Troubled Water, Troubled Times

Future Forecast

Climate change resulting from human activities could be the greatest environmental threat facing life on this planet. Scientists use computer-generated global circulation models to determine which regions are at risk and how. They show, for example, that aquatic ecosystems are especially vulnerable because of their lim­ited ability to adapt to climatic changes; that, as a northern nation with a longer coastline and more freshwater than any other coun­try, we may be among the hardest hit. What else do they forecast?

• As temperatures rise, ocean waters could expand and polar ice caps, glaciers, and sea ice could melt faster than before, raising sea levels by up to one metre, causing higher tides, submerging islands, eroding shorelines, inundating farmlands, flooding coastal wetlands, and polluting ground and surface waters.
• Extreme weather events, such as hurricanes, typhoons, and tor­nadoes, may happen more often, with more severe impacts on coastal and inland areas.
•  Rain and snow could increase in some regions, such as the Great Lakes, but decrease in others, such as the Prairies.
• As the Arctic warms up, huge amounts of methane and carbon dioxide (CO2) frozen under the ocean may escape into the atmosphere, further increasing the greenhouse effect.
• Warmer temperatures in the Arctic could also diminish the albedo effect — the reflection of sunlight off the Earth's sur­face — as less snow and ice curbs the planet's ability to reflect solar heat back into space and allows it to stay in the Earth's atmosphere.
• Farmers may enjoy longer growing seasons, but increasing cycles of drought and flood would stress freshwater resources, lower river and lake levels, and make it harder to cultivate crops.
• Human health could suffer from increasing heat and the north­ward spread of tropical diseases, such as dengue fever and malaria.
• Higher water temperatures could change the course and intensi­ty of major ocean currents, disrupting entire ecosystems, and altering the dispersion of nutrients and warmth that sustain marine life.

Between the Devil and the Deep, Blue Sea

Climate change could mean troubled times ahead for an untold diversity of aquatic life, from the equator to the ends of the Earth:

• The fate of countless plants and animals will depend on their ability to move from unfavourable climatic conditions to ones that meet their survival needs. Those that are endangered, slow- moving, or isolated in fragmented areas could find themselves stranded. Physical barriers, like urban developments and open seas between remote islands, may prevent some life forms from moving to suitable habitats.
• Migrators whose arrival and departure dates are no longer in sync with the rhythms of nature may miss the food sources they need to survive, the warm weather they need to breed, and the wind and ocean currents they need to travel.
• Changes in the timing and duration of ice cover will affect the life cycles of many species. Northern wildlife associated with sea ice, such as polar bears, seals, walruses, narwhals, belugas, guillemots, and arctic cod, could suffer great population declines.
• Some marine mammals and birds may flourish as a result of climate change. Those that cannot adapt may become extinct.
• Unseasonable warmth could collapse the snow dens of ringed seals and polar bears, imperilling their young.
• Changing distributions, migration patterns, and growth rates of salmon, cod, mackerel, and herring will disrupt commercial fisheries.
• Heavier rainfall in coastal regions could result in more polluted run-off entering estuaries and bays, which provide food and shelter for fish and shellfish and are important stopovers for migratory birds.