Burn baby, burn!
Yorkshire Dales Moorland Group
The heather burning season has commenced (1st October – 15th April). Our upland landscapes and vegetation can now be managed with prescribed cool fires with consent from DEFRA and Natural England. Why is this important and what is heather burning all about? Here are some familiar questions and answers that will hopefully allow our followers and those with an interest to get the real information not from the misinformed journalists and antagonists but directly from those practitioners whose lives and professions have evolved on our moors of Yorkshire and beyond.
Q. Why burn heather?
A. Heather and some other moorland plants (primarily Calluna vulgaris) dominate our uplands. Heather or ‘ling’ is the most common. It’s an acid loving shrub that likes high rainfall. It has an average life expectancy of twenty to thirty years, sometimes older. It has the capacity to grow to a metre high or higher before it eventually collapses and begins to decay. Older plants like this are more like trees than plants and can develop stems over 40mm thick. It is a fire evolved plant that grows from seed or root stock and there is research that demonstrates seeds may need fire and smoke (vernalisation) to germinate and grow successfully. When green and young these young pioneering plants grow quickly absorbing carbon from the air as they photosynthesise. Within a few years they can develop a dense canopy that not only prevents sphagnum moss growth but also lichens and other specialised species. Maturing plants become more ligneous and woody and their use as a food source not only for grouse but grazing livestock is drastically reduced. Once this stage is nearing or has been reached the plant barely absorbs carbon and is unpalatable to wildlife. Using fire to regenerate the plants is a proven and reliable practice.
Q. Why can’t you just cut the heather instead of burning it?
A. Cutting heather with machinery does indeed have a role to play in upland vegetation management. However, it is not a suitable alternative to most prescribed cool burns. Wet, soft ground or steep inclines with moraine or rocky outcrops can prevent the use of mechanical cutting especially as the equipment needed can be heavy and cumbersome. Research has shown that the cut brash and resulting decaying mulch releases more methane (harmful greenhouse gas) than if it was burned quickly with a rapidly moving controlled fire. Similarly cutting invariably damages the plants by breaking the stems. Cutting stresses the plants which then have to repair themselves before they can recover and begin to produce shoots. Regrowth is slowed and the left over material from cutting can hinder the growth of other moorland species and build up into combustible fuel creating a fire hazard.
Q. Burning heather damages peat and releases carbon. Is this true?
A. Moorland keepers have generations of expertise about heather burning behind them. No other profession or established authority knows more about moorland management and heather burning than they do. Protecting the substrate (peat growing medium and mossy understorey) is of paramount importance to moor keepers because without it there would be no heather. Before any heather burning begins the keepers assess the conditions, the wind and speed, predicted changes in wind direction, dryness of the heather and the ground beneath. Most estates have agreed burning plans and maps to make sure all activities are compliant and in accordance with strict agreements. If these optimised weather and ground conditions are not met then no heather will be burned. Once lit, the fire will travel across the surface vegetation taking with it only the canopy and leaving behind charred stems and an undamaged, moist under layer of peat and moss. The only time peat is damaged is when wildfires occur on moorland in arid conditions often in summer. Dry peat can ignite and burn uncontrollably for days releasing stored carbon. This is why controlled burning occurs in late autumn and winter. During cool, managed fires some carbon is indeed released from the combustion of the heather plant but this is carbon already absorbed from the atmosphere during the growing phase. Much of the smoke that is seen during controlled burning is water vapour. The small amount of carbon emitted during managed burning is negligible compared to that lost in hot wildfires as seen at Saddleworth and other sites in recent years.
Q. So does heather burning actually protect carbon stores and help wildlife?
A. Absolutely, but the ill-informed journalists and other grouse moor opponents choose to ignore these important key facts. Rotational strip fires not only create a patchwork of varying sward lengths they also break up the combustible material which significantly reduces the incidence of wildfires. This protects the carbon stored beneath and creates havens for a wide range of flora and fauna. Having a landscape with diverse stands of vegetation is scientifically proven to be critical for ground nesting birds such as merlin, hen harrier, golden plover, curlew and red grouse to name but a few. These red and amber listed birds have become reliant on our managed uplands as breeding grounds. Sphagnum mosses are supressed under dense heather and as these bryophyte plant types are marvellous at building peat and storing water the mosaic like burning patterns that result from heather burning are categorically proven to increase sphagnum cover and capacity. All managed moors still have areas of long heather. Quite often these are specifically managed to host raptors, amphibians and reptiles. It is the rotational management of the heather with fire that yields all the different micro-habitats and hence the rich diversity they host.
Q. What would happen if heather wasn’t burned?
A. As mentioned earlier, heather will grow into a shrub if left unmanaged. Ultimately it will crowd out the other companion species including sphagnums before finally degenerating and collapsing into a decaying fire prone heap. Whilst it is fair to say that this process in itself would create an alternative type of habitat, the process would take decades and would eliminate diversity. From an ornithological and environmental viewpoint this would be an extremely dangerous experiment to pursue. Every fire expert has stated that wildfires under such circumstances would be a guaranteed inevitability. With incidents of summer wildfires on moorland increasing year on year it would be a case of ‘when’ not ‘if’ a fire broke out on such landscapes. In such an event the fuel load would be tremendous, the heat generated would ignite the peat store beneath and the carbon that took millennia to accrue would be gone. Trying to protect peat by banning controlled burning is pure folly. In other countries where rotational burning was neglected or banned the consequences have been heartbreaking. Landscapes destroyed, habitats impoverished, property and human lives lost too. It is therefore no surprise that today these cool burning strategies are being reinstated across continents. We would also see a quick but steady decline in ground nesters as foraging and nesting areas became inaccessible. The suite of insects would change and the recovering vegetation would be dominated by grasses like Molinia (Purple Moor grass) and brackens. Cool, controlled burning is providing us with an immense level of bio-diversity but it is also protecting the carbon that is locked beneath our internationally recognised moorland ecosystems.