Interesting paper recently published:
Szabo JK, Khwaja N, Garnett ST, Butchart SHM (2012) Global Patterns and Drivers
of Avian Extinctions at the Species and Subspecies Level. PLoS ONE 7(10):
e47080. doi:10.1371/journal.pone.0047080
PDF can be downloaded here:
http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0047080
Abstract
Birds have long fascinated scientists and travellers, so their distribution and
abundance through time have been better documented than those of other
organisms. Many bird species are known to have gone extinct, but information on
subspecies extinctions has never been synthesised comprehensively. We reviewed
the timing, spatial patterns, trends and causes of avian extinctions on a global
scale, identifying 279 ultrataxa (141 monotypic species and 138 subspecies of
polytypic species) that have gone extinct since 1500. Species extinctions peaked
in the early 20th century, then fell until the mid 20th century, and have
subsequently accelerated. However, extinctions of ultrataxa peaked in the second
half of the 20th century. This trend reflects a consistent decline in the rate
of extinctions on islands since the beginning of the 20th century, but an
acceleration in the extinction rate on continents. Most losses (78.7% of species
and 63.0% of subspecies) occurred on oceanic islands. Geographic foci of
extinctions include the Hawaiian Islands (36 taxa), mainland Australia and
islands (29 taxa), the Mascarene Islands (27 taxa), New Zealand (22 taxa) and
French Polynesia (19 taxa). The major proximate drivers of extinction for both
species and subspecies are invasive alien species (58.2% and 50.7% of species
and subspecies, respectively), hunting (52.4% and 18.8%) and agriculture,
including non-timber crops and livestock farming (14.9% and 31.9%). In general,
the distribution and drivers of subspecific extinctions are similar to those for
species extinctions. However, our finding that, when subspecies are considered,
the extinction rate has accelerated in recent decades is both novel and
alarming.
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