Smoke from the fires covered 70% of California

May 23. () –

Up to 70% of California was covered in smoke from severe wildfires during parts of 2020 and 2021according to a study from the University of California at Davis.

The study, published today in the journal Communications: Earth & Environmentcombined sensors located in lakes with satellite images to find that the maximum smoke coverage has increased by approximately 257,000 square kilometers since 2006.

The study measured lake responses to wildfire smoke in 2018, 2020 and 2021, the three largest fire seasons on record in California. It found that the lakes were exposed on average to 33 days of high-density smoke between July and October, with August and September having the highest number of smoky days.

The magnitude of wildfires in California — a territory the size of Sweden — has quintupled since the 1970s, the study says. However, little is known about the impact of smoke on lake ecosystems.

“We are facing a scenario in which for the next 100 years or more, smoke will be a feature of the landscape,” he said it’s a statement lead author Steven Sadro, a UC Davis limnologist and associate professor in the Department of Environmental Science and Policy. “What does that mean for fundamental ecology? What are the implications of those changes? Those are the big questions we focus on in aquatic systems.”

Answering those questions requires a bit of serendipity. It is necessary to have scientific instruments in lakes when and where smoke from forest fires is produced to measure the effects.

As the smoke settled over the state throughout the three main years of the study, scientific sensors in 10 lakes took note of the changes.

The lakes spanned a gradient of California landscapes, from cold mountain lakes to warm, murky waters. They ranged from Castle Lake in the Klamath Mountains, to Lake Tahoe and Emerald Lake in the southern Sierra Nevada, Clear Lake in the Coast Range, and a site in the Sacramento-San Joaquin River Delta.

“We were measuring things like temperature, light and oxygen in the water,” said lead author Adrianne Smits, a research scientist in the Department of Environmental Science and Policy at UC Davis. “These are all components of lake productivity and health. “We were interested in how those things change in smoke conditions.”

Scientists hypothesized that smoke and ash would “dim the light,” affecting the photosynthesis and respiration rates of the lakes’ plant and aquatic life, the foundation of healthy lake ecosystems.

CHANGES IN THE LAKES

The study verified that smoke from wildfires changes light, water temperature and oxygen in lakes (the basic factors of lake function and health), but those changes are as variable as the single lakes studied.

Smits said that There is no single answer to how wildfire smoke affects lakes., apart from “It depends.” Lake size, depth, smoke coverage, nutrient levels and more dictate how a lake responds to changes. But the lakes are changing.

“We are seeing changes (often decreases) in photosynthesis and respiration rates that drive almost everything else,” Smits said. “Food webs, algal growth, the ability to emit or sequester carbon depend on these rates. They are all related and the smoke is transforming them“.

This points to the need for more research to understand how the scale, scope and intensity of recent and future wildfires affect lake ecosystems.

“We need to reframe the way we think about wildfire smoke: as a seasonal climate phenomenon and not simply as an ‘event’ that comes and goes,” Smits said. “We think about it for our health, but we should also think about it for the health of the ecosystem.”