Why Give A DAMn? – Biodiversity

Posted In: Education


Keystone Arch

Back in 1998 when I first learned that beavers are critical for biodiversity I was amazed. I was immediately hooked by the realization that if we learned to coexist with beavers we would be supporting a myriad of other species at the same time. How cool is that?! Rather than just helping one species, there was a multiplier effect. Coexisting with one species, saved many!

So exactly how do beavers create biodiversity? To understand the answer to that important question let’s take a trip back in time.

Since the last ice age approximately 10,000 years ago, it is estimated that 60 to 400 million beavers were spread across North America cutting trees and building dams. Over all that time countless species evolved through natural selection to take advantage of the ecological niches beavers created. Due to the myriad of species across the continent that began to rely on beaver created habitats, beavers became a Keystone species necessary for supporting biodiversity in North America.

When beavers open the forest canopy by damming streams and cutting down trees they create new ecological niches and ecotone habitats where various species thrive. These ecotone and mosaic habitats, are necessary for many declining species such as turtles, bats, grouse, and salmon. According to the EPA in 2018 more than one third of our threatened and endangered species live only in wetlands, and nearly half use wetlands at some point in their lives.

Killing trees in and around a beaver pond may appear destructive, but these dead trees create critical habitats for honeybees, wood ducks, swallows, herons, and others. The loss of these trees also allow grasses, sedges, bushes and saplings to grow on the perimeter of the pond. These plants provide habitat variety, food and cover for foraging animals.

Since beavers prefer not to travel far from the water, eventually they exhaust their woody food supply. When this happens they move to a new location. Then the old dams develop leaks and the ponds drain out. The rich pond sediment gives rise to a lush, grassy meadow. Eventually successional shrubs and trees become established, and after 10 -15 years there is enough woody vegetation to attract new beavers. Then the beaver cycle repeats itself. This natural beaver cycle creates a series of successional habitats that support biodiversity.

While opening the tree canopy creates valuable land-based habitats, it also allows sunlight reach the water where it triggers an explosion of aquatic biological activity. Algae and aquatic plants grow in the sun-drenched, nutrient rich water. This organic material supports microscopic organisms, which are eaten by a variety of invertebrates. These become food for fish, birds and mammals. An entire food chain is created which is why beaver ponds become magnets for wildlife.

As discussed in our last blog, salmon and trout evolved to take advantage of the food, cover, thermal refuges, woody debris, and expanded edge habitats provided by beaver ponds. Once thought of as detrimental to salmon, scientific research has increasingly shown that beaver dams are critical to healthy salmon populations. Salmon are also a Keystone species. This dramatizes the biodiversity multiplier effect of beavers. It is postulated that simply having more beaver dams on our streams could lead to the delisting of endangered and threatened salmon. Isn’t that amazing?!

All this aquatic and terrestrial biodiversity makes beavers a prototypical Keystone species. They truly are Nature’s ecosystem engineers. Whenever conflicts with beavers arise, please educate and promote efforts to co-exist with beavers. By doing this you can personally help to protect and promote North America’s biodiversity.

Our “Beaver Primer” downloadable pdf document was posted on our website yesterday. It briefly describes the history, ecological effects and management of beavers. Please download and share it.

If you have a question, comment or would like to share your own story please Contact Us or go to our Beaver Institute FB page.

Posted 2-28-18