As world leaders gather for the COP15 summit, arguably to bloviate about biodiversity while it falls off a proverbial cliff, Britain has – amazingly – seen its first trial reintroduction of ‘free-roaming’ bison.
In July, an initial three female bison were released into an enclosed area of West Blean woods in Kent as part of the Wilder Blean project, and will soon be joined by Exmoor ponies and Iron Age pigs. Their ecological impacts on the woodland will be monitored, while a separate area will release cattle instead of bison, to allow their respective ecologies to be directly compared.
Wilder Blean is off to such a successful start that it has already been unexpectedly joined by a bison calf, thanks to an undetected pregnancy in one of the females.
Rewilding at Waterhall
Viewed from Sussex, this project less than 100 miles away is crying out for replication. And one particular location looks tantalisingly promising: Waterhall.
Waterhall, a former golf course, is in the early stages of (partial) rewilding. The site is already being grazed by cattle and ponies fitted with electronic tracking collars that give the animals a short shock when they approach virtual fence lines around the site, eliminating the need for disruptive physical fencing.
Site managers, I’m reliably informed, are actively investigating the possibility of bringing bison into the project, which would be both a wonderful attraction for Waterhall and another step towards nationwide reintroduction.
Managing free-roaming herbivores
The reintroduction of free-roaming large herbivores is, to paraphrase Isabella Tree’s book Wilding, exponentially beneficial to biodiversity. Nowhere in Britain illustrates this better than Knepp, the estate owned by Tree and her husband, which has become the national posterchild for rewilding.
Free-roaming wild herbivores would promote greater habitat and species diversity than monotonous fields packed with sheep. Restoring large herbivore guilds across the British landscape does, however, present some challenges, and will require accompanying actions to facilitate its success.
Firstly, free-roaming animals the size of bison or elk could present hazards to road traffic, and vice versa. Among the most effective ways to mitigate the risk of such wildlife-vehicle collisions, and facilitate wildlife dispersal, is to construct wildlife overpasses (also known as green bridges or ‘ecoducts’) across major highways, ideally combined with fencing to funnel wildlife towards the overpass rather than the roadside.
The Netherlands already has – depending how they’re classified – between 47 and 70 wildlife overpasses, which are aiding the recovery of wildlife in a country with the densest motorway network in Europe. The UK, by contrast, has fewer than five.
Re-introducing natural predators
Currently, the UK is a denuded land. Our woodland cover of just 13% compares to almost 40% across Europe. That’s partly because for decades our concentrated landownership benefited from perverse economic incentives in terms of farm or land subsidies.
It’s also because of high populations of deer with no natural predators. Although these deer populations may not be excessive relative to what the landscape could theoretically support, they find themselves in ecosystems degraded over centuries by many factors, and their densities are sufficient to prevent recovery.
Reintroducing additional herbivores, while increasing disturbance and heterogeneity in many areas, would exacerbate this problem unless they were closely followed by large predators.
Predators like lynx and wolves can, at least to an extent, exert top-down control over food webs, not only by reducing prey numbers, but by altering the foraging behaviour of prey species. This can in some circumstances reduce herbivore browsing pressure, facilitate vegetation regeneration and reduce the need for culling herbivores.
Decomposition aids eco-diversity
Perhaps more significant, and widely overlooked, is the combined impact of large herbivores and predators on the availability of carrion. With more than half of UK land used for grazing livestock, most of which are removed for slaughter, and those that die in the field legally required to be removed and disposed of, the countryside is excessively sanitised and ecologically bereft.
Large decomposing carcasses are a unique ecological resource. Habitats in miniature, they’re a hub for invertebrate activity and a ready food source for a multitude of wildlife. Large carnivores aren’t merely useful in providing carcasses through predation, but are also key pillars of scavenger communities. It’s estimated that in functional ecosystems scavenging plays a major role in the transfer of energy through food webs.
A potential concern with this might be the risk of disease transmission from carcasses. In fact, there’s no evidence that this is a significant risk outside of regions of anthrax endemism. To be clear, I’m not recommending an imminent reintroduction of wolves to Sussex, but a lynx trial in Scotland would be a good first step.
In the meantime, domestic cattle and horses used in conservation and rewilding projects could be explicitly prohibited from entry into the human food chain, which would potentially enable their carcasses to be left in the landscape, to the great benefit of scavengers, particularly recovering populations of raptors.
Let’s rejuvenate British ecosystems
There is therefore great scope for reintroductions of herbivores and their predators to rejuvenate British ecosystems – currently among the most depleted in the world – to say nothing of the ecotourism potential. This is already in evidence from reintroductions of other keystone species in Britain, like the beaver, and now too as the bison project gets underway in Wilder Blean and hopefully Waterhall.
This should create a snowball effect, gathering momentum for returning other missing species and in more parts of the country. Without it, UK contributions to summits like COP15 will never be anything more than ‘blah blah blah’.