Geoscience Reference
In-Depth Information
species can be preserved through human intervention, so the extinctions
generally refer to species in the wild. Moreover, the techniques used in
these studies are quite controversial and may not apply to situations
where species have adapted to human habitations. In other cases, the
damage is being done by habitat destruction, overuse, overfi shing, over-
hunting, and pollution that would occur even in the absence of climate
change. Finally, the estimates of the climatic ranges are often statis-
tically biased by assuming that the ranges shrink but cannot expand,
which leads to a declining number of species by assumption. In reality,
some climatic ranges will shift, and some areas might grow, so the
number of species for growing ranges would be predicted to increase
rather than decline.
Perhaps we can solve problem one. Perhaps we can devise reliable
estimates of the risk of extinction for different species. We must now
confront problem two: Ecologists and economists have not developed
reliable techniques for valuing ecosystem and species losses. There is no
price tag on the value of a species or a rare ecosystem.
Let's take some specifi c examples of species that are threatened by
climate change: the Arctic fox, the leatherback turtle, and the koala
bear. Consider specifi c endangered ecosystems such as Australia's Great
Barrier Reef or South Africa's Cape Floral Kingdom. How can we place
a value on these species and ecosystems so that we can weigh the costs
and benefi ts of different climate-change policies?
The diffi culty can be described by comparing this issue with the eco-
nomic impacts of damage to wheat production, discussed earlier. When
the production of wheat declines, economists typically value that loss at
the market price of wheat. If climate change leads wheat production to
decline by 100 million bushels and the price of wheat is unchanged at
$5 per bushel, then the social cost is calculated as $500 million. (There
are still lots of further refi nements, such as whether this decline will
raise the price of wheat, and whether the impact is particularly severe
on low-income families, but we ignore those for now.)
How can we value these natural systems? Specialists have looked at
the market or near-market values, and at the “externality” values. Begin
with the market or near-market value of these losses, often called the
