Beaver - Ecology


Text by Liz McKenzie and Photos by Richard Nelson


The Animal That Redesigned a Continent

There are two species of animals that profoundly changed the ecological face of North America before Europeans arrived: First, Native Americans with the controlled use of fire, and second, beavers with the controlled use of water.


In pre-colonial times, beavers were found over most of the North American continent. An essential fact of beaver behavior is that they dam streams to raise the water level and make ponds. These water catchments provide excellent habitat for fish and turtles, frogs and toads, ducks and geese…plus aquatic plants and other species. And by cutting trees, beavers create openings in the forest, which diversify habitat for a wide assortment of plants like willows and alders, and for wildlife such as moose, elk, and deer.

There were tens of millions, possibly hundreds of millions of beavers across almost the entire continent, continuously reshaping and enriching ecological communities.

And importantly, for thousands of years Native Americans trapped beavers for fur and meat, without depleting this important resource.


Trappers and Frontiersmen


The quest for beaver pelts, highly valued in Europe especially for making beaver felt hats, was a prime motivator for French and British frontiersmen to move west and north across North America. Beginning in the 1600's, beavers profoundly affected the ways that European people explored and settled the continent.

The rising availably of beaver pelts from North America coincided with declining numbers of the native European beaver, so the market on this continent was very strong. For two centuries, beavers were trapped and sold by the thousands every year, without regard to possible decimation of beaver populations, as had already happened to the beavers in Europe. For example, just between 1853 and 1877, the Hudson Bay Company alone shipped nearly 3 million beaver pelts to England.

Beaver pelts were so prevalent on the western frontier that they were often used as a form of currency or medium of exchange in place of money.

Along with the westward march of the trappers and trading companies, significant changes were taking place in Native American cultures. As white men moved into traditional native homelands, they brought their culture and goods with them—including guns and traps. Some married into native communities and settled with them; many learned subsistence skills from native teachers; and all brought a new economy with them.

For some highly mobile indigenous hunters and gatherers, the arrival of Europeans profoundly changed their ancient way of life. In places like Alaska and northern Canada, First Nations people began trading furs and other resources from the land in exchange for European goods; rifles and steel traps displaced older ways of making a livelihood; people began to settle in cabins along their privately claimed traplines; and eventually the missionaries and schools attracted them to gather in villages.

The fur trade remained strong for two hundred years, but by 1900, the beaver population was nearly wiped out—only about 100,000 remained, mostly in Canada. It may have been a change in fashion that saved these remarkable animals from extinction—just in time, silk hats replaced beaver felt as the most popular style in Europe.


The Vanishing Hydrologist

Without the beavers to maintain dams, the barricades broke and decayed—and as a result literally millions of water catchments dried up. Ponds became meadows; meadows became forests or agricultural land.

This reversed the important work that beavers had done…greatly reducing the ecological richness and biodiversity on a continental scale. What was once a lacework of bogs, ponds, small openings in the forests, meadows and trees, had become something more uniform, no longer providing habitats for the many plants and animals it had once supported. 


Recovery and a New Understanding

Eventually, the Canadian and United States governments began to pass laws protecting the beaver, and over time they've made a significant comeback, though their numbers are only a small percentage of what they were before Europeans arrived. Today the North American population is estimated at 10 to 15 million beavers.

Ecologists have come to understand something that was probably well known among Native American people—how important beavers are for the enrichment and diversity of ecological communities. And in the dry western states, we have learned that beavers are also powerful conservators of water—by creating reservoirs, stabilizing water levels and preventing streambed erosion.

Imagine the potential benefits from millions of small ponds and wetlands that slow the runoff from periodic rains and store water that would otherwise quickly disappear. And all of this vitally important work being done by a full time volunteer force of beavers.

As beaver numbers have increased, they have been hard at work reclaiming old territory. A good example is a pond created by beavers along busy Route 2 in Massachusetts. Trees had recolonized a field, but when the beavers moved in and dammed a stream, they created a 45-acre pond with a beaver lodge along the shore, and now it's also a home for many other animals, including spectacular birds like wood ducks and ospreys.

The pond effectively slows and filters runoff that follows heavy rains and it stores the spring flush of water from melting snow. Without such ponds the sediment from heavy water flows would be lost down stream. But the pond absorbs these sediments and will eventually fill up. When the beavers move to another area, the dam will fall into disrepair and the pond will eventually drain. Left behind will be a lot of very rich soil…another benefit of the beaver's work.

But the story of the beaver's recovery isn't all good news. In some areas, it's not a matter of protecting or reintroducing the animals, but of finding ways to coexist with them.


The beaver's handiwork has caused lots of problems for people, leading to a constant unfolding of mini battles when beavers cut down trees in people's yards, block culverts and build dams that inundate roads, farmlands, backyards, and even buildings. In fact, the U.S. Department of agriculture estimates that beavers cause millions of dollars in damage each year.

People go to elaborate efforts to discourage beaver activities. They wrap metal sheathing around tree trunks or paint the trunks with a mixture of paint and sand. They use lots of tricks to keep beavers from damming culverts or to prevent them from detecting the outflow of water. There are also clever ways to put drains through beaver dams and keep the water at manageable levels.

It's a complex situation, managing the benefits and costs of beaver ecology, but people are busy finding ways to minimize the conflicts and maximize the benefits. Above all, we are learning to coexist as harmoniously as possible with an animal that provides many important benefits to the environment and to ourselves.

With support and protection from people, beavers are once again changing the face of the continent and creating essential habitat for dozens—or perhaps hundreds—of other species.

Mark Bethka