Achim Steiner, 45, a former director general of the World Conservation Union who was elected to the position in March, said he would strive to end the "antagonism between economic and environmental policy" in the world.

"For too long economics and environment have seemed like players on rival teams. There have been a lot of nasty challenges and far too many own goals. We need to make these two sides of the development coin team players, players on the same side," he said in a statement released by the Nairobi-based agency.

Steiner said UNEP would focus on how markets, economic incentives and international treaties can be made to work in a way which is "pro-environment, pro-poor and thus pro-sustainable development".

"Economic issues that touch on the environment are all too often pushed out of environmental conventions," he said.

"Environmental issues are generally left standing on the touch line, little more than spectators and rarely asked to play a real role in the great economic game. Everyone, not just those in the developing but also those in the developed world stand to lose out if this continues," he added.

Steiner takes office as a UNEP panel said that, apart from greenlands, the world's deserts were being threatened "as never before", particularly by climate change, yet can be used as a key resource if action is taken to protect them.

The UNEP study, released in London on Monday, highlighted the problems facing desert areas but also their potential uses in vital sectors such as energy, food and medicine.

Shafqat Kakakhel, of UNEP said: "Far from being barren wastelands, (deserts) emerge as biologically, economically and culturally dynamic while being increasingly subject to the impacts and pressures of the modern world."

"They also emerge as places of new economic and livelihood possibilities, underlining yet again that the environment is not a luxury but a key element in the fight against poverty and the delivery of internationally-agreed development goals," he added on Monday.

At least 25 percent of the Earth's surface -- 33.7 million square kilometres (13 million square miles) -- has been defined as desert and is home to more than 500 million people, according to the report "Global Deserts Outlook".

Other notable challenges include worsening environmental degradation in China with excessive logging, shrinking wetlands, overuse of fertilizers and expanding deserts.

Following 25 years of unbridled economic growth, China's environment has paid a huge price, with increasingly polluted waterways exacerbating water shortages and croplands and pastures spoilt by pesticides, fertilizers and acid rain, according to its government report.

Experts have warned that fast dwindling forest cover and pollution of rivers in Africa and Latin America poses a massive environmental challenge.

But despite mounting challenges, Steiner said there were positive indications on the future of the environment.

"There is a real tide of opinion that is now running in the direction of environmentally sustainable economies upon which we must and should sail," he said.

"A new mood that increasingly recognizes that, while money may make the world go round, what makes money go round is ultimately the trillions of dollars generated by the planet's goods and services, from the air cleaning and climate-change countering processes of forests, to the fisheries and the coast line protection power of coral reefs," he added.

Related Links
the missing link