Editor’s Note: Reporter Cara Hollis is studying Sustainability and Journalism at the Incline Village-based Sierra Nevada University.


By Cara Hollis

State of the Lake

The winter that we just lived through, in which an extreme dump of snow was followed by a long dry spell, is looking like our new normal, and winters like this one spell trouble.

The pattern has long been documented in the annual Tahoe: State of the Lake Report produced by the University of California, Davis, Tahoe Environmental Research Center. The research facility monitors Lake Tahoe’s ecosystems and charts how natural variability, long-term change, and human activities are affecting the lake’s physics, chemistry, and biology.
It has found that the confluence of warmer temperatures, a smaller snowpack, more algae, and an increase in invasive species mean that Lake Tahoe is being altered by warmer weather in many ways that aren’t always apparent to the human eye.

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LESS SNOW, MORE RAIN: This graph charts the percentage of precipitation that falls as snow in the Tahoe Basin. The trend shows a consistent decline — only 33% of the precipitation fell as snow in 2020 compared to 52% in 1910. Graph by Shohei Watanabe/UC Davis TERC

The Tahoe Environmental Research Center and its forebearers have been taking direct depth measurements around the lake since 1968 and have obtained further lake data from as far back as 1911 from partners like the National Oceanic and Atmospheric Administration. With this team and the historical data, TERC has been able to put together a picture of the past that allows scientists to forecast trends. And current trends show a changing future.

“The most pressing issues facing the lake are climate change — because climate change effects everything — and human impacts,” said Alison Toy, who, as TERC’s education program manager and Tahoe facilities manager, compiled the 2021 State of the Lake report.

The report data contains many indications that in the future the lake may be quite different than the one we experience today — it could be devoid of snow and replete with algae. But the same data also lays pathways toward solutions that could change this trajectory. Whether we stay the course or take new action, our choices have a bearing on Lake Tahoe.

As Toy said, “Everything you do is going to impact the lake.” The report shows how true that is.

Hotter air

While warmer air makes for pleasant days, it does not bode well for the lovers of snow and the health of the lake. 

According to State of the Lake, daily air temperature measurements taken at Tahoe City for the past 109 years show that the average minimum temperature has increased by 4.9 degrees; the average daily maximum air temperature has increased by 2.22 degrees.

These climate-change-driven increases have pushed the average annual minimum temperatures above the freezing mark for the past 15 years, and directly led to a decrease in the percentage of precipitation that falls as snow versus rain. In 1910, 52% of the precipitation fell as snow, versus 2020, in which 33% fell. The trend is not improving.

“We could have persistent low-to-no snow conditions as soon as the 2040,” said TERC Education and Outreach Director Heather Segale. 

The impacts of this change go far beyond negatively impacting the ski season, and the economic implications associated with it. 

Rain washes detritus and chemicals straight into the lake, according to a 2020 UC Davis report on lake clarity. So, decreasing snow percentages can negatively impact the clarity of the lake.

When the historical data is combined with climate models that incorporate current levels of atmospheric carbon emissions, the future of Tahoe looks even warmer.

HOT WATER: This water temperature profile map illustrates how the different layers of Lake Tahoe water measured up in 2020. In comparison to earlier studies, the stratification season — warmer water on top, colder water on bottom — has extended by nearly a month, leading to less deep-water mixing, which is a key factor in maintaining water clarity. Graph by Shohei Watanabe/UC Davis TERC

UC Davis TERC uses globally recognized modelling techniques to predict future temperatures in the Tahoe Basin. Researchers can use these techniques to model what the different temperature futures look like for Lake Tahoe. If CO2 emissions stay on their current trajectory, we are looking at a 9.5-degree F increase in both maximum and minimum temperatures in the Tahoe area by 2094. If this future is allowed to happen, snow will be a thing of the past and the lake will suffer for it.

Warmer water

Lake Tahoe’s water is famous for its clarity, but in the future the warm days on sunny beaches might be spent splashing in water that is not as clear as it used to be.

Increased air temperatures have direct impacts on the temperatures of the lake water, which in turn can have long-term negative impacts on clarity.

“During the summers, Lake Tahoe’s waters become stratified with a lighter, warmer layer of water sitting on top of a denser, colder bottom layer,” Segale said.

With the lake stratified, the colder bottom layer is cut off from the oxygen-rich surface waters.   The State of the Lake report explains that typically, during the winters, when the top layer of water becomes colder and denser, the stratification disappears and allows the oxygen-rich waters at the surface to mix with deep water, creating an oxidized layer at the top of the sediment at the bottom of the lake.

“Having this oxidized layer allows the sediment to hold on to the phosphorus and prevents internal loading,” Segale said. Internal loading occurs when there is an increase in nutrient levels, like phosphorus, that can cause an algae bloom.

According to the report, since 1970 the average annual temperature of the lake has increased by 1.1 degrees F. While that may not seem to be a big increase, the implications are significant: According to the report, in 2020, the stratification began 22 days earlier than it did in 1968 and ended six days later, meaning the stratification season has extended by nearly a month. This negatively impacts the lake’s ability to mix oxygen to the deepest levels.

“The only time you can get deep water mixing is when you have the same temperature top to bottom,” Segale explained. “If the winters keep getting shorter and shorter the window of opportunity for mixing narrows, computer models show that within decades we won’t have deep water mixing anymore.”

If the lake does not fully mix, the oxidized layer may disappear, releasing nutrients that have been stored in the sediment for millions of years.

Toy echoed the warning. “If we lose the oxidized cap, we will start seeing a huge influx in algal growth, which means our blue lake will not be as blue,” she said. “If the algal blooms are cyanobacteria, it will not be safe to swim in anymore.”

Tiny shrimp, big problem

Lurking in the depths of Lake Tahoe is a tiny little invader that, like a heavyweight fighter, has thrown the natural ecosystem of Lake Tahoe out of balance.

Mysis shrimp are one of the most prevalent invasive species in Lake Tahoe, and they directly impact the water clarity. These macroscopic crustaceans (mysis shrimp are not true shrimp, but their resemblance earned them the name) were intentionally introduced into the lake from 1963 to 1965 in the hopes that they would be a food supply for game fish that were also introduced to the lake. 

However, the plan backfired. According to UC Davis TERC, mysis shrimp are light sensitive, so they hide in the dark depths during the day. As most of Tahoe’s game fish are sight feeders who stay in the shallower water, the shrimp were not available to be eaten. 

With no natural predators, the shrimp multiplied. Moreover, the small creatures thrive on the native zooplankton in the lake called Daphnia. 

Daphnia serve a very important purpose in Lake Tahoe because they consume algae and removed fine sediment from the water column, so they contribute tremendously to the clarity of Lake Tahoe’s waters. Since the mysis shrimp introduction, the population of the native Daphnia has collapsed, and the clarity of the lake has been measurably reduced. Trillions of mysis shrimp now reign supreme.

TRAWLING FOR CLARITY: An aerial view of the UC Davis Research Vessel John Le Conte pulling a large custom designed trawl to harvest mysis shrimp from Emerald Bay. Photo by Brandon Berry

There is Hope

Where there is challenge, there is opportunity. That is the motto of many who refuse to bow down to a “certain” future. For Lake Tahoe, that means hope.

From menace to foodstuff

An all-volunteer nonprofit called Shrimply Blue is looking to join in the fight to keep Tahoe’s waters clear by turning the tiny mysis shrimp invaders into dog treats.

TERC researchers first made the connection between the mysis shrimp and clarity in 2011 when the small creatures mysteriously died off in Emerald Bay and the Daphnia population rebounded. Clarity improved by 40 feet.

Since then, much research effort has gone into how to remove the shrimp. This research has presented a practical problem: what to do with the shrimp.

Food scientists at UC Davis were asked to analyze the shrimp and found them to be clean and good to use as a food ingredient. The shrimp were also high in omega-3 fatty acids.

UC Davis Graduate School of Management class of 2020 took on the challenge of what to do with the shrimp as their capstone project.

“The challenge presented was, we have this invasive shrimp that need to be removed, and they are a great source of Qmega-3s: What can we do with them?” said Yuan Cheng, director and co-founder of Shrimply Blue.

After much analysis, Cheng and the team determined that the best business model was a nonprofit focused on producing pet treats.

“If you can get this running and it can be self-sustained ecosystem restoration effort, we think that is super cool,” Cheng said.

SNOW FUTURE: This graph, showing historical snow amounts with predicted future trends, shows a grim future, with an estimated 20 inches in year 2100. Yet reducing emissions turns the trend significantly upward. The red line shows snow amounts with current emissions levels, while the green line shows snow amounts if emission levels are reduced by individuals taking action now. Graph courtesy UC Davis TERC

To figure out how to turn mysis shrimp into dog treats, Shrimply Blue tapped third-year food science student Melissa Huang, who began working on prototyping the treats.

“The first step was to look at other treats on the market that we wanted to mimic the texture or look of and then get a sense of ingredients,” Huang said. “Then it was a matter of trying different amounts and ingredients considering cost and the kind of label we want to see.”

After 25 different batches and testing them out on a group of loyal tasters, Shrimply Blue has a prototype that the target audience is happy with. 

But it will be a while before you can buy Shrimply Blue treats.

“Currently the treats aren’t for sale because they are being collected under a scientific collection permit,” Cheng said.

The California Department of Fish and Wildlife, the issuing authority, wants to see more data, specifically answering questions like: How much trawling is necessary to reduce the mysis population? Will the Daphnia bounce back? How much bycatch (other species) will be caught in the nets before issuing a commercial fishing permit?

UC Davis TERC put together a 30-month research plan in collaboration with the Tahoe Science Advisory Council to look at the ecosystem of lake clarity and how it is impacted by mysis shrimp.

Emerald Bay will be the testing grounds, the plan is to trawl in late summer and early fall in 2022 and 2023 to remove the shrimp and observe the results.

It will require professional fishing crews with larger nets to pull in the kind of numbers needed to knock back the mysis shrimp. Therefore, it will require fundraising.

Donations are being accepted by UC Davis TERC and you can purchase Shrimply Blue swag from their online store.

“100% of profits go to the science,” said Cami Harris, marketing intern for Shrimply Blue.

Once the science is completed, the results will be shared with CDFW and the dog-treats team will hope for the best.

“We will never get rid of all of the shrimp, but if you can get the volume down to 27 per square meter, about a quarter of the current population, the Daphnia can coexist and this is the key to helping water clarity,” Cheng said.

SAY IT AIN’T SO: An Instagram augmented reality filter allows you to enter Tahoe’s snow past and its low-snow future. Courtesy image

Save Our Snow

Tahoe loves the snow. Whether you’re a winter sports diehard or someone who “stayed for the summers,” that white gold is necessary for your fun. It is also vital for fire suppression and healthy ecosystems. Thus, it is a natural rallying point to encourage people to take action.

Climate modeling shows that at the current rate of greenhouse gas emissions, Tahoe is on track to have winters with no or little snow by as early as 2040. That’s right, in less than two decades, this region is likely to lose what it’s known for the world over.

To change the projected future, a powerhouse group has banded together to try to “Save Our Snow.” The campaign is a collaboration between UC Davis Tahoe Environmental Research Center, Protect Our Winters, BrandXR, and Palisades Tahoe. The goal is to show the lovers of snow that making changes in their habits can really impact the future of snow in Tahoe. According to Save Our Snow, if everyone reduced their CO2 emissions by 1 ton annually, it would make a measurable difference in Tahoe snow levels by 2040.

“If you are a skier or snowboarder, or have a business that depends on snow, global warming is going to harm you personally, and to avoid the worst-case scenario outcomes we have to act now,” TERC’s Segale, said.

The Save Our Snow campaign shows how easy it can be to lower emissions. Its website contains an easy-to-use carbon reduction calculator and a form to share your carbon reduction commitment with TERC. It offers tips on how to make your home energy efficient, a guide to voting like your winters depend on it, and the science that shows what the changing climate will really mean for the Tahoe Basin.

While a “ton” sounds like a lot, the goal to reduce by that much is doable. For example, the carbon reduction calculator shows how making small changes in your home can make a big impact on carbon emission: Making a habit of turning off the lights when not in use can save .2 of a ton annually. Double-sided printing can save .3 of a ton annually. Carpooling to work can save .9 of a ton annually. Adjusting your diet to have two meatless days a week can save .5 ton. Small changes can lead to a big impact.

The most eye-opening piece of the campaign is the Instagram augmented reality filter designed by Manhattan-based BrandXR to help users visualize themselves in the future climate.

“With this technology seeing is believing,” said BrandXR CEO and co-founder Moody Mattan. “I could try and describe it to you in an hour or show you in less than a minute.”

BrandXR designed the filter to let users time travel to snows of winters past and then to a low-snow future, all with decade-appropriate ski outfits. The augmented reality brings to life the troubling future predicted by TERC climate scientists.

For POW, which is an advocacy group dedicated to helping people protect the places and lifestyles they love from climate change, the Save Our Snow Campaign is a chance to take their advocacy efforts to the grassroots level.

“Incremental acts lead to cumulative change and if you do nothing that is exactly what you are doing,” said Brennan Lagasse, professor of sustainability at Sierra Nevada University and a creative alliance member at POW. “By actively engaging in a campaign like Save Our Snow you are doing something to contribute and that is what we need right now to deal with the climate crisis.”

The ultimate goal of the campaign is to let people know that Tahoe will be impacted by climate change but also let them know there is something they can do about it.

“It is our duty to promote the actions that will alleviate the worst-case scenario from coming true,” Segale said.

The full State of the Lake Report, and all the past reports, can be found at tahoe.ucdavis.edu/stateofthelake. Find the Save Our Snow campaign at tahoe.ucdavis.edu/saveoursnow.

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