Eachspecies evolves to thrive in its own particular ecological
niche - tolive in a particular "home" with specific living
conditions (includingtemperatures ranges and other plant and animal
species). Some speciesare more adaptable, or "opportunistic", than
others. For example,rats and dogs can survive under many different
conditions, but koalascan only live where there is eucalyptus.
Human caused climate changewill alter temperatures, precipitation
and sea level - wiping out somehabitats and shifting others faster
than many species can migrate.
Unless we drastically reduce our greenhouse gasemissions, we can
expect several factors to combine that will make thecoming die out
astonishingly severe. The climate is changingfaster than at almost
any time in our planet's history. Also,many ecosystems are already
stressed by human activities - destructivelogging, excessive
grazing, over fishing, toxic pollution and the like.And, human
development and habitat destruction impedes many speciesfrom
migrating - superhighways effectively block land animals,
forexample.
A recent major study indicates that if globaltemperatures
increase 1.8-2° Celsius (3.2-3.6°F), which is considered amid-range
estimate, a million species would be threatened withextinction over
the
next fifty years.This can only be avoided by rapid emissions
reductions in the next fewdecades. There is still time to save many
species, but it is fastrunning out. Of course, if temperatures go
even higher, morespecies will be lost.
Some examples of species and habitats at risk:
Coral reefs
Coralbleaching is a condition that can seriously damage and kill
entirecoral reefs. Corals contain microscopic algae called
zooxanthellae thatprovide the coral with food and give them their
vibrant colours. Risingocean temperatures cause corals to become
stressed, and they expel thezooxanthellae and turn white or
"bleach". If zooxanthellae do notreturn to the coral's tissue, the
coral will die.
As little asa 1° Celsius (1.8°F) increase in temperature above
the summer maximumcan cause corals to bleach. Tropical sea
temperatures have increased by1° Celsius over the past 100 years
and are predicted to continuerising.
An example of this problem is Australia's world famousGreat
Barrier Reef, which lies off the state of Queensland. At
around2,000 kilometres (1,243 miles) long it is the world's largest
reef.
Butin 2002 the reef experienced its worst ever case of coral
bleaching,with over 60 percent of the reef being affected. Unless
projectedlevels of climate change are slowed, much of the reef will
be dead indecades. Deprived of their living homes, hundreds of
species relying onthe reef will also die out.
Polar bears
Arctic sea ice could disappear within 70 years, and wild polar
bears with it.
Polarbears are the world's largest land predator. They can go
for longperiods, even months, without eating, but need to build up
fat to livethrough lean times. The polar bear does this mostly by
eatingseals they catch on the ice. Without the ice they can't get
to theirprey. In fact, without sea ice, much of the Arctic
ecosystem wouldchange or collapse. Polar bears also use floating
sea ice platforms fortravel, and pregnant polar bears build snow
dens for the winter, whichthey give birth in. In the last two
decades, Arctic ice cover hasretreated five percent and the ice
that is left has lost at least 30percent of its thickness; and an
average of two weeks have been lostfrom the bear's hunting
season.
Plants
Likeanimals and insects, plant species require specific
climates. You don'tfind yellow birch trees growing next to Saguaro
Cactus, forexample. Changes in precipitation and temperature will
mean that somespecies can no longer survive where they are now
growing. Also, likeanimals plants, are vulnerable to competition.
As warming occurs,species that have adapted to living in cooler
climates can be pushedout of existence by newcomers better suited
to the newtemperatures.
Most plants can't migrate very quickly,compared to animals and
insects. They are restricted by how far theirseed or pollen can
travel, and the climate will change too fast formany of them if
current trends continue. Human barriers (such as farmsand urban
areas) will also impede plant migrations.
Many animalsand insects need specific plants, or types of
plants, as part of theirhabitat. So the loss of plant species will
have a ripple effect -leading to more animal and plant
extinctions.
More information:
PBS -
Great White Bear
Greenpeace
Australia Pacific - Climate impacts
Observed Impacts of Climate Change in the US - Pew study
Ecology: Clouded futures - Nature magazine
Global Warming and Terrestrial Biodiversity Decline - WWF
report
Climate
change and diversity - IPCC technical paper V
United Nations Framework Convention on Climate Change