Much has been made of the complex relationship between a changing climate and the world’s oceans, and for good reason. But the blue of our spinning marble isn’t just from seawater, it’s freshwater lakes, streams and rivers too. Water managers are keeping a close watch on freshwater supplies as droughts intensify, but of course, fresh water doesn’t just exist so it can come spurting out of our faucets whenever we need a shower or a drink. The world’s freshwater resources are a magnificent and fragile ecosystem supporting abundant plant and animal species. While fresh water covers just one percent of the globe, it supports 10 percent of all animal species on Earth.
Now, a new report from the National Wildlife Federation puts a magnifying glass on freshwater, climate change, and the most well-known denizens of lakes and waterways – fish.
According to the report released today, increasingly severe droughts, warming winters, and wildfires, are expected to destroy approximately 50 percent of the nation’s coldwater fish habitat by the end of the century.
The report highlights many of the direct impacts that climate change is having on fresh water. Lakes and streams, for example are getting warmer and prolonged droughts are intensifying this by making lakes and streams even shallower and more prone to rapid warming.
In Yellowstone, several tributaries important for trout spawning now run dry in the summer, and in 2012, the National Park Service closed large stretches of the Madison, Gibbons and Firehole Rivers to anglers in response to the extreme drought.
Last summer also saw 58,000 fish — including 37,000 sturgeon worth $10 million — wash up dead along a 42 mile stretch of the Des Moines River.
As the temperature rises, aquatic wildlife metabolisms increase which increases respiration rates. Yet warmer water also holds less oxygen, which has the perverse effect of making it harder for fish to breathe. Last month, 1,100 Alaskan king salmon died while traveling to their hatchery because of 80 degree water temperatures.
Days with mean stream temperatures exceeded 70 degrees Fahrenheit and were thermally stressful for trout in the Madison River, near McAllister, Montana. Source: USGS.
Snowpack in the West, which now melts as much as four weeks earlier than it did fifty years ago, is also confusing fish life cycles which have adapted to historically predictable flow regimes.
There are also a host of more subtle consequences. Warmer waters can throw open the doors to invasive species, and the wildfires which are expected to grow in intensity and frequency in coming years will dump massive amounts of ash and silt into rivers, choking out native species.
“Temperature increases of even a few degrees can have dramatic impacts, harming iconic game fish like salmon, trout and walleye and giving a leg up to destructive invaders like sea lamprey,” said Jack Williams, Trout Unlimited senior scientist and one of the lead authors of the report. “We need to manage our water resources in a way that ensures that both people and fish have the clean, cool, and abundant water they need to survive
Following the Hayman Fire in Colorado in 2002, the South Platts River lost 70 percent of its trout. The Whitewater-Baldy Fire of 2012 was so damaging to the local Gila trout of New Mexico that wildlife mangers manually relocated the fish to unaffected rivers to save them.
A study published last spring by researchers at UC Davis predicted that climate change would eliminate 82 percent of California’s 121 native freshwater species by the end of the century.
While most of the news for freshwater fish is grim, there is at least a glimmer of hope in the growing awareness of the problem and the scientific commitment to continue studying the issue. Just this week, officials in Ontario pledged to invest $2 million a year to keep the Experimental Lake Area in Northwest Ontario up and running. ELA is only large-scale, freshwater experimental research area in the world.
Angling is enjoyed by at least 27 million Americans who collectively pour $26 billion into the economy.
“Sportsmen are on the front lines of conservation. They’re already seeing changes where they fish and they know we can’t leave this problem for our children and grandchildren to deal with,” said Larry Schweiger, president and CEO of the National Wildlife Federation. “We need action on the local, state and federal levels to cut industrial carbon pollution, invest in clean energy, and make communities and habitats more resilient to the impacts of climate change. President Obama’s plan to act on climate is a major step in the right direction.”