The burning of heather moorlands to create the right conditions for unnaturally high densities of Red Grouse may be harming the aquatic life in the rivers draining such uplands according to a new study.
The authors, from Leeds University, studied the aquatic animals in 10 rivers in the north of England – five from burned catchments (2 Peak District, 2 North Pennines and 1 Yorkshire Dales) and five from unburned catchments (3 North Pennines, 2 South Pennines). The study areas were matched, as best as possible, for underlying geology, land use etc.
Burned catchments had different aquatic invertebrate communities than unburned catchments – they were less diverse and had fewer mayflies and more midges and stoneflies. Their pH was lower and the impacts noticed in this study matched those found in similar studies elsewhere in the world.
The full scientific paper is published by Public Library of Science and is therefore available for all to read (click here).
This type of study is valuable but has its weaknesses compared with other types of study. Maybe the five burned catchments varied in other respects from the five unburned ones and so the differences found were not only (or even perhaps not at all) to do with burning. The authors have tried to minimise this problem by selecting the study areas in a fairly narrow geographical area and making sure the moorlands were pretty similar in other respects (forestry, mining, sheep densities etc) – but you can never be sure.
A stronger line of evidence would be to take an unburned moor and start burning it and see if the same changes came about – but that’s quite an enterprise! And how long would it be reasonable to wait to see whether differences emerged – five years? 10 years? 20 years? longer?
The fact that this study produced similar results to studies elsewhere in Europe and in North America increases its interest, I would say.
It certainly, perhaps unsurprisingly, suggests that management for red grouse can influence the wildlife living in the watercourses draining upland catchments. Another thing to think about.