摘要
亚马孙正经历着火的快速改造。采伐和森林破碎化通过增强森林干燥作用、增加易燃物而使火灾发生率急剧上升,一直经历低强度地表火灾的森林更易遭受灾难性的火灾。卫星一般每年检测到亚马孙流域4万～5万处分散起火点的热成像图斑,随着新的公路和基础设施在该地区扩张,这一数字还会增加。大范围毁林会通过减少区域蒸散并产生隔绝水汽的烟羽(smoke plumes)而使得亚马孙流域易于遭受火灾,这与许多因素有关。尽管人们尚有许多不确定的地方,亚马孙地区可能也受未来全球变暖和大气变化的影响。大多数模型认为该流域在本世纪将变得更暖,降水量将受何种程度影响则看法不一。最令人悚然的情景预言了厄尔尼诺-南方涛动的持久破坏作用,导致亚马孙强烈加剧的干旱或区域与全球气候变化之间的破坏性协同作用。
The Amazon is being rapidly transformed by fire.Logging and forest fragmentation sharply elevate fire incidence by increasing forest desiccation and fuel loads,and forests that have experienced a low-intensity surface fire are vulnerable to far more catastrophic fires.Satellites typically detect thermal signatures from 40 000 to 50 000 separate fires in the Amazon each year,and this number could increase as new highways and infrastructure expand across the basin.Many are concerned that largescale deforestation,by reducing regional evapotranspiration and creating moisturetrapping smoke plumes,will make the basin increasingly vulnerable to fire.The Amazon may also be affected by future global warming and atmospheric changes, although much remains uncertain.Most models suggest the basin will become warmer throughout this century,although there is no consensus about how precipitation will be affected.The most alarming scenarios project a permanent disruption of the E1 Nin~~o-Southern Oscillation,leading to greatly increased drought or destructive synergisms between regional and global climate change in the Amazon.
