ScientistsintheUnitedStatessayplantlifehasincreasedonEarthinthepasttwentyyearsandthatineveryareaofplantgrowththeincreaseistheresultofweatherconditions.

EightscientistsfromacrosstheUnitedStatesdidthestudy.ThespaceagencyNASAandtheDepartmentofEnergypaidforit.ThefindingswerepublishedinthemagazineScience.

Theresearchersspentoneandahalfyearsexaminingweathersatelliteinformation.Theinformationwasrecordedfrom1982to1999.Thatperiodwasoneofthewarmestonrecord.Researchersfoundthatrainfallgenerallyincreasedduringthattime.

Thesatellitesmeasuredthenumberofleavesonplantsandtheamountofsunlighttakenin.Thescientistsusedthatinformationtoestimatewhatiscallednetprimaryproduction.Thisistotalamountofcarbonstoredinlandplants.

Thescientistsreporta6%increaseinstoredcarbonsince1982.Theysaygainswerehighinequatorialareas,especiallyaroundtheAmazonRiverinSouthAmerica.Theareaalonehada1%increaseinthenetprimaryproduction.

RamakrishnaNemanioftheUniversityofMontanainMissoulaheadedthestudy.HesaysreducedcloudcoverledtogrowthinAmazonarea.Healsosaysthelackofcloudsallowedmoresunlighttogetthrough.Moresunlightmeantincreasesinphotosynthesis(光合作用).Thatistheprocessbywhichplantsuseenergyfromsunlighttoproducethechemicalstheyneedtogrow.

NorthernCanada,thenorth-centralUnitedStatesandnorthernEuropeweresecondinincreasedplantgrowth.RamakrishnaNemanisaysariseintemperaturehelpedplantsthere.

Alltogether,thereportsays25%ofareasofplantlifeonEarthexperiencedincreases.ButthescientistsalsonoteincreaseinthenumberofpeopleonEarthandcarbondioxidelevelsintheatmosphere.RangaMyneniofBostonUniversityinMassachusetts,anotherstudyscientistsayshumansuseabouthalfthenetprimaryproductiononEarth.Andhenotesthattheworldpopulationgrewby36%duringtheperiodoftimestudied.

小题1:Whichofthefollowingisinchargeofthestudy?