Rewilding: rare birds return when livestock grazing has stopped
There is something very different about many of the UK’s national parks compared to those found in much of the rest of the world: the British uplands are hardly the natural wilderness that many perceive.
These upland habitats are in fact far from what they would have been had they remained unaffected by human activity. In particular, grazing by livestock has been carried out for centuries. In the long run, this stops new trees from establishing, and in turn reduces the depth of soil layers, making the conditions for new vegetation to establish even more difficult. Instead of the woodlands that would once have covered large areas of the uplands, Britain is largely characterised by rolling hills of open grass and moorlands.
Government policy has long been to keep these rolling hills looking largely as they do now. But the future of the British uplands is uncertain. There are a range of competing interests. Some wish to rewild vast swathes of the land, while others want to intensify farming, forestry and other commercial interests. The rewilders tap into the increased interest in restoring natural woodland due to its potential in carbon uptake, increased biodiversity and reintroduction of extinct species such as wolves and lynxes, while some farmers argue that this will be bad for the economy. The UK stands at a crossroads, and interests are rapidly diverging.
Whatever path is taken will obviously have an impact on the unique assemblages of upland plants and animals, many of which are internationally important. But upland birds and biodiversity have for a long time been on the decline. Whether rewilding is the answer to this or not has long been debated: some claim that we need to stop grazing animals to allow the natural habitat to reassert itself, while others claim that some species, such as curlews, rely on such grazing practises for their survival.
But our new research, published in the British Ecological Society’s Journal of Applied Ecology, provides the first experimental evidence to our knowledge, that stopping livestock grazing can increase the number of breeding upland bird species in the long term, including birds of high conservation importance. This is interesting, as it is often argued that land abandonment can result in lower biodiversity and that livestock grazing is essential for maintaining it.
Our research shows that, depending on how the uplands are managed, there will be bird “winners” and “losers”, but overall when sheep have gone the number of bird species returning increases.
Before going into the research itself, it’s important to consider the history of British upland land management. Truly “natural” habitats in the UK are few and relatively small. Deciduous woodland, and to a lesser extent coniferous forests, used to cover most of the British uplands below the treeline. For example, only about 1% of the native pine forests that once covered 1.5 million hectares (15,000km²) of the Scottish Highlands remain today.
These woodlands provided homes for charismatic species such as pine marten, red squirrel and osprey, together with now-extinct species such as lynx and bears. But centuries of farming has shaped most of the upland landscape to what it is today: a predominantly bare landscape dominated by moorlands, rough grasslands, peatlands and other low vegetation.
These marginal areas tend to have low financial profitability for those who farm the land. And so a range of other activities, such as grouse shooting and commercial forestry, exist to boost rural community incomes.
Despite their low profitability, however, many grazed areas are considered to represent “high nature value” farming. This seems paradoxical, but basically means they are considered important as habitats to protected species benefiting from open upland landscapes. One such species is the iconic curlew.
Because farming is tough in the uplands and it’s a struggle to make a profit, landowners receive and often rely on, subsidies to maintain their farms. At the moment, the scale of these subsidies are based on the size of the farm, but they also require that the farmer maintains the land in a good agricultural state. This leaves little room for shrubs or trees, except along field edges.
But these subsidies will soon no longer be allocated through the EU – and so it’s time to reconsider what kind of land management should be supported. It seems sensible to consider introducing financial support for other land management types, such as reforestation, natural regeneration or wildflower meadows. Such habitats have other public and nature conservation benefits.
But rewilding, or any form of restructuring land management, can be costly. It therefore needs to be based on the best scientific evidence, preferably from well-designed experimental research studies. In controlled experimental studies, the cause for any effects found can more easily be determined, as opposed to observational studies, which risk being biased by other, confounding, factors. But due to the cost and complexity of maintaining them, long-term, experimentally manipulated land use studies are rare, and with it the necessary evidence base for long-term management decisions.
The Glen Finglas experiment, managed by the James Hutton Institute, was set up in 2002 in Scotland’s Loch Lomond and Trossachs National Park. The experiment examines the long-term ecological impacts of different livestock grazing intensity levels on plants, arthropods (insects and spiders), birds and mammals.
Since the start, the Glen Finglas experiment has shown that grazing intensity affects plants and the amount of insects and spiders. The highest amount of plants, insects and spiders were found in the ungrazed areas.
Meanwhile, the research on birds within this experiment has, from the start, focused on meadow pipits.
These small, brown birds are the “house sparrows of the uplands”, yet often go unnoticed. But they are the most common upland bird and an important part of upland food webs, forming key prey for birds of prey such as hen harriers and a common host for cuckoos.
In just the first two to three years, it became clear that meadow pipits could be affected by grazing intensity. But there were no differences in how many meadow pipit chicks were produced and fledged between the grazing treatments, at least not in the very early phase of the experiment.
I wanted to test whether these results changed in the longer term. Together with colleagues from Newcastle University, the British Trust for Ornithology, The James Hutton Institute and The University of Aberdeen, we looked at whether 12 years of continuous experimental grazing management had affected the breeding success of meadow pipits.
We assumed that low intensity grazing, compared to high intensity or no grazing, was most beneficial for pipit breeding productivity. We found the low intensity grazed areas did indeed seem to be better for meadow pipits, but the effects were not clear enough to be statistically significant. And there seemed to be potentially more important factors, such as predation, affecting their breeding outcome.
But although we did not initially set out to test it, we found other, more significant, effects on the wider bird community.
When the experiment started, there were almost no bird species other than meadow pipits in and around the treatment areas, hence the focus on them. But in 2015, while looking for meadow pipit nests, we came across a few other beautiful nests in the low intensity grazed areas. These nests had colourful blue eggs or eggs that appeared to have been painted with dark brown watercolour paint. These turned out to be stonechat and reed bunting eggs, two bird species that had not previously been seen in the experiment.
Later on, we saw that they had fledged successfully: the parents would call them to warn about human intruders. If we didn’t get too close, the newly fledged young would curiously nudge their heads up through the vegetation. By this stage of the experiment – 12 years in – the vegetation had actually become quite dense and high in the ungrazed and some of the low intensity grazed areas.
Thanks to all these encounters, we decided to test how the different grazing treatments affected the species richness of breeding birds. Over the first two years, we found that there was basically no difference. But another decade on and there were clearly more bird species found in the ungrazed areas compared to the other experimental plots.
Rewilding is such a fractious debate because of the difficulty in obtaining solid scientific evidence on which to base decisions. It takes a very long time – far longer than our political cycles, most research studies, perhaps even a lifetime – to determine what the ultimate effects of large scale land management on the environment are.
There is no one management practice which creates the perfect environment. Some bird species (skylark and snipe) were only found in grazed areas. Other species were more abundant in the ungrazed areas. There is no one size fits all.
But much more consideration and effort needs to be given to unattended land and its potential for boosting biodiversity.
Biodiversity is incredibly important. It creates a more resilient ecosystem that can withstand external stresses caused by both humans and nature. It also keeps populations of pollinators strong. At the moment, perhaps the most current and urgent reason is that it could be instrumental in protecting us from future pandemics. A wider range of species prevents unnatural expansions of single species, which can spill over their diseases to humans.
There are many ways to rewild. The Woodland Trust have been successful in restoring ancient woodlands and planting new trees by protecting them from large herbivores such as deer and livestock. Another method is to let “nature have its way” without intervening at all. This has been successful in restoring natural habitats, including woodland, such as the Knepp estate in West Sussex, which Isabella Tree has made famous in her book Wilding.
After 19 years of no conventional management, The Knepp estate now hosts a vast range of wildlife, including all five native owl species, the rare purple emperor butterfly and turtle doves. Large herbivores, including both livestock and deer, graze the area on a free-roaming level. These animals are replacing the large natural herbivores such as aurochs, wisent and wild boar which would have grazed the area thousands of years ago.
So there is room for discussion on what environmental and financial benefits there may be of different rewilding, or woodland restoration projects, and where they are most suitable.
Long-term research of land-use change would give us a better evidence base for future decisions. But this must go hand in hand with much needed serious evaluations of rural communities’ long-term income opportunities under alternative management scenarios, which will always be a cornerstone in land use politics.