“Most of the great coral reefs on the planet will likely be gone by 2020,” says U of T’s Dr. Rowan Sage, a botanist and climate change ecologist.
While many Canadians have accepted the reality of global warming, it is commonly believed that we have yet to see any major consequences. Most of us are aware of some of the more dire predictions-that the ice caps will melt, that polar bears will disappear and that some oceanic islands may be submerged-but we tend to think that while the effects may one day be dramatic, most of us will not live to see them.
“[But] biological systems throughout the world have already responded to the relatively small amount of warming that has taken place,” said professor Dr. Chris Thomas, a conservation biologist based in England.
“Probably the greatest [effect seen so far] is the coral reef die-off, which pretty clearly results from episodic heat events,” said Sage.
Corals often die when stressed by heat, turning white in a process called bleaching. It is estimated that most species of coral will bleach if the average summer temperature rises by only one degree Celsius, and as corals live in shallow waters, their habitat can warm extremely easily. Since 1979 scientists have observed six mass bleaching events. The largest occurred in 1998, when 16 per cent of all corals on Earth died.
The global temperature rose by an average of 0.6 degrees Celsius in the 20th century, and is expected to rise by two or even three degrees in the next 100 years. This may sound like a small increase, “but it is not the average that is critical, it is the timing and distribution [of the changes],” said Sage. “Warming tends to be non-uniform, with greater warming at night, at high latitudes, and in the winter. So a global one degree Celsius increase has a much greater effect in the high arctic, especially during the winter. The ice pack may thin, with consequences for sea level rise, and the arctic ecosystems can be wiped out.
“[With abnormally high temperatures] drastic changes can come into play quickly,” continued Sage. His research shows that vegetation worldwide is going to be dramatically affected by global warming, primarily due to increased heat, drought, and fires. “Large areas of ecosystems will burn up, and they will be replaced by [fire-tolerant] grasses and shrubs. This has already happened with the great Indonesian fires of the late 1990s. It is happening as we speak. You can watch it by logging into NASA’s website and seeing recent satellite photos of widespread landscape burning.”
Canada is also experiencing more forest fires. “Our recent increase in fire activity is a result of human-caused climate change,” says Canadian Forest Service ecologist Dr. Mike Flannigan.
Scientists the world over have documented hundreds of biological anomalies that they have linked to global warming. “Changes in the geographic distributions of species, their abundances, and the times of year at which they breed seem to be ubiquitous,” says Thomas.
Many migrating animals are moving north and south, away from the equator, as regions closer to the poles become warmer. Storms are becoming more frequent and more intense. Many species of plants and animals are declining in numbers, and even disappearing.
Since the 1960s, higher temperatures have caused spring to come early in many places throughout the world, by a full week in some areas. The onset of spring can be seen for example in butterflies appearing earlier, frogs spawning sooner, and plants flowering prematurely.
Dr. Donald W. Thomas of the Université de Sherbrooke in Quebec reported in the journal Science in 2001 that early springs have been linked to the decline of a population of blue tits in southern France. The birds are genetically programmed to breed at the precise time of the year when caterpillar populations explode, giving them an abundant supply of food for themselves and their fledglings. But early springs have caused the caterpillars to hatch out of syn with the leafing of oak trees, leaving insufficient numbers of insects to sustain the blue tit population.
Other species of birds have also suffered as a direct consequence of warming. In 1997 short-tailed shearwaters died in huge numbers in the Bering Sea. Dr. Sharon Smith at the University of Miami says the warmer water caused plankton to bloom, turning the water opaque and preventing the birds from being able to see and catch prey.
The disappearance of the golden toad is also being blamed on global warming. Prior to its disappearance in the late 1980s, tourists flocked to see this animal during its mating season, when thousands of the small, brilliantly coloured toads gathered in the mountainous cloud forests of Costa Rica. Dr. J. Alan Pounds and Dr. Robert Puschendorf, conservationists working in Costa Rica, reported in Nature in 2004 that increased cloud cover and drier seasons, both a direct result of global warming, allowed a frog skin disease to proliferate and wipe out the toads.
Dr. Chris Thomas says that the loss of the golden toad is not an isolated incident-he says that global warming is going to lead to mass extinctions. “My greatest concern is that climate warming could, in the end, drive a quarter or more of all of the land animals and plants to extinction,” he said. “In some cases, they may experience new extreme conditions that they are unable to survive. In other cases, some species are expected to be out competed by other species that thrive in hotter conditions.”
In a study he published in the journal Nature in 2004, Thomas estimated what percentage of all species will be able to adapt to the Earth’s changing climate. He calculated that anywhere from 18 to 37 per cent of all species on this planet will be “committed to extinction” by 2050 due to global warming-meaning that even if some individuals remain, the species will never recover.
Of greatest significance to us, however, is the impact global warming is having on our own species.
“The heatwave of 2003 in Europe caused several tens of thousands of excess heat-related deaths in [older people]. These conditions are expected to be close to the norm in 25 to 50 years,” says Thomas.
“And when it is hot you are more likely to lose the power grid [as in North America in 2003],” says Sage. “Without air conditioning, people will not be able to escape the heat. With North Americans being heavier than in the past (and hence more prone to heat stress), it seems likely that heat-related deaths could soar into the hundreds of thousands.”
Global warming will also have dramatic consequences for our food supplies. In 2004, the International Rice Research Institute (IRRI), located in the Philippines, reported in the Proceedings of the National Academy of Sciences (PNAS) that an average daily temperature rise of one degree Celsius resulted in a 10 per cent drop in rice yields, one of the world’s most important crops. Rice, like coral, grows in shallow waters, and is particularly vulnerable to warming.
While some contend that the evidence for warming is weak, it is important to note that the majority of the studies mentioned here were reported in the journals Science and Nature, considered the two most prestigious scientific publications in the world.
“The scary thing is, many, if not most, don’t think [global warming] is real but instead is a left-wing plot,” said Sage.
Such a “plot” is in fact the topic of Michael Crichton’s new book, State of Fear, which contends that global warming is merely a hoax devised by environmentalists trying to get research funding. The book, generally reviled by ecologists, was praised by Capitalist Magazine for illuminating the “the flawed science behind the global warming and other imagined environmental crises.”
“How is a member of the public to know where the truth lies?” asked biologist Chris Thomas. “It is not a topic like education or health, where everyone can judge pronouncements against their personal experience.”
“One thing to keep in mind,” said Sage, is that “humans are impacting the global environment in a number of major ways, for example by deforestation, by using excessive amounts of fertilizer, by spreading new species into virgin ecosystems. These combine with global warming to produce dramatic effects. [But] these environmental insults are more tractable, so we could be making real progress.
“Climate change is a human-caused problem that requires a human-based solution,” Sage said.
