A comprehensive report on the health of Lake Champlain says there’s still too much phosphorus pollution in the big lake.
The report does note some good news, such as declining mercury concentrations in fish.
But floods last year boosted phosphorus levels to their highest level in two decades. And environmentalists worry that the problem will only get worse as a changing climate causes more precipitation in the Lake Champlain basin.
The report was released by the Lake Champlain Basin Program, which every three or four years takes a comprehensive look at the lake ecosystem. Scientists assess everything from invasive species to the concentrations of phosphorus in various lake segments.
And the news on phosphorus isn’t good. Bill Howland directs the basin program, which oversees the management plans for the lake. He says most segments of the lake have not meet phosphorus reduction targets.
"When the main lake is not meeting a very rigorous target, well we need to be concerned because it’s not meeting a target. But keep in mind that target is very rigorous," he says. "But in other parts of the lake – Missisquoi Bay and St. Albans Bay and the south lake – the targets are not very rigorous and we’re not meeting them. That’s a cause for even greater concern."
Phosphorus is a nutrient and it flows into the lake from farm fields, sewage treatment plants, eroding stream banks and fertilized suburban lawn. It fuels the growth of toxic blue-green algae which can spread in pea-soup like blooms across the water.
The report points to signs that phosphorus reduction efforts are starting to pay-off. But the report also notes that the floods of 2011 brought record levels into the lake as the nutrient was washed in from eroding stream banks.
Scientists say climate change will bring more precipitation and more floods. Howland says climate change presents an additional challenge to reduce phosphorus loads to the lake.
"We have to expect more severe storm events and we may have more storm events. And we are going to have more rainfall overall," he says.
Natural Resources Secretary Deb Markowitz says the report shows positive trends as well. Mercury levels are declining in fish. Efforts to control invasive water chestnut are working. And sport fish such as lake trout and Atlantic salmon are showing fewer signs of being wounded by lamprey.
But Markowitz says controlling phosphorus remains a vexing problem, in part because it comes from so many sources.
"What it really points to is the challenge with stormwater management. And it’s stormwater management from farm fields; it’s stormwater management from our local roads. Our dirt roads send a lot of sediment into the system," she says. "And it’s stormwater management from our … urban and suburban areas."
For environmentalists the message from the report is two-fold. Climate change is making conditions in the lake worse, and society needs to step up efforts to control pollution. Louis Porter is a clean water advocate with the Conservation Law Foundation.
"I don’t think the controls we’ve been using were adequate before we started to see the effects of climate change, which are arriving and will continue," Porter says. "They certainly won’t be under the increased precipitation, increased storms… Climate change makes almost every threat and almost every problem for the lake worse, from invasive species to phosphorus pollution."
The report does not suggest new regulations or controls to limit phosphorus. But it does outline steps that people can take – such as not fertilizing their lawns – to stop the nutrient from entering the environment.