BEIJING, June 5 (Xinhua) -- From China to Kenya, activists mark World Environment Day on Monday with the United Nations warning that desertification was a main obstacle to ending poverty and cantrigger conflicts.

The World Environment Day theme selected for this year is "Desert and Desertification" and the slogan is "Don't Desert Drylands!"

In a statement specially delivered on World Environment Day, UN Secretary-General Kofi Annan urged governments and communities to focus on challenges of life on desert margin.

"The theme of this year's observance of World Environment Day, 'Don't Desert Dryland', reminds us all of the importance of caringfor the world's vast areas of arid and semi-arid land," Annan saidin his statement issued on Monday.

The U.N. chief also warned that up to one-fifth of the world's land surface is desert - from the Sahara to the Gobi - and that other regions are at risk of turning arid.

World Environment Day was established by the UN General Assembly in 1972 to mark the opening of the Stockholm Conference on the Human Environment and the adoption of the Human Environment Declaration. Another solution, adopted by the General Assembly thesame day, led to the creation of the United Nations Environment Program (UNEP).

From 1974, the UNEP annually choose a theme for world environment day to stimulate worldwide awareness of the environment and enhance political attention and action.

Across the planet, poverty, unsustainable land management and climate change are turning drylands into deserts, and desertification, in turn exacerbates and leads to poverty.

Statistics released by the UN showed that 110 countries, about 1 billion people in the world are now threatened by desertification. Among them, 135 million are becoming destitute and homeless.

UN researches also suggested that climate change is degrading about 41 percent drylands -- including many of the world's crop-growing regions -- on the planet's land surface which are home to 2 billion people.

"It is estimated that between 10 percent and 20 percent of drylands are already degraded," Annan said. "The problem is particularly acute in sub-Saharan Africa and South Asia."

Africa is seriously threatened by desertification. Statistics showed about two-thirds of the continent are deserts or drylands and in the past 30 years the continent lost 50 percent of its forest.

The problem is also acute in South Asia, where dryland degradation is a serious obstacle to eradicating extreme poverty and hunger, and is jeopardizing efforts to ensure environmental sustainability.

The United Nations said that land degradation causes an estimated loss of 42 billion U.S. dollars a year from agricultural production -- without counting human suffering from famine.

Among pressures on land, the world's population has surged to 6.5 billion from about 2.5 billion in 1950. Enditem