Humanity can no longer deny the manifestation of climate
change on our planet, and with every new season, we witness more and more
dramatic alterations in the lives of plants and animals around us. Plants have
changed the timing of their seasonal flowering; animals are suffering from
habitat degradation in natural ecosystems, and humans watch hopelessly how the
planet changes before their eyes.
Thanks to naturalist Henry David Thoreau’s 150-year-old observations
in Concorde on the Walden Pond flora, modern scientists have now a solid
informational base on the species’ abundance and flowering time to establish a
link between climate change and alterations in their phenology (the time of
seasonal activities).
First of all, they explained, the changes in plant species
abundance is under the influence of flowering-time response. With temperatures
rising an average of 2.4 °C in the past century, 27 percent of the species
documented by Thoreau have already been lost, while 36 percent of them face
imminent extinction. Furthermore, the flowering season now begins 7 days
earlier than 150 years ago, and scientists have identified a selective pattern
of change in abundance that is shared among close relatives.
The study shows high decreases in abundance in certain
clades, including asters, bladderworts, buttercups, dogwoods, lilies, spans,
which comes to support the idea that the risk of extinction is taxonomically and
phylogenetically shared among relatives. The scientists concluded that the
species most vulnerable to extinction are the species that are not responsive
to changes in temperature.
“Climate change appears to have had a dramatic role in
shaping the contemporary composition of the Concord flora,” the scientists
wrote. “Given that climate models predict at least a 1.1 – 6.4 °C increase in
temperature during this century, changes in the Concord flora will likely to
continue to be shaped in a phylogenetically biased manner.”
In another study, scientists at Stanford University, Boston
also warned that climate change affects the amphibian populations in the Yellowstone
Natural Park, a place where species have been protected “longer than anywhere
else on Earth.” Despite of that protection, at least 4 common species of
amphibians here are now becoming uncommon, due to climate change and wetland
desiccation.
Drought is now more common than in any other period of the
past century, temperatures are increasing, precipitations become scarce, and
the landscape in general suffers transformations. There are four times more
permanently dry ponds now than there were 16 years ago.
The scientists warned that even if there are still a number
of ponds in the Yellowstone National Park, the amphibian populations living
there have suffered a severe decline. “Our results indicate that climatic
warming on our planet has disrupted one of the best-protected ecosystems on our
planet and that current assessments of species’ vulnerability do not adequately
consider such impacts,” the scientists concluded.
Both studies appear in this week’s early edition of
Proceedings of the National Academy of Sciences.
