Ecosystem engineer

Beaver dams hold back water and push it out onto the floodplain increasing the resistance of water as it passes downstream and releasing water more slowly. This process slows and stores water, reducing peak flows during heavy rainfall events, contributing to the reduced risk of flooding to communities downstream.

The slowing and storing of water and the creation of complex wetland habitat can significantly reduce the peak of the flood, even in high flow or flood events. Even in saturated environments, beaver dams can attenuate flow between 30 and 60% as water is held back. The presence of beavers may however, depending on location, result in localised undesirable flooding due to damming and infrastructure may require intervention because of burrowing. 

Beavers can significantly change the environment to meet their ecological needs. Their activities can help restore natural processes and reconnect rivers with their floodplains. The habitats created by beavers are dynamic and the space available for the river to move will affect how much restoration can happen. This change to the river landscape, through the activity of beavers, can re-connect the river to its floodplain, increase the amount of bends in the river and create different habitats in the river and next to the river. 

Beaver dams are good at filtering sediments and pollutants (such as nitrates and phosphates), which can lead to improved water quality downstream. This could be especially beneficial in agricultural landscapes by helping to mitigate the negative impacts of soil erosion and pollution from excessive fertiliser use (although it is still essential to tackle pollution at source).

Typical beaver activities include felling trees and building dams. Overall, the evidence suggests that the complex habitats created by beavers produce corresponding increases in temperature complexity. Their activities have an overall buffering effect on water temperature, increasing the potential availability of thermal refuges. Beavers can help restore flow as the habitats they create attenuate water and slow the flow helping to maintain a steady water supply during dry periods. This also allows water to go into the ground, raising the water table and recharging groundwater.

The impact of climate change is already resulting in more frequent and intense flood events, wildfires, and severe droughts. There is clear evidence that beavers can help to mitigate these effects and create catchments that are more resilient to a changing climate.

Beavers can play a significant role in climate change resilience. The creation of complex wetland habitats, slowing and storing of both surface and ground water, provides the resilience to mitigate the effects of extreme environmental pressures such as drought, flood, wildlife and species loss. Beaver wetlands can store significant amounts of carbon in sediments and vegetation, however they also release methane in certain conditions so the picture is complex and can vary from site to site and across time. Beaver activity can also buffer temperature extremes and, in some circumstances, create and maintain cold water refuges for aquatic species

Through their engineering activities, beavers create complex wetland habitats that provide food, shelter, and breeding habitat for a diverse array of wildlife, including fish, amphibians, insects, birds, and mammals. Their activities enhance water quality, increase drought resilience, and establish wildlife corridors, all of which further supports biodiversity. 

These ponds, marshes and wet woodlands support significant increases in biodiversity, benefiting many species including fish, amphibians, reptiles, birds and mammals. The felling of trees can also have a positive impact through creating opportunities for other species to colonise and thrive. Woody material and standing deadwood are important habitats for many other species. Beavers' ability to transform landscapes and create diverse habitats makes them essential for species recovery and ecosystem restoration efforts.

The interaction between fish and beavers is complex. The creation of varied river and wetland habitats by beaver provides benefits to water quality and aquatic species, especially where rivers have space to behave naturally in their floodplain. Potential benefits for fish populations include improved areas for spawning, increased food resources and safety from predation. However, some fish species are likely to benefit more than others risk and benefits will depend vary over time, location and other things going on in a catchment. There may be other barriers in the river, or the river may not be natural and have re-enforced banks.  It is important to focus on restoration opportunities and to consider fish species whenever carrying out management work, avoiding important spawning areas. Beaver dams may limit fish passage in certain conditions, for example when the river is low. Beaver dams vary in size and how long they last and not all dams will be a problem. Where possible river buffers should be created and side channels allowed to form around dams. 

Beavers are herbivorous, feeding on leaves, twigs, bark and aquatic plants. They feed on a variety of materials and have often eat willow, birch, alder, aspen, ash, poplar and hazel, what they eat also depends on what is available. Most native species regenerate naturally, creating more diverse woodlands and benefiting biodiversity and tree protection may be needed where there are cattle or deer present. Where trees do die, from beaver felling and flooding, the deadwood habitat is important for many species. Beaver activity can also raise water levels in woodlands creating or restoring wet woodland habitat if tree species that can tolerate this are present. Tree planting where beavers are present should use coppicing, native, water tolerant species close to the water’s edge. It is also advised to overplant and accept that some trees will be felled by beavers.