Burning Theory

The effects of a cool burn (above) and a hot burn (below)

The more heather I burn and see burnt, the more I’m learning. We’ve now had three burning days down on the coast, and while two have been a little on the damp, cloudy side, one was a bright, breezy day in perfect conditions. Heather burning is about far more than just dropping a match, and working with a changeable wind can make the process very interesting. There are different kinds of fire, and they move at different speeds and at different depths through the undergrowth. There are many different ages and structures of heather, some of which will readily burn in almost any condition while others require a sustained effort to catch alight even in prime conditions. What had initially seemed like a simple job started to look pretty complicated after a few hours spent watching the flames, but provided that you bear a few basic principles in mind and always plan where the fire is going to end up in advance, it’s not so hair raising as it seems.

What is most interesting to me is the fact that different conditions create different burns. A cool burn through old, rank heather does little more than singe off the leaves. Thick, greenish smoke indicates that the heather is too sappy and wet to burn properly, so rather than incinerate the actual heather stalks, the fire just skims over the top. A burn like this may bring about regeneration from the surviving heather stalks provided that they are not too old, but with a thick layer of heather brash covering the soil, regeneration from new plants is almost impossible. This sort of burn took place on the last two days we burned down on the Solway (pictured top).

By comparison, a fire that is too hot will kill all the heather seed and burn through the moss, into the peat. In extreme cases, this can mean that the moor itself can catch fire and smoulder away for weeks, leaving nothing whatsoever. It sounds like the wise men at Natural England and now RSPB are paranoid about this or something similar happening at Walshaw estate in the Pennines, where an attempt was recently made (and continues to be made) to ban burning on blanket bog, given that it supposedly dries out sphagnum moss and restrict’s the moor’s ability to absorb atmospheric carbon.

The best sort of burn is midway between the two extremes – a fire which burns down the heather stalks so that they are little more than short black stumps and which also burns away all the litter left by dead plants from previous years. This not only means that grouse and moorland birds are left with a clear open patch to roost on, but it also ensures that heather regeneration takes place from stalks as well as new plants which grow up from the soil. This sort of neat burn happened on the first day we burnt down on the Solway (pictured above, bottom).

At any rate, burning heather in any conditions is generally better than doing nothing at all, because even if a single cool burn over rank heather may not bring much regeneration, it helps to break up the monotony of undergrowth and creates a more interesting and accessible habitat for birds of all species.


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