Bales of heather fell from the sky onto a peat plateau in the Peak District yesterday, in the latest attempt to halt what scientists believe is a dangerous emitter of carbon dioxide.

Instead of acting as a natural store, or sink, for CO2, peat bogs such as the district's Bleaklow are leaking the gas, a process which experts put down to exposure to 200 years of pollution, overgrazing and fire. The gas is thought to be a big contributor to climate change.

Helicopters interrupted the January tranquillity of a few sheep and muddy walkers to drop billions of heather seeds embedded in bales of brash, or cut heather, which should start sprouting in the spring. The seeds will also be spread across the moorland by volunteers in the coming weeks.

The rate of CO2 emission from eroded peat bogs is a matter growing concern for scientists: along with neighbouring Peak District hills such as Kinder Scout, it is thought the 700 sq km of the southern Pennine hills could be leaking as much CO2 as a town of almost 50,000 people. Britain's peat bogs store the equivalent of 10 times the country's total CO2 emissions.

Fiona Reynolds, director general of the National Trust, said emissions - a "ticking timebomb" - from the land are potentially as serious as those from cars and planes. Instead of being a squelchy green blanket covered in moss and cotton grasses, Bleaklow is, in parts, dry as southern Europe, and gullies 4m deep cross the moor.

"Along with Kinder Scout, Bleaklow is one of the most degraded peat moors in Britain. The idea is to turn it back from being a source of carbon dioxide to a sink," said Mike Innerdale, property manager of the trust's High Peak estate. When exposed to the air, the peat soil, prized by generations of gardeners and used to fuel homes, quickly crumbles and runs off.

According to Dr Fred Worrall, a leading peat researcher at Durham University, land-based carbon emissions are potentially as serious as cars and aviation. Peat, one of the most efficient natural reservoirs of CO2, is vulnerable to degradation, and the Peak District is one of the worst affected because it is at the southern end of global peat stores. "The further north you go, the less the danger. If you do nothing, it will only get worse," Worrall said.

On the moor, landscape expert Rebecca Burtt was supervising the drops. "This is pioneering work," she said. "We've been encouraging cotton grass, bilberries, crowberry and heather to grow. The ultimate plant we want up here is spaghnum moss. The [degradation] comes from a combination of old industrial pollution and sheep stopping anything growing back."