Effects of Climate Warming Already in Evidence
WASHINGTON, DC, March 29, 2002 (ENS) - Ecosystems around the globe are showing the effects of climate warming. Earlier arrival of migrant birds, earlier appearance of butterflies, earlier spawning in amphibians, earlier flowering of plants - spring has been coming sooner every year since the 1960s, researchers reported Wednesday.
The report from German scientists investigates all regions of the globe. They predict some species will vanish because they cannot expand into new areas when their native climate heats up.
"Although we are only at an early stage in the projected trends of global warming, ecological responses to recent climate change are already clearly visible," write Gian-Reto Walther of the University of Hanover, Germany, and colleagues in this week's issue of the journal "Nature."
After reviewing changes in various animal and plant populations over the past 30 years of warming at the end of the 20th century, the authors found "a coherent pattern of ecological change across systems" from the poles to the equatorial seas.
"There is now ample evidence that these recent climatic changes have affected a broad range of organisms with diverse geographical distributions," Walther and his team report.
"The implications of such large scale, consistent responses to relatively low average rates of climate change are large," the researchers warn, adding that, "the projected warming for the coming decades raises even more concern about its ecological and socio-economic consequences."
The Earth's climate has warmed by about 0.6 degrees Celsius over the past 100 years, the researchers note. Starting around 1976, the rate of global warming more than doubled, changing faster than at any other time during the last 1,000 years.
However, average global climate has far less effect on local ecosystems than do local and regional climate changes.
The reproduction of amphibians and reptiles is disrupted by changes in temperature and humidity. In painted turtles, the ration of male to female offspring is related to the mean July temperature, said Walther, and the production of male offspring could be compromised even by modest temperature increases.
In the polar regions, winter freezes are now occurring later and ending earlier, leading to a 10 percent decrease in snow and ice cover since the late 1960s.
These dramatic local changes are having equally dramatic effects on cold weather species such as penguins, seals and polar bears, the researchers found.
Miniscule Southern Ocean crustaceans called krill, a key food source for higher predators such as penguins and other seabirds, whales, seals, as well as a fishery target, are being influenced by climate change. Walther's team found the warming climate is affecting the reproductive grounds of krill by reducing the area of sea ice formed near the Antarctic Peninsula, which leads to both food web and human economic consequences.
Rapid environmental warming has been reported over the last 30 to 50 years at a number of stations in the Antarctic, particularly in the Antarctic Peninsula region and on sub-Antarctic islands, along with changes in precipitation patterns.
Likewise, tropical oceans have increased in temperature by up to eight degrees Celsius over the past 100 years, the research team has found, triggering widespread coral bleaching.
Climate linked invasions of warm weather species into traditionally colder areas includes the immigration of unwanted neighbors - epidemic diseases. "There is much evidence that a steady rise in annual temperatures has been associated with expanding mosquito borne diseases in the highlands of Asia, East Africa and Latin America," the study says.
Geographical differences are evident for both plants and birds, with delayed rather than earlier onset of spring phases in southeastern Europe, including later bird arrival in the Slovak Republic, and a later start of the growing season in the Balkan region, the team has found.
Later onset of autumn changes were recorded, too, but these shifts are less pronounced and show a more variable pattern. In Europe, for example, the length of the growing season has increased in some areas by up to 3.6 days per decade over the past 50 years.
Overall, Walther's team reports, "trends of range changes show remarkable internal consistency between studies relating to glaciers, plant and insect ranges and shifting isotherms," which are lines of constant temperature.
The study concludes that based on the evidence "only 30 years of warmer temperatures at the end of the 20th century have affected the phenology [timing of seasonal activities] of organisms, the range and distribution of species, and the composition and dynamics of communities."
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