Ancient Rain Forests Found Upside in Heat Stress
Francy Carvajal/Smithsonian Tropical Research Institute Pollen from the era known as the Paleocene-Eocene Thermal Maximum, magnified with an electron microscope, reflect how new species thrived as temperatures jumped.
Once again, scientists from the Smithsonian Tropical Research Institute have published a thought-provoking paper highlighting how little is understood about how climate change will affect tropical rain forests.
Several years ago, one of the institute’s staff scientists, Joe Wright, set off a firestorm when he suggested that the loss of tropical rain forest wasn’t as bad as some models predicted, because it was regrowing on farmland in the developing world that had been abandoned as rural residents moved to cities.
Last week, a group of scientists from the institute, based in Panama, proposed in an article in the journal Science that warming temperatures could mean a proliferation of jungle species instead of species loss. Many scientific models, including those used by the Intergovernmental Panel on Climate Change, predict a wave of extinctions because of climate change.
Analyzing pollen in rock cores, the geologist and botanist Carlos Jaramillo focused on a period called the Paleocene-Eocene Thermal Maximum, which occurred about 56 million years ago. It was an age in which temperatures suddenly jumped by three to five degrees and carbon dioxide levels doubled.
Faced with those temperature and atmospheric stresses, the rain forests of the time actually thrived, the scientists found, with a rapid increase in plant diversity and the emergence of new species. New plant species — including plants from the passionflower and chocolate families — appeared. New species evolved much faster than old species became extinct.
“The tropical rain forest was able to persist under elevated temperatures and high levels of atmospheric carbon dioxide, in contrast to speculations that tropical ecosystems were severely compromised by heat stress,” the scientists write.
Of course, the researchers note, this period of biological abundance was characterized by warmer temperatures and more rain. If, as some scientists predict, climate change brings the world’s rain forests warmer temperatures as well as drought, the feared wave of extinctions could be more likely.
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