The EMBER study by the University of Leeds (funded by NERC and Yorkshire Water) has been a five-year study of 10 river catchments – five that have lots of heather burning for driven grouse shooting and five that do not. The study area was the North Pennines.
The British uplands collect and distribute rainwater, sequester carbon in the form of peat and provide the habitats for many important species. In some areas, land management is dominated by the industry of driven grouse shooting where burning of heather to produce artificially very high densities of Red Grouse for shooting is part of the traditional management regime.
Rotational burning of heather is important for grouse shooting but what does it do for the rest of us?
These are the results of this major study and they indicate, in just about every respect, that burning of heather imposes a cost on the taxpayer and society.
Prescribed burning on peatlands was shown to have clear effects on peat hydrology, peat chemistry and physical properties, river water chemistry and river biota.
- Burning reduces the organic matter content of the upper peat layers. The net result is that the peat is less able to retain important particles known as exchangeable cations. In other words, the peat in burned sites is deprived of chemicals which are important for plant growth and for buffering acidic rainfall.
- Lower concentrations of nutrient elements found in peat soils in burned river basins do not support the idea that burning enriches the peat with nutrients from ash.
- Rivers draining burned catchments were characterised by lower calcium concentrations and lower pH relative to rivers draining unburned catchments. Rivers draining burned sites had higher concentrations of silica, manganese, iron and aluminium compared to unburned catchments.
- There was no difference between burned and unburned catchments in peat nitrogen concentrations or in carbon to nitrogen ratios (high C/N is considered unfavourable to microbial decomposition of peat), and no significant difference in peat soil pH.
- Water-table depth is very important in peatlands for maintaining their stability and function as a carbon store. Water tables were found to be significantly deeper for burnedcatchments than for unburned ones. Deeper water tables would suggest a greater scope for degradation of the peat and loss of carbon to the atmosphere.
Sphagnum is an important peat-forming species. Changes in the hydrological properties of the peat after fire make the peat less conducive to moss growth.
- River flow in catchments where burning has taken place appears to be slightly more prone to higher flow peaks during heavy rain. However, this was not a conclusive finding.
- Burning vegetation alters the natural peat hydrology in the upper layers of the peat affecting the balance of where water flow occurs. Recovery of many hydrological properties appears to be possible if a site is left unburned over many years.
- Prescribed peatland vegetation burning leads to significant increases in mean and maximum near-surface soil temperatures in the years following burning as well as lower minima (and thus wider thermal variability).
- Thermal regimes appear to recover as vegetation regrows. This recovery was also seen in soil hydrology data from burned plots of different ages.
Macroinvertebrates play a vital role in aquatic food webs by feeding on algae, microbes and detritus at the base of food chains before they themselves are consumed by birds, fish and amphibians. The research found that river macroinvertebrate diversity was reduced in burned sites.
- Particulate organic matter (predominantly peat) deposits were increased up to four-fold in the bed sediments of burned rivers compared to unburned rivers.
- In burned sites, river macroinvertebrate populations were dominated by groups that are commonly found in higher abundance in disturbed river systems, such as non-biting midge larvae (Chironomidae) and burrowing stonefly larvae (Nemouridae).
- Increases in the abundance of disturbance-tolerant taxa counteract declines and/or losses amongst some groups (e.g. mayflies) which are typically sensitive to reduced pH, increased aluminium and deposition of fine sediments. These changes show that burning increases the effect of biological stressors compared to unburned rivers.
In other words, the researchers say that heather burning puts particulate matter into your rivers, makes rivers more acidic, reduces the numbers of many invertebrates (some of which are replaced by ones characteristic of knackered rivers), reduces the soil quality and organic matter of the peat, reduces the water table and makes carbon loss to the atmosphere more likely.
Farmers simply wouldn’t be allowed to behave in this way.
A day’s driven grouse shooting has a cost of maybe £45,000 for a group of six guns. The environmental damage caused by heather burning is picked up in increased water bills, increased risk of flooding and increased climate change impacts by all of society.
Any policy-maker or politician, unless they shoot grouse (as have several recent Defra ministers, of course), should see that the public costs of grouse shooting vastly outweigh the private benefits.
The sport of the few should not be allowed to degrade the environment of the many. Sign here to ban driven grouse shooting.