There is a lack of overall data around kelp beds along the coast, said Costa, who heads the Spectral lab at the University of Victoria, which specializes in using remotely sensed imagery to monitor change in marine environments. Some individual kelp beds in BC have been studied, but not consistently over time in a wider way, leaving a poor understanding of what’s going on with the giant algae populations so critical to the marine ecosystem, Costa said. “It’s one thing to look at kelp beds for just one year, but the important part is looking at several years of data,” said Costa, noting that kelp bed growth or loss can be quite dynamic over short periods of time.
Establishing a widespread picture of where and why kelp is diminishing or growing is critical to determining management or conservation policy and even the commercial harvest of these marine forests, she said.
Mapping the Future of Kelp With Old Sea ChartsBut, curiously, to establish a baseline measurement of kelp on the coast, Costa’s high-tech research team relied on antiquated marine maps for the job. Using information from British admiralty charts from 1858 to 1956, the team created the first historical digital map of BC’s coastal kelp beds.Considered navigational hazards, large kelp beds were carefully notated on British charts, which turned out to be an unusual but valuable source of information about coastal habitat in the 19th century, said Costa. A total of 137 charts were scanned, with the coordinates and kelp beds included on digital maps after ensuring the scale and quality of the data, according to the study.
The chart data suggests most concentrated kelp beds are around the north and west coasts of Vancouver Island, in the Johnstone Strait and in northern waters and northwestern Haida Gwaii.
Periods of extremely warm sea surface temperatures persisted for a prolonged period of time and extended thousands of kilometres [Photo: Dave Allen, NIWA]. For the past two summers, the Tasman Sea has experienced a marine heatwave, where periods of extremely warm sea surface temperatures persisted for a prolonged period of time and extended thousands of kilometres.
Vast Quantity of Satellite Images
The next step to map the distribution of kelp on the coast over time is compiling satellite data from 2005 to the present, along with available scientific and government data from kelp inventories from the 1970s to 1990s, Costa said. “You wouldn’t believe the amount of data we have [to analyze],” she said. “For the BC coast, we have almost 6,000 satellite images. The amount of time spent processing data, it’s almost surreal.”
The project is looking at both Bull and giant kelp with help from the Hakai Institute and funding by Fisheries and Oceans Canada (DFO), the Canadian Hydrographic Service and the Pacific Salmon Foundation, Costa said.A complete kelp map for the Salish Sea, which stretches across the inside passage of Vancouver Island, is expected to be complete by mid-2021, she said, adding maps of BC’s central and north coasts will follow.
That was one of the findings in research, published this month in leading scientific journal Natural Hazards and Earth Science Systems, in which NIWA researchers describe how small increases in sea level rise are likely to drive huge increases in the frequency of coastal flooding in the next 20–30 years.