Land degradation is on the rise in many parts of the world and is affecting more than 20 per cent of all cultivated areas, a new United Nations report says.

The study involving data taken over a 20-year period shows, the phenomenon is increasing in severity and extent, with more than 20 per cent of all cultivated areas, 30 per cent of forests and 10 per cent of grasslands undergoing degradation.

The degradation of land has direct consequence on an estimated 1.5 billion people  or a quarter of the world's population  the UN Food and Agriculture Organisation has warned.

"The study shows that land degradation remains a priority issue requiring renewed attention by individuals, communities and governments," Rome-based FAO said.

The degradation is witnessed in most places except in some areas in rain-fed crops lands and pastures in prairies and planes of western India, northern China and North America which show improvement, it said.

Consequences of land degradation include reduced productivity, migration, food insecurity, damage to basic resources and ecosystems, and loss of biodiversity.

"Land degradation also has important implications for climate change mitigation and adaptation, as the loss of biomass and soil organic matter releases carbon into the atmosphere and affects the quality of soil and its ability to hold water and nutrients," notes Parviz Koohafkan, director of FAO's Land and Water Division.

Despite the commitment of countries that have signed onto the UN Convention to Combat Desertification, land degradation is worsening rather than improving, and is being driven mainly by poor land management.

It also shows that land degradation has affected new areas since 1991.