The flow of water in Montana's rivers is lifeblood for its economy, both through tourism and agriculture. Montana's trout and the $300 million recreational fishing industry depend on cool waters flowing from melting snow high in the mountains throughout the summer. Irrigated crops play a prominent role in Montana's $2.4 billion agricultural industry, and these crops rely on the same strong river flows during the summer when soils are driest and plants thirstiest. But a broad trend is changing the way streams and rivers flow in Montana.

The pattern over the past fifty or so years is unmistakable. Across Montana, temperatures in March have been rising. An analysis by Climate Central shows that average March temperatures have risen over 7°F since the 1950s. This rise matches general expectations from other research on effects of human-caused global warming in the US West; and the climb is projected to continue (see animated map), although its steepness will depend on how many more greenhouse gases go into the atmosphere.

Warmer March temperatures mean that snow in the mountains begins melting sooner. Earlier snowmelt means less snow remains during the summer months — especially late in the summer — which translates to less water flowing down Montana's rivers. This means less water for irrigation, and slower flows in streams. Slow-moving water heats up more easily when the weather is hot, so slower summer flows mean more opportunities for water to get above the lethal 78°F threshold for trout.

Beyond this, Montanans also have to cope with increased wildfire activity and more outbreaks of tree-killing insects. Both trends, which have been linked to human-caused warming, cost the economy dearly.

Montanans are not sitting idly in the face of these challenges. They have already begun to tap their massive potential to produce climate-friendly wind energy. In fact, it is estimated that Montana's winds could generate as much electricity as nineteen western states consume today; currently, Montana is tapping about 4% of this potential. Making energy from wind produces essentially no greenhouse gases.

Montana also sits on about a quarter of the nation's coal reserves. Governor Brian Schweitzer wants to build coal to liquid (CTL) plants, which use coal to make liquid fuels that can replace gasoline or diesel fuel. However, CTL plants are water-intensive, and the production and use of CTL fuels generates twice the greenhouse gases that regular petroleum products do. Recognizing the carbon challenge from coal, Montana is aiming to be a leader in a new technology that would harvest coal's energy while capturing and burying deep in the ground carbon dioxide that would otherwise be released in liquid fuel production. Even with this step, however, using CTL fuels would still release about the same amount of greenhouse gases overall as burning gasoline or other crude oil products.

Footage credits: Environmental Defense Fund, Government of Canada, Invenergy & the Andy Nebel Company, Getty Images, University of Montana, Broadcast Media Center, American Museum of Fly Fishing, Western Governors’ Association, Phil Takatsuno/ Yellowstone Media, Casey A. Cass/ University of Colorado

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