Impacts on Living Things

Among the biological consequences of global warming that might be expected are those that depend on climate cues that a variety of organisms take from annual temperature cycles. The flowering times of plants, the arrival times of migrating birds, and collateral events are collectively called phenomenological effects. In zoos, Jon zen ET at —an international group led from Sweden but including representation from Italy and other Scandinavian countries—published a Science Report examining what has happened to the arrival times in Europe of birds char migrate over various distances. Making use of sites in Scandinavia and one located in southern Italy, the authors compared arrival times of short-distance migrants (those whose migrations begin from points close to the breeding grounds) with those of long-distance migrants whose trips begin in Southern Africa. One theory predicted that short-distance migrants would be most affected by global warming; the rationale is that because the climate signals where they begin their migration closely resemble those on the breeding grounds, birds might advance their departure on that basis. But the data showed that long-distance migrants advanced their arrival times more—especially in the early phases of the migration. Different hypotheses might explain the effect: either these migrants accelerated their speed during the northward trip, or they left earlier. or both. The evidence suggested that the effects are not due to changes in forage availability on the wintering grounds, which might have triggered an earlier departure. Instead, it seems more probable that rapid evolutionary change, brought about during the period in which global warming was changing the signal, was responsible. Many animals exhibit strong temperature optima and exhibit preferences dependent on them. For stationary species, global warming would be expected to initiate policewoman or up-slope changes in distribution. For migrants, the situation is more complex. Changes in the distribution of prey species or food plants could take place both on the wintering ground and in the breeding locale. Either could result in evolutionary changes in behavior that would be reflected in altered migratory patterns. Perhaps the most dramatic indicators of the influence of global climate change on animal species are the sad pictures of polar bean, apparently trapped on ice floes floating in the Arctic Ocean. Climate models have consistency shown that the effects of rising average global temperatures will be more severe at high latitudes, and popular recent accounts have suggested that the "Northwest Passage," once a fiction, may become open to shipping