This is the VOA Special English Agriculture Report.

这里是美国之音慢速英语农业报道。

South America's Amazon is the largest tropical rainforest and river system on Earth. But the Amazon is disappearing at the rate of about eight hundred thousand hectares a year. This deforestation is caused by an increase in agriculture and cattle ranching and the building of roads and dams. Another cause is the illegal cutting of trees for logging companies.

南美的亚马逊河流域是全球最大的热带雨林和河流系统。但亚马逊河流域正以每年约八十万公顷的速度消失。这一森林破坏是由农业、养牛、道路及水坝建设造成的，而另一原因是伐木公司非法砍伐树木。

Now, a new study says ancient Amazonian farming methods could offer valuable lessons for today. The study looks at the pre-Columbian period. Christopher Columbus and other European explorers began arriving in the Americas in the late fourteen hundreds.

现在，一项新研究声称，亚马逊河流域的古代耕作方法可以为今天提供宝贵的教训。该研究着眼于前哥伦布时代。克里斯托弗·哥伦布（Christopher Columbus）和其他欧洲探险家于15世纪末期开始抵达美洲。

The researchers studied a coastal wetland area where ancient farm beds and canals remain unchanged. The site is in French Guyana.

研究人员研究了一块远古农田和沟渠保持未变的滨海湿地。该遗址位于法属圭亚那。

A widely held belief is that pre-Columbian farmers used a great deal of fire to manage Amazonian ecosystems. But the scientists say their study calls this idea into question. It shows that raised-field farmers limited their burning to improve agricultural production.

一个普遍的观点是，前哥伦布时期的农民大量使用烧荒来管理亚马逊河流域的生态系统。但科学家说，他们的研究对此观点提出怀疑。研究显示，沟洫台田（raised-field，又译高架田等）农民限制烧荒以提高农业产量。

Jose Iriarte from the University of Exeter in England was lead author of the study. Mr. Iriarte says fire results in the loss of important nutrients for crops. When land is not being used for farming, periods without fire are most effective in rebuilding soil organic matter and preserving soil structure. "So in this sense," he says, "we interpreted that they were limiting fires because it was better to grow crops in these raised field systems."

英格兰埃克塞特大学的乔斯·伊里亚特(José Iriarte)是该研究的主要作者。伊里亚特先生指出，烧荒会导致对作物非常重要的营养物资的流失。当土地不再用于耕作，不烧荒期间是重建土壤有机质和保护土壤结果最有效的时期。他表示，“从这种意义上说，我们理解为他们限制烧荒，因为这在这些沟洫台田种植作物要更好。”

He says this fire-free method by the pre-Columbian farmers helped change the seasonally flooded savanna, or grassland, into productive cropland. Raised fields provide better drainage and soil aeration and also hold moisture during the dry season.

他说，这种前哥伦布时期农民的免烧荒方法有助于把这种季节性淹没的热带草原改造成高产农田。沟洫台田提供了更好的排水和土壤透气性，在旱季期间还保持住了水分。

This fire-free method of agriculture would have been labor intensive. It ended when up to ninety-five percent of the native people died from diseases brought by the Europeans. Mitchell Power is curator of the Natural History Museum at the University of Utah.

这种农业免烧荒方法可能属于劳动密集型。当高达95%的当地人因为欧洲人带来的疾病死亡后，这一农业方法就消亡了。米切尔·鲍尔（Mitchell Power）是美国犹他大学自然历史博物馆馆长。

MITCHELL POWER: "Once the Columbian encounter happens, we don't see that type of agriculture any more. We start to see increased burning and a shift towards dry-land farming. So people were then clearing forests and making their raised beds in the forests. And so, what we think is happening is that there was a huge demographic collapse in this region."

鲍尔：“一发生'哥伦布大遭遇'，我们就再也看不到这种类型的农业。我们开始看到不断增加的烧荒，以及向旱地农业的转变。于是人们随后清理了森林，在森林中建造他们的沟洫台田。因此我们目前认为，该地区发生过巨大的人口崩溃。”

注：本段中的Columbian encounter(哥伦布大遭遇')应该是指历史上所谓的Columbian exchange（哥伦布大交换时期）。它是一场东半球与西半球之间生物、农作物、人种（包括黑奴）、文化、传染病、甚至思想观念的突发性交流。它是人类历史上的跨越种族的一件重要事件。

The European colonizers brought slash-and-burn methods of agriculture that remain a threat to the rainforest. Experts say at current rates, more than half of the Amazon's tropical rainforest could be gone by twenty-thirty.

欧洲殖民者带来的农业刀耕火种法仍然是雨林的一大威胁。专家表示，以当前的速度，到2030年，超过一半的亚马逊热带雨林将会消失。

The study is in the Proceedings of the National Academy of Sciences. You can find a link at www.voanews.cn. And that's the VOA Special English Agriculture Report. I'm Jim Tedder.

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Contributing: Rosanne Skirble