Reporter's notebook: A Costa Rica journal
Monitor contributor Moises Velasquez-Manoff set down some on-the-spot observations as he and Monitor photographer Andy Nelson traversed this tiny Latin American country investigating the effects of climate change.
from the June 21, 2007 edition
Page 2 of 4
May 13: When jungles spew carbon
Biologist Deborah Clark works in Costa Rica studying how tropical forests respond to fluctuations in climate.
Today as I talk with her during a break at a symposium on climate change's impact on La Selva Biological Station and Reserve, an old-growth jungle here, she says something rather profound:
In optimal conditions, a tropical forest absorbs carbon. Trees take it from the atmosphere in their photosynthetic processes. But trees also emit carbon when burning their energy stores, although it's normally a very small amount compared to what they're sucking up.
Here's the clincher: When it gets too hot – especially at night – the normally large gap between how much CO2 they produce and how much they remove from the atmosphere narrows. And when this happens, the tropical forest as a whole – emissions associated with the activity of fungi, insects, animals, and trees in the forest – may become a net producer of CO2.
In other words, if temperatures get too warm – especially night temperatures – tropical forests could begin exhaling vast amounts of carbon into the atmosphere, further heating the earth.
Long ignored, the tropics' response to climate needs more study, Dr. Clark says. So far studies here show that tropical forests indeed are quite sensitive to increasing temperatures.
The Arctic receives more attention both because the greatest temperature changes are predicted there and because, when there is change, it's easy to spot: The ice melts. Tropical systems, it's assumed, are somehow more resistant to change.
That's a false assumption, Clark says. Much has changed here over the past 30 years. Amphibians and reptiles are less numerous than they once were. Bird species have declined. Whether or not this is due to climate change is still unclear.
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