Two years ago, that bothersome Ludwigia weed was choking some of Sonoma County's key waterways, clogging spawning paths for endangered fish while offering safe harbor for West Nile-carrying mosquitoes.
Today, the battle to clear the channels leading to and from the Laguna de Santa Rosa is showing real-life signs of success.
"We're seeing whole families of otters out there that we've never seen before," said Julian Meisler, restoration manager for the Laguna de Santa Rosa Foundation.
The "there" Meisler refers to is 5.5 miles of drainage creeks west of Rohnert Park and along Occidental Road near Sebastopol and 80 acres of flood plain in the Sebastopol area. Two years ago, the area was judged to be the most heavily infested with the invasive aquatic weed, and thus the target of a three-year effort to reverse its spread.
Ospreys and kingfishers have also returned to the reopened waterways, once fully carpeted with Ludwigia, a member of the water primrose family.
Signs of the fast-growing plant began showing up a dozen years ago. Nothing was done to combat its spread until fears arose that the intertwined plants were providing a protective umbrella from pesticide sprays designed to kill the potentially disease-bearing mosquitoes that bred in its thicket-like midst.
That alarm helped overcome environmental opposition to a coordinated plan carried out by the Laguna foundation and its contractors to use herbicides to kill the Ludwigia.
The foundation, with nearly $2.1 million in funding provided by the Sonoma County Water Agency, the city of Santa Rosa, the Marin/Sonoma Mosquito & Vector Control District and the California Wildlife Conservation Board, has spent $1.5 million on the battle to date.
Meisler said the balance of the funding will be spent this summer on another round of spraying, removal and mapping, similar to what was done the first two years.
In the first year, 5,300 tons of dead Ludwigia were hauled out of the waterways near Rohnert Park and Sebastopol. This summer, about 25 percent of that amount was removed, partly because the larger areas had been cleared the year before.