In the days before scientific instrumentation, miners survived the underground buildup of methane and other noxious gases by watching a little yellow songbird, the canary, that they carried in a cage. If the canary died, it was time to get out. Birds are sensitive indicators of environmental conditions, and they are still speaking to us today, if we are interested in listening. Our survival might depend on it.
While millions of dollars are spent by industry-funded groups to persuade the public that climate change is some sort of conspiracy theory, the temperature continues to rise and birds are on the move. This decade is the hottest on Earth since accurate records began in 1850, and wildlife are not waiting for an international agreement before trying to adapt. According to the National Audubon Society, 58 percent of the 305 bird species that winter in North America have shifted north since 1968, some of them by hundreds of kilometres. The same phenomenon is being observed in Europe, where a northward shift of birds has been documented over the last 30 years. The observed range expansions and contractions match well with predicted climate change responses, with increasing species diversity in some areas and declines in others. Astoundingly, the European study showed that the potential future range of many species, based on climate change, did not overlap with the current range at all, with an average overlap of only 40 percent. Since the distribution of birds depends on many factors besides temperature, particularly the availability of suitable habitat, this does not bode well for them on a crowded planet.
Movement toward higher latitudes in the Northern Hemisphere is a predictable dispersal response by plants and invertebrates to warmer conditions, and birds follow these food sources. Another response for species is to move upwards in altitude, and in both situations successful integration into the new geographical location can be constrained by habitat limitations. The Audubon study showed that far fewer grassland than forest species were attempting to shift their range. In the Okanagan, for example, most of the sage and antelope brush habitats have been developed for housing and vineyards, leaving no room for northern movement of birds like the sage thrasher and sage sparrow from south of the border. There is a risk therefore that many species will decline rather than expand in number, since dispersal will not be an option.
Climate change has had other effects on birds, such as the spread of new parasites, competitors, and predators, as well as a mismatch for some species in the timing of egg-laying and the emergence of insect prey so that fewer chicks survive. Ecological, climate-driven change is apparent in British Columbia’s forests, where the lack of killer frosts helped the widespread invasion of mountain pine beetle. Mature forests are an important carbon sink, so their loss is devastating on many levels. Pest and disease transmissions are frequently correlated with weather and climate, and we can expect more mosquito-born diseases in the coming years, like the West Nile virus which impacts both birds and humans. Ocean warming has ripple effects all down the marine food chains by contributing to the poor survival of salmon and bringing new species to our shores, such as the predatory Humboldt squid. Storm surges and heavy rainfall are causing flooding in low-lying districts, and with sea level rise we can anticipate the increased loss of coastal salt, sedge, and cattail marshes, all important wildlife habitat and carbon sinks.
The Earth’s climate is changing: all the signs are here. The Swedish scientist Svante Arrhenius predicted as early as 1896 that carbon dioxide levels in the atmosphere would raise the world’s temperature by several degrees. Since then substantial evidence has accumulated that the Earth is warming. Temperature records have been kept in B.C. since the late 19th century and show an upward, if uneven, increase across the province. Coastal B.C. has warmed by about 0.6 C, close to the global average of 0.7 C, but the Interior has warmed at twice that rate, over 1 C, in the last century. Warmer, drier summers have already resulted in a higher fire hazard and less water available for irrigation. Continuing trends must inevitably affect freshwater supplies, forests, agriculture, wildlife, microbes, and every aspect of our landscape, natural resources, and health. Along with controlling greenhouse gases, some urgent and comprehensive planning on adaptation to a changed world needs to begin. Safeguarding healthy ecosystems, biodiversity, and ecological services must be an essential first step.
Anne Murray is the author of two books on Lower Mainland nature and ecological history, Tracing Our Past: A Heritage Guide to Boundary Bay and A Nature Guide to Boundary Bay.