Keystone Species in Britain
What are they, why do we need them & what species are missing from Britain?
Have you ever heard of the term, ‘keystone species’? Or perhaps ‘ecosystem engineer?’ If not, you are in for a treat. And if you have, you can expect to learn some more about these fascinating species below. We will shine a light on the unsung heroes of our landscapes which play a fundamental role in keeping our ecosystems healthy and balanced. Let's explore what they are, which species are missing from our landscapes and why we should care.
What Are Keystone Species?
Think of keystone species as the glue that holds our ecosystems together. The word, keystone, originates from the central stones which are placed in the middle of arches to keep the whole structure from collapsing. This term fits for species, because it refers to certain animals that have a disproportionately large impact on the health of the ecosystem around them. Without them, ecosystems can rapidly deteriorate and lose balance. They are also sometimes referred to as ecosystem engineers, because their behaviour engineers habitats which other species rely on.
British Keystone Species:
Across Great Britain, we have important keystone species of all shapes and sizes. Here are a few that you can still spot today:
Water voles are keystone species in Britain
Earthworms: Often overlooked, earthworms are essential soil engineers. They enhance soil structure, support nutrient cycling and water filtration, all of which benefits plants and other organisms that rely on healthy soils.
Badgers: Badgers are ecosystem engineers through their burrowing behaviour. The abandoned burrows they leave behind become homes for other animals, like rabbits, otters and foxes. Furthermore, they’re burrowing and eating behaviour helps to decompose leaf litter whilst dispersing seeds through their dung.
Water voles: Water voles are considered ecosystem engineers due to their remarkable impact on the habitats they inhabit, particularly riparian (water-edge) environments. These small, semi-aquatic rodents create burrows in the banks which creates habitat for other species, firms up the river banks and can lead to pond creation.
Red Deer: Weighing in at up to 180kg, these majestic animals play a significant role in shaping woodlands through their browsing habits. They influence plant growth and regeneration, impacting the composition of forest ecosystems. When the population size is at an appropriate level, their browsing and wallowing can create & maintain open areas, like glades, within woodlands which provides habitat for a large array of insects and smaller mammals.
Missing keystone species from Britain
Sadly due to hunting & habitat loss, there are also several keystone species missing from our Isles whose absence is having a detrimental effect on our ecosystems. For example:
European Lynx are bred in captivity in Britain and efforts are being made to release them into the wild.
European Bison have been reintroduced in captivity to Kent after 11,000 years of absence!
Grey Wolves: As apex predators, wolves have a significant impact on controlling herbivore populations. Their presence can help regulate deer numbers, preventing overgrazing and promoting healthier vegetation growth, like woodland regeneration.
Beavers: Although beavers are now being reintroduced across Britain following years of activism, their activities as "ecosystem engineers" are still missing from many British waterways. Beavers create wetlands, improve water quality, reduce floding and enhance biodiversity.
European Lynx: Lynx roamed Britain’s isles up until 1000 years ago when they were hunted to extinction. Fortunately Lynx survived in Scandinavia and Russia and are now making a come back across Germany, Switzerland & France. These carnivores are efficient hunters of ungulates (hooved animals) and would help control burgeoning deer populations, preventing overgrazing and supporting woodland regeneration. Lynx are smaller predators than wolves and are a more likely candidate for reintroduction in Britain.
Wild Boar: Wild boar were once abundant across Britain. For a long period they were absent from our isles, but after some escaped from captivity, we have a small population of around 4,000 boar in the wild. Boars influence vegetation through their feeding habits and rootling behaviour. This overturning of the soils provides a foothold for many other species of flora and fauna to flourish.
Aurochs: An extinct wild ancestor of domestic cattle, aurochs played a role in shaping landscapes through their grazing and trampling activities. Rewilders now use rare-breed cattle which are closely related to aurochs, like English Longhorn Cattle, to replicate the ecosystem function these species provided.
European Bison: Bison roamed Britain’s landscape until about 11,000 years ago and have been absent until they were reintroduced into captivity in Kent. Bison are large scale ecosystem engineers, whose grazing keeps grasses and scrub from overtaking an area, and their browsing of tree’s bark can kill off larger trees and creates clearings within woodlands. This disturbance is crucial in keeping ecosystems vibrant and diverse.
Keystone Species Reintroduction Success Stories
Rewilding often advocates for the introduction of keystone species because their behaviour can create a more balanced ecosystem which is able to thrive with less human management. This effect is sometimes known as a trophic cascade, which is a theory which explains the knock on effect that the interactions between predators and prey can have on the complexity and structure of the ecological system and ecosystem processes. Lets dive into some species re-introduction success stories:
A wolf in Yellowstone National park, USA
Grey Wolves in Yellowstone National Park, USA: One of the most famous examples, the reintroduction of grey wolves in 1995 had cascading effects throughout the Yellowstone ecosystem. Wolves controlled elk populations, which led to less grazing pressure on vegetation. As a result, plants like willow recovered on river banks, which in turn benefited beavers, songbirds, and even fish populations that relied on healthier stream ecosystems. Carcasses left by the wolves also provided necessary food for a range of scavengers including cougars & wolverines. Beyond reducing the population size of grazing animals, wolves can also change their behaviour, forcing grazers to move more frequently and avoid open areas. This limits over-grazing and allows saplings to grow into fully fledged trees.
European Beaver in the River Otter, Devon: In recent years, there have been an abundance of beaver trials across the British Isles, holding these wonderful creatures in captivity across stretches of river. These trials have been tremendously successful and have consistently demonstrated that beavers’ dam-building behaviour has a profound positive impact on reducing flooding risk downstream of their habitat, decreasing fire & drought risk, improving water quality, increasing the number of fish in the river (yes Beavers are herbivores and DON’T EAT FISH), whilst boosting biodiversity of a number of species like kingfishers and otters. One of the most exciting beaver experiments is taking place in the River Otter in Devon. In 2014, beavers were discovered on the river and had arrived either through an escape from an enclosure or a non-authorised release. Fortunately, instead of removing the beavers, DEFRA decided to run a wild beaver experiment, recording the impact that these creatures had on the ecosystem and landscape. The results have been incredible and have demonstrated (unsurprisingly perhaps) that beavers in the wild benefit the ecosystem even more profoundly than beavers in captivity. Since their discovery, the river Otter has seen a drop in the amount of chemicals, like nitrates and phosphates, biodiversity has increased and flooding downstream has reduced. The beavers have already travelled 12 miles along the river and are expected to continue their expansion across our Isles. With just 14% of the UK’s rivers deemed in good ecological health and flooding expected to increase as a result of climate change, we should be doing everything we can to help beavers populate our river systems.
European Bison in the Carpathian Mountains, Romania:
European bison holds the status as a keystone species due to its significant ecological role in shaping the environment where it lives. Besides consuming substantial quantities of grass and foraging on shrubs, these bison exert a profound influence on the landscape. They alter the vegetation by stripping tree bark, breaking through dense undergrowth, and creating exposed patches of soil through their wallowing behaviour, thereby facilitating pioneer plants to flourish and even forming small ponds after heavy rainfall. Furthermore, bison contribute to the dispersion of nutrients and seeds throughout their habitat via their dung, spreading more than 200 plant species (1). This activity promotes floral diversity and provides crucial support for pollinators. Breeding birds make use of bison winter fur for nesting material, while magpies trail the bison herd to prey on ticks and other parasites. These benefits have been recorded following the reintroduction of Bison in the Carpathian mountains, where after 200 years of absence, their re-release is helping to positively influence the landscape and improve the dangerously low genetic diversity of this endangered species.White-Tailed Eagles, West Coast Scotland: The reintroduction of white-tailed eagles, a large bird of prey, has had positive effects on the Scottish coastal ecosystems. Their presence has led to reduced numbers of seabirds, such as gulls, which has improved the survival rates of ground-nesting birds like terns and waders. Additionally, white-tailed eagles contribute to nutrient cycling through their feeding habits.
What Happens Without Keystone Species?
Without keystone species, ecosystems get out of whack. Too many plant-eating animals, not enough plants. Habitats get worn out and out of balance, resulting in a loss of species diversity. This is very much the case in Britain right now, where the lack of predators like wolves, lynx and wild cats have led to a huge increase in the number of deer. These deer over-graze our woodlands and fields, stopping the regeneration of new trees and scrub. Fortunately we have now started to reintroduce beavers back into Britain and some have managed to escape into the wild (arguably with a helping hand). But whilst this is a big victory, we should be looking far beyond just beavers, but to lynx, wild cats & even wolves to create a healthier and more balanced Britain!
Its not only predators and beavers that are missing from our landscapes, sadly some species can’t be reintroduced to Britain at this point, either because they’ve gone extinct, or because the laws of the land prohibit their re-introduction. In these cases, rewilders look to proxy rare-breed species which can fulfil a similar ecosystem role in its place. For example, using Tamworth pigs instead of Wild Boar, or longhorn cattle instead of aurochs, or Exmoor ponies over Wild Horses. In the absence of these free-roaming grazers and browsers, vegetation would relatively quickly succeed from grassland into scrubland and then eventually into closed canopy forest. On the face of it, a closed canopy forest sounds like a positive thing, but counterintuitively mature woodland that isn’t regularly disturbed by the likes of bison, long-horn cattle and deer can be relatively poor for biodiversity. The most diverse ecosystems are those that are constantly changing over time in a constant tug of war between flora and fauna. This is why rewilders advocate for species introductions, because without a balanced set of characters each fulfilling their own ecosystem roll, the system will unbalance in one direction and eventually reach stasis.
Conclusion
We know from our own lives that balance is central to good health, and ecosystems are no exception. But over thousands of years, humans have interrupted that delicate balance by removing native species from our landscapes. Rewilding is about re-establishing that balance to create healthier and more resilient ecosystems which will support the many services we receive from nature, like flooding reduction, crop pollination, water filtration, soil health and air purification. Without these services, organised human civilisation will become much harder to sustain, yet we continue to take these invaluable services for granted. Its time to rewild our country and bring back ecosystem balance in order protect these services upon which we so fundamentally rely.
Sources
1 - Rewilding Europe