Environmental Engineering Reference
In-Depth Information
range size, population size, and the vulnerability of a population depend-
ing on some limited factor at risk. Reaching the cool refuge is crucial. For
example, Sinervo et al. (2010) reported lizards, which have body tempera-
tures determined by habitat temperatures, on four different continents are
having to spend more time than before escaping warming temperatures by
going into burrows or other locally cooler places. This means they have
less time to forage and hence do not have the energy reserves needed to
successfully reproduce, which of course can lead to population decline and
possibly extinction. These species and others could probably avoid extinc-
tion by moving into new other areas in the region that are cooler (e.g., up
in elevation). If a species in question has a maximum dispersal distance
that is shorter than the distance to the refuge, or if the species is not a good
colonizer and fails to become established in the refuge once it gets there,
then the species will be in trouble unless it gets human assistance. Species
that are in trouble unless aided by humans are called functionally extinct.
Examples of functionally extinct species are those that are on oceanic islands
or mainland islands, such as oasis within a desert, because unless they fly,
dispersing to a cooler refuge is not possible. For example, the Akiapolaau
(
Hemignathus munroi
) on the Hawaiian Islands, Aruba island rattlesnake
(
Crotalus durissus unicolor
), and the black robin (
Petroica traverse
) on Cha-
tham Islands off the coast of New Zealand are all critically endangered and
will go extinct without help from humans.
Hubbell and co-workers (2008) looked at possible extinction rate in
the Brazilian Amazon due to land-use change. He estimated that a total
of 11,210 tree species occur in the Brazilian Amazon. About 30% of these
trees (~3,250) have populations greater that 1 million, and consequently, do
not currently face extinction. Fifty percent (~5,300) of all the species have
populations less than 10,000. Roughly 35% of these have a high probability
of going extinct even without the effects of climate change. This would also
result in insects and other species that depend on these tree species to also
be facing extinction. Climate change and other drivers could exacerbate the
vulnerability of these species of concern.
Deutsch and co-authors (2008) investigated the physiological tolerances
of species from pole to pole. They found, as expected, that the extent of
physiological tolerance was wider at the higher latitudes and narrower near
the equator. From this they reasoned that the tropical species could very well
have a more difficult time as the globe warms, because the temperature to
be experienced by species in the tropics could well be higher than that ever
experienced by the tropical species. Temperate, boreal, and arctic species
will also be subjected to warmer temperatures, but those temperatures, for
