Inthepasthundredyears,therehaveheenfrequentnaturaldisasters,suchasfloods,droughts,mud-rockflows,seismicseawaves,earthquakes,windstormsandthestretchingofnewdeserts.Thedisastershavekilledmillionsuponmillionsofpeople,destroyedcountlesshomes,andwipedoutnumerouspiecesoffertileland.Nowmoreandmorepeoplebecomeawarethatthosedisastershavemuchtodowithwhatwehavedonetotheearth.Wehavecutdowntoomanytreesintheforests,wehavebadlypollutedtheenvironment,wehaveshockedourownhome-planettimeandagainwithtremendouslypowerfulexplosionsofnuclearbombs.Asaresult,climateshavebecomeabnormal,rainwaterrushesdownhillsidesangrily,andtheundergroundenergygoesuptorevengeitselfonus.Theearthisouronlyhome-planet.Itisurgentforustostopdamagingit,andtodoourbesttoprotectitandmakeitalovelyplacesuitabletolivein,forwehavenowheretogoandsurviveexceptwherewearenow.