Deep Past Offers Clues into
Climate-Driven Biotic Shifts

Invasive palm image
P.T. Green. Symbols used courtesy of the Integration and Application Network, University of Maryland Center for Environmental Studies

Warmer winter temperatures in the deciduous forests of southern Switzerland in recent years have allowed the invasive palm, Trachycarpus fortunei, to flourish (A), altering the plant composition of the forest. On Easter Island, the introduction of yellow crazy ants by humans during the early 20th century caused the demise of the red land crab, the island's dominant omnivore. As a result, scientists say, the island's rainforest ecosystem shifted from an open (B) to a dense understory (C).

Global climate change is altering the way that organisms interact in ecosystems worldwide, changing the abundance and range of some species, driving some toward extinction, and creating systems where generalist species thrive.
But it's hardly the first time in the planet’s history that this has occurred, according to a new article published in the journal Science. Writing in a special issue of the journal, four scientists, including Phoebe Zarnetske of the Yale School of Forestry & Environmental Studies, review dozens of studies that have documented how climate change has repeatedly altered biotic relationships for millions of years.
According to the authors, the deep past reveals patterns that might provide key insights into how ecosystems will respond to future climate changes. 
Of course, the changes facing plant and animal species today are unlike any previous era, says Zarnetske, an ecologist and Postdoctoral Fellow with the Yale Climate & Energy Institute. Not only does the rate of warming exceed that of any period during the last 10,000 years, organisms today also face a range of other threats, including invasive species, changing land use and other human-driven changes, Zarnetske says. 
Zarnetske cites modern case studies that she says illustrate the profound changes in biotic interactions occurring worldwide as a result of human activities and climate change. For example, in the deciduous forests of southern Switzerland, warmer winters have allowed the invasive palm, Trachycarpus fortunei, to flourish, altering the plant composition of the forests; and on Christmas Island, in the Indian Ocean, the human introduction of yellow crazy ants during the early 20th century caused the demise of the dominant native omnivore, the red land crab, triggering abrupt changes in the rainforest ecosystem.
“As common as this is to say, we have to understand that everything is connected,” Zarnetske said. “The deep past even shows that species interact with each other in important ways, and when certain groups of organisms die off or increase it has a major impact on the functioning of an ecosystem.
“And since we’re a part of ecosystems, we need to keep in mind that everything that we’re doing is also having an effect.”
The article, "Climate Change and the Past, Present and Future of Biotic Interactions," was published August 2, 2013, in a special issue of Science entitled "Natural Systems in Changing Climates." The National Science Foundation press release is available here.
– Kevin Dennehy    203 436-4842
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PUBLISHED: August 2, 2013

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