|
正在消失的机会
 马达加斯加贝其布卡河口被侵蚀的鲜红土壤. (Photo courtesy of NASA/JSC)
|
写 Rhett Butler. 翻译 Che Fei
07/12/2007
侵蚀及其影响
树根扎根固定于土壤中，在整个热带地区树木的消失引起了普遍的土壤侵蚀.仅有少数地方土壤保持很好，森林砍伐后，这些土壤很快就会被大雨冲走.因此农作物产量下降，人们不得不花钱进口外来的肥料或者去砍伐另一片森林.哥斯达黎加每年丧失的很有价值的表层土就达8.6亿吨,而大红岛也因侵蚀而失去如此之多的土壤，以致流经它的河流都呈血红色，就连周围的印度洋也受到影响.宇航员评论说马达加斯加看起来就像因流血过多而死亡的样子，一个大家都认可的说法就是一个国家严重的环境危机和衰退的经济皆因这个国家的土壤被破坏而致.森林砍伐后的土壤消失的速度是惊人的;一项在象牙海岸进行的研究发现每年每公顷森林坡面区失去0.03吨的土壤;耕种坡面每年每公顷会丢失土壤90吨,而光秃坡面则会丢失达138吨.
| 
马达加斯加境内森林砍伐导致的土壤侵蚀平面图 |
大雨降落到被砍伐过的森林土地上后，携带而走的土壤流进了当地的溪流.河流载着侵蚀泥土流向下游,引起了重大问题. 水利电气工程项目 和灌溉基础设施由于河流的淤积而丧失了"生产力",而由于缺水，工厂设备安装也被延缓操作了.泥沙沉积也抬升了河床,增加了洪涝的危险性；它也使得浅滩和沙洲得以形成，从而给内河航运带来更多的麻烦.河中越来越多的沉积淤泥使鱼类产卵受到阻碍，卵孵化率降低.随着水中悬浮物进入海洋，水开始变的浑浊，会引起地域性的珊瑚礁数量下降，也对沿海渔业产生不良影响. 世界上珊瑚礁(通常称为"海洋雨林")的丧失,使得很多科学家痛苦不已，因为它们有着丰富的多样性，并且它们提供了很重要的服务.沿海渔业不仅受到珊瑚礁和它们生存环境消失的影响，而且受到河流泥沙淤积使得红树林生长受到严重破坏的影响.
除了给渔业产业带来破坏外，森林砍伐导致的土壤侵蚀也破坏了穿过森林的道路交通设施.政府没有封锁道路，而不得不重复修建,这将花费好多本应用于其他有更多成果方面的资金.
土壤侵蚀对发展中国家来说代价是很大的.除了对基础设施、渔业、财产的影响外，全世界光因珍贵的表层土侵蚀每年就会耗掉数十亿美元.例如，在20世纪80年代后期，爪哇印度尼西亚岛每年丢失表层土达7.7亿吨，估计损失稻米150万吨,这足够满足1,150-1,500万人的生存需要.
环境难民
环境的恶化使人们沦落成 "环境难民"—人们的迁移正是由于环境恶化造成的.联合国提到截止到2010年，世界上将有多达5,000万人类因为森林砍伐、海平面上升、沙漠扩张和灾难性气候事件等而沦为"环境难民".红十字会研究表明由于环境灾难而引起的迁移的人数比战争引起的还要多.
复习题:
- 为什么雨林能阻止土壤侵蚀的发生?
- 为什么说土壤侵蚀是一个很严重的问题?
- 什么是"环境难民"?
[打印版]
续: 物种的损失、灭绝和疾病
|
|
 |
|
404 Error: Page Not Found
|
|
|
 |
|
|
|
APOLOGIES, BUT THIS PAGE IS NO LONGER AVAILABLE
RAINFOREST INFORMATION
FOR KIDS
TROPICAL FISH
DATA
|
Data aggregations found on mongabay.com
Deforestation figures for selected countries: deforestation statistics for more than 200 countries worldwide. Figures come from the Food and Agriculture Organization of the United Nations.
Country statistics: Other country-specific statistics including land area, human, population, economic indicators, and environmental conditions. Figures come from the Food and Agriculture Organization of the United Nations.
AIDS Statistics: for selected countries. From the U.S. Census Bureau.
2005 city population estimates for the world: proprietary population estimates for more than 10,000 cities.
World's Largest Cities by Country
United States Zip Codes: proprietary aggregation of U.S. postal codes.
World's Largest Cities by Country
Countries and Capitals
World's Largest Cities
World's Largest Urban Areas
World Population Projections - 2002, 2010, 2015, 2020: United Nations projections.
World Population Projections: United Nations projections for individual cities.
Country studies: Text excerpted from on-line versions of books previously published in hard copy by the Federal Research Division of the Library of Congress under the Country Studies/Area Handbook Program sponsored by the U.S. Department of Army.
Occupations in the United States: By job title. Includes job description and overview, number of people employed in a given occupation, and other data.
Occupations in the United States: Comparison statistics by job title for cities in the US. For a given city, includes number of people employed in an occupation and salary data.
Regional Occupational Data for the United States: By city. For a specific city, includes the number of people employed in a given occupation and salary figures.
Tax Data for the United States
World's Largest Countries by Land Area
World's Largest Countries by Population
|
|
XML / RSS / Syndication options
There are three XML feeds for mongabay.com
|
|
|
MONGABAY.COM
Mongabay.com seeks to raise interest in and appreciation of wildlands and wildlife, while examining the impact of emerging local and global trends in technology, economics, and finance on conservation and
development >>
|
|
