Thermal Vent, New Zealand, 2004
Photograph by Peter Essick
Scientists believe that forests, grasslands, and the waters of the oceans act as carbon sinks—stealing back roughly half of the carbon dioxide we humans emit, slowing its buildup in the atmosphere and delaying its effects on climate.
Eons pass before carbon, buried in the Earth's crust, issues as a gas from a volcanic vent in New Zealand (above), or locked up in limestone, erodes off mountains. Carbon cycles faster when decaying from a leaf or traveling as wind-tossed pollen.
