It was December 1826 and mountain man Jedediah Smith was in San Diego, California, standing before Governor General José María Echeandía trying to explain why he and his party had crossed the bleak Mojave Desert, trespassing into Spanish territory. The story he told was, in the governor general’s view, preposterous. The Spaniards knew about quests for riches. For the past 300 years they had marched across the harshest landscapes of the New World in search of gold. But who would wander the empty quarters of the West trying to catch the nocturnal aquatic rodents known as beavers? The concept was so strange to Echeand’a that the only Spanish word he could summon to describe the lanky American fur trapper was pescador—fisherman.

But Smith (who was eventually sent on his way) was telling the truth. The luxurious beaver fur that was pressed into the felt that made up the hats worn by fashionable, prosperous men of the day was gold—soft gold. In the early nineteenth century, thousands of beaver trappers roamed the West under the employ of fur companies that were building great business empires. When beaver felt hats fell out of fashion in the mid-1800s, the trappers, who had learned every nook and cranny of the West in their quest for beavers, guided American settlers to Oregon and California, helping to build a nation. This unremarkable-looking animal unwittingly served as a catalyst for the creation of human empires—both business and political. Remarkably, it turns out, in the realm of ecological processes, beavers have had an empire of their own all along.

If you’ve ever seen Castor canadensis up close, the first thing you are likely to notice is that they are a bit funny looking. The largest rodent in North America (and second largest in the world), American beavers range throughout the continent with the exception of the extreme southeast and southwest. They average forty-five to sixty pounds, although some will tip the scales at 100. Pudgy and virtually neckless, beavers are built for life in the water. Webbed hind feet provide underwater propulsion and their flat, scaly tail is their rudder. They have dark-brown fur made up of a dense undercoat and long outer guard hairs, kept well oiled from glands in their posterior regions. This makes beaver fur so water-resistant that their skin is dry even after a seven-minute dive, although they are capable of holding their breath for more than twice that long.

Water is the beavers’ medium, and they work wonders with it. Beavers, like all living creatures, struggle to survive and reproduce. For beavers, that means stopping moving water. From that simple mission grows a profound chain of ecological events, earning them a place as a keystone species. The effects of beavers on the environment are so comprehensive that natural resource managers working with them are as likely to be hydrologists and soil scientists as wildlife biologists.

“Beavers are hydraulic modifiers of the system,” says Bureau of Land Management hydrologist Dennis Doncaster. By that he means they build dams to stop the flow of water. Beavers will move into almost any environment with running water—typically a stream with a good supply of willows, aspens or cottonwoods for food and building materials, which they gnaw at with their four large incisors, although they can make do with less-desirable tree species. Constructing a dam using sticks and mud is their first order of business. This creates a pond, a safe haven where they build an underwater stick lodge that is deep enough to not completely freeze over in the winter and large enough to flood adjacent timber, giving them access to their food supply.

“Once the beavers have constructed a dam, you have a slowing of water behind it,” explains Andy Talabere, a research fish biologist with the Oregon Department of Fish and Wildlife who recently finished a two-year study of beavers and Lahontan cutthroat trout on a Great Basin desert stream. “Over time, as the pond starts to fill [with sediment] and other ponds are built upstream and downstream, you get a series of ponds strung together. You increase the extent of the beavers’s influence.”

That influence can be substantial and far-reaching. Formerly fast-moving streams slowed by a beaver dam begin to drop sediment out of the water column to the streambed, changing the substrate. This alters the mix of insects from those adapted to fast water and a rocky bottom to those that like litter and detritus-strewn substrates. That can potentially change the species of fish and other creatures that live there, providing new habitat, for example, for frogs and salamanders.

As the filling pond spreads onto the adjacent riparian zone, the water table rises and wetlands form, creating additional habitat for fish-eating birds, such as kingfishers and herons and neotropical migrants. Flooding and higher water tables also make better habitat for the fast-growing, water-loving trees that make up the beavers’ preferred diet. “One of the misconceptions about beavers,” Talabere says, “is that they wipe out all the willow and aspen and move on. Under very natural conditions without the influence of humans, beavers aren’t going to wipe out the willows. Willows and beavers have existed together for millions of years.” Even after a pond fills with sediment, the beavers will simply build another dam nearby. “The only reason they’ll leave,” says Talabere, “is if they can’t find a place to back up water.”

If beavers stay and back up water long enough, say hundreds of generations, they will literally reshape the landscape. A succession of dams built on top of each other over the centuries can raise the level of a river bottom, creating broad, flat valleys and a wide stream— something a free-flowing stream is not be capable of doing. Some notable examples of the geomorphological impacts of beavers can be found in places in the Colorado Rockies and upstate New York.

Beavers have been around for a long time in central Oregon’s Ochoco National Forest, and their influence is almost everywhere if you know what to look for. “Just about every place I dig in this country I find old beaver-chewed sticks,” says forest soil scientist Jim David. Flooding caused by beaver dams creates riparian soils, providing the rough materials and sediments they consist of to produce a rich brew for growing plants. “There’s a huge productivity difference between riparian soil types and drier soil types,” explains David. “These thick, organic soils near the surface are an indication of beaver influence.” David thinks so highly of these soils that he’s coined his own term for them—“beaverine” soils.

Once abundant, beavers are much less common on the Ochoco National Forest than they once were, although David finds evidence of their former presence throughout the area in the remains of ancient dams and his beaverÐ ine soils. The primary reasons for their decline include a changing climate, from wetter to drier as recently as 1,200 years ago, along with heavy trapping pressure in the early 1800s.

In the late 1980s to the mid-1990s, David and other forest staffers began transplanting nuisance beavers from private lands onto the forest in an attempt to use them to improve local habitat. “We wanted to get the beaver population to expand, grow and perform their ecological function,” he says. Looking for low-gradient streams with a decent supply of aspens, willows or cottonwoods to release the beavers, they often had to give them a jump-start by building loose-rock dams, which raised the water table in the area, making it more desirable for the new residents. The beavers often built their first dam on top of the loose-rock dam.

The trick to reintroducing beavers is to avoid putting them in too soon; that is, before the riparian hardwoods have reached a vigorous enough stage of growth to withstand a little culling. This can be a significant factor in determining where and when to use beavers in restoration, since many areas that can benefit most from beaverreintroductions have lost much of their riparian vegetation to overgrazing by cattle and aren’t ready for the rodents.

“The key to beavers is habitat,” says David. “As part of that habitat, we need to have grazing control.” Although they occupy two distinct habitats, cows and beavers don’t mix where they mingle—in riparian areas. In a natural setting, beavers won’t polish off their food supply. But in combination with cattle—as well as large numbers of elk—the browsing pressure may be too great, especially on young shoots and saplings.

The trapping and transplanting phase has run its course on the Ochoco, and now the emphasis is to provide conditions that will allow the beaver population to expand its range within the forest. “We’d like to have them return to their historical range,” says forest wildlife biologist Dave Zalunardo, “because there are a lot of hydrological, water quality and wildlife habitat benefits. We think we have the cottonwood seed source in all the drainages, so our focus is on habitat restoration.” Most recently, that focus has involved an extensive grazing management effort involving fencing to keep cattle out of sensitive riparian areas and vegetation plantings.

One of the early efforts to deliberately use beavers for habitat restoration was by the BLM’s Rock Springs field office in southwestern Wyoming’s Green River drainage. This is an area that was so hard hit by the mountain men that BLM hydrologist Doncaster thinks the ecological impacts of a substantially reduced beaver population, such as increased stream erosion and sedimentation, lower water tables and more flood-prone stream systems, were in place and regarded as the normal condition by the time the region’s first Europeans arrived.

In the late 1970s, BLM staff members had finished a stream restoration project using in-stream structures, cattle exclosures and other traditional methods. It was highly successful, turning what was little more than a dirty irrigation ditch into a viable trout stream. Then they turned their attention to Currant Creek, a tributary of the Green River south of Rock Springs.

“The reason we started working on that stream is because there are Colorado cutthroat trout in it that had been hybridizing with nonnative trout,” says Jim Dunder, BLM wildlife management biologist. They noticed that there were a couple of beaver dams on the upper creek that were doing a fine job of blocking interloping fish out of Flaming Gorge Reservoir, keeping them from intermingling with upstream cutthroats. “So we put in an electric fence on the lower end of the stream to keep livestock out,” says Dunder. “Then we trapped some beaver from the upper end and put them in the lower end. We did some willow plantings and let nature take her course.”

The colonies built dams, reproduced and pioneered up and down the creek, bestowing beaver benefits along the way. But the beavers took success a step too far when they established a colony upstream on a rancher’s land. “He wasn’t too happy when the beavers built a dam and flooded his hayfield,” says Dunder. The irate landowner went to the Wyoming Game and Fish Department demanding compensation for the value of his lost hay. When he was refused, he went home, killed the beavers and took out the dam. Shortly thereafter, without the stabilizing influence of the dam, the creek “head cut” and washed away his entire meadow. “He doesn’t cut hay there anymore,” says Dunder.

Unfortunately, with the upper dam gone, the upper stream eventually unloaded its sediment into the lower reaches. All that extra soil deposition was great for willows, giving them lots of new places to grow. But the beavers didn’t care for it much and left. “If it wasn’t for the interference of man,” says Dunder, “we’d be in pretty good shape.”

Nevertheless, the BLM’s experiments with beaver-driven habitat restorations were largely successful. Dunder says, “We’ve been able to stabilize and reduce the silt load on all the streams we’ve done beaver work on. Reintroducing beavers for creating habitat has expanded trout populations and created perennial streams where some of the other streams, where we haven’t done beaver work, are dried up.” Dunder cautions, however, that using beavers in habitat restoration is a long-term, labor-intensive undertaking.

But if some natural resource managers would like to have more beavers, there are others who would gladly give them theirs if only they could. Chrissie Henner, furbearer biologist with the Massachusetts Division of Fisheries and Wildlife, may be one of them.

In 1996, Massachusetts voters passed Question 1, a referendum banning the use of Conibear traps, neck-grabbing, quick-kill traps considered the most effective way to catch beavers.

“Before Question 1,” says Henner, “we harvested about 2,000 animals annually, which is pretty good for a place like Massachusetts. But when the trapping ban came on, the catch was way down and the beaver population has exploded. So even though we weren’t harvesting a lot of beavers, it had an impact on the population.”

Trapping beavers for recreation and pin money is an old tradition in the United States and Canada. Each year, more than a half-million beaver pelts are taken by trappers throughout North America. But trapping is increasingly controversial, and voters in other states, including California, Washington, Colorado, New Jersey and Arizona, along with Massachusetts, have enacted laws restricting trapping methods to varying degrees.

Nevertheless, many wildlife managers rely on trappers to help manage furbearer populations, and beavers just happen to be one furbearer that is not only prolific, but can and will cause problems for human endeavors. Typically, it’s dam building in inconvenient places or plugging culverts that flood property, roads and septic drainfields or gnawing down a homeowner’s favorite tree. Beavers can be especially problematic for highway departments. For example, local highway departments in New York state average nineteen days of work and $2,500 to clear and repair each culvert.

With the kill trap ban in effect, Massachusetts trappers were forced to use bulkier, more expensive and less effective live traps, resulting in a drop in the number of practicing trappers. Massachusetts beavers, on the other hand, proliferated, growing from a pre-trap-ban population of about 20,000 to around 60,000 as of the last comprehensive survey in 1998.

As a result, damage complaints rose and angry landowners began demanding a return to a more lethal way of getting rid of nuisance beavers. In response, state legislation was passed in 2000 giving town boards of health authority to issue Conibear trapping permits to aggrieved landowners who can prove the wayward rodents are a threat to their health or safety. State wildlife managers are not entirely happy with the special permitting since it has proved difficult to track the numbers of beavers being killed. “The law change has killed more beaver than we killed during trapping seasons,” says Ralph Taylor, a wildlife district manager for the Massachusetts Division of Fisheries and Wildlife. “The health boards are issuing kill permits left and right.”

But in every controversy lurks potential opportunity, and the Massachusetts beaver issue is no exception. It’s how Mike and Ruth Callahan of Hadley got into the beaver business. “It was in the news a lot about how people were having flooding problems,” says Mike Callahan. “It was really polarizing. Landowners were saying that the beavers were destroying their homes and that they were going to kill them. The animal lovers were saying you can’t touch them. We thought there must be a middle ground.”

That middle ground became Beaver Solutions, a company the Callahans formed in 1998 to help people solve beaver-related problems on their lands, preferably using nonlethal means. The two issues they deal with most often are beaver-plugged culverts that flood adjacent roads or railroad beds, and dams that turn backyards and wood lots into wetlands. Culverts are the easier problem to tackle, generally solved by unplugging them and then fencing them off so the animals can’t get in. Beaver dams require finesse.

If you knock a beaver dam out, the beavers will rebuild. The traditional approach is to kill the beaver colony and then take out the dam. If you want to eliminate the flooding but still keep the beavers around, you need to apply some cunning and some plumbing. The Callahans do this by determining how much the level of the beaver pond needs to drop to eliminate the encroaching water. Then they will run a pipe through the dam, fencing it off at the upstream side so the beavers can’t plug it and sinking the other end into the pond downstream, far enough away that beavers don’t realize it is allowing water through their dam. This works more often than not. When it doesn’t, they reluctantly trap.

Although the work sounds esoteric, there are a number of similar firms around, particularly in the Northeast, and they keep busy. The Beaver Solutions client list includes dozens of Massachusetts towns, conservation commissions, highway departments and railroads. Recently, they went to the rescue of a research project in the Harvard Forest when beavers flooded a research plot and scientists feared the trees would die. “It’s gratifying to solve problems so the wildlife can stay,” says Callahan. “Beavers are so important for biodiversity. That’s what hooked me on them.”

“If you don’t have beavers in a stream,” says Talabere, “the stream isn’t going to fall apart. But they create diversity and complexity.” Much of that complexity is still being discovered. A continent was explored and settled, in part, over the quest for the beavers’ soft gold. In the long run, the real gold beavers offer is more likely to be found in what they do than in what they wear.