Invasive weeds are threatening to take over Lake Tahoe. Here’s what’s being done.
Aquatic invasive weeds are plaguing Lake Tahoe.
Despite expensive and regular mitigation efforts, a collection of invasive species of weeds, namely Eurasian watermilfoil and curlyleaf pondweed, has overtaken parts of south Lake Tahoe, and is threatening the rest of the lake.
“The aquatic weed infestation covers over 90 percent of the Tahoe Keys lagoons in the summer and provides sources of continuing infestations in the lake itself including popular recreation areas like Emerald Bay,” the Tahoe Regional Planning Agency said in a news release. “The invasive weed growth degrades water quality and clarity, disrupts the natural ecosystem, impedes boating and recreation and releases nutrients that can contribute to harmful algal blooms. Despite considerable investment by property owners, the weeds continue to spread and officials and the scientific community are urging immediate action.”
The infestation is densest in the shallow, warm lagoons of Tahoe Keys, a development of man-made waterways in the city of South Lake Tahoe that is home to 1,529 homes and town homes, 900 docks, a commercial marina, and a commercial center. The neighborhood’s lagoons encompass 172 acres of waterways, according to Tahoe Keys Weeds, a collaborative group working to address the spread of invasive weeds in the lake.
The neighborhood has a large number of vacation homes and vacation rentals, making it a popular destination for tourists. In the summer when the weeds are at their worst, boats traveling in and out of the lake from the lagoons have spread the invasive species to popular recreation areas such as Emerald Bay and Sand Harbor.
“The plant’s swift and multiple modes of establishment, coupled with its ability to tether to boats, strongly suggest that this invasive species could become well established in much of Lake Tahoe’s nearshore – depths of 30 feet and less – within the next few years,” Tahoe Keys Weeds said on its website.
The Tahoe Keys Property Owners Association began researching mitigation techniques in the mid 1970s. Despite efforts, the problem has persisted. Cutting the weeds back and mowing them down was the primary method of abatement for decades, but still the weeds spread.
Since 2001, the property owners association has spent approximately $5.7 million on weed control and water quality issues.
“The aquatic invasive weeds have continued to spread, despite our investments of millions of dollars to contain and remove the plants,” said Greg Hoover, water quality manager for the Tahoe Keys Property Owners Association, in a statement. “Recent collaborative efforts to slow the spread into Lake Tahoe have shown some promise, but new control methods such as aquatic herbicides shown to be safe and successful in similar settings need to be tested to help prevent widespread infestations around the lake.”
To get a handle on the issue, the property owners association will propose a new plan in a public hearing on Jan. 26. The new plan includes “testing EPA-certified aquatic herbicide” and “innovative methods such as aeration and ultraviolet light,” the Tahoe Regional Planning Agency said.
“This is not a (Tahoe Keys Property Owners Association) problem, this is a lake-wide issue,” said Joanne S. Marchetta, executive director of Tahoe Regional Planning Agency, in a statement. “We’ve seen public and private partners come together to improve and fund elements of this environmental process because everyone understands that we are at a tipping point. The results of this decision will influence the future of Lake Tahoe for years to come.”
This story was originally published January 10, 2022 at 1:19 PM with the headline "Invasive weeds are threatening to take over Lake Tahoe. Here’s what’s being done.."