As invasive plants encroach on the pristine waters of Lake Tahoe, officials are weighing whether to use aquatic herbicides for the first time to contain their growth and prevent them from clouding the waters.
Plants like curlyleaf pondweed and eurasian watermilfoil have long thrived in the Tahoe Keys, a boating community located on a lagoon off the southern end of the lake. The local property owners’ association says the methods it has historically used to contain weeds — including taking them out manually — are no longer sufficient.
Along with some scientists and lake protection groups, they’re lobbying the Tahoe Regional Planning Agency Governing Board and the Lahontan Regional Water Quality Control Board to permit herbicide use in the Keys.
“This fact is beyond debate: If we do nothing, or fail to act quickly, the worst fate for Lake Tahoe is unavoidable,” Darcie Goodman Collins, chief executive officer of the League to Save Lake Tahoe, told the Reno Gazette Journal.
The League and the Tahoe Keys Property Owners’ Association are among a longer list of supporters of using herbicides to contain the invasive plants from spreading that also includes scientists at the Tahoe Environmental Research Center; University of California, Davis; the University of Nevada, Reno; and the Tahoe Resource Conservation District.
They argue the weeds could harm lake clarity, inhibit boating and affect the rest of the lake’s ecosystem. They’re advocating for a trial program that would use UV light, manual weed extraction and herbicides to remove up to 75% of the invasive plants over a three-year period.
Groups such as the Sierra Club, Friends of West Shore and the California Sportfishing Protection Alliance oppose herbicides, which have never been used in federally-protected Lake Tahoe or the Keys. A similar effort to introduce herbicides in 2015 was scuttled.
Instead, they are pushing to wall off the Keys to contain the invasive plants and returning parts of the lagoon to the native marshland — an idea that property owners’ oppose.
“Making sure the Keys homeowners can take their boats out of their backyards is more important than saving the lake?” said Tobi Tyler, Vice Chair of the Tahoe Area Group of the Sierra Club and a former water resource engineer with the Lahontan Regional Water Quality Control Board.
Charles Goldman, a longtime professor of limnology Emeritus at the UC-Davis who has studied Lake Tahoe for 60 years and supports the use of herbicides, said that over the years, herbicides have been developed which degrade in days instead of weeks.
He said the lake is warming measurably due to climate change, fueling accelerated growth of weeds, and it’s time to adopt new methods to eradicate them. He said another step that could be taken to suppress toxic algal growth in the Keys is to do away with irrigated and fertilized grass lawns.
“It is important to give lake science a chance to prove that this is not only a safe and desirable approach but also a very important one for the good of Lake Tahoe, our increasingly threatened lake ecosystem,” Goldman said.