style="font-size:15px;"> The landscape remodeling brought home to me those other likely effects of global warming—not just an increase in air and water temperatures, with their direct implications, but lower stream flows in summer (reducing habitat areas and increasing stream temperatures even more), stream-scouring floods in the fall (wiping out eggs and egg-laying habitat), changes in the timing of freeze and thaw cycles, and sedimentation.
Sedimentation could come from sources previously unthought of. Alarms had sounded recently about Skilak Lake, a critical rearing habitat for red salmon that ascend the nearby Kenai River.4 There, the glacier that feeds the lake is melting more rapidly, depositing more ground-up rock “flour” into the water. The resulting turbidity means sunlight can’t penetrate the lake water as far, which means less photosynthesis, less plankton production, less food for the young salmon.
Downstream of the Stariski bridge, Mauger took a water sample to check turbidity and filled out a data sheet to describe the current river conditions, high and fast. I watched a pair of mergansers, looking like passive wooden decoys, take a wild ride downstream. Then we crossed the highway and walked upstream, past riverbanks restored with fabric and willow plantings and a section where more recent erosion had undercut a bank. We walked through dead, flattened grasses and twisted alders and into the shade of cottonwoods, where snow patches still lingered. Mauger pointed away from the river. “It’s interesting,” she said. “This area’s never been logged, but it’s all open.” Indeed, the “forest” was more grass than trees; most of the spruce trees were broken off, leaving splintery stumps at various heights, and the deadfall of their tops lay under and over the twining grasses.
This was a story that Mauger and I knew all too well. In the warmer temperatures of the last couple of decades, spruce bark beetles in the region had flourished. They not only survived the winters that had previously kept them in check with cold temperatures, but were able to complete their life cycle in a single year instead of two. They loved the hot summers that enticed them from their galleries beneath the bark and propelled them to new trees. The infestation, which eventually killed thirty million trees (decimating four million acres of spruce forest—that is, a land area larger than all of Connecticut)—was the largest insect infestation ever documented in North America. (It was recently overtaken by an even larger attack of pine beetles in British Columbia, also linked to climate warming.)
Spruce bark beetles (Dendroctonus rufipennis), like the Ichthyophonus salmon parasite, are a natural part of the ecosystem in our region—thought perhaps to be the instrument of forest succession, rather than fire—but their success in attacking and killing nearly every adult spruce tree across an entire landscape is unprecedented in either historic or prehistoric (judged by tree-ring evidence) times.5 I well remember the summer “flights” in the 1990s, when a series of overly warm days would release swarms of beetles, like a biblical plague, that would, literally, drive people to the shelters of their closed homes. And I remember the march of death across the landscape—the forest turning red as needles died, then gray, then splintered as the dried-out trunks shattered in winter winds.
Parts of the peninsula were logged, the dead trees turned to chips and shipped to Asia, while others were left “natural” as habitat for insect-eating birds, for building new soil, for eventual regrowth. In both cases, our woods were being replaced with grasslands; it’s thought that the tall native grasses may, for a long time, keep any trees from gaining a foothold.
The changed landscape can, of course, have profound effects on water resources and salmon. Trees provide shade, which can help cool rivers. Trees also provide woody debris, beneficial to salmon streams for breaking up the flow and providing resting and hiding spots for fish.
Mauger waded into the raging stream to take another water sample. She pointed out, against the far bank, a pole and instrument she uses, when she can reach it, to measure stream height. A dead tree had fallen against it, and next visit, when she hoped to be able to wade across, she’d bring a chainsaw to clear the area.
All around us, grasses and other debris were hung in the willows, showing how high the water had been earlier. Mauger surveyed the banks, alert to another climate change threat: invasive species. Two that had devastated habitats elsewhere on the peninsula were northern pike—a toothy, predatory fish that can take down ducks and muskrats while also gobbling up young salmon—and exotic grasses. Neither had moved in naturally, as some species did, mile by mile, as the climate changed. They had been introduced—pike by people who valued them as a sport fish, and exotic grasses by being mixed with grass seed, seed packets, or imported hay. Still, in a hospitable climate, they can flourish. Such “weedy” species can outcompete native ones.
Reed canary grass (Phalaris arundinacea)—“a huge deal,” Mauger said—grows into mats that turn flowing streams into marshes. It’s been used for revegetation of roadsides precisely because it spreads rapidly and builds sod that helps with erosion. All along the West Coast, from California to British Columbia, it’s destroyed wetlands and salmon habitat. Plant specialists once thought that in Alaska’s cold the grass wouldn’t produce viable seed, but recent surveys had found infestations in at least 259 locations on the Kenai Peninsula, including along salmon streams.
“It’s all additive,” Mauger said, capping her water sample. Warmer temperatures, more flooding, greater drying, less shade and debris, human alterations to the river corridor and uplands, invasive species—“the system is getting hammered.”
We made our way back along the river, past the fallen forest and the eroded muddy banks, to the highway. We drove back toward Homer through more dreary rain, and I asked Mauger whether, with all that she knew about consequences, she considered herself an optimist or pessimist about the future.
She hesitated a few seconds before drawing a breath. “I do have optimism that some of the repercussions of climate change can be minimized. We’re going to do that with having better information. That’s what this project is about—getting the information that we need so that we don’t have a collapse in fisheries with no warning.”
She paused again and then added that she was also hopeful that, after so much delay and denial from our political leaders, our national politics would change enough, soon enough. “To make the transitions that we need to make, I think it will be a painful ten years. But we have to start now.”
That summer, the stream temperature work Mauger had pioneered on the four Kenai Peninsula rivers was being extended, with state funding, to the rest of the Cook Inlet watershed—forty-eight sites in all. Mauger had worked all winter on the protocols so that data would be collected in a consistent, reliable manner. “We want to try to identify what types of streams are likely to warm fastest, and what types of systems are likely to remain coolest, so we can make some decisions about where to study more about the habitats and the fish. This is really a first cut at looking at different stream sizes and types, the role of wetlands, the role of lakes.” The plan was, after that, for the same monitoring system to be employed by partners and volunteers in the major salmon streams of Bristol Bay (the location of the most valuable salmon runs) and elsewhere in the state.
In this way climate data would be broken out of the broad models and brought down to a local, real-time, and real-place level, to empower communities with the tools and data they need to protect salmon habitat and watershed health. Biologists and land use planners, it’s hoped, will use the data to identify streams most vulnerable to change, then apply it to decisions about further research, habitat protection, water use, and restoration activities. In that ideal world, fishery managers will incorporate temperature information into their modeling of run strengths and escapements (the numbers of fish allowed upstream to spawn). They will also use everything they know about stock structures and life histories to maintain genetic diversity within Alaska’s salmon, knowing that such diversity is critical to the ability of salmon populations to respond to climate change; elsewhere in the world,
