CAMBRIDGE, Mass., Feb. 3, 2010 -- Invasive plants could become
even more prevalent and destructive as climate change continues,
according to a new analysis of data stretching back more than 150
years.
Writing in the journal PLoS ONE, the Harvard University
scientists who conducted the study say that non-native plants, and
especially invasive species, appear to thrive during times of
climate change because they're better able to adjust the timing of
annual activities like flowering and fruiting.
"These results demonstrate for the first time that climate
change likely plays a direct role in promoting non-native species
success," says author Charles C. Davis, assistant professor in
Harvard's Department of Organismic and Evolutionary Biology.
"Secondly, they highlight the importance of flowering time as a
trait that may facilitate the success of non-native species. This
kind of information could be very useful for predicting the success
of future invaders."
Davis and his colleagues analyzed a dataset that began with
Henry David Thoreau's cataloging of plants around Walden Pond in
the 1850s, when the famed naturalist kept meticulous notes
documenting natural history, plant species occurrences, and
flowering times. Since then, the mean annual temperature around
Concord, Mass., has increased by 2.4 degrees Celsius, or 4.3
degrees Fahrenheit, causing some plants to shift their flowering
time by as much as three weeks in response to ever-earlier spring
thaws.
"We set out to use this dataset to examine which plants have
been the beneficiaries of climate change," Davis says. "Our
research suggests quite decisively that non-native and invasive
species have been the climate change winners. Climate change will
lead to an as-yet unknown shuffling of species, and it appears that
invasive species will become more dominant."
Davis and colleagues compared a plethora of plant traits --
everything from height at maturity to flower diameter to seed
weight -- against species' response to more than a century and a
half of climate change. Alone among all these traits, plants that
have fared well share a common phenology, a suite of traits related
to the timing of seasonal events such as flowering, leaf growth,
germination, and migration.
By contrast, many plants with a less flexible flowering schedule
-- and thus prone to flowering at suboptimal times -- have declined
in population, in many cases to the point of local extinction.
The current work builds upon a 2008 paper by Davis and
colleagues which showed that some of the plant families hit hardest
by climate change at Walden Pond include beloved species like
lilies, orchids, violets, roses, and dogwoods. The scientists also
reported that some 27 percent of all species Thoreau recorded from
1851 to 1858 are now locally extinct, and another 36 percent are so
sparse that extinction may be imminent.
"Invasive species can be intensely destructive to biodiversity,
ecosystem function, agriculture, and human health," Davis says. "In
the United States alone the estimated annual cost of invasive
species exceeds $120 billion. Our results could help in developing
predictive models to assess the threat of future invasive species,
which may become greatly exacerbated in the face of continued
climate change."
SOURCE