What happens when a catastrophe destroys your home? A fire, an earthquake, maybe even a war rips through your living room, tears your walls down and leaves a crumbled heap of drywall, rebar, and debris. If you survived, you’d probably move, find a new home and start over.
But what if those events keep happening and your entire neighborhood disappears — rubble, all of it? You’d look for a new neighborhood.
Imagine that repeated catastrophes destroy 85 percent of human habitat in the United States. Small pockets survive — not more than villages. But they’re disconnected. If something goes wrong, the next village might be impossibly far away. You would have nowhere to go. You’d just have to try to survive in the devastation. Sounds extreme, right?
This is exactly what has happened to the residents of the primordial forest ecosystem that once stretched unbroken all along North America’s Pacific coast. Today, after decades of logging and development, only about 15% of historic Pacific old-growth forest remains in California, Washington, and Oregon.
In California, the situation is most critical. Two million acres of ancient forests used to grow here. While there are still nearly two million acres of coastal forest, about 96% to 97% has been logged at some point in the past 150 years; only 3% to 4% of ancient, untouched forest remains.
Without the old trees, which take centuries to reach their great size, and without large unbroken tracts of the forest systems they shelter, species like coho salmon and marbled murrelet cannot survive.
“Habitat destruction leads to population decline” is a familiar conservation refrain. But as Maxxam’s Pacific Lumber Company continues to log its old-growth stands [see p.16], what actually happens to individual animals that must try to cope with a devastated neighborhood?
Fish Out of Water
To understand the challenges these animals face, one must first understand how their world is supposed to work.
A coho salmon’s perfect world would begin before it’s born. Near the outlets of their natal stream, the coho’s parents would congregate to await the fall rain to raise river flows. They would have eaten their last bites before heading upstream. The trip would be a one-way effort to reproduce. Guided by the familiar scent of their birthplaces the coho would have navigated through cool, clear streams running through the old-growth forests. Ferns overhang the banks. Hollowed remnants of massive trees break the current, creating pools and hiding places. This is where a coho is born.
Here, the mother searched for a deep pool with a gravelly bed. Just where the pool grew shallow and the current began to ripple, she scoured a depression in the streambed, using her tail to make a nursery, or redd.
She laid hundreds of bright orange eggs, which a male fertilized with milt. Then she covered them with gravel and perhaps guarded them until she died a week or two later.
After her death, as the embryos matured, a gentle current brought oxygen to the redd and flushed waste products downstream.
Now, about fifty days after incubation, the coho and its siblings have hatched, yolk sacs still attached to their newborn bodies. They will hide in the gravel for a little over a month, feeding on small insects drifting by.
When this juvenile coho works its way out of its gravel nursery, it’s tiny and vulnerable to a host of hungry forest creatures — raccoons, birds, other fish. It must establish a safe territory with plenty of insects to eat and protection from predators and from currents that could flush it downstream. Now is the time to concentrate on feeding, to grow fat and hearty in the year to come. The bigger it is when it migrates to the ocean, the better chance the fry will have to survive.
The following spring, when the coho is just over a year old, it will start its migration to the Pacific and its body will begin a transformation to cope with the salty water ahead. It will spend its last time as a smolt in the brackish water of an estuary, plumping up a bit more before heading out to sea.
In this coho’s perfect world, a nutrient-rich upwelling of cold water just along the coast provides ample food during its adult life at sea. When it’s time to reproduce, it will seek out the same river and same stream that its parents sought by scent. Fewer than one coho in ten strays from its birthplace when returning to spawn, so year after year, the same habitat will rear this coho’s descendants. That is, unless there is a catastrophe.
Back in your neighborhood, a storm could blast holes in your walls and lift the roof right off your house. You’d have no way to stay warm and dry and once the storm passed, there would be nothing to keep looters from crawling right through that gaping hole in the wall.
When chainsaws topple giant trees along streams, the most immediate effect on the salmon’s home is to remove its protective roof.
In sunny months, once-shaded creeks now tumble along under the full glare of the California sun. Their temperatures can soar from about 50˚F to nearly 80˚F. That’s what’s happened, for example, in places like Jordan Creek and Bear Creek, where Maxxam Corporation’s intense logging since 1997 has drastically set back a $120,000 restoration project for recovering coho, steelhead, and chinook.
In the fall and winter, the forest canopy would have protected the creek’s watersheds, catching raindrops in branches to evaporate and binding saturated soils with roots. Now, unobstructed rainwater carries loads of sediment and mud straight into the swollen streams.
According to Laurie Weitkamp, a lead coho salmon researcher for the US Fish and Wildlife Service, the fish would be lucky just to hatch at all after logging.
“The eggs are the most vulnerable because they’re just sitting there,” says Weitkamp. “A big flood can easily scour out the eggs” — to be easy lunch for other stream dwellers.
Even a small flood can be lethal to the unborn coho because of fine sediment carried into the water, says Weitkamp. Silt can plug the gaps between gravel particles, so no gentle current can carry fresh oxygen to the eggs and flush away toxins. The eggs suffocate.
But if our coho manages to hatch, its problems with sediment and flooding have only just begun. Fine sediment can trap the small fry in the redd, and block its normal food supply — those drifting insects. The little fish will exhaust any remaining nutrients in its yolk sac and then die from starvation, unable to seek food or escape.
If the newly hatched coho does find drifting insects and eventually manages to wriggle out of the gravel, it may emerge into a featureless moonscape, silt filling in many of the good hiding places between rocks. Now, when the fry comes face to face with a hungry green heron or steelhead, it won’t even have the chance to dodge into a safe nook.
Fine sediment is also dangerous when it stays in the water, muddying clear creeks.
“It would be like living in a very dusty environment,” says Carl Schreck, a professor at Oregon State University who studies salmon physiology. “Those particles are sharp.”
Silty water scrapes through gills, scratching tissues and stripping them of protective mucus. Gills raw and clogged, the coho will have a harder time getting oxygen and the stress can suppress its immune system. Meanwhile, all those microscopic scratches provide the perfect entry point for disease. The coho will have a harder time spotting food in the murky water too. Just as the juvenile needs to be fattening up, it can end up undernourished, and sick from clogged gills.
At any stage in the juvenile salmon’s life, a massive flood might flush it downstream to face more predators and more difficulty finding food. If the coho hangs on through the rainy season, its next big challenge will be the summer sun. Shallowed by logging-related sediment, the water gets warmer and so does the fish.
“The warmer the fish, the faster chemical reactions in its body happen,” says Schreck. “[So] as the water gets warmer, the fish is metabolizing faster and faster.” The result is our coho needs to eat more and more just to keep up, and has less energy for growing.
There’s another challenge.
“When we alter the habitat this way, it begins to favor warm-water species,” says Jeffrey Jahn, a fish biologist with the National Marine Fisheries Service. Species like bass, sunfish, and bluegill begin to flourish, and some of these like to eat juvenile salmon.
Over time, logging makes creeks begin to lose their habitat diversity. Old trees no longer fall into streams to create cover and break the current. Our coho must try to survive in wide-open water with fast currents and no places to rest and hide from those added predators.
California forest practice rules today have some protective measures. They limit clearcuts. A logging company can’t take out more than about 40 acres at a time. Streams and rivers must have buffer zones, a swath of forest left on either side.
“These measures do help,” says David Hines, a National Oceanic and Atmospheric Administration (NOAA) Fisheries biologist. “But NOAA Fisheries’ official position is that the California practice rules are not adequate to protect coho.”
Weitkamp says logged habitat can sometimes support salmon in the good years, “but when you add droughts, El Niño years or other major catastrophes, those populations can’t survive.”
As Jim Lichatowich, author of Salmon Without Rivers, points out, the development stages of the salmon are like a chain. “And if one of those links fails,” Hines says, “the species is not able to complete its lifecycle.” What’s choking the coho out of existence in California is a compound of challenges — an incremental strangulation.
Even within a lifecycle stage, coho face cumulative pressures. The sediment, the flooding, and the heated water may not kill a coho outright. After all, says Schreck, it evolved to cope with the occasional disaster. But too many pressures for too long will cause a general stress response in the fish. Just like a human, a fish that is chronically stressed can experience a depressed immune system, stunted growth, and compromised reproductive ability.
Chronic exposure to stress hormones can even kill neurons, says Schreck. And any compromise to one developmental stage makes the salmon that much more vulnerable to pressures at the next stage.
Meanwhile, as our juvenile coho negotiates the environmental repercussions of a catastrophe, nearby habitats and their coho populations have also been devastated. Some streams, even whole watersheds, are so altered they no longer support coho.
That means the juvenile and his stream-mates are on their own. “They don’t have nearby populations to help recolonize or compensate for lack of reproduction [if disaster strikes],” Hines explains. Should a massive flood wipe out the salmon in our coho’s stream, there would be no neighboring populations to replenish that stream with salmon over time. The population would be gone forever.
Such habitat fragmentation is a harsh reality in much of the coho’s southern range, including California. “Across the landscape,” as North Coast fisheries biologist Pat Higgins has put it, “there is nowhere to go.”
A Bird in the Bush
The marbled murrelet, like the coho salmon, spends its adult life at sea, except for breeding. Like the coho, it faces daunting odds at sea — of being eaten, sickened by pollution, malnourished, caught in fishing nets. The robin-sized murrelets fly inland to their home range in the spring. And like the coho, they depend on the woody giants of the old-growth forests for breeding and rearing their young.
Probably monogamous for life, a marbled murrelet pair will return to the same stand of trees every year. The couple chooses a high, broad, moss-padded branch in one of the old trees.
They’ll have only one egg to look after, and the pair will take turns incubating and flying out to sea for food. In about 30 days, their single downy chick will hatch, complete with tiny webbed feet. For the next 30 to 40 days, its parents will make about ten daily trips to the ocean to bring back food. When the chick is ready to fledge, it will plunge from its nest site, fly out to sea, and probably never see its parents again.
For the thickly feathered marbled murrelet, adapted to diving for fish in cold ocean waters, the shady coastal forests are ideal nesting places because they stay cool. They also provide shelter from predators — crows, ravens, and jays love to dine on eggs or chicks.
For the marbled murrelet, disaster in the coastal forests comes in two forms — annihilation of their breeding site (the storm blows your entire home away) or partial destruction (you lose the south-facing wall and maybe part of the west wall too).
“We don’t really know what happens when their home range is destroyed,” says Kim Nelson, a marbled murrelet researcher and professor at Oregon State University. If the marbled murrelets are anything like some of their close relatives, Nelson says, “they may lose years of nesting, and some may not breed again.”
Since marbled murrelets evolved to nest in old forests that rarely changed over the years, scientists don’t know how easily they can adapt to a lost stand or how quickly they
can find a new nest site, if at all. And what happens if that pair returns to its nest site to find that south-facing wall completely gone? Part of the stand was felled. Or maybe a logging road was cut straight through. Now crows, ravens, and jays can wander deeper into the fragmented forest, following roads, attracted by the berries that often grow in recent clear-cuts, and find a murrelet nest for an easy dinner. Whether the murrelets lose their nest site, or a raven kills their single chick, that pair has lost a year’s chance to reproduce.
Murrelet pairs successfully raise about 30% of their chicks. That number isn’t too different from other bird species, but because marbled murrelet pairs lay just one egg per year, only once every three years do they have a chick that survives. If that number becomes once every four or five years, the pair could die before they’ve raised enough chicks to sustain the population.
That’s probably what happened, for example, following Maxxam’s logging in places like Bear and Yager creeks, where murrelets occupied several stands according to a 1993 State Fish and Game Report.
But scientists have studied the effects of fragmentation and predators only through artificial nest studies or experimental, small-scale clear-cuts and partial harvests. No one has yet studied marbled murrelets whose stands have been destroyed or partially cleared by commercial logging, even where known nesting habitat is being cleared.
Still, scientists do know the murrelets aren’t keeping up. According to a 2001 Department of Fish and Game report, 60,000 marbled murrelets once lived in California. Between 3,000 and 6,500 remain. The surviving population continues to disappear at a rate between 4% to 7% a year. And like the salmon, marbled murrelets in California are trapped in small pockets of surviving forest. If they disappear from those pockets, there will be no neighboring populations to fill the
vacuum.
Once disaster abates, you could rebuild your home. A marbled murrelet or coho salmon can’t. Even if logging were stopped tomorrow and forests were allowed to regenerate, Nelson says scientists don’t know how quickly the murrelet could rebound.
“It’s not just the forests, it’s the ocean too,” she says. “There are oil spills and overfishing, El Niño, anything that affects the food supplies.”
The picture is complicated for the coho also. If logging stopped, Hines says, “in-stream habitat has a long way to go to recover.” It could take years to flush sediment downstream, and centuries for trees along creeks to age, die, and fall into the streams to diversify the streambed. This logging legacy means forestry practices should include measures that fix degraded areas, he says.
If those restoration efforts begin, the coho would do their part quite well: they lay hundreds of eggs. “If you had [good] habitat [for] high survival,” says Hines, “the coho might be able to bounce back fast.”
