NASA has collected the first continuous global observations of the biological engine that drives life on Earth. Researchers expect this new detailed record of the countless forms of plant life that cover land and oceans may reveal as much about how our living planet functions today as fossil and geologic records reveal about Earth’s past.

“This is a period of exploration for us,” said lead author Michael Behrenfeld, an oceanographer at NASA’s Goddard Space Flight Center, Greenbelt, MD. “We’ve never been able to see the Earth this way before.”

The study, which appears this week in the journal Science, is based on the first three years of daily observations of ocean algae and land plants from the Sea-viewing Wide Field-of-View Sensor (SeaWiFS) mission, creating the most comprehensive global biological record ever assembled. Scientists will use the new record of the Earth’s surface to study the fate of carbon in the atmosphere, the length of terrestrial growing seasons and the vitality of the ocean’s food web.

“With this record we have more biological data today than has been collected by all previous field surveys and ship cruises,” added Gene Carl Feldman, SeaWiFS project manager at Goddard. “It would take a ship steaming at 6 knots over 4,000 years to provide the same coverage as a single global SeaWiFS image.”

The new study presents a global assessment of the fundamental work that plants perform to make life possible ñ producing food, fiber, and oxygen ñ and how their productivity changes from season to season and year to year in response to our changing environment.

The biological record from SeaWiFS indicates that global plant photosynthesis increased between September 1997 and August 2000. Photosynthesis by land plants and algae absorbs carbon dioxide from the atmosphere and ocean, which plays a critical role in regulating atmospheric carbon levels. The initial increase in carbon fixation was largely due to the response of marine plants to a strong El NiÒo to La NiÒa transition, but the cause of the continued increase during the later portion of the record is not yet clear.

“With three years of observations we can see seasonal changes in plant and algae chlorophyll levels very well, but we don’t yet have a long enough record to distinguish multi-year cycles like El NiÒo from fundamental long-term changes caused by such things as higher carbon dioxide levels in the atmosphere,” Behrenfeld concluded.

“The SeaWiFS record provides a baseline against which future estimates of Earth system carbon cycling can be compared,” said Feldman.

NASA plans to produce a five-year record using SeaWiFS observations and extend the continuous biological record with two Earth Observing System (EOS) spacecraft, Terra, launched in December 1999, and Aqua, scheduled for launch later this year. This constellation of EOS satellites allows U.S. scientists to examine practically every aspect of Earth’s atmosphere, oceans and continents from space in an unprecedented way.

The new biological record benefits ongoing studies of desertification and changes in growing-season lengths by joining an existing 20-year record of land plant productivity based on observations from meteorological satellites with the new generation of spacecraft instruments. These records will compliment ongoing observations obtained on land and at sea.

“SeaWiFS not only adds finer detail to our observing capability, it supplies essential continuity between data records that is critical to long-term monitoring of changes in the biosphere,” says biogeochemist James Randerson of the California Institute of Technology, a co-author on the study.


Add’l contact: David E. Steitz
Headquarters, Washington, DC
(Phone: 202/358-1730)

This research was conducted by NASA’s Earth Science Enterprise, a long-term research effort dedicated to studying how human-induced and natural change affects our global environment.

Scientists also are using the biological record from SeaWiFS to monitor the health of coral reefs, track harmful “red tides” and algae blooms, and improve global climate models.

Additional information is available on the Internet at:

More information about the SeaWiFs program is available on the Internet at:

Contact: Cynthia M. O’Carroll
NASA/Goddard Space Flight Center–EOS Project Science Office