Researchers examined pollen trapped in rock cores and outcrops—from Colombia and Venezuela—formed before, during and after an abrupt global warming event called the Paleocene-Eocene Thermal Maximum that occurred 56.3 million years ago. The world warmed by 3-5 degrees C. Carbon dioxide levels doubled in only 10,000 years. Warm conditions lasted for the next 200,000 years.
Contrary to speculation that tropical forests could be devastated under these conditions, forest diversity increased rapidly during this warming event. New plant species evolved much faster than old species became extinct. Pollen from the passionflower plant family and the chocolate family, among others, were found for the first time.
“It is remarkable that there is so much concern about the effects of greenhouse conditions on tropical forests,” said Klaus Winter, staff scientist at STRI. “However, these horror scenarios probably have some validity if increased temperatures lead to more frequent or more severe drought as some of the current predictions for similar scenarios suggest.”