Species Extinction more common closer to the Equator

A paper published in PLoS ONE by Jana Vamosi and Steven Vamosi
outlines that the risk of extinction for plants is higher in countries
close to the equator than previously thought. “The tropics contain
many ancient species of plants, leading many to consider tropical
species as less susceptible to extinction — but our study indicates
that quite the opposite is, in fact, the case,” says Steven Vamosi, an
assistant professor in the Department of Biological Sciences at the U
of C.

“The extinction risk for plants is high in countries close to
the equator and even higher on islands, even after we take into
account factors related to human activities and their use of the
natural resources.” Previous studies on biodiversity in the tropics
have focused on beetles, birds, mammals and molluscs. The Vamosi study
mined worldwide databases for the number of plant species at risk in
each country of the world, from Falkland Islands in the south to
Greenland in the north, and looked at human factors such as GDP,
population density and deforestation. Vamosi concentrated on data from
vascular plants (ferns, conifers, and flowering plants), which
includes such threatened species as the Canada Hemlock, Western
Prairie Fringed Orchid, and Desert Lily, among many others.

Vamosi
says he was surprised that human activity was not the primary cause of
the increasing risk of extinction in the equatorial regions. “Our
findings differ from previous ones in that factors tightly linked to
human activity were not particularly important in determining how many
plant species were threatened with extinction. Instead, the most
important factor seemed to be simply latitude. So, extinction dynamics
may be very different between plant and animal species. Plant species
near the equator may persist at naturally low population sizes or have
small ranges, making them intrinsically more susceptible to a given
amount of disturbance.” He adds that he would like to see the findings
spur other researchers to bring more data to bear on this issue, given
that most attention to date has focused on vertebrates. Does this
study put human disturbance off the hook? Vamosi says: No. “This is
not to say that human activities are not underlying contemporary risk
of extinction; instead, it implies that plant species in a tropical
country will, on average, be more sensitive to a given amount of human
disturbance than those in a temperate country,” he says.
http://www.enn.com/ecosystems/article/38838

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