EFFECTS ON ECOSYSTEMS
FROM CLIMATE CHANGE
Climate change is already affecting ecosystems
in a number of ways:
• Reduction of arctic and antarctic regions
• Changes in rainfall patterns and climates
• Loss of species and habitat.
negative impacts of climate change on ecosystems
Rising temperatures are beginning to have a noticeable
impact on ecosystems. Secondary evidence of global warming — lessened
snow cover, rising sea levels, weather changes — provides examples
of consequences of global warming that may influence not only human
activities but also the ecosystems. Increasing global temperature
means that ecosystems may change; some species may be forced out
of their habitats (possibly to extinction) because of changing conditions,
while others may flourish.
Few of the terrestrial ecoregions on Earth could
expect to be unaffected. Many of the species at risk are arctic
fauna such as polar bears, emperor penguins, many salt wetland flora
and fauna species, and any species that inhabit the low land areas
near the sea. Species that rely on cold weather conditions such
as gyrfalcons, and snowy owls that prey on lemmings that use the
cold winter to their advantage will be hit hard.
Butterflies have shifted their ranges northward
by 200 km in Europe and North America. Plants lag behind, and larger
animals’ migration is slowed down by cities and highways. In Britain,
spring butterflies are appearing an average of 6 days earlier than
two decades ago. In the Arctic, the waters of Hudson Bay are ice-free
for three weeks longer than they were thirty years ago, affecting
polar bears, which do not hunt on land.
Two 2002 studies in Nature (vol 421) surveyed
the scientific literature to find recent changes in range or seasonal
behavior by plant and animal species. Of species showing recent
change, 4 out of 5 shifted their ranges towards the poles or higher
altitudes, creating “refugee species”. Frogs were breeding, flowers
blossoming and birds migrating an average 2.3 days earlier each
decade; butterflies, birds and plants moving towards the poles by
6.1 km per decade. A 2005 study concludes human activity is the
cause of the temperature rise and resultant changing species behavior,
and links these effects with the predictions of climate models to
provide validation for them. Grass has become established in Antarctica
for the first time.
Forests in some regions potentially face an increased
risk of forest fires. The 10-year average of boreal forest burned
in North America, after several decades of around 10,000 km² (2.5
million acres), has increased steadily since 1970 to more than 28,000
km² (7 million acres) annually. This change may be due in part to
changes in forest management practices.
Possible benefits from global warming
Increasing average temperature and carbon dioxide
may have the effect, up to a point, of improving ecosystems’ productivity.
Atmospheric carbon dioxide is rare in comparison to oxygen (less
than 1% of air compared to 21% of air). This carbon dioxide starvation
becomes apparent in photo respiration, where there is so little
carbon dioxide, that oxygen can enter a plant’s chloroplasts and
takes the place where carbon dioxide normally would be in the Calvin
Cycle. This causes the sugars being made to be destroyed, badly
suppressing growth. Satellite data shows that the productivity of
the northern hemisphere has increased since 1982 (although attribution
of this increase to a specific cause is difficult).
IPCC models predict that higher CO2 concentrations
would only spur growth of flora up to a point, because in many regions
the limiting factors are water or nutrients, not temperature or
CO2; after that, greenhouse effects and warming would continue but
there would be no compensatory increase in growth.
Research done by the Swiss Canopy Crane Project
suggests that slow-growing trees only are stimulated in growth for
a short period under higher CO2 levels, while faster growing plants
like liana benefit in the long term. In general, but especially
in rain forests, this means that liana become the prevalent species;
and because they decompose much faster than trees their carbon content
is more quickly returned to the atmosphere. Slow growing trees incorporate
atmospheric carbon for decades.
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