1．Today there are more fires than in the past．Over 100，000wildfires burn each year in America．Russia has 20，000to 35，000wildfires every year．Australia has on average 60，000each year．These fires destroy（损害）huge areas of forests and burn hundreds of homes．
Many experts believe there are several reasons for this sudden increase in fires．The first reason is climate（气候）change．Recent weather has been warmer and drier．This leads to dangerous fire conditions．When lightening strikes（发生雷电），dry grass easily catches fire．Hot winds add to the problem．The wind spreads a fire quickly．In 2010，Russia had the hottest and driest summer in a century．In just one month，500fires destroyed over 2，000homes．Some people lost their lives．
Traditional fire-fighting practices are another reason for the increase in fires．In America，firefighters used to quickly put out every fire．They didn't allow the grass and trees to burn．As a result，today many forests have thicker vegetation（植被）．Thicker vegetation means more fuel（燃料）for fires．Also，without fires from time to time，forests become overcrowded and unhealthy．Some trees are dead．The dead wood then easily catches fire．So surprisingly，America has many more fires today partly because of its past fire-fighting practices．
Scientists now understand that a fire can be a natural part of a healthy forest．As a result，countries like Australia allow more fires to burn naturally．Sometimes，fire fighters even start fires to get rid of（去除）dead wood．Of course，they carefully control the fires．The fire thins out old trees．This allows sunlight to reach the ground．As a result，fires help new trees to grow．Therefore，if a fire is not a serious threat（威胁）to people，firefighters may let it burn naturally．
61．How many wildfires are there in Australia in one year？60，000．
62．Why did Russia have so many fires in one month in 2010？Because Russiahadthehottestanddriestsummerinacentury．
63．What are the reasons for the increase in fires？Climate change and traditionalfire-fightingpractices．
64．Are forests very healthy without fires from time to time？No，they aren't．
65．What is the main idea of Paragraph 4？Afirecanbeanaturalpartofahealthyforest．．
