We all know the story of a feathered friend in a noxious, underground environment . . . My favorite definition of an indicator species is from The World Atlas: “Any living organism that can be used to measure certain environmental conditions.” My favorite example is of salmon health measuring the effects of climate change. To get dramatic: Where salmon go, humankind will follow. If our actions as a species drive salmon to extinction, we will suffer the same fate. Granted, we will use technology to delay the inevitable, but our fate will be sealed.
Photo Credit: Friends of the Issaquah Salmon Hatchery
Where are we now as a race, according to our selected indicator species? Pacific salmon are in decline. Precipitous decline. Present returns to the Columbia River system are estimated to be 5% of what Lewis & Clark reported in 1805. More locally, all 8 of the Chinook runs in the Puget Sound are listed as ‘threatened’ or ‘endangered’. Even more locally, the fish at the Issaquah Salmon hatchery have been more impacted by disease in the last few years. The common element? Temperature. Salmon are cold water animals. Extended exposure to >70F is lethal. As water temperature goes above a comfortable (for salmon!) 50F, they are more disease prone.
Higher temperatures during the winter mean more of the precipitation in the mountains comes down as rain, as opposed to adding to the snowpack, whose slow melt in the spring and summer feeds cold water into salmon streams, and recharges groundwater. With increases in rain as opposed to snow, river levels fluctuate wildly, leading to flooding during winter and spring, and drought in the summer. Those floods are hazardous to salmon in several ways. Silt and muddy water are to salmon as wildfire smoke is to humans and other air-breathers. It hurts. Silt erodes the fishes gills, which can lead to disease and death. Worse, the silt settles into the gravel that makes up the bottom of a healthy salmon stream, smothering life there, especially when the salmon have laid there eggs in the gravel. In extreme flood conditions, the water flow rolls the stream bed downstream (known as ‘scouring’) effectively killing any salmon eggs there.
Warming of the ocean surface water has had momentous impacts on salmon and other species. The 'Alaska Gyre' is a huge counterclockwise circular current in the arms of the Aleutian islands. The Gyre pulls nutrient-rich water from the depths up where sunlight and photosynthesis conspire to provide the bottom of a food chain, from phytoplankton to [larger] plankton, to forage fish (herring, anchovy, sand lance) and to our favorite indicator, salmon. The warming of the ocean has changed the timing and place of these upwellings, shifting the availability of food all along this chain. Salmon have been in their present form for almost 4 million years, and have adapted to changes like this many times in the past, but never so much change in so short a time.
Next topic: What Can We Do Individually to Avert This Fate?
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