Study: Sierra Nevada forests shifting to higher elevations as temperatures warmBy Paul Rogers, email@example.com
POSTED: 05/25/2016 06:48:58 AM PDT
http://www.mercurynews.com/drought/ci_2 ... elevations
In another sign of the warming climate, key species of trees in California's Sierra Nevada mountain range -- including lodge pole pine, red fir and western white pine -- are shifting to higher elevations in search of cooler temperatures, a broad new study by state biologists has found.
From south of Lake Tahoe to the northern Sierra, the areas where the trees are growing has moved on average nearly 500 feet higher over the past 80 years, as new saplings are taking root farther up mountainsides, according to researchers from the California Department of Fish and Wildlife.
"The good news is that trees are adjusting. They aren't just all dying in place as conditions become unsuitable," said David Wright, a senior environmental scientist with the department who helped lead the study. "The bad news is that if they have to move up at all, it shows our impacts are happening and are continuing, and that some of these trees might end up with no place to move up to."
From 2009 to 2015, the scientists compared detailed forest surveys taken by researchers in the 1930s with hundreds of the same locations today. The study, published in the journal California Fish and Game, is the latest to document how climate change already is affecting California's landscape, from rising sea levels to migrating species.
In the Sierra Nevada, overnight low temperatures in June, July and August have risen by 2.34 degrees Fahrenheit over the past 100 years. The warming of the planet is driven by emissions from the burning of oil, gas and other fossil fuels, which trap heat in the atmosphere.
Last year was the hottest year on Earth since modern record-keeping began in 1880, breaking the record set in 2014, according to NASA and the National Oceanic and Atmospheric Administration. All 10 of the hottest years since 1880 have occurred since 1998.
"Nature's many thermometers -- from shifted ranges of plants and animals to earlier snow melt -- confirm the pattern in weather-station thermometers," said Chris Field, a professor of Earth system science at Stanford University who was not involved in the study.
"Climate change is real and local," he said. "When forests operate like rapidly shifting pieces on a chess board, we face a growing risk of losing pieces or even an eventual checkmate."
Scientists around the world have documented that some species of plants and animals that rely on cooler temperatures already have been gradually moving their ranges higher, like castaways on islands in a rising ocean. That's because the air is cooler at higher elevations.
But mountains are cone-shaped, so the higher that plants, animals and trees move, the less habitat is available. And that means wildlife that depend on the affected forests for food and shelter are likely to be squeezed in the coming decades as warming continues.
"Eventually, you run out of ground," said Wright.
One bright spot: Eight other species of conifer trees in the Sierra Nevada that can better tolerate warmer weather, including ponderosa pine and Douglas fir, did not show shifts to higher elevations. The researchers worry, however, that as the climate continues to warm, they too could reach a tipping point, along with the animals that rely on them.
"It's like the frog sitting in the pot. He says 'so far everything is fine,' " said Wright.
Other studies in California have shown similar trends. Nearly 20 years ago, Rafe Sagarin, a researcher at Stanford, found an old thesis from a Stanford student in the 1930s in the library at Hopkins Marine Station in Pacific Grove. The study, done by Willis Hewatt, documented the number and types of sea urchins, anemones and other creatures living in the tide pools along Monterey Bay in the 1930s. Sagarin painstakingly located the same tide pools 70 years later, including the metal markers that Hewatt had pounded into the rocks. When he resurveyed them, he discovered far more warm-water species, historically found...
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