In November 2018 there was a Paper 1 on the Algonquin Park in Canada where beavers and wolves coexist with First Nation (indigenous) Americans. One of the questions was about the potential for the reintroduction of beaver in the UK. This case study is inspired by that question and the news that beaver will be reintroduced into the UK and will be a protected species from 2022. The focus of the reintroduction is for the potential to improve (and rewild) British waterways.

 Teacher only box

This is a good opportunity to practice Paper 1 skills with a focus on Topic 2. The idea is to help students visualise and conceptualise ecological concepts with the addition of societal pressures.

Location of River Otter

The River Otter is located in the south-west region of the United Kingdom.

Eurasian Beaver (Castor fiber)^[2][3]
•Large animals – Around 1m long and 18kg
•Beavers are a native ‘keystone’ species
•They were hunted to extinction in Britain about 400 years ago
•Entirely herbivorous
•Fiercely territorial
•1 litter a year with 2-6 kits (average 3)
•Mainly nocturnal and semi-aquatic
•Live in burrows and lodges
•Build dams to create ponds if necessary 

The Reintroduction of Beavers

Beavers went extinct in the UK in the late 1700s due to hunting for their fur and castoreum (a smelly oil they produce).

The River Otter Trial was a five year trial reintroduction of Eurasian beavers that began in 2015 with a two family group of beavers. In 2019 ca. 13 territories were established.

In 2020 the government announced that the beavers could stay and in 2022 they would receive protected status in England (they already were allowed in Scotland after a trial there ended in 2014).

There are already (following escapes and unapproved re-introductions,an estimated 1000 beavers in Scotland and 500 in England).

Beavers as Ecosystem Engineers

In this video (length 9min 42 sec) from the BBC and David Attenborough we learn how the North American species of Beaver builds dams and channels to engineer their ecosystems and a look at their feeding behaviour. The video also shows a pair of musk rats living in the beaver lodge.

Beavers burrow and dig channels into the woodlands, they raise water levels with dam building and form wetlands and flood plains.

This results in a net increase in habitat heterogeneity.

Their feeding behaviour coppices trees which then regrow at their base, clearing the canopy and providing more sunlight to forest floor.

Beaver Reintroductions in the River Otter

In this video (about 5 min 40) we learn about the River Otter Beaver project and how the reintroduced beavers benefit the local habitats and local communities.

Important Habitats in River Otter Trial

The landuse in the River Otter catchment includes 50% improved grassland, 28% arable and horticulture and 5% urban and suburban land.

Due to the foraging habits of beavers, with 99.8% of feeding signs detected within 30 m of the banks of watercourses, scientists propose 30 m buffer zones along water courses. Buffer zones would be non-agricultural / farmed land which is able to rewild.

Action of Beavers on Watercourses

Beaver dams:

Beaver dams cause streams to cut into the river banks widening the channels as dams trap sediment and flood water helps recharge ground water.

Reduce the risk of flooding with a reduction in peak flow of water.

Attentuate average flood flows from extreme weather events by 60%

Grasses and reedbeds line the rivers providing a storm defence.

Nitrates and phosphates don't enter the water

In a study on the River Tamar, water downstream of beaver dams contained 3 times less sediment, 0.7 times less nitrogen and 5 times less phosphate.

Impact of Dam Building on Sediment Composition

This data comes from a study in Lithuania^[4] published in Wildlife Biology 2020(3) by D. Čiuldienė et. al. The results are expressed as the mean ± SE.

OC = Organic Carbon; N = Nitrogen; P = Phosphorous; MeHg = Methyl Mercury

Impact on Agriculture and Land Use

Elevated water levels can result in flooding of edges of floodplain fields.

This can reduce the access to heavy machinery.

Beavers occasionally make pathways through arable crops and fed on corn (maize) when close to watercourses.

Riverside footpaths may be flooded along with low lying rural roads.

Fallen trees may block paths.

Small riverside orchards saw some beaver feeding on both windfall apples and the trees.

Fish Biodiversity and Populations

Beavers create greater habitat diversity for fish.

Surveys by the University of Southampton found that total abundance in a beaver pool was 37% higher than other nearby areas with the highest total fish biomass and more trout than in either upstream or dowstream sites.

Shallow fast flowing areas created in areas where a beaver dam had washed away dhowed spawning in the loose clean gravel beds.

Minnow and lamprey numbers were higher.

Atlantic Salmon, European Bullhead and Brook Lamprey are all listed in Annex II of the Habitats Directive.

Atlantic Salmon and European Eels are a UK Biodiversity Action Plan Priority Species.

Brook Lamprey is also in Annex III of the Bern Convention.

European Eels are also covered by the European Eel Regulations.

In high flow periods, trout and salmon (which migrate from the sea to the rivers to spawn) were observed to jump beaver dams but in low flow conditions, the dams may be an obstacle to the fish migration.

Health of River

The Amber Project has found that 99% if UK rivers are fragmented by dams or other water barriers.

The Water Framework Directive 14% of UK rivers are in good ecological health. None of the rivers pass good chemical health standards and more than two thirds of the ground water bodies  are impacted due to over extraction and agricultural run offs.

The ecological status of the Lower Otter was classified as Poor in 2016 due to man-made barriers to fish.

Issues identified included elevated levels of phosphates and phytobenthos caused by poor soil management on arable farms and poor nutrient management from livestock and sewage discharge from waste-water treatment.

Effects on Vegetation and Canopy Structure

The area with beavers was surveyed using a drone in December 2016 and January 2018. The data shows canopy height and extent.

The results showed that the riparian (riverside) woodland, where beavers are foraging, had a structure significantly different from where they were absent. This included canopy gaps and greater light penetration.

Beavers Feed on Invasive Plant Species

Changes in Biodiversity

Following beaver reintroductions,

8 new species of birds

55 species of bryphytes increased in abundance

26 species of wetland beatle

41 species of aquatic invertebrates

Plant species richness 33% higher

Social and Community Factors

Public perception questionnaires found that in 2017 86% (n=2,741) and in 2019 90% (n=386) were supportive of beaver reintroduction. In the same surveys 75% and then 79% felt that the beavers should receive strong legal protection.

Engagement activities included talks, guided walks and school visits.

Willingness to pay studies showed that local residents would be willing-to-pay for a ‘typical’ beaver-watching experience on the river near to their village. From those who provided an answer to the question, the average value obtained per respondent was £7.74. Tourists had not been surveyed.

Local Business quote:

"I think any opportunity that affords itself to us and promotes the business we could potentially use that as a vehicle to do that. With the wildlife, whether that be beavers or otters, then we would seize that opportunity. So as far as we’re concerned, wildlife tourism is a growing market and fundamentally if the river and the environment here promotes something along those lines then that suits us."

A cost and benefit analysis showed that those who benefit from the reintroduction were not the same as those who bear the costs, e.g. the community who benefits from flood alleviation is not the same as the farmer whose agricultural land is impacted by the backlog of water behind the dam.

Ecological Fieldwork Methodology

Beavers are trapped, given a health check and tagged		Fish are caught using electrofishing, identifed and counted.
The river height is monitored.	Botanists identify species along transects.	The river flow is monitored using a flow guage.	Signs of feeding by beaver are recorded using GPS mapping.
Macroinvertebrates are sampled using kick sampling, identified and counted.