Saving Tarboo Creek

by Scott Freeman

  Streams that are ponded with beaver dams also provide the best of all possible worlds for juvenile salmon. Instead of burning up energy swimming against a stiff current, the small fry can congregate in calm, ponded water that is deep, cool, and well oxygenated and where organic material and insect food are abundant. When it’s time for the juveniles to make their way to the ocean, they can navigate the dams by wriggling through the leaks.

  If you were designing the perfect salmon stream, then, it would start with long stretches of relatively fast-moving water close to the headwaters that provide gravelly spawning habitat. Downstream, there would be even longer stretches of rearing habitat, with a meandering channel broken by a series of beaver ponds.

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  So when that favored cedar fell early in our restoration effort, we didn’t respond by killing beavers. Instead, we started to protect selected trees with hoops of chicken wire. As beaver activity in the restoration became more frequent over the next several years, we experimented with different approaches. A long series of failures followed by eventual success told us that the most reliable and affordable system was a 4-foot-high hoop of 1-inch mesh poultry netting held in place with a stout wooden stake. A pattern got established: we protected western redcedars that were close to the creek, thinking that the Sitka spruce needles were too stiff and prickly to be edible. Then the beavers started dropping spruces near the water. So we protected them. Then they took cedars up to 10 yards from the creek. So we protected them. Then they started on spruces farther from the water, so we put wire hoops around them. And so on. They kept us on our toes.

  After a couple of years of our gradually making the long-lived conifers we’d planted beaverproof, two small dams appeared. They were just disorganized jumbles of old logs and branches, or what biologists call found wood—not stems that had been cut for the purpose. But still, they were obvious beaver work. And they were holding water.

  A week later, Susan and I were clearing a streamside trail so we could walk near the newly ponded area when I found myself sinking rapidly. As I hoisted myself out of the hole, I realized I’d inadvertently collapsed a tunnel leading to a newly excavated bank lodge. We found the second entrance later but were never convinced that the beavers ended up raising a family there.

  Two years later, one of the original dams doubled in size almost overnight. We inspected the old lodge again and saw that a small hole had opened in the ground surface. When I stuck my hand down inside it, I found I could sweep my arm around a cavern 3 feet across. Not long after, the dam got bigger and ponded the creek for a good 50 yards upstream. About the same time, beaver-chewed sticks started showing up to cover the hole I’d stuck my arm into. The stick mound grew into a 3-foot-high weatherproof barrier, making it look almost like the lodges you see in the middle of lakes, but on the creek bank. The dam also continued to grow.

  The following spring, Susan and I were standing near the lodge, scouting for any recent sign of activity, and heard a series of pips and squeaks. She looked up at the trees, trying to find passing kinglets. There was nothing there, and she looked at me, confused. I pointed down at the lodge—the noises were coming from inside, from beaver kits. We were grandparents in a way. Our boys were relieved when we made the announcement—the pressure was off them for a while.

  So beavers are now a feature. The pond they created drowned big trees and shrubs we enjoyed, and even some we planted, but the deaths created snags that attract pileated woodpeckers and red-breasted sapsuckers. The open water has brought in kingfishers, great blue herons, mallards, and wood ducks; it’s a paradise for frogs and aquatic insects.

  We’ve also learned to anticipate an intense beaver chew-down sometime each March or early April, right before spring green-up. At this time of year, the parents are hungry from being on short rations all winter and the female is probably pregnant or lactating. Either way, she’s eating for a family of four or more. So we have chicken wire at the ready and make the rounds to protect any cedars or spruces we’ve neglected, trying to direct attacks to willow, salmonberry, and red alder. The willow and salmonberry will resprout efficiently after being cut, and the red alder will seed in without our help, so we consider those species expendable.

  When friends and family come to visit now, the first thing they want to see is the beaver dam and pond, and they go hunting for freshly chewed sticks. Everyone wants to see what the beaver family has been up to lately.

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  Beavers were abundant when Europeans landed in North America and took up residence. Castor canadensis was found from Mexico to the Canadian Arctic, and from the Atlantic to the Pacific. Extrapolating from their density in the Adirondack Mountains of New York, the naturalist Ernest Thompson Seton estimated the North American population at 100 to 200 million when the Mayflower landed in 1620.

  At that time, European beavers had been trapped so intensively that they had disappeared from Great Britain. There was still a booming market for their carcasses, though; the fur was being felted to make hats and the scent glands sold to treat headache and fever—they don’t help, actually—and as an ingredient in perfumes. The trapping continued, and Eurasian beavers were eliminated from almost all of their former range between 1700 and 1900. By the early part of the twentieth century, only about 1,200 remained. They were threatened with global extinction.

  The decline of Eurasian beavers was a boon to the early colonists in North America, though, because beaver hats were still high fashion. The New World species was superabundant, and shipping their pelts to the old country was one of the few ways the early white settlers could earn cash. A cross-Atlantic trade in beaver pelts was under way by 1624.

  Beaver felt was used to make the tricorne hats favored by the Colonial army, the top hats worn by aristocrats on outings, and the everyday hats worn by everyone else. By 1800, mountain men were trapping beaver in the Rocky Mountains; soon after, the California fur rush lured the first waves of prospectors to the Pacific coast.

  By 1850, the North American beaver was virtually extinct. It was probably raw luck that saved the remaining few: beaver felt went out of style. Silk hats, like Abraham Lincoln’s signature stovepipe and the headgear worn by the fashionable gentlemen in Gustave Caillebotte’s famous painting of a rainy Paris streetscape, were in.

  The beaver tale is the same as the story of Atlantic salmon and old-growth forests: people exploited a resource until it was gone, or nearly so, and then they moved on to something else.

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  Beavers have come back in North America. The current population is estimated at 10 to 15 million and rising. And the resurgence of beavers isn’t isolated. The year I was born, a long list of charismatic megafauna was declining or already extinct in my home state of Wisconsin. The list included sandhill cranes, wild turkeys, fishers (big cousins of mink), cougars, timber wolves, prairie chickens, peregrine falcons, and bald eagles.

  In the 1930s, Aldo Leopold wrote the heartrending essay “Marshland Elegy,” collected in A Sand County Almanac, about the loss of sandhill cranes. His theme was simple: our world is diminished when species like sandhills disappear. But when I was twenty-five, I helped organize a statewide crane count that turned out more than five hundred volunteers—many of them Girl Scouts and Boy Scouts and 4-H kids with their moms and dads. Each team was assigned a wetland that local organizers had mapped, then tasked with arriving at the marsh in the predawn to listen and watch for sandhills. For many of the participants, it meant a 3:00 or 4:00 a.m. wakeup. But that year the census turned up almost three thousand cranes, and five hundred people had a great morning together. Being at a marsh in the predawn of a mid-April Saturday is a memorable experience. The cold is bone chilling, the quiet unsettling, the rising light mysterious. You just sit or stand, watching and listening. Almost always, something happens. It might be a red-tailed hawk floating low over a hayfield or a coyote trotting home after a night’s hunt in the woods, or what you came for—the sound of cranes bugling from a hidden recess
in the marsh or the sight of a pair flying past, stiff winged, toward their foraging grounds.

  Sandhills are now so common that my cousins who farm have trouble keeping them out of their corncribs. And from the steps of Aldo Leopold’s Shack today, you can hear breeding pairs of cranes giving territorial calls in wetlands to the north, and hundreds of individuals coming in to roost each evening on the Wisconsin River to the south. In the distance, you can also see and hear a constant stream of east-west traffic on Interstate 90.

  Turkeys and fishers were reintroduced to Wisconsin after being wiped out and are now thriving. The Milwaukee-area business leaders who run the Society of Tympanuchus Cupido Pinnatus have purchased enough habitat to give prairie chickens a fighting chance of hanging on in the central part of the state. In 2008 biologists confirmed the first evidence of cougars in a century, and peregrine falcons are nesting on old brewery buildings in downtown Milwaukee.

  Almost every state and province has witnessed similar events. When Susan and I moved to Washington in 1985, there were no grizzly bears or timber wolves; both are now being sighted regularly. Comebacks like these are not smooth or easy: in 2009, a father-and-son poaching operation shot and killed the first female wolf to breed in Washington in more than fifty years.

  The Tarboo Creek restoration has its own set of comeback stories. We’ve seen black bear tracks in the mud along the creek and scat in the younger parts of Carl’s forest; Peter Bahls took a photo of a bobcat hunting voles near one of our eagle poles; river otter follow the coho run up every fall; cougar are in the neighborhood often enough now to make me nervous walking alone at night; elk were seen just downstream from us recently; fishers have been reintroduced to the Olympic Peninsula and have also been seen in our neighborhood. It’s not yet clear, though, whether these animals are coming or going. If the county retains an economy based on timber production and small farming operations, and if citizen action like nwi’s plant-a-thon continues, the large mammals and the salmon have a chance. If the area succumbs to the type of exurban and suburban sprawl found in the counties to the south, west, and east, the big animals will be gone.

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  I reread A Sand County Almanac every few years and am always struck by the desperate tone of Aldo Leopold’s writing. The things he loved and lived for were disappearing, and no one was mourning their loss. He was a prophet crying out in a wilderness. Like Amos or Hosea, he railed at times about the ungodliness of his nation and the retribution to come.

  Much has changed in the seventy years since, and much remains the same. In the industrialized countries, most people now profess a strong commitment to environmental protection. There is a growing recognition that the old economy-versus-environment dichotomy is not only tired but also false. Well-organized conservation groups with vocal constituents and access to resources have done a great deal of good. But the deep ethical commitment Carl’s father was advocating is still rare. For example, species that have attracted concern, attention, and resources in North America are coming back. But a lot depends on looks. Freshwater mussels have faces that only a mother could love, and they remain in deep trouble. It takes an effective ecological education—and an ethical commitment that borders on the spiritual—to understand that mussels matter, too.

  What has changed most since the publication of A Sand County Almanac is the globalization of the conservation crisis. Aldo Leopold studied the places he knew best—New Mexico and Wisconsin—and was heartsick at the long-term damage being done to the soils, vegetation, and wildlife. Today, ecologists study habitats around the globe and are overwhelmed by the same emotions. A few popular and well-studied species are being saved, but today’s teenagers will probably live to see an extinction crisis parallel to the one triggered by an asteroid that smashed into Earth 65 million years ago.

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  One of the most famous graphs in the scientific field of paleontology has time on its horizontal axis, plotted in increments of a million years. A million years is a long time, but scaled to the 4.6 billion years Earth has existed, it’s equivalent to less than a week of your life. This axis starts at about 600 million years ago, when marine animals got big enough to leave fossils that could be studied reliably. (Land plants and fungi appear about 130 million years later.) The vertical axis on this classic graph plots how many species went extinct during each of those million-year intervals. If you look at the trace made by the data, five spikes jump out. These were episodes where more than 60 percent of the species alive at the time went extinct in fewer than a million years. The spikes are called the Big Five and are considered mass extinction events.

  The most recent mass extinction was the one that occurred 65 million years ago. Although it was not the most severe cataclysm in history—life forms larger than single cells were almost snuffed out 250 million years ago—the so-called end-Cretaceous or Cretaceous-Paleogene (K-Pg) extinction is easily the most famous. Among other things, it finished off all dinosaurs except the ones that fly—the birds. Although the causes of the other four mass extinctions identified in the fossil record are still hotly debated, the extinction event that closed the Cretaceous period is no longer a whodunit. It wasn’t the butler or even Mrs. White in the study with a candlestick. It was an asteroid.

  The evidence for an asteroid impact 65 million years ago is overwhelming. We have shell casings near the point of impact—rock fragments that were melted or deformed by the shock waves and heat. We have gunpowder residue in the form of iridium—a mineral that is vanishingly rare on Earth but abundant in asteroids. A dusting of the stuff forms a layer precisely at the point in rock formations where most Cretaceous species disappear. We have bloodstains in the form of soot and ash from wildfires that were triggered by a searing blast of heat following the impact. These are found across the globe in rock layers that are 65 million years old. We have reenactments of the crime—computer models detailing the consequences of spraying enormous volumes of pulverized, sulfur-rich rocks into the air. The sulfurous dust would have triggered acid rain and darkened the sky for months or years, crippling photosynthesis enough to cause mass starvation. Finally, we have the murder weapon itself: a crater that formed when the asteroid plowed into what is now the Gulf of Mexico just north of the Yucatán Peninsula.

  A mass extinction like the end-Cretaceous is fundamentally different from what paleontologists call background extinctions. Background extinctions occur at a nonspike rate that varies around a low long-term average. As far as we know, all species eventually go extinct; paleontologists are fond of pointing out that many more species have gone extinct than are alive today.

  Although background extinctions are difficult to study, they are routine events. In general they are thought to result from natural selection. For example, one species might die out when mutation and natural selection create traits in a competitor that allow it to harvest resources more efficiently than the declining species can. Or normal rates and types of climate change might eliminate a preferred habitat faster than an unlucky species can adapt to the new habitats that are appearing.

  By contrast, mass extinctions appear to occur when the environment changes so profoundly and so quickly—due to some extraordinary, not-to-be-repeated circumstance—that evolution can’t keep up, meaning that no species has time to evolve adaptations to the novel conditions. Instead, survival is mostly a matter of dumb luck. The birds may have made it through the end-Cretaceous simply because some could fly around to the few habitats that offered anything at all to eat; the mammals that made it may have been able to hibernate through long periods of food shortage. Most other species weren’t poorly adapted or somehow biologically inferior—they were simply in the wrong place at the wrong time.

  The one pattern that jumps out from research on the Big Five is that species with broad geographic ranges—that are found in a wide array of areas—tend to survive better than close relatives with narrower geographic ranges. Apparently, the broadly ranging species are more likely to have individu
als living in areas that are not as devastated as most places, meaning that at least some populations get lucky and make it through the environmental crisis.

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  In the 25 million years following the K-Pg impact, mammals underwent an astonishing diversification that included the origin of the primates. That lineage eventually produced the Old World monkeys, the New World monkeys, and most recently the great apes. The gibbons (also known as lesser apes) and great apes lost tails; the ancestors of today’s great apes also gained thumbs that are flexible enough to manipulate objects adroitly. Most great apes also walk on two legs, at least on occasion. The lineage of humanlike species called the hominins walks on two legs mostly or exclusively.

  Our own species, Homo sapiens, is the only remaining representative of the dozen-or-so species of human or humanlike species in the fossil record. The first of our bipedal ancestors appear in the fossil record about 4.5 million years ago; for most of the intervening period at least two or three hominin species have been walking around Earth at the same time, often in the same place. For most of our lineage’s history, it’s been unusual to have just one species of human around. Science fictional and medieval-like fantasy worlds populated by elves and orcs and dwarves may have accidentally mimicked reality.

  According to the fossil record, all of the human species originated in Africa. But about a million and a half years ago, members of Homo erectus emigrated to Asia. They spread throughout the region, leaving stone tools and traces of fire associated with their now-fossilized bones. They stopped leaving fossils, however, about 300,000 years ago. About the time H. erectus was disappearing, Homo neanderthalensis began to occupy the Middle East, then the Caucasus, and then western Europe. The Neanderthals buried their dead and had larger brains on average than we do; they died out some 40,000 years before the present. The first fossils of Homo sapiens, our direct ancestors, are found in African rocks that formed about 190,000 years ago. Early sapiens lived among Neanderthals in Europe; they may also have lived just an island or two away from the tiny Homo floresiensis in Indonesia—a dwarfed species of hominin nicknamed the Hobbits. At 45,000 years before the present, our Homo sapiens ancestors were leaving traces in Australia. And perhaps as long as 30,000 years ago, we’d spread to the New World so that we now occupied every continent except Antarctica. Agriculture developed at several points around the world, independently and with different crops, beginning about 8000 bce; metalworking in copper started not long after, about 7000 bce. But the total human population was still small—perhaps 500 million people.