Beaver Lake and Lost Lagoon in Vancouver’s Stanley Park are under threat from invasive plants and pollution, and more must be done to protect the park’s aquatic ecosystems, says a report to be released Monday by the Stanley Park Ecology Society.
The State of the Park report, written by the Society’s conservation programs manager Robyn Worcester, is the first of its kind and was commissioned after a December 2006 windstorm toppled around 10,000 trees in Stanley Park.
When it came time to address the destruction, officials were stumped by the lack of information available on the park’s ecosystems. So the Stanley Park Ecological Society, a not-for-profit organization established in 1988, set out to document the park’s ecological history. The result was a two-year study that will be presented to the park board at its meeting Monday evening.
The park’s ecosystems were divided into four categories: Native wildlife, which has been rated fair and likely to hold steady; Terrestrial ecosystems, rated fair but improving; Climate and Atmosphere, rated fair but expected to decline; and aquatic ecosystems, rated as poor and declining.
The report found that pollution and invasive species — such as the water lilies that are choking Beaver Lake — are major contributors to the aquatic ecosystems’ demise.
According to the report’s most recent data, Beaver Lake shrank to 3.9 hectares in 1997 from 6.7 hectares in 1938 because of sedimentation, increased plant growth and a depletion of oxygen in the water.
“It is going at an accelerated rate,” said Patricia Thompson, executive director of the Stanley Park Ecological Society.
She said the report highlights the need to protect the lake, which is on course to becoming a bog.
“It is an empowering document that will inform the park board and help with these decisions. That’s what really excites us.”
Thompson said park-board commissioners have already asked staff to come back in September with a report on what to do to save Beaver Lake, a direct result of the society’s study.
Lost Lagoon, the second most significant body of water in the park, is also suffering. The water quality of the lagoon, a shallow, brackish pool that was an intertidal mud flat before it was separated from Coal Harbour in 1916, is deteriorating.
Because it is an artificially created wetland, the lagoon suffers from high summer temperatures and low dissolved-oxygen levels, frequent and severe algal blooms, low influx of fresh water run-off, saltwater flow from Coal Harbour, and high levels of E. coli, owing to a high density of feces.
The lagoon is frequented by ducks, swans, geese, raccoons and great blue herons, among other animals.
Last summer, the water turned a bright turquoise, the result, it was eventually discovered, of an algal bloom caused by July’s hot weather combined with an increase in animal feces.
“This is a perfect example of how this [report] will be helpful. When [the lagoon] turned turquoise we had people asking us what it was. No one knew. So we’ll start measuring and monitoring these trends,” said Thompson.
Small wetlands and streams in the park are also in need of protection because they serve as refuge for potentially at-risk species such as the Pacific water shrew and the red-legged frog, which are under threat from the bullfrogs in the larger wetlands, the report found.
The study recommends more environmental monitoring and research, restoration and enhancement work, with priority given to the aquatic environments.
West End MLA Spencer Chandra Herbert, who spent last weekend pulling up the invasive English ivy in Stanley Park, called the report “a springboard to action” for addressing the threatened aquatic life.
“We have to do something or we are going to lose Beaver Lake,” he said, adding he hopes the park board will consider the recommendations included in the report.
There are 50 invasive alien species in the park, seven of which have been identified by the International Union for Conservation of Nature as being in the top 100 worst invasive alien species in the world.
The report also found that the health of Stanley Park’s forest ecosystems is improving thanks to restoration work that came as a result of the 2006 windstorm and continuing conservation activities carried out by Stanley Park Ecology Society staff and volunteers.
Forests cover 256 hectares of Stanley Park, or 66 per cent of the total land, with around 500 trees that are more than 150 years old.
Stanley Park is also home to more than 500 different types of animals and 670 plant species.
The report was funded by grants from HSBC and Vancity.
ticrawford@vancouversun.com