some experts say that deserts could become new sources of power. An area 800 km by 800 km of the Sahara desert, for instance, could capture more than enough solar energy to generate all the world's electricity needs.