Beavers. Lynx. Pine martens. White stork. The list of species that are or may soon recolonise parts of the British countryside is steadily growing. Yet just how beneficial to Britain’s ecological landscape will bringing back these mammals and birds actually be?
Rewilding, a process which is now gaining momentum right across mainland Europe, involves restoring large areas of land back to their natural state, and reintroducing species that were once native but disappeared thanks to the influence of man. It can bring a wide range of benefits for people, and could be the boost that UK biodiversity – which has declined by almost 60 per cent since the 1970s – so urgently needs.
But until now it has been difficult to evaluate the success of rewilding initiatives. Because rewilding is a process involving the complex interaction of different elements within an ecosystem, it is difficult to predict the results with any great accuracy.
This uncertainty over just how beneficial rewilding can be has contributed to various counter-arguments against the process. What’s the point in reintroducing wolves to the Scottish Highlands or beaver to West Country rivers if they don’t improve biodiversity, say some sceptics.
As a dynamic, organic transformation, the rewilding process may, in itself, be more important than reaching an arbitrary end point. Nevertheless, within each project, reference points are still essential in order to gauge progress and to check things are moving in the right direction.
‘Stakeholders such as farmers and conservationists who can’t see the tangible benefits of rewilding naturally question the entire process,’ says Cain Blythe, managing director of UK-based ecological consultancy Ecosulis. ‘In such a polarised debate, well-presented, scientifically collected data is crucial.’
The results of rewilding projects have, until now, either been measured in qualitative terms, or in ways that make wider data comparisons and predictions difficult. As rewilding projects become more common, the adoption of a universal methodology for establishing baselines and measuring changes in biodiversity is critical.
‘Demonstrating evidence of the benefits of rewilding will be crucial to its success,’ says Helen Meech of Rewilding Britain, an organisation now working to rewild at least one million hectares of Britain’s land, and 30 per cent of its territorial waters, over the next 100 years. ‘We are keen to work with ecologists and academics to develop the evidence base, which must include assessment of the potential impact on biodiversity.’
Cain Blythe and Sara King of Ecosulis, together with Dr. Alan Feest – a senior research fellow at the University of Bristol – may have the solution. The team’s Biodiversity Quality Calculator (BQC) tool, uses a range of standardised indices to accurately measure changes in biodiversity.
‘Unlike many other biodiversity measurement tools, the BQC doesn’t focus on specific species,’ explains Feest. ‘Instead it takes five primary biodiversity ‘indices’, which are then used to assess key indicator groups at the site.’
Employing the BQC, ecologists measure the changing biomass of such groups, as well as the changing richness, dominance, rarity and evenness within each group. Taken together, these five indices give an accurate measure of the evolution of on-site biodiversity after the rewilding process has begun.
‘The BQC has already been successfully used in a number of rewilding projects, including those assessing the impacts of beaver and overgrazing by sheep,’ says King. ‘Going forward, the list may soon include pine marten, white stork and other species.’
On the River Otter in Devon, a family of beavers – origin unknown – has been allowed to go about its business. Regarded by some as a keystone species, or one which has a large impact on the health of ecosystems which they inhabit, beavers were once native to the UK. They disappeared around 300 years ago, largely as a result of overhunting.
As aquatic engineers, beavers can play a major role in improving natural flood defences, fish stocks and water quality. By diversifying riverine habitats, they also enhance local biodiversity. Those on the River Otter have already had a huge impact, creating a series of ponds, as well as areas of open grassland, marsh, deadwood, moss and low scrub.
At a nearby site, called Boldventure, a more recently installed beaver population is now being watched closely to assess the potential for reintroducing these industrious animals to other parts of the UK. As part of this evaluation, the BQC tool is playing a vital role.
Working with the Devon Wildlife Trust and key stakeholders, it was decided that three key species groups – bats, aquatic invertebrates and bryophytes (mosses) – would best indicate any changes in biodiversity brought about by the beavers’ activity.
‘All three of these species groups are highly sensitive indicators of change within an environment,’ explains Ecosulis’s Blythe. ‘Measuring the changes within each group threw up some interesting results.’
Increases in biomass and the presence of rare species at the Boldventure site show that that the increased habitat variation caused by beaver activity is already boosting biodiversity. More unexpected was an observed reduction in nitrogen levels, as indicated by the increased diversity of mosses, especially nitrogen-intolerant ones. This supports recent research suggesting that the ponds and slower water flows that beavers produce can act as nitrogen sinks.
Data from the BQC analysis of the Boldventure site clearly provides further support for beaver reintroductions elsewhere in the UK. The beneficial impact of these animals has already been seen in ongoing trials in Scotland, while feasibility studies have also shown that beaver reintroduction in Wales is both ecologically and economically possible. The first introductions could take place in the mid-Wales county of Ceredigion by the end of this year.
Assessment of rewilding initiatives involving other keystone species would also benefit from BQC analysis. Earlier this year, pine martens were recorded in Shropshire woodland for the first time in over a century. While small populations of pine martens survive in Scotland and Wales, they were thought to be extinct in England.
As predators of grey squirrels, pine martens have been mooted as a natural way to boost red squirrel populations (which are suppressed by grey squirrels). BQC analysis of the biodiversity of this Shropshire woodland could provide useful data leading to the reintroduction of pine marten in other areas of the UK.
The lynx effect
More controversial UK rewilding proposals currently under discussion include the reintroduction of the Eurasian lynx, a specialist roe deer predator. As a reduction in roe deer numbers would almost certainly mean reduced damage to woodland flora, the reintroduction of this keystone species would likely bring about an overall increase in on-site biodiversity.
A recent vote, conducted by Lynx UK, resulted in a unanimous decision in favour of reintroduction. Farmers, understandably, are far less keen, because of concerns over livestock predation.
Analysis in the areas of Europe where lynx have already been introduced may prove critical if polarised opinions on lynx are to be reconciled. Data obtained using methods such as BQC, from places such as Norway and Switzerland could be interpreted in the context of local differences, such as variations in farming methods, and used to inform stakeholders accurately about various issues raised by rewilding.
Share or spare?
High-profile British rewilding advocate George Monbiot recently caused a stir when he attacked sheep farming as ‘a slow-burning ecological disaster which has done more damage to the living systems of this county than either climate change or industrial pollution.’ In Wales, Monbiot notes, the hillsides are so heavily grazed they can barely hold water. He calls for nothing less than the rewilding of the entire country.
Countering Monbiot’s argument, British farmers claim that there isn’t enough land to feed the British population through organic farming, which would be the dominant agricultural process if large areas were given over to rewilding. They would prefer to intensify agricultural production in certain areas through the use of chemicals, plastic coverings and genetically modified crops.
Rather than attempting to ‘share’ land with nature through more benign farming methods, such as organics and low-input agriculture, this process would see ‘spare’ land set aside for nature.
The UK’s National Sheep Association (NSA) has admitted that in some situations so-called ‘undergrazing’ can benefit biodiversity. But it is not in favour of the undergrazing of semi-rural habitats by removing sheep from uplands, claiming this would result in the loss of biodiversity.
Unfortunately, studies suggest that the NSA is wrong. Undergrazing improves the coverage and quality of natural grassland. This boosts floristic diversity and opportunities for wildlife. This is the very reason why ecologists and wildlife trusts encourage the establishment of ungrazed habitats within their management plans.
Such anecdotal evidence is now supported by quantitative data, following a BQC study conducted by Ecosulis. On a 3-hectare site, sheep were allowed to graze half the land, while the other half was left ungrazed and cut for hay. Bat surveys were then conducted across the site using the five BQC indices.
The BQC tool revealed higher species richness in the ungrazed area. Biomass was also higher in this area, suggesting the bats had found more invertebrate prey to feed on. Species rarity across both parts of the site appeared roughly equal, although the evenness score indicated a better spread of species (and less dominance of one species) in the ungrazed area.
‘In short, the BQC tool revealed a marked difference in biodiversity between ungrazed and grazed areas,’ says Dr. Alan Feest. ‘If the same methodology was used to assess a range of UK sites, the data produced could be invaluable in determining the future of our countryside.’