THE tradition of burning heather on sporting estates causes significant environmental damage to both peatlands and nearby rivers, according to a new authoritative scientific study.

The practice, which has been carried out for almost 150 years, is used predominantly to support red grouse populations for gun sports by ensuring a supply of new shoots for the birds to feed.

But the new report from the School of Geography at Leeds University suggests it has a damaging impact on both the peat and rivers nearby.

The researchers found the water table depth, the level below which the ground is saturated with water, is significantly deeper in areas where burning has taken place, compared to unburned areas.

"A deeper water table means that the peat near the surface will dry out and degrade, releasing stored pollutants, such as heavy metals into rivers, and carbon into the atmosphere," they said.

Professor Joseph Holden, one of the report's authors, said: "Altering the hydrology of peatlands so they become drier is known to cause significant losses of carbon from storage in the soil. This is of great concern, as peatlands are the largest natural store for carbon on the land surface of the UK and play a crucial role in climate change.

"They are the Amazon of the UK."

The Ember (Effects of Moorland Burning on the Ecohydrology of River basins) project compared 120 patches of peat in 10 river catchment areas across the English Pennines.

However, Dr Lee Brown, also a co-author of the study, said that, while the study sites were all south of the Border, there was no obvious reason why the findings were not transferable to Scottish grouse moors.

Other important findings include a decrease in the diversity and population sizes of invertebrates, such as insect larvae, in rivers draining from burned areas. There is also up to a 20ÚC increase in soil temperature in the immediate years after burning.

Dr Brown said: "Even small changes in soil temperature can affect the decomposition of organic matter and the uptake of nutrients by plants. But we found increases as high as 20ÚC, with maximum temperatures reaching over 50ÚC in some cases."

Dr Sheila Palmer said the authors hoped their findings would help all parties in assessing the range of benefits and impacts of moorland burning to work together in developing policies.

Tim Baynes, director of the landowners' organisation Scottish Land & Estates' Moorland Group, said: "The research is an interesting addition to a growing body of science about moorland burning although we need to be aware of differences between moors in the north of England where this study was carried out and cooler, wetter moors particularly in the north of Scotland."

He said the practice was governed by the Scottish Government's Muirburn Code which is undergoing a "comprehensive review".

That work will "take into account all the emerging science, including that which shows the benefits of well-managed muirburn for reducing wildfire risk and improving habitat for endangered bird species," he said.

Scottish Gamekeepers' Association Chairman Alex Hogg said it was also important to monitor the effects of all management practice on land. He added: "Controlled heather burning only takes place within very short, regulated, seasons. Following best practice, it only takes place when the fire will not burn into peat edges."