Taking the Pulse of the Planet

Along the southern tip of the Florida peninsula, where the pinelands have gone relative ly undisturbed by civilization, Earthwatch volunteers like Lisu Derungs, trek through subtropical forests to take stock of the trees.

Some 4,000 volunteers participate annually in Earthwatch projects around the world. From its Boston headquarters, the organization arranges a wide range of trips to support teams of scientists in the field. Some volunteers conduct research on sea turtles in Baja California, while others study maternal health in Africa.

Earthwatch volunteers will spend an average of $1,600 this year to take part in what is usually a two-week stint.

Some slots are easier to fill than others. On its Web site, Earthwatch describes a project in the woods of Indonesia by saying: “You might as well have stepped into Jurassic Park. You’ve just been dropped off on a remote, mountainous island that was marked on old mariners’ maps, ‘Here be dragons.’” The group says this expedition calls for “seasoned hikers with good health records — and a very good attitude.”

The Florida Everglades project in which Ms. Derungs participated was somewhat less taxing, but its results could nevertheless be important. Scientists are using tree-growth measurements to better understand how natural disturbances like hurricanes and floods affect the life cycle of trees and the ecology of the forest.