"Care for the environment is often portrayed as detrimental to economic growth," he told on his first day as head of the United Nations' top environment body.

"We hope to lay that myth to rest in the 21st century," he said by telephone from UNEP headquarters in Nairobi, setting out priorities for a four-year term.

Most conventional economic theory places no value on natural phenomena such as the coastline protection given by coral reefs or forests' role in absorbing heat-trapping carbon dioxide.

Steiner said a shift was needed to recognise the "enormous wealth of nature's services" underpinning all life on earth. In turn, that would show that environmental protection is a condition for economies to survive and thrive in the long term.

"We have to get environmental concerns into the mainstream of economics ... to include what we are consuming and destroying," he said.

By conventional yardsticks nations can -- at least briefly -- boost growth by axing all their forests for timber or dynamiting reefs for fish. A shift in accounting would place a higher value on intact natural systems.

"Environmental sustainability in the 21st century is not only the preserve of environmentalists, but of everybody who uses resources on this planet," Steiner said. He succeeds Klaus Toepfer, also German, who has retired after eight years at UNEP.

CARBON TRADING

Steiner, former head of the World Conservation Union, hailed a European Union market in industrial emissions of carbon dioxide as an example of a project placing value on nature.

The market was set up in 2005 as part of the UN's Kyoto Protocol to combat global warming, blamed by most scientists on emissions by power plants, factories and vehicles. Carbon prices are now around $15 a tonne.

"One of the great breakthroughs on an environmental issue is carbon trading," Steiner said, expressing hope that such markets would grow. "We are far from trading at a level or a scale that is yet meaningful for the actual climate challenge," he said.

UN studies say that costs of inaction over climate change could be far greater than higher electricity bills because of carbon trading. Many scientists say global warming could spur heatwaves, droughts, floods and a rise in global sea levels.

Steiner said public pressure could spur other mechanisms to protect the environment. Supermarkets or travel agents, for instance, find that consumers are willing to pay more for foods or holidays if they do not damage the environment.

US President George W. Bush pulled out of Kyoto in 2001, arguing it was too costly and wrongly omitted developing nations from caps on emissions of greenhouse gases by 2012. Bush prefers big investments in technology such as solar energy or hydrogen.