By Alister Doyle, Environment Correspondent

OSLO, May 16 (Reuters) - Big airlines should imitate a tiny, profitable Costa Rican company that invests in forest protection to help soak up greenhouse gases spewed out by its planes, Costa Rica's tourism minister said on Wednesday.

Carlos Ricardo Benavides said that airlines had to do more to fight global warming, partly to encourage tourists worried about climate change to keep visiting remote jungles, mountains and beaches in poor countries that rely on the income.

"Nature Air represents a way to do it," he told Reuters during an international ecotourism conference in Oslo. Costa Rican domestic airline Nature Air calls itself "the world's first and only zero emissions airline".

The firm, with 17 Twin Otter propellor-driven planes, 160 employees and 80 flights a day, pays farmers to grow and protect forests to soak up carbon dioxide emitted by burning a total 480,000 U.S. gallons (1.8 million litres) of fuel a year.

Benavides urged other airlines to follow the example.

"Each flight to our country should have the offset in forests and production of oxygen, so we can finance more and more purchases of forests," he said.

U.N. scientists say aviation, a fast-growing sector, emits about 2 percent of world greenhouse gases blamed for global warming that could bring more droughts, floods and rising seas.

Some major airlines, such as British Airways <BAY.L> and Scandinavian airline SAS <SAS.ST>, offer clients an option of paying a supplement to invest in planting trees or in renewable energies to offset the greenhouse gas emissions.

Nature Air instead takes an annual one-off cost of about $60,000 to pay farmers to protect forests and stop clearing them for cattle grazing. Trees absorb heat-trapping carbon dioxide as they grow but release it when they burn or rot.

PROFITS

"I'd say we've sold at least that much in tickets and more because we're doing it," sadi Alexi Huntley Khatjavi, Nature Air sales and marketing director.

"There are some tour operators who will only do business with us," he said. The Central American nation, with both Pacific and Caribbean coasts, is home to many rare plants and animals that draw many tourists.

Nature Air says it has expanded about 45 percent a year and stayed profitable since 2004 when it began paying for annual offsets totalling about 5,000 tonnes of carbon dioxide a year, helping protect forests on the Pacific Coast.

He said that Nature Air makes annual profits equivalent to between 4 and 7 percent of its sales, after accounting for the environmental charge. He declined to give exact figures.

Many countries such as Costa Rica, Papua New Guinea and Brazil want any extension of the U.N.'s Kyoto Protocol on fighting global warming beyond 2012 to include some mechanism to reward them for preserving or growing forests.

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