The Pacific and Atlantic oceans off the coast of Canada have been warming over the past 20 years, in some places by as much as 1 degree C. In the north, Canada’s Arctic is warming faster than anywhere else on Earth.
As temperatures rise, species that are accustomed to colder temperatures will be forced further north, while tropical species may expand their range into our waters. Invasive species can quickly become pests competing with native species for food in ecosystems where they have no natural predators.
Increased temperatures could easily upset the balance of native species as well. Pacific salmon have been proven to be very temperature sensitive, with populations heading up the wrong spawning rivers and showing poor physical condition in warmer temperatures. Integral ecosystem species such as zooplankton decreased by a whopping 70 per cent between 1951 and 1993 as water temperatures increased.
In the north, winter ice is now breaking up a full three weeks early and nearly one million sq. kilometres of sea ice have already disappeared, preventing polar bears from catching seals and destroying their habitat. As the Arctic Ocean becomes easier to navigate, increased traffic and pollution could further damage the ecosystem.
Melting ice and increased temperatures could cause the sea level to rise, but by just how much remains unclear. However, even a metre increase could submerge low-lying coastal areas, and increase sedimentation, floods and landslides in sensitive coastal ecosystems where many marine species go to spawn or feed.
Globally, one of the most dramatic effects of ocean warming is coral bleaching. Corals are very temperature sensitive, and when exposed to temperatures outside of their comfort range, they expel the algae that give them their colour and provide them with food. Prolonged bouts of bleaching can kill off entire coral forests, with devastating consequences for the plants and animals that depend on them. In 1997 and ’98, during a warm spell, the most widespread coral bleaching event on record took place, with an estimated 16 per cent of the world’s coral reefs incurring serious damaged. More recently, in 2002, 60 to 95 per cent of Australia’s Great Barrier Reef was affected by coral bleaching. It is expected that as the oceans temperature warms, severe bleaching episodes will increase and we will lose large portions of these fascinating underwater worlds.