NASA satellites reveal restoration power of beavers

If humans went extinct tomorrow, who would rule the world? Beavers.

Well, at least in the Northern Hemisphere. These tree-felling, water-slowing, wetland-creating rodent engineers have a massive impact wherever they live. Indeed, when it comes to their power over water flow, Cory Mosby says, “I’m not aware of another species that does this (save humans) on the scale that a beaver population can.”

A biologist with the Idaho Department of Fish and Wildlife, Mosby knows the power of these mammals intimately. And now NASA — yes, the same agency that sends people into space and searches for killer comets — is helping researchers get a more detailed look at how beavers can transform our world for the better, including combating climate change.

“NASA is interested in how satellite Earth observations can be used for natural resource management,” says Cynthia Schmidt, the associate program manager for the NASA Ecological Conservation Program. In this particular case, Schmidt says, NASA is keen to use satellite research to help scientists “better understand the impacts of rewilding for ecosystem restoration.”

Working with Jodi Brandt, a professor of human-environment systems at Boise State University, they are tracking just how quickly and verdantly reintroduced beavers change Idaho’s landscape. Already, the program has been able to produce images taken from space of how areas with reintroduced beavers are greener — i.e. have more vegetation — than areas without them.

Water lords

North America once housed more beavers than humans — by a lot. Even before Europeans showed up and built an entire extractive economy on beaver pelts, estimates put the number in the hundreds of millions (during the Pleistocene, there were even giant species of beaver, as large as bears). The North American fur trade, which lasted for centuries, nearly wiped beavers off the continent — and, unknown to trappers, vastly changed its ecosystems from sea to sea.

“There is evidence that riverscapes across the West were much more complex and ‘anastomosed’ prior to European colonization,” says Nicholas Kolarik, a Ph.D. student working with Brandt, who is focusing on mapping data sets of wetlands. Anastomosis denotes branches connecting two things, like organs in the body, but in this case, he means streams, since waterways in the U.S. West used to be much more interconnected.

Today, they’re “starved of wood,” he says, but by adding wood into streams and rivers, especially by building dams, beavers slow water down significantly.

“In doing so, sediment is stored, water infiltrates into the aquifers, riparian vegetation establishes, habitat is created, and carbon is stored,” Kolarik says.

Given that Idaho is an arid state, most of the state’s water comes from snowmelt in the mountains. If that water isn’t slowed down, it speeds through streams and into rivers and soon exits the state. During the warm summer, shallow streams and wetlands often dry up completely.

“Any way to retain more water, or keep it a little longer into the season, is typically beneficial,” Fish and Wildlife’s Mosby says. Slowing down water creates new habitats, like marshlands and flooded pasture, and keeps streams flowing later and deeper into the year. This provides vital habitat and forage for innumerable species, from fish to birds and ungulates. In all, Mosby says, there have been “several hundred” beaver reintroductions in Idaho in the last decade.

Kolarik says they don’t yet have any “exhaustive analyses that could speak to an average effect on mesic vegetation or other broad data driven conclusions” on beavers’ impact in Idaho. What they do have is a number of streams that have been transformed by beavers, he says, pointing to the Yankee Fork, a tributary of the Salmon River, which had been degraded by decades of gold mining. After restoration work was done, beavers returned naturally. Unpublished research by Trout Unlimited found that the beavers in Idaho helped maintain the restoration, increasing vegetation and connecting this part of the river back to the floodplain.

Generally, scientists have explored beavers’ impacts in dryland streams less than in other places. A 2014 paper in Aquatic Conservation reported that “surprisingly little is known about the ecology of beaver in dryland streams.”

That said, scientists are well aware that beavers boost biodiversity and increase wetlands. For example, research from the Adirondacks in New York, published in Oecologia in 2002, found that the beaver presence the boosted the diversity of plants by one-third.

Despite this, the U.S. Department of Agriculture’s Wildlife Services has a long history of killing beavers, which have been deemed to be pests, as their dams can lead to flooding of infrastructure and crops. In 2022, the agency killed 26,731 beavers.

However, experts like Peter Busher say that “Any potential negatives are minor in regard to the ecosystem services the beaver wetlands provide.” A professor and beaver expert at Boston University, who was unconnected to this project, Busher says that “beaver activity may be the most cost-effective method of creating functional wetland systems.”

After decades of recovery, the North American beaver population stands at only around 15 million, from subarctic Canada to northern Mexico. That’s still a long, long way from its pre-European population, but it’s a big comeback.

Rewilding results seen from space

When NASA joined the project in 2020, it brought new data to initiatives already underway. Schmidt says the project is using the satellite data for two main purposes, the first being to find potential locations for future beaver reintroductions.

“It’s difficult and expensive to get people out on the ground to try and figure out where beavers should go, so satellite imagery gives a comprehensive view of a region, which can tell you if it’s appropriate for beaver,” Schmidt says.

Before reintroducing any animals, Mosby says his department has much to consider. First, they have to determine if the area has enough food and year-round water for beavers, and enough wood for their dams. Then they have to make sure there are no concerns over disease or invasive species that could hamper reintroductions.

If the biological conditions look good, then they have to move on to social questions, including land ownership of the location and surrounding areas, water rights, and whether any introduced beavers might negatively impact crops or infrastructure.

Mosby says views on beavers in Idaho are “are all over the board.” But he notes that many ranchers have come around, as they see the tremendous benefits of having beavers on or near their land, including more water and grazing for their cattle. He says the least tolerant people to beavers are often those living in more developed areas.

“Transportation infrastructure and their associated culverts and bridges can be put at risk when beavers begin damming these areas,” Mosby says. “When beavers begin cutting large trees next to popular walking paths or residential and commercial buildings, this becomes a safety concern. Also, these same animals will remove and browse the landscaped vegetation. In these situations, people that have never strongly felt one way or the other often want those beavers removed.”

If a reintroduction gets the go-ahead, Mosby says the department will begin to find animals, capture them, and then move them quickly. After that, it’s really about allowing the beavers to do what they do best: shape the ecosystem.

And that’s where the second role of NASA’s data comes in again. From above the clouds, NASA can track the landscape’s transformation after beavers arrive, helping researchers understand the pace and nuance of beaver impacts without having to send researchers into remote areas. In addition to the data, NASA also helps with funding as a part of its Research Opportunities in Space and Earth Sciences grants. The program doesn’t cover all costs, but shares costs with the research group.

Furry fire fighters

Beavers are also likely to become more important as the world continues to rapidly heat up due to climate change.

A 2016 federal report on how climate change will impact Idaho shows that its vital mountain snowpack was already decreasing, lessening the availability of water in late summer. It also predicted that some streams could see 50% less flow by 2050. The report further predicts that global warming will increase the likelihood of fires, which already burn about 1% of the state annually. Climate change could even push some ecosystems into regime shifts: forests could become grasslands, and grasslands, deserts.

Beavers could help mitigate all of these issues. By slowing down the flow of water melting from the snowpack, they could allow streams to stay deeper and last longer, perhaps saving habitat for fish, and vegetation for cattle. They could even mitigate forest fires.

“As our collaborator Joe Wheaton [from Utah State University] likes to say, ‘water doesn’t burn,’” Kolarik says. “Beavers maintain healthy riverscapes which store carbon and water. Consistent access to water is key to mitigating the effects of climate disturbances like drought.”

Beavers’ role as firefighters has already been documented in Idaho. A 2018 technical report by Anabranch Solutions, a river restoration company, found that beavers were a major factor in decreasing burn intensity along Baugh Creek during that year’s Sharps Fire.

“Where active beaver dams were present, native riparian vegetation persisted, unburnt,” the authors wrote. In our hotter and fierier world, beavers are a buffer.

“I once heard a rancher use the analogy of sponges when referring to valley bottoms. If we can successfully rewet the sponges, the West will be much more resilient to climate change, and beavers can keep those sponges wet,” Kolarik says.

If the species that was once pushed nearly to extinction can help humanity survive the next tumultuous century, that would be a true, full-circle restoration story.