Near the Dallas Road breakwater in Victoria, rich kelp forests thrive just below the water’s surface, benefitting from the cold temperatures, according to Brian Timmer, a PhD student at the University of Victoria (UVic). However, as different parts of British Columbia experience localized warming pockets known as microclimates, some areas that were once abundant with kelp forests have vanished.
A recent study led by Timmer from UVic and published in Ecological Applications revealed that historical data on kelp and macroalgae communities in the northern Salish Sea indicated a significant decline. By analyzing maps, scuba surveys, and aerial photos dating back to 1972, the research team compared the data with findings from 2023.
The study uncovered that vast bull kelp forests, which once covered over 5.5 million square meters in the northern Salish Sea near the Comox and Denman Island region, have vanished entirely. This loss is ten times greater than the previous baseline set around 2000. Notably, the majority of the bull kelp decline occurred between 1972 and 1984.
Contrary to the belief that recent heatwaves were solely responsible for the disappearance of B.C.’s bull kelp forests, the study indicates that the most significant loss occurred several decades ago. Timmer’s research specifically focused on a warm water pocket near Comox and Denman Island within the Strait of Georgia, which ranks among the top 10% of global ocean warming temperatures.
Over the past 50 years, sea surface temperatures at the Chrome Island lighthouse, off Denman Island, have risen by 0.25 degrees Celsius per decade, totaling a 1.66-degree Celsius increase. These rapid warming periods have been detrimental to kelp populations, as experts emphasize the critical role of kelp as a foundation species and primary producer in marine ecosystems.
The decline in kelp populations, including a 78% decrease in sugar kelp and a 98.5% decline in red bladed algae since 1972, is attributed to the warming waters along British Columbia’s coast. Timmer, in collaboration with the Kelp Rescue Initiative and First Nations, is actively working to restore kelp forests in the region by identifying suitable habitats for long-term kelp growth and replanting kelp species.
William Cheung, a professor at the University of British Columbia, stressed the importance of understanding historical baselines to inform conservation efforts and climate adaptations accurately, noting the necessity of preserving kelp-rich areas to protect marine ecosystems.