The Architect, the Builder, the Engineer, and the North American Beaver.

What if I told you that in the middle of the forest, in the deepest quarters of the woods, exists one of the greatest architects, builders, and construction workers of all time. Would you believe me?

No, no, I am not talking about Antoni Gaudí. I am talking about the Canadian Icon – the one and only – the North American Beaver, the most influential rodent of our times.   

I know, I know… a rodent… influential? If you are a bit skeptical of the idea that any rodent could be influential, you probably aren’t alone. But over the next few minutes, you will understand why one particular rodent is not only Canada’s national animal, but also, a key player in the world as we know it. 

Fur the past and fur the future 

When the Europeans first arrived in North America, beavers were everywhere – and I mean everywhere. Basically, anywhere that wasn’t too dry or too steep likely had beavers living there. In fact, it has been estimated that between 60 to 400 million beavers roamed across the northern half of the continent, occupying most streams and headwaters. That’s a LOT of beavers. To put that into perspective, there are just over 300 million humans living in the United States of America, meaning that beaver numbers in the 1400s could have been greater than there are Americans today.

Given the popularity of beaver fur hats at the time, North American beavers became a very valuable resource to the colonizers. At the same time, many Indigenous peoples across the land also shared a connection and held value to the semi-aquatic rodent. Unlike the Europeans though, the Indigenous peoples saw beyond the beaver’s waterproof fur pelts and would also take advantage of the special oils they secrete, called castoreum, and use the meat for food. The Indigenous trappers also shared a deep connection and respect with the brown mammal. Because of this, beaver trapping occurred for centuries without any risk of extinction.

On the other hand, the Europeans were more focused on the value of the beaver that the rodent nearly went extinct by the 20^th century due to greedy over trapping. Luckily, though, the beaver did persist. This was mainly a consequence of fur hats going out of style by the 1900s, taking the need for extensive trapping away.  

Nonetheless, the beaver became a staple of the North American economy and acted as a symbol for the people living here. This connection persists today, with a clear appreciation for the beaver and its role over time. Although, while humans have a connection to the beaver economically and culturally – the beaver’s place on our planet extends so much farther.  

Dams. Lodges. Canals. The Beaver and the Ecosystem Engineer 

Other than humans, the beaver is the only mammal in North America capable of cutting down fully grown trees for building materials. Beavers have been observed cutting down massive trees and can chew through an 8-foot (2.4m) tall tree in 5 minutes! They achieve this with their specialized teeth and strong jaw muscles that are optimized for gnawing through difficult and hard material, like the wood of a tree. Interestingly, to best gnaw through trees, beaver teeth have evolved to be ever-growing and are made up of extremely strong materials that are also self-sharpening. Specifically, their beautifully dark orange incisors (front teeth) have thick enamel on the front side that contains iron, making them strong and durable. While on the backside, the tooth is made of soft dentine that wears away as they gnaw, helping the teeth stay sharp and ready to cut down more trees!  

But why do beavers cut down trees?  

Well – it’s because they are builders! Using the trees they cut and rocks from the ground as building materials, and mud as cement, beavers build dams and lodges. The rodent’s building is unmatched, having built nearly 800m long dams that can be seen from space.  

They do this to improve the habitat for themselves, similar to how humans modify land for their own uses. By building dams, beavers slow the flow of water and sediments, creating nutrient-rich ponds that become beautiful wetlands. These wetlands are composed of different ponds, channels burrowed out by the beaver, and a lodge, or home, that is only accessible underwater. This intricate system allows beavers to maneuver and forage for food while staying safe from predators and keeping warm in the winter below the ice.  

All of this building and modifying of the land has led beavers to be called ecosystem engineers. This is because they totally disrupt and modify their ecosystem by flooding large areas across the landscape. It may sound like a problem, but this type of disturbance is actually very natural, and greatly benefits the natural world, as well as humans. In fact, beaver-modified wetlands become home to tremendous biodiversity of plants, fish, amphibians, mammals, and birds, while also acting as a barrier against flooding and wildfires. That is why beaver engineering is considered to be very helpful across most of the continent. But what happens when beavers end up in areas where they do not belong….?  

Beavers… beyond the tree line? 

With the help of climate change, the tundra – or subarctic – has greatly changed over the last century. Over the last decades, the arctic and the tundra have been continuously breaking new record highs in temperature and experiencing shortening winters. In fact, the arctic and tundra are warming up over 3 times faster than the global average. Consequently, shrubs have begun to take over the landscape and have greatly increased in size. This is known as the shrubification of the tundra and has led to the immigration of new species that have never lived in the tundra before – including the moose, the red fox, and our friend, the beaver.  

Beavers are of course ecosystem engineers, and the impact they have on, say, the boreal forest, is not the same as the impact they will have on the tundra. As an ecosystem historically unoccupied by beavers, this is of concern – especially for the people living there. Remote Indigenous communities who make use of their land are implicated by the potential impacts. Beaver damming may cause harm to fish populations downstream by blocking them from moving passed beaver constructions, while the beaver’s flooding may impact the community’s ability to travel across their land and hunt.  

On a more global scale, the presence of the beaver in the tundra is also of concern. This is because the tundra has a huge proportion of permafrost – a layer of soil that remains partly frozen throughout the year – that releases tons of greenhouse gases when thawed. As beavers flood the tundra, it increases the rate that the permafrost thaws, and consequently releases warming gases into the atmosphere. Beaver ponds also warm up the water downstream of their dams, potentially impacting the fragile ecosystems below, accustomed to colder waters for survival. Alternatively, this effect may actually improve the habitat for the fish and life living in the tundra, but at this point, the impacts of downstream water warming are still unknown.  

Overall, one thing is clear: beavers are critical to many ecosystems across the continent but have drastic effects across all. The impacts they may have on the subarctic are still unclear, but it is critical that conservation biologists, in close collaboration with Indigenous communities, take extra care to monitor and manage the newfound beavers in the North. Beavers contribute so much to the land and to humans, that it is critical that we do our part to repay them by finding solutions for living together in harmony.  

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Featured Image: Cartoon beaver gnawing on a stem. Created by Sarah del Buey.