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” … has led to dramatic ecosystem shifts as far south as North Carolina
and extensive geographic range shifts of many plant and animal species.”
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News Release
Public release date: 6-Nov-2008
Cornell University
Evidence found for climate-driven ecological shifts
in North Atlantic, says Cornell study
ITHACA, N.Y. – While Earth has experienced numerous changes in
climate over the past 65 million years, recent decades have
experienced the most significant climate change since the beginning
of human civilized societies about 5,000 years ago, says a new
Cornell University study.
The paleo-climate record shows very rapid periods of cooling in the
past, when temperatures have dropped by as much as 18 degrees
Fahrenheit (10 degrees Celsius) in a matter of years to decades, “the
rate of warming we are seeing [now] is unprecedented in human
history,” said Cornell oceanographer Charles Greene, the lead author
of the paper appearing in the latest issue (November 2008) of the
journal Ecology, which is published by the Ecological Society of
America.
During the past 50 years, melting Arctic ice sheets and glaciers have
periodically released cold, low-salinity slugs of water from the
Arctic Ocean into the North Atlantic. This has led to dramatic
ecosystem shifts as far south as North Carolina and extensive
geographic range shifts of many plant and animal species. One
microscopic algal species from the Pacific Ocean, not seen in the
North Atlantic for over 800,000 years, has successfully crossed over
the Arctic Ocean and reinvaded the North Atlantic during the past
decade.
By reviewing climate changes in the past, the researchers were able
to more clearly observe how this influx of fresher water has led to
changes in ecosystems as well as the geographic distributions of
species, said Greene.
Interestingly, the study reports findings counter to the expectations
of most ecologists: that the distributions of southern species will
move northward and those of northern species will retreat as the
climate warms. Instead, as colder, fresher Arctic waters flow south
along the Northwest Atlantic shelf, from the Labrador Sea south of
Greenland all the way to North Carolina, the distributions of many
northern species have actually moved southward, said Greene.
In addition, the periodic freshening of shelf waters can extend the
growing seasons of phytoplankton and tiny drifting animals, like
copepods, which together make up the base of the marine food chain.
Such climate-driven changes can alter the structure of shelf
ecosystems from the bottom of the food chain upwards, said Greene.
“While it is true that cod stocks never rebounded from 20th-century
overfishing, part of their failure to recover can be attributed to
the climate bringing colder waters to Newfoundland since the 1990s,”
said Greene. Cod don’t grow and reproduce as rapidly in the colder
water. The decline in cod, combined with the ocean’s colder
temperatures, enabled populations of cold-water crustacean species,
like snow crab and shrimp, to increase.
“As climate changes, there are going to be winners and losers, both
in terms of biological species and different groups of people,” said
Greene. “The cod fishermen are out of luck, but the fishermen that
have decided to go after snow crab and shrimp are very successful
now.” He added that adapting to climate change is partly being able
to predict what we can expect.
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The study was funded by the National Science Foundation.
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