Sierra Nevada lakes changed more in past 100 years than in three millennia: study

Sierra Nevada lakes changed more in past 100 years than in three millennia: study
The Sierra Nevada’s lakes and streams supply water for millions of Californians

Wildfires and droughts exacerbated by the climate crisis have already taken a devastating toll on the majestic Sierra Nevada mountains in the US West.

Now, researchers have taken clues from the past to discover that global heating has also impacted the range’s aquatic ecosystems in rivers and lakes.

A study, published this week, used fossils and sediments to discover that water and nutrient concentrations are at the lowest levels in the past 3,000 years.

Researchers from the University of Kentucky collected sediment core samples from the bottom of June Lake, east of Yosemite National Park. They also looked at the fossils of diatoms, a type of algae, within the samples.

The samples allowed researchers to recreate California’s climate history over the past 3,000 years, and discover how and when the aquatic ecosystem responded.

While change had occurred over the past three millennia, the most profound shifts in the aquatic ecosystem took place in the period of 1840-2016, otherwise known as the Industrial Era.

The changes, particularly in diatom species, indicate that the lake’s ecosystems are impacted by the heating of the planet caused by greenhouse gas emissions being pumped into the atmosphere.

Along with low water levels and depleted nutrient concentrations, the water column has also become stratified – an indication of the earth’s warming temperatures.

“The lake is stratified and ice-free for a longer period of time. It’s essentially absorbing more of the sun’s energy and as a result of that, the sorts of algae that are in the lake are different,” Dr Michael McGlue, associate professor at the University of Kentucky’s Department of Earth and Environmental Sciences and co-author, told The Independent.

Not only has hotter and drier weather significantly impacted species, but the Sierra Nevada’s lakes and streams also supply water for millions of Californians.

The Sierra Nevada runs north from the Mojave Desert to the Cascade Range of northern California and Oregon. It is home to some of the country’s most loved state parks including Yosemite and a popular destination for millions of people each year.

Earlier this month the Dixie, and soon after the Caldor Fire, became the first wildfires to earn the dismal record of burning from one side of the mountain range to the other.

Dr McGlue said that the climate crisis could have significant impacts on fishing, boating, and swimming in the area.

“With climate change, you know the potential for those resources to exist may change,” Dr McGlue said.

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