It seems to me that anglers, especially trout and salmon anglers, should be clamouring to get beavers into their rivers. And where there are already beavers, they should be doing all they can to support their presence. The fact that they’re not may speak of the crippling state of nature disconnect even amongst those that spend their leisure time in wild places.
Aside from having clean water and food (both of which beaver can help with), the primary factor in determining how many salmon smolts a river can send to sea, or for that matter how many trout it can support, is the amount of suitable habitat. The more suitable habitat, the more fish.
Beaver are expert habitat creators. People who work in river restoration do engineering work on rivers to turn straight into winding, create clean gravel, fell trees to pinch flows, pack brash against banks to reduce erosion. Lots of tasks that beaver will also do – and for free – with no need for carbon-emitting engines or plastics or purchased materials, or noisy chainsaws. Whats more they’ll do it while we sleep!
If you are an angler and anti-beaver, I’d like to ask you to ponder and research these four points:
- Beaver and salmon have tens of thousands of years of living in close proximity under their evolutionary belts. What leads you to believe they’re going to fall out now?
- If beaver negatively affected Atlantic salmon numbers would we find them on seven of Norway’s top ten salmon rivers, or Russia’s incredibly productive Ponoi?
- The evidence for beaver creating habitat is undeniable. Would you really wish there to be less suitable living area for fish when we have the opportunity to continually increase it?
- How would you propose we approach the questions of skilled labour, time scale and funding for much needed river restoration projects on the scale that beaver are capable of?
The Benefits Beavers Bring
Here’s my attempt to list and then explain the fish benefits that beaver presence can bring to a watershed:
- increased insect abundance (ie fish food), both aquatic and terrestrial
- cleaner water
- reduced negative effects during flood events
- reduced negative effects during droughts
- increased refuge sites where fish can avoid predation and high flow events
- more available habitat for fish in all stages of their life cycle
- woody structure in the water removing ‘fines’ from the flow
- greater overall water retention
- more dappled shade (the best kind)
To expand on these points one at a time:
1. Increased Insect Abundance
Aquatic invertebrates need somewhere to live and something to eat. Wood in the river can provide both these requirements. The more wood, the more inverts; the more inverts, the more fish food.
2. Cleaner Water
The process of water passing through a dam – and beaver dams are leaky – filters the water, cleaning it.
3. Reduced negative effects during flood events
The state of the river and the surrounding land will dictate how damaging or dramatic a flood event will be. The worst flood events happen in places where the tributaries to the main stem and upper catchment are heavily modified by man.
The major factors are:
- interruptions to flow,
- sinuation of the river course,
- infiltration rate of the soil
- and access to energy releasing sites like natural floodplains or alternate channels.
The worst scenario is a river which has been ‘tidied up’ and had the fallen trees pulled out (no interruptions to flow); has been canalised (straightened) by man (no sinuation); is surrounded by fields with high density livestock numbers or commercial forestry (poor infiltration); and is unable to connect to its floodplain. This scenario dumps all the water into the main stem at once and the river is very likely to burst its banks.
The best scenario is a river where there are lots of trees and other interruptions in the water; where there are many bends in the river – effectively lengthening it; where the surrounding land is old growth forest; and the floodplain has never been tampered with.
Beaver can positively affect three of these factors. Their dams and felled trees provide interruptions and their engineering will often result in a longer, more sinuous river course with more bends. Braided channels, often created by water finding its way around beaver dam are a flood energy release valve. They also happen to be superb juvenile fish nursery areas and bring more potential spawning sites to the river.
One study with good baseline data showed that the presence of beavers slowed the flow by 30% during floods. That means fewer parr and fry will be killed, less erosion and less siltation.
4. Reduced negative effects during droughts
Because the activity of beaver raises the water table this means there will be more water for longer. When there have been weeks of no rain those extra flooded areas and soaked ground can gradually release their load and keep more habitat accessible within a river. This is especially important during the summer months and also during months when trout and salmon eggs are laid in the gravel, often in shallow areas, and spend months there before hatching.
5. Increased refuge sites
Trees and tree roots are the gold standard in fish hidey holes. Without roots or submerged trees fish like trout and salmon will use rocks, boulders, weed or whatever they can find. Sawbill ducks can easily chase a parr around a rock and get it but that’s a lot harder amongst branches or roots.
6. More available habitat
Beaver engineering over time creates a longer river with more water in it. Their efforts will turn a straight channel into a meandering course. As we all know the shortest distance is a straight line, so a weaving wandering river has greater length and also a greater variety of pools and riffles.
During different stages of their life cycle salmonids need different habitat types. Shallow clean gravel to be born into, thin riffle 0-20cm for fry, 20-40cm for parr, the same and deeper riffles for smolts, and deeper holding water for adult fish. This extra habitat means the river can have a higher fish carrying capacity; there is simply more river.
7. Removing ‘fines’ from the flow
‘Fines’ or fine sediment are a big and increasing problem for salmonid survival on many of our rivers. There are more fines in rivers now due to grazing and trampling of river banks, mostly by livestock. The grazing chomps the little trees before they – and crucially their root systems – can become established and the trampling exacerbates erosion.
These small particles, when they settle into gravel, can choke the oxygen out of a redd (salmon/trout nest) and kill the eggs. Fines also cover up suitable spawning habitat meaning would-be spawners have to look elsewhere for a suitable site to lay their eggs. Although a few aquatic invertebrate species do well in fine sediment most need clean gravel with a flow of oxygenated water through it.
Beaver activity, both with dams and woody structure, provides a place for the water to slow down enough that the fines will drop out of the flow and collect – usually against the bank – re-enforcing it and reducing the prospect of future erosion. The effect is a sorting of sediment size, where the fines are against the bank and gradually coarser material is found further out, just the way the fish like it.
You might think beaver eat more and bigger trees than sheep and it’s those big trees that benefit the river most with their roots, insect life and shade. That’s true, but after a large tree is felled it will take several decades for its roots to degrade away, that is if it dies at all.
Many stumps will coppice after a beaver has felled it, and coppicing trees actually increases their life span. Several decades is plenty of time for a new tree to replace it, but only if it can avoid the grazers.
The other aspect to this is the choice of tree. Sheep will eat almost any small tree with the exception of yew and spruce. Beaver in the UK often eat willow.
Willow is an incredibly regenerative tree. Felling a willow means more willow, not less. Their stumps will coppice, and their felled stems, if there’s any connection to the stump, will often shoot anew. Any twig that’s finger thick or more and manages to pierce the ground where felled will often grow as well.
The other effect of submerged or partially submerged trees being in the channel is a ‘pinching’ effect on the channel. If you imagine felling two trees on opposite banks into a river the flow will make their crowns point downstream, so they’re at an angle of about 45 degrees to the bank. The flow becomes pinched between the two crowns and the effect is to clean the river bed, freeing it from fines and gradually deepening it. Instead of having a uniform flow and uniform depth across the width of the river you now have slow shallower flow near the banks, where the fines can collect – keeping them out of the critical spawning sites – and swifter flows in the middle.
Biodiversity is dependent upon variety – the variety of depths and flow speeds in rivers with beaver are far greater than those where fallen trees are removed.
8. Greater overall water retention
Greater water retention means more water is available. As previously described beaver raise the water table. This is not only an advantage during drought but also means more complexity of habitat. The less drastic fluctuations in water level decreases erosion and all the other the sorts of damage to habitats and stability that ‘flashy’ rivers suffer.
9. Dappled shade
Dappled shade is what you get under some native trees and especially under coppiced trees. Lots of trees react to being felled by coppicing. The dappled effect gives some areas of warmer and some areas of cooler water. So the fish can choose where they’d like to be.
All this can be summed up by saying that where there are beavers, there’s: more food, more river, less danger and as a result more fish and bigger fish. What’s not to like?
Even a cursory look at the areas of the world with the greatest salmon, sea trout and steelhead numbers reveals a map of beaver presence. Alaska, Canada, the Kola Peninsula in Russia, Kamchatka to name a few.
More wild Atlantic salmon return to Norway than any other country. Seven of the top 10 salmon rivers in Norway all have beaver. Six of those rivers are at capacity.
More facts about beavers
Time to dispel another fear. Beaver are territorial, one family won’t permit another family within a 2-5 mile stretch of river. So the image of beavers being everywhere in great densities isn’t a realistic one. A river at capacity is a river with a family every few miles, within the suitable habitat. Not all riverside is suitable beaver habitat.
The reasons often given by anglers for disliking beaver include blockage of passage for migrating fish, burrowing into banks which can cause them to collapse and tree loss or gnawing being unsightly.
Several studies have been done on whether beaver dams block fish passage. The broad stroke return is that beaver dams are leaky and the fish can get through them. If pressed, salmon can jump pretty well (their Latin name salar means ‘leaper’).
On the larger river systems, where the flow is too strong for their lodges to hold out, beaver will burrow into banks. Beaver burrowing can indeed cause banks to collapse and fines to be deposited into the water. The mitigation for this is the engineering the beaver do to capture that sediment.
Deciphering whether the net effect is more sediment or less is largely dictated by how much the beaver are left to do their own thing. If their engineering efforts are undone by man, so are the sediment capture sites removed. If they are regularly shot, well, nature hates a vacuum, and a colonising two-year-old male kit will look to make a new home for himself rather than use his predecessors. Obviously that means more holes and more sediment.
Tree loss is an undeniable result of beaver presence, and it may occur to trees we care about. I love trees, but I also have an appreciation for dead wood, it’s just as wonderful as live wood. Dead wood can house far more insects than live wood. In these times of low insect numbers the more dead wood the better. Not only does that mean more food for fish, but also for birds and myriad other creatures.
Beavers and climate change
In an effort to address the upcoming demands of climate change having a higher water table will be very useful. Thank you beaver. Not only to keep more water in the rivers for longer, as mentioned, but perhaps more importantly in wetland creation.
We all know that minimising atmospheric C02 is critical to reduce the potential negative effects of climate change. Wetlands are very effective carbon sinks where atmospheric carbon can be stored for as long as the wetland remains wet. Thank you beaver.
Beavers are a part of nature
There is an image that lingers with many Brits and comes from Victorian times. It’s an image of total dominion over nature with humans at the centre. All blades of grass must be in their proper place, the chosen animals and plants present whether they belong or not (peacocks on the lawns, western red cedars in the arboretum), all so called ‘vermin’ disposed of. It’s the anthropocentric view. It seems to me to deny the best of what nature is. It’s a desperate expression of a group of people with big egos, little empathy and an identity based on domination. It’s a long way from being ‘tuned in’ to nature’s way.
Beaver belong here in Scotland. Beaver are part of the natural system. The same system that includes salmon and trout, and should – were it not for our wilful self isolation – include us. You can not manage a population of one species without affecting others, and upsetting the balance. As the pioneering Scottish conservationist John Muir wrote: “When we try to pick out anything by itself, we find it hitched to everything else in the Universe.”
It’s time to change the way we think about the natural world and our role in it. It’s not just our earth and it’s not just to be used and abused to meet our human whims. Nor is it an extensive garden that needs to be manicured half to death. It’s a place we share.
We teach our toddlers to share with other kids, but we seem to neglect the lessons on sharing with other life forms. I believe that the greatest joy in experiencing the natural world is in embracing and observing what it wants to do. Lawns and straight lines of trees seem terribly limited when compared to the diversity and intrigue of truly wild land (a very rare thing in the UK).
There’s no doubt that there’s intelligence in the natural process. Simple plant succession shows us that nature has a plan, it’s going somewhere. It starts with a single colonising species and climaxes with old growth woodland supporting thousands of creatures.
Must we arrogant humans keep thinking we know best? It’s such a common story – we stick our noses in, mess it up and then wonder why there’s no longer a chorus of birds, just a duet. Let us realise that we are part of the natural world, not separate from it.
Feeling separate from nature keeps us in a state of suffering. We have to continually fight nature to make it look or be the way we want it to be. This is not a recipe for a peaceful life.
What is it you want from the outdoor world you live in?
Would you like it all to conform to your will? Should it appear ordered and neat, manicured and controlled, or are you happy to allow nature to do its own thing?
Judgement is separation, and separation causes suffering. Saying this species is a weed or vermin, and that species is favourable or good, demonstrates our separation from nature. Separation from nature, and each other, may well be our present day’s greatest ill.