This is the VOA Special English Environment Report.

　　Scientists in the United States say plant life has increased on Earth in the past twenty years. And they say in every area of plant growth the increase is the result of weather conditions.

　　Eight scientists from across the United States did the study. The space agency NASA and the Department of Energy paid for it. The magazine Science published the findings.

　　The researchers spent a year-and-a-half examining weather and satellite information. The information was recorded from nineteen-eighty-two to nineteen-ninety-nine. This period was one of the warmest on record. Researchers found that rainfall generally increased during this time.

　　The satellites measured the amount of leaves on plants and the amount of sunlight taken in. The scientists used that information to estimate what is called net primary production. This is the total amount of carbon stored in land plants.

　　The scientists report a six percent increase in stored carbon since nineteen-eighty-two. They say gains were high in equatorial areas, especially around the Amazon River in South America. The report says that area alone had a one percent increase in net primary production.

　　Ramakrishna Nemani of the University of Montana in Missoula led the study. He says reduced cloud cover led to the growth in the Amazon area. He says the lack of clouds permitted more sunlight to get through. More sunlight meant increases in photosynthesis. That is the process by which plants use energy from sunlight to produce the chemicals they need to grow.

　　Northern Canada, the north-central United States and northern Europe were second in increased plant growth. Ramakrishna Nemani says a rise in temperatures helped plants there.

　　All together, the report says twenty-five percent of areas of plant life on Earth experienced increases. But, the scientists also note increases in the number of people on Earth and carbon dioxide levels in the atmosphere.

　　Study scientist Ranga Myneni of Boston University in Massachusetts says humans use about half the net primary production on Earth. And, he notes that world population grew by thirty-six percent during the period of time studied.

　　This VOA Special English Environment Report was written by Caty Weaver.