Lake Tahoe, described as the 'Jewel of the Sierras', glistens in a basin surrounded by the majestic Sierra Nevada Mountains, on the border of California and Nevada. And like many of the great lakes around the world, this one is under strain thanks to a warming trend that may affect its pure clarity, its surroundings and the native species that call it home.
Plummeting to a depth of 1,645 feet, Lake Tahoe is the second-deepest lake in North America, formed around two million years ago. For much of its more recent history, it's been admired as a top tourism destination for winter and summer active holidays, boasting some of the best skiing resorts in the US.
But recently, the Lake Tahoe area has been experiencing extreme weather conditions, see-sawing from very wet and cold winters to drier, less eventful years. Record snowfalls that made local skiers very happy in 2010 and 2011 were followed by years that were far from ideal. Many experts are concerned about how these weather fluctuations are going to affect the state of the lake and what they mean for its long-term future.
Research is being conducted on the lake all the time and the most relevant document to date is the Tahoe: State of the Lake Report 2012 released by the UC Davis Tahoe Environmental Research Center (TERC). Luckily for the researchers, data on the lake goes back as far as 1968, allowing them to draw from over 40 years of statistics. One thing that's become very clear is that the lake is warming ... at all of its depths.
Since 1968, temperatures have jumped by 1.5-2°F (around 1°C), causing a multitude of problems. A warmer lake ecosystem invites invasive species, as well as algae that can significantly affect the water clarity – both of which are bad news for Tahoe's native animal inhabitants. Sudeep Chandra, the associate professor of limnology and conservation ecology at the University of Nevada, Reno and the associate director for the Castle Lake Environmental Research & Education Program, is heavily involved in the research and management of non-native species in Tahoe.
"Temperature is very important for the wildlife of the lake," Chandra says. "[The warming trend] allows [invasive] species to move around the lake more freely than they have been able to before. There is also a lengthening in the growing season of species so they can spawn more often."
Mike Collopy, the executive director of the Academy for the Environment at the University of Nevada, Reno notes that some of Tahoe's invasives got a helping hand from humans, getting transported on boats travelling from other parts of the country or getting dumped in the Tahoe aquatic ecosystem from home aquariums or as live bait. "Down in Tahoe Keys, the water is shallow and tends to really warm up a lot," he says. "Lots of non-native fish species are being found there. Somebody had dropped an aquarium fish in the lake and it was living in the warm water, feeding on the vegetation and it grew to this giant size. There are also small-mouth bass and all these other critters that have been dumped into the lake," he adds.
Invasive animals and proliferating algae are also affecting the lake's famed clarity, which is suffering thanks to nearby urbanisation too. Urban stormwater runoff carries tiny, inorganic particles from developed areas into the lake, dirtying its waters. Much of the water that enters the lake is naturally filtered through the marshes and meadows that surround it, so keeping these ecosystems healthy is crucial for the well-being of the lake.
Tahoe's changing climate is impacting the region in other ways, too. Predictions are that precipitation in the area will fall more and more as rain instead of snow in the coming decades. "The vast majority of snow that falls in the Sierras is within about 2 degrees of freezing, so if temperatures rise [a few] degrees over the next 50 to 100 years, the precipitation is more likely to fall as rain instead of snow,” says Collopy.
Even more worrying are the flood-causing storms that occur when the rain falls on snow, like the one that hit Reno in Nevada in 1997. "[If rain falls instead of snow], we won't get the big snow packs on the mountains or it will be a rain-on-snow event. [During the] big floods in Reno, they had a big snowpack ... and then it got really warm and it rained and it all melted at once. It completely flooded downtown Reno," Collopy recalls.
So what does the future hold for Lake Tahoe? For Chandra, there are reasons to be optimistic. "Science is catching up very quickly and has been able to guide the community with activities like restoring the wetlands and preventing invasive species."
Numerous local charities and organisations have sprung up to monitor and maintain the area, and educational programmes are now in place to create awareness. The efforts are paying off. "In the last decade they have done a really good job of improving those land management practices in the communities and managing the forests," Collopy notes. "A lot of the [recent] increase in lake clarity has been attributed to those successful programmes."
Collopy ends with some sobering thoughts. "Lake Tahoe is located in a very small basin ... and it is going to be sensitive to climate change," he warns. "What [we] really need to worry about is how to respond to these changes. Many of the people in Tahoe are already thinking ahead about [that]."
Top header image: Angela Sevin, Flickr
Human Impact
Human Impact
Human Impact
