Found this interesting article on the Rewilding Britain site. I would suggest that the truth lay somewhere between the two proponents of the debate. To use chalk grassland and lowland heath here in Sussex as examples, I have related my view as a ‘Page’ – To Graze Or Not To Graze, on the home page of my blog.
The lynx debate: why claims that sheep increase biodiversity are wrong
The National Sheep Association believes that grazing enhances biodiversity. The independent environmental consultancy Ecosulis isn’t so sure. Here’s why, including its views on reintroducing lynx
25 Apr 2016
The National Sheep Association (NSA) recently published a report entitled The Wider Consequences of the Introduction of Eurasian Lynx to the UK. In the report, the NSA raises a host of concerns about proposals to reintroduce lynx to the UK. This article is a response from independent environmental consultancy Ecosulis, with particular focus on biodiversity associated with many sheep farms.
The Eurasian lynx is a keystone species, similar to beavers and pine marten, both subject to separate reintroduction projects. A keystone species is one that has a large impact on its community by controlling the dominance of other species or by changing habitat structure (beaver dams, for instance). It can therefore have a big impact on biodiversity and wildlife.
In its report, the NSA states that traditionally grazed woodlands should be introduced to enhance biodiversity. It is accepted by many ecologists and habitat managers that woodlands are reduced in biodiversity and structural quality as a result of intensive grazing, both from deer and sheep, and that efforts to minimise deer populations in woodlands are a priority. The reintroduction of lynx could reduce deer numbers by introducing an ‘ecology of fear’ and therefore restore the health and biodiversity of our woodlands by allowing ground flora and associated species to regenerate. Indeed, ambush predators such as the Eurasian lynx may have a stronger affect than wolves. Sheep can also damage woodland edge habitats where intensive grazing can reduce floristic diversity of grassland (and therefore have impacts on other wildlife, including bats) and expose woodland to disturbance.
Grasslands – undergrazing is good too
The NSA advises that undergrazing of semi-natural habitats by removing sheep from the upland would result in a loss of biodiversity. Undergrazing, however, would lead to increased grassland sward and, consequently, greater floristic diversity and opportunities for invertebrates. This, in turn, would enhance opportunities for other wildlife, including bats and byrophytes. Ecologists and wildlife trusts encourage areas of ungrazed habitats within management plans and mitigation strategies. This is because they allow grassland swards, wildflower meadows and woodland edge habitats to mature and flourish.
The measure of biodiversity
Bats can be used as an indicator of biodiversity change because they show trends in invertebrate prey and the quality of habitat structure
Ecosulis, driven by its shared vision of Rewilding Britain, uses the Biodiversity Quality Calculator (BQC) developed by Dr Alan Feest. This tool measures biodiversity quality and was recently used to quantify the changes that resulted from beaver reintroduction at the Okehampton reserve in Devon. We have used it to illustrate the biodiversity value associated with a site in Sussex where sheep graze half the site and the other half is left ungrazed (each section is 1.5ha).
Bats can be used as an indicator of biodiversity change because they show trends in invertebrate prey and the quality of habitat structure. So, in September 2014, we undertook bat activity surveys on the site, with bat counts taken for each sample area. This is by no means a comprehensive study but it can be used to illustrate the differences for the site.
Our BQC findings show several changes in biodiversity when comparing the sheep-grazed half of the site against the ungrazed area. Species richness and density increase within the ungrazed area. In addition, biomass is higher, indicating more invertebrate prey for bats. Species rarity across the site appears to be the same, although the evenness score indicates that there is a better spread of species (or less dominance of any one species) in the ungrazed area of the site. These all indicate that, in this example, biodiversity is higher in the ungrazed area than the sheep-grazed half of the site. We would hypothesise that this trend would be consistent in similar comparisons and across other species groups. We suggest, therefore, that the NSA claims regarding the benefits of grazing to biodiversity are flawed.
Rewilding – with informed decisions
The NSA concludes that “sheep play an important part of maintaining the biodiversity of the current, perfectly functioning ecosystem, which would be disrupted by the introduction of an unnecessary predator. Reintroduction of lynx would be a costly, complex process, with little benefit to the woodlands or ecosystems as a whole”.
This article questions the basis for that statement and we would welcome any details from the NSA concerning the valuation methods that show this correlation between sheep grazing and biodiversity. Our initial studies, and our work with wildlife trusts on biodiversity change associated with the reintroduction of keystone species, reveal a significant increase in biodiversity following the reintroduction of beavers, for example. Lynx are a keystone species and could assist with controlling deer numbers, which would increase biodiversity and habitat structure in our woodlands.
We agree that more information is needed on the impact of lynx on biodiversity and ecosystem services and this is currently in development. We also strongly believe in partnerships between stakeholders, including sheep farmers, for all proposed reintroductions and consideration must be given to the potential impact on sheep farming as well as other related factors. Furthermore, reintroduction and rewilding projects should adopt robust biodiversity valuation methodology to clearly demonstrate the direction of change. This can then be used to inform decisions on reintroduction suitability, scale and locations.
About the authors
Cain Blythe is Managing Director of Ecosulis.
Sara King is a Senior Ecological Consultant at the company.