Pummeled By Drought And Climate Change, Beloved Lake Tahoe In Hot Water

Lake Tahoe and the community around it are increasingly battered by climate change and drought, with the lake’s temperature climbing 10 times faster than the historic average in the past four years and algae threatening the Sierra Nevada gem’s famous emerald and blue clarity. Intense seasonal changes in 2016 — hallmarks of climate change — killed huge swaths of forest around the lake and nourished invasive species, according to the annual Tahoe State of the Lake Report released Thursday by the UC Davis Tahoe Environmental Research Center. The beloved vacation spot, researchers said, now sees summer conditions for 26 more days than it did in 1968, boosting the danger of devastating wildfires, while the spring snowmelt has moved up 19 days since 1961. If it is increasingly dominated by dead and dying trees and stringy algae washing up on the beach, it will change the way people experience the environment here. Insects, disease and stress — combined with the transition from a historic drought to unprecedented rainfall last year — felled tens of thousands of trees. Invasive Asian clams, spread around the lake by boaters who take on and them dump water during wakeboarding excursions — a heavier craft creates a bigger wake — repopulated on the northern end. Average water clarity, one of the most noticeable symptoms of a warming planet, degraded to 69.2 feet in the nation’s second-deepest lake, a 3.9-foot decrease from 2015. Mark Twain likened boating on Lake Tahoe to floating on air, and when they first started measuring clarity in 1968, researchers could see the Secchi disk 102.4 feet below the surface. Last summer, over just a few months, clarity dropped by 16.7 feet to 56.4 feet as tiny algae amassed in the lake’s upper reaches, clouding the view. In the last four years, the average temperature of the lake at all depths has increased by an average of 0.26 degrees a year to 43.3 degrees Fahrenheit — a rate 10 times greater than the long-term warming rate, the report found. Surface temperatures did fall by 2.5 degrees last July — but it was an anomaly caused by strong summer winds, according to the research center, which started tracking water temperature records in 1970.