THE HUMAN TOLL ON NATURE
Throughout history, human activities have altered the natural world in many ways. We have transformed woodlands into farmland, wetlands into grazing pastures, and rivers into canals. And this process of land management has led to the extinction of thousands of species1. However, luckily, many of these belong to the category of ‘local extinctions’, meaning the species disappears from a specific area but still exists elsewhere.
What makes these local extinctions so unique is that they can be reversed, and this is the foundation of the modern ‘rewilding’ movement, which aims to bring species back to the environments where they have historically thrived.
Here in the UK, one of the most notable species in the rewilding effort is the beaver, which is making a slow but steady return after being absent for 400 years2. But why are these particular species so important?
ENVIRONMENTAL ENGINEERS
Beavers are known as a ‘keystone species’. This means that they have a disproportionately large impact on their environment in comparison to their size3-4. As a result, reintroducing beavers to the landscape can set off a chain of positive changes which help to re-establish the natural functionality of an area.
Beaver dams, for example, create wetlands that not only help prevent flooding downstream but also serve as thriving habitats for many other species. Shallow ponds formed by these dams provide a safe space for fish, frogs, newts, dragonflies, and other insects. These ponds protect the species from larger aquatic species, allowing them to mature and eventually become prey for birds and bats, thus supporting the wider food webs.
Moreover, as beavers fell trees to build their homes, they open up spaces in the forest canopy, allowing younger trees to grow. This results in a healthier and more diverse woodland ecosystem as there is a greater diversity in tree ages. However, despite ecologists having long observed all of this, evidence of how beavers help other species is still scarce in the scientific literature.
BEAVERS AND BATS?
To fill this gap, a team of scientists set out to study how bats might benefit from the return of beavers.
The research took place between June and September 2022, and it started with the team identifying 12 suitable sites. These where a mix of wetland and woodland areas in England and Wales where beavers had been present for at least 6 months. Why 6 months? Because this gave beavers enough time to make a noticeable impact on the ecosystem.
Each site was then given a twin: a nearby area, maybe a bit up or down river, whose only difference was its lack of beavers. Gathering data in such twin sites would allow scientists to make comparisons between each pair to ensure that any difference can be attributed to the effect of the beavers alone.
Now that they had their study areas, the team made the most of the summer, the period of peak bat activity, They set up two bat detectors at each of the 24 sites, leaving them in place for seven nights at a time to recorded bat activity from 30 minutes before sunset to 30 minutes after sunrise. All the data was then processed using a software called BatClassify, which not only determined how active bats were on each site but also classified the calls into different species groups.
THE BATOMETER
By the end of the study, the researchers had recorded a whopping 144,548 bat “passes,” with each pass representing a distinct bat call. While the exact number of bats present couldn’t be determined from these calls alone, more bat passes suggest higher activity and, by extension, a healthy environment for bats.
The results were clear: seven out of the eight bat species identified were significantly more active in areas where beavers had been reintroduced, especially in wetlands. Two species, Common Pipistrelle and Soprano Pipistrelle, were even found to be more active in woodlands where beavers had made their home. This indicates that beavers can positively impact bat populations, which is great news for conservation efforts.
What’s more, some bat species showed astonishing increases in activity. The Barbastelle, a rare species in the UK, was four times more active in beaver-influenced wetlands. The Long-eared bat, including the endangered Grey Long-eared bat, was three times more active. These findings suggest that reintroducing beavers to areas where these bat populations have declined could help support their recovery.
HOW WE CAN HELP
Since their first reintroduction in 2009, beaver populations have been slowly rising in the UK. However, their return is not always welcomed. Some people oppose beavers due to the beliefs about their behavior, such as the belief that they eat fish, damage trees, or cause flooding. While these affirmations are easy to disprove, many people aren’t yet willing to coexist with them, and their opposition slows down conservation efforts 5.
But there are ways to help. Educating your local community, starting with your family, is something anyone can do. You can also sign relevant petitions and, if you have the necessary skills, volunteer for the Beaver Trust. Their website and events are also great for learning more about these amazing animals. Just remember: beavers can be the key to unlocking a healthy ecosystem; all they need is a chance to turn things around.
Article written by Maria Giulia Checchi
Primary paper:
Hooker, J. et al. (2024) ‘Re-establishing historic ecosystem links through targeted species reintroduction: Beaver-mediated wetlands support increased bat activity’, Science of The Total Environment, 951, p. 175661. doi:10.1016/j.scitotenv.2024.175661.
Other references:
Turvey, S.T. and Crees, J.J. (2019) ‘Extinction in the anthropocene’, Current Biology, 29(19). doi:10.1016/j.cub.2019.07.040.
Ward, K. and Prior, J. (2020) ‘The reintroduction of Beavers to Scotland: Rewilding, biopolitics, and the affordance of non-human autonomy’, Conservation and Society, 18(2), p. 103. doi:10.4103/cs.cs_19_63.
Law, A. et al. (2017) ‘Using ecosystem engineers as tools in habitat restoration and rewilding: Beaver and wetlands’, Science of The Total Environment, 605–606, pp. 1021–1030. doi:10.1016/j.scitotenv.2017.06.173.
Brazier, R.E. et al. (2020) ‘Beaver: Nature’s ecosystem engineers’, WIREs Water, 8(1). doi:10.1002/wat2.1494.
Auster, R.E., Puttock, A. and Brazier, R. (2019) ‘Unravelling perceptions of Eurasian beaver reintroduction in Great Britain’, Area, 52(2), pp. 364–375. doi:10.1111/area.12576.
