Climate change
is not a new phenomenon, nor is extinction. Many times in Earths history,
the climate has changed sometimes rapidly and drastically and
species have become extinct. At least five times, more than 50 percent of species
inhabiting the planet have died out, and as few as 2 to 4 percent of the species
that have ever lived are believed to survive today. Some scientists say that
in the face of impending climate change, the world may be headed into another
mass extinction event.
As temperatures warm, the American pika, which lives on moist, cool mountaintops,
such as Mount Evans in Colorado, shown here, does not have much room for upslope
migration. Courtesy of Steven Morello.
The difference today is that the world is inhabited by close to 7 billion
people and biodiversity has been put into small refuges rather like islands,
said Richard Leakey, one of the worlds foremost anthropologists and wildlife
ecologists, at the Stony Brook World Environmental Forum,
which he convened last May on Long Island to discuss climate change and biodiversity.
Scientists, he said, need to be talking now about what climate change is going
to do to life as we have known it. Developing a better understanding of climates
effects on various species, as well as better protecting and connecting the
existing refuges, will help better prepare the world for any changes to come,
meeting participants said.
In its Third Assessment Report, the Intergovernmental Panel on Climate Change
(IPCC) estimated that Earth will warm by between 1.4 and 5.8 degrees Celsius
by 2100. While humans may be able to adapt to warming at the low end of this
range, other life forms might face more serious consequences; warming at the
high end of the range could be catastrophic for all life on the planet, considering
5 to 7 degrees Celsius is the difference between an ice age and an interglacial
period, says Stephen Schneider, a climatologist at Stanford
University who has served on the IPCC.
Still, the climate change debate is characterized by deep uncertainty,
Schneider says, noting that there will always be uncertainty about future events.
Still, he says, if the IPCC projections are correct even on the lower end of
the range, likely effects could include more frequent heat waves and less frequent
cold spells; increased weather extremes, including drought and storms; loss
of farming productivity; and rising sea levels and sea-surface temperatures.
No place will be immune, he says, including areas set aside as protected habitats.
More than 1.9 million species have been cataloged on Earth, but scientists believe
that at least 5 million to 30 million species exist, according to the World
Conservation Union (IUCN). Over the past 500 years, human activity has forced
844 known species to extinction, and 15,589 known species are facing extinction
right now. The current extinction rate, since A.D. 1500, is estimated to exceed
the natural extinction rate by 100 to 1,000 times, IUCN says. And climate change
will only exacerbate this rate as further stress is put on an already stressed
system, says Lee Hannah, a climate change biologist at the Center
for Applied Biodiversity Science with Conservation International.
But just as
climate change will not affect the whole world equally, it will not affect all
species in the same way, Hannah says. The fossil record clearly shows, he says,
that species respond individually to climate change, not as coherent communities.
So although scientists are already seeing some of the changes to come, especially
in higher latitudes, such as birds migrating and breeding earlier in spring,
and fish moving to cooler waters farther north, it is important to conduct bioclimatic
modeling studies to give us a better picture of what could happen,
Hannah says.
Three hundred species of these exotic plants called proteas, which are endemic
to the Cape Floristic Region of South Africa, stand a 21 to 40 percent chance
of extinction if the climate warms as projected in mid-range estimates by the
Intergovernmental Panel on Climate Change, according to new research in BioScience.
Courtesy of Guy Midgley.
Not only warming temperatures pose problems, says Thure Cerling, a geologist
at the University of Utah in Salt Lake City. The water balance will also change,
causing trouble for species that depend on certain equilibriums of precipitation
and evaporation. For example, the American pika, which depends on moist, cool
mountaintop climates, is quickly facing extinction due to climate change. Because
the small rodent-like mammals already live in tiny niches atop mountains, they
do not have much room to move up-slope and they are not physiologically designed
to migrate, according to the World Wildlife Fund (WWF).
Although some species can migrate, such as the grizzly bear, species that depend
on cooler temperatures, such as those that live in higher latitudes or altitudes
such as pikas or polar bears, will be even more threatened because of less room
for habitat expansion, Hannah says.
Climate change impacts are equally dramatic in the oceans, says Jane
Lubchenco, a marine ecologist at Oregon State University in Corvallis. Were
already seeing increased sea-surface temperatures, upwelling, more storms, increased
acidification and circulation changes, she says. Although scientists do
not know enough yet about all the effects of these changes on marine organisms,
Lubchenco says, they do know that corals, which cannot migrate, are bleaching
and dying quickly, and fish that can migrate, such as tuna, are moving to cooler
waters.
Climate change is a reality that at this point cannot be turned around, Hannah
says. But we dont have to throw up our hands into the air
in exasperation, Cerling adds. We dont have to lose the rest of
the megafauna we have on the planet. But we do have to do something now to protect
it if we dont want to lose it.
A key step in that process is resilience building, says Lara Hansen,
chief scientist of the Climate Change Program at WWF. Resilience building changes
the way protected areas and resources are managed by considering not only what
the ecosystems or habitats (and everything in the ecosystems) need right now,
but also what they might need 20, 50 or 100 years from now. Part of what ecosystems
need is more connectivity between protected areas a way to change what
are now postage-stamp-sized refuges surrounded by human activities to interconnected
systems that give plants and animals more room in which to operate, she says.
About 12 percent of Earths land surface is protected, says Jeff McNeely,
chief scientist at IUCN, while less than 1 percent of the ocean is protected,
Lubchenco says. Merely setting aside land or ocean acreage, however, is insufficient,
Lubchenco says its hugely important to pay attention to whats
happening around the reserve as well as whats happening inside.
As the climate changes, for example, threatened species may need to change locations
to survive, McNeely says. Having spaces between and surrounding protected areas
managed in ways that do not discourage species from spreading out would then
become key, he says. Even better, would be to manage these in ways that actively
encourage dispersal, for example, by creating national forests and building
wildlife underpasses or corridors where highways cut through the habitat, such
as has been done in the Los Angeles area, he says.
Protected areas are great, but they wont [preserve biodiversity]
alone, Hansen says. Countries also need to take active steps to reduce
greenhouse gas emissions to curtail global warming, she says. Indeed, Hannah
says, we need to stop anything that is currently threatening ecosystems
because climate change will only heighten the threats. It is important
to emphasize that extinctions estimated due to climate change are not inevitable,
he says, but if we cant do the simple stuff like protecting parks
now, we have little hope of addressing a complex threat like climate change
later.
Megan Sever
Links:
Climate
Change Program at World Wildlife Fund
World
Conservation Union (IUCN)
Stephen
Schneider's Web site
Jane
Lubchenco's Web site
Stony
Brook World Environmental Forum
Center
for Applied Biodiversity Science at Conservation International
Convention
on Biological Diversity
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