David E. Steitz<br />Headquarters, Washington June 5, 2003<br />(Phone: 202/358-1730)<br /><br /><br />Krishna Ramanujan<br />Goddard Space Flight Center, Greenbelt, Md.<br />(Phone: 301/286-3026)<br /><br /><br />RELEASE: 03-182<br /><br /><br />GLOBAL GARDEN GROWS GREENER<br /><br /><br /> A NASA-Department of Energy jointly funded study <br />concludes the Earth has been greening over the past 20 <br />years. As climate changed, plants found it easier to grow.<br /><br /><br />The globally comprehensive, multi-discipline study appears <br />in this week's Science magazine. The article states climate <br />changes have provided extra doses of water, heat and <br />sunlight in areas where one or more of those ingredients may <br />have been lacking. Plants flourished in places where <br />climatic conditions previously limited growth. <br /><br /><br />"Our study proposes climatic changes as the leading cause <br />for the increases in plant growth over the last two decades, <br />with lesser contribution from carbon dioxide fertilization <br />and forest re-growth," said Ramakrishna Nemani, the study's <br />lead author from the University of Montana, Missoula, Mont.<br /><br /><br />>From 1980 to 2000, changes to the global environment have <br />included two of the warmest decades in the instrumental <br />record; three intense El Nino events in 1982-83, 1987-88 and <br />1997-98; changes in tropical cloudiness and monsoon <br />dynamics; and a 9.3 percent increase in atmospheric carbon <br />dioxide (CO2), which in turn affects man-made influences on <br />climate. All these changes impact plant growth.<br /><br /><br />Earlier studies by Ranga Myneni, Boston University (BU), and <br />Compton Tucker, NASA's Goddard Space Flight Center (GSFC), <br />Greenbelt, Md., also co-authors of the study, reported <br />increased growing seasons and woody biomass in northern <br />high-latitude forests.<br /><br /><br />Another co-author, Charles Keeling, Scripps Institution of <br />Oceanography, La Jolla, Calif., cautions no one knows <br />whether these positive impacts are due to short-term climate <br />cycles, or longer-term global climate changes. Also, a 36 <br />percent increase in global population, from 4.45 billion in <br />1980 to 6.08 billion in 2000, overshadows the increases in <br />plant growth.<br /><br /><br />Nemani and colleagues constructed a global map of the Net <br />Primary Production (NPP) of plants from climate and <br />satellite data of vegetation greenness and solar radiation <br />absorption. NPP is the difference between the CO2 absorbed <br />by plants during photosynthesis, and CO2 lost by plants <br />during respiration. NPP is the foundation for food, fiber <br />and fuel derived from plants, without which life on Earth <br />could not exist. Humans appropriate approximately 50 percent <br />of global NPP.<br /><br /><br />NPP globally increased on average by six percent from 1982 <br />to 1999. Ecosystems in tropical zones and in the high <br />latitudes of the Northern Hemisphere accounted for 80 <br />percent of the increase. NPP increased significantly over 25 <br />percent of the global vegetated area, but decreased over <br />seven percent of the area; illustrating how plants respond <br />differently depending on regional climatic conditions.<br /><br /><br />Climatic changes, over approximately the past 20 years, <br />tended to be in the direction of easing climatic limits to <br />plant growth. In general, in areas where temperatures <br />restricted plant growth, it became warmer; where sunlight <br />was needed, clouds dissipated; and where it was too dry, it <br />rained more. In the Amazon, plant growth was limited by sun <br />blocking cloud cover, but the skies have become less cloudy. <br />In India, where a billion people depend on rain, the monsoon <br />was more dependable in the 1990s than in the 1980s.<br /><br /><br />The climate data for NPP calculations came from the National <br />Oceanic and Atmospheric Administration (NOAA) National <br />Center for Environmental Prediction. Researchers used two <br />independently derived 18-plus-year satellite datasets from <br />the Advanced Very High Resolution Radiometers on NOAA <br />satellite. The team processed and improved the data at GSFC <br />and BU. <br /><br /><br />"Systematic observation of global vegetation is being <br />continued by NASA's Earth observing satellites. Earth <br />observing satellites are paving the way to find out if these <br />biospheric responses are going to hold for the future," adds <br />Steve Running, another co-author from the University of <br />Montana. <br /><br /><br />NASA's Earth Science Enterprise is committed to studying the <br />primary causes of the Earth system variability, including <br />both natural and human-induced causes.<br /><br /><br />For information about the research on the Internet, visit:<br /><br /><br />http://www.gsfc.nasa.gov/topstory/2003/0530earthgreen.html