Jeremy Miller

Artichoke thistle flower in Wildcat Canyon Regional Park. Citizens with smartphones can help in a statewide weed-mapping initiative.

If you have a sharp eye for invasive plants – and a smartphone – you can help a Bay Area non-profit in its effort to document the distribution and spread of invasive plants across California.

The Berkeley-based California Invasive Plant Council, or Cal-IPC, has found that weeds cost the state at least $82 million annually in terms of increased erosion and flooding, degraded agricultural land and reduced water supplies.

California is hardly alone. A 2005 study by researchers from Cornell University put the nationwide cost of battling invasive weeds at a staggering $120 billion [PDF].

Climate change is making the issue even more complex, says Doug Johnson, Cal-IPC’s executive director, who is trying to better understand how non-native plants may respond and how they may gain advantage over native plants during prolonged bouts of warming or cooling.

“It’s not as simple as saying climate change is going to make everything worse in terms of invasives,” Johnson told me. “But in general, invasive species are generalists and are able to outcompete native plants. They also tend to thrive on disturbance, so a change in conditions that may impact other species more harshly may end up favoring invasives.”

In order to keep track of California’s weeds, and, more importantly, where they’re spreading, Cal-IPC has worked with state and local experts to evaluate a list of invasive and noxious plants.

“We went through those plants, looking through all the quadrangles of various counties or regions and decided how generally abundant they are, whether they are spreading and if they are under management,” said Johnson.

With the data compiled, the group built an interactive, public site called CalWeedMapper, which uses a mosaic of 7.5-minute quadrangle tiles (covering an area of roughly six by eight miles). Though the map’s resolution is still very “coarse,” according to Johnson, the group has begun to harness the collective power of thousands of smartphone-wielding amateur botanists. Mountain bikers in Mendocino, say, or hikers in the Alabama Hills on the east slopes of Mount Whitney can take note of invasive plants and upload their locations to CalWeedMapper by way of a smartphone app called Observer.

The site is tied in with two other large databases operated by the Consortium of California Herbaria and Calflora, which, Johnson says, enhance the precision and reach of the group’s citizen mapping effort.

The effort comes at an opportune time, particularly with so many fires burning across the state and the West. Cal-IPC is particularly concerned with so-called “fire followers,” invasive plants such as cheatgrass, star thistle, knapweed and scotch broom that tend to expand their range as fires scour the land.

“With climate change, one of our main areas of concern is the Sierra. As temperatures warm, invasive species may be able to move up in elevation,” said Johnson. “There are also rangeland species from Plains states, which are often brought in [inadvertently] on heavy equipment and can take off in areas cleared by fire.”

If you are interested in helping Cal-IPC in its weed-plotting effort – and in downloading the Observer smartphone app – you must first register with CalFlora.

Lauren Sommer

Climate change and invasive species threaten Lake Tahoe just as restoration funding dwindles.

Over the last 15 years, more than a billion dollars has been spent to protect Lake Tahoe’s clear waters from runoff and erosion. Now, new threats to lake’s clarity are emerging, just as restoration funding is drying up.

Researchers from UC Davis are hot on the trail of one of those threats. On a recent late summer morning, Katie Webb and a team from UC Davis’s Tahoe Environmental Research Center went looking for it on a boat near South Lake Tahoe.

Hear the radio version of this story Wednesday on The California Report.

“So what we’re looking for is a metal clam corral,” Webb says, pulling on her scuba gear. The “clam corral” is a wire basket that holds clams living on the lake bottom. Webb swims down to it and attaches a rope, so the team can pull it on board.

The clams inside are Asian clams, an invasive species. They were not a welcome visitor when they were discovered in Lake Tahoe in 2002. Webb and her team are monitoring these corralled clams to see how fast the population is growing.

“So you can see this individual is number 11,” she says, pointing to a tiny number super-glued on its shell. They use the numbers to track individuals over time. “We can see how much they’ve grown since we checked them in February and it should be a lot. They grow a lot in the summertime,” Webb says.

“What they do is somewhat disturbing,” says Geoff Schladow, director of the Tahoe Environmental Research Center. Asian clams filter massive amounts of lake water and that’s where the problem starts.

“Of everything they filter, they consume about 10 percent of it and 90 percent they excrete. So their excretions are like these huge nutrient bombs,” Schladow says.

Lauren Sommer

UC Davis researcher Katie Webb holds an Asian clam from their population study.

With thousands of clams per square meter in some parts of the lake, their “nutrient bombs” help create algae blooms.

“So you have this bright green, stringy algae, sort of clinging to the bottom, a few tens of yards from the beach. People would be astounded to see this cause it looks like any place but Tahoe,” he says.

In the face of this invasion, a team from UC Davis has been experimenting with rubber mats that suffocate Asian clams on the lake bottom. So far, the treatment looks promising.

Tahoe Basin Building Boom

Keeping the lake blue – and not green – has been a rallying cry for both environmental groups and Tahoe’s tourism industry. Forty years ago, scientists could see 100 feet into the lake. Today, the clarity has decreased significantly to 64 feet.

“We’re essentially like a bowl and what happens on the land affects the water,” says Julie Regan of the Tahoe Regional Planning Agency. The agency oversees development on both the California and Nevada sides.

“What happened on the land in the 50s, 60s and 70s is that we had a lot of development – rampant overdevelopment,” she says. Tahoe hosted 1960 Winter Olympics at Squaw Valley. Casinos went up. Building was booming. And soon, the region had a runoff problem.

“It’s driveways. It’s houses. What you cover on the land then interferes with the soils ability to filter runoff. That’s what’s causing clarity loss,” says Regan.

Over the past 15 years, local agencies have tried to stop this decline with $1.5 billion of federal, state and local money. They’ve preserved open space and built projects to control erosion and filter runoff.

“In 2008 we got the news from the scientific community that we had stopped the slide and decline of lake clarity. That was great news,” says Regan.

Scientists See Climate Change Impacts

In 2010, however, researchers at UC Davis found the second worst clarity level ever recorded. Geoff Schladow says runoff isn’t the only culprit.

“What we’ve had just in the last few years is this explosion, this large increase in algae and they seem to be concentrated right near the surface,” says Schladow.

These algae are invisible to the eye, but they’re the right size to make the water look cloudier. Normally, they’re competing with large algae near the surface. But Schladow says that’s changing. Algae are heavier than water, so they gradually sink.

“The algae in the past tended to be mixed by the wind every few days. So if you’re a large algae and you sank down 50 or 100 feet, you could be brought up again into the light by mixing.”

Recently, the lake hasn’t been mixing as much. The reason, Schladow thinks, is that the surface waters of the lake have gotten warmer with climate change. Warmer water is lighter than the cold, dense water at the bottom of the lake. So it’s little bit like oil and water. The layers of the lake are more resistant to mixing.

“Now when we have less mixing, the large algae sink out. All we’re left with are the small ones. And so their numbers are going up,” says Schladow.

After decades of conservation work to reduce runoff, a lot of people are disappointed to see climate change posing a new threat to Lake Tahoe’s clarity.

Schladow thinks it’s not hopeless. “It’s a call to redouble what we’re doing, not to give up and walk away. It’s now needed not just to restore clarity but to ward off what may be some pretty uncomfortable and disturbing features of climate change.”

Restoration Funds Running Out

After an unprecedented influx of restoration funding, resources are now running low. Senator Dianne Feinstein introduced the Lake Tahoe Restoration Act of 2011 in Congress to authorize more, but has said she’s not optimistic about getting it passed.

“We know the funding picture could potentially be bleak, so we’re looking to any strategy that we can to keep this momentum going in terms of restoration,” says Julie Regan of TRPA.

On top of that, Nevada is threatening to end its forty-year partnership with California by pulling out of the Tahoe Regional Planning Agency, unless concessions are made about its voting power on new development. Regan says it’s just one more challenge that will make the next few years a critical time for Lake Tahoe’s future.

Spring in the United States comes ten days sooner than it did just 20 years ago, according to scientists on a media call Tuesday.   This phenomenon, known as “spring creep” (or “season creep“), may be good news for flip-flop fans, but it doesn’t always work out well for native species in certain habitats.  According to Reuters, scientists on the call (which was sponsored by the Union of Concerned Scientists) explained that when spring comes earlier, it doesn’t just bring warm weather sooner — it actually throws off the balance of entire ecosystems by encouraging the spread of invasive species, many of which are better able to adapt to the changing conditions than are native plants and animals.  In the American West, warmer weather is already shrinking the habitat of the American pika, and more of it could make wildfires more frequent and intense.