Since the start of a building boom spurred by the 1960 Winter Olympics at Squaw Valley, development and car exhaust have been blamed for Lake Tahoe's declining clarity.
Now, a group of property owners thinks there could be another source of pollution at the Sierra Nevada lake famed for its pure, blue waters: geese.
Members of the Tahoe Lakefront Owners Association say goose feces could be contributing to pollution that's stealing Tahoe's clarity at an average rate of more than a foot per year.
The feces contain phosphorus and nitrogen, nutrients that help fuel the algae growth that combines with sediments to reduce Tahoe's clarity.
"We're just surprised the agencies haven't taken this problem more seriously," said Jan Brisco, executive director of the property owners' group.
Brisco said she's raised the issue with officials from the Tahoe Regional Planning Agency and other groups charged with protecting the scenic lake straddling the Nevada-California border.
"Everyone just sort of chuckled or laughed as if it were funny," Brisco told the Reno Gazette-Journal. "We think it's far from funny."
Officials at the U.S. Agriculture Department's Wildlife Services office in Reno say Tahoe's Nevada side alone is home to about 1,000 geese.
Because an adult Canada goose can account for up to 3 pounds of feces daily, tons of feces could wash into Tahoe each year, Brisco said.
Scientists at the University of California's Tahoe Research Group said while the feces could affect water quality where the birds are thickest, it's probably not a major source of Tahoe's pollution.
"In a lake like Tahoe, my gut feeling is they are probably going to have very little to do with the decline in clarity we're seeing," said group scientist John Reuter.
But Glenn Miller, an environmental scientist at the University of Nevada, Reno, said the impact of goose feces probably is "something to look at. It's something some of us have wondered about."
In recent years, scientists have warned that algae growth spurred by sedimentation and other pollution, including car exhaust, threatens to turn Tahoe's waters green.
Development around the lake has caused Tahoe's clarity to decline from a depth of about 100 feet to 60 feet over the past 40 years.
The property owners' group is working with wildlife officials in Nevada and California on a goose management program.
The group has called for the relocation of more geese from the lake.