一項由國際科學家團隊完成的研究指出,保育腹地廣闊的亞馬遜森林保育區,其重要性比我們先前所認知的更多。這項研究登於12日出刊的《科學》期刊中,強調保護亞馬遜免於破碎化的重要性。
巴西國家亞馬遜研究院長年執行一項大規模的森林破碎化研究,名為「森林破碎化之生物動態計劃」,這篇發表在《科學》期刊的報告,便是總結自此計劃中的鳥類調查。
從2000年5月到2006年8月,有15萬平方公里(57915平方英哩)的森林自巴西消失——面積比希臘還大。1970年至今,整個亞馬遜森林消失面積已超過4個希臘。每年,農業、牧業和伐木業合法或非法清除森林的動作,都使亞馬遜森林減少數千平方公里,並造成一塊塊小面積的破碎森林。
原本棲息在完整森林的物種,很多無法在破碎的小面積森林繼續生存;科學家希望探討的問題是:這些物種能否在未受侵擾森林所包圍的小面積土地上存活?
這個問題可以釐清森林面積和隔離性對物種的相對重要性,定然深深影響執行層面有關森林管理和劃分保護區的政策。科學家發現,面積是保育物種的關鍵因素,因為大面積森林裡豐富的生物多樣性有利於物種生存。
致力於整合環境研究的約翰漢斯三世中心(H. John Heinz III Center)院長羅芙喬伊(Lovejoy)表示:「森林裡看起來和諧一致的綠色,實際上是由色彩繽紛的馬賽克所組成。對每個物種來說,森林裡都有一個符合自己特殊需求的位置,那位置雖然不大,卻是在浩瀚森林中一個精細且無可取代的區位。」
這份史無前例的研究中,透過55種鳥類族群動態分析,深入探討保留區面積和隔離性對於物種形成群落和滅絕的影響性。結果顯示,某些鳥因為無法在新地點生存而絕跡,某些則是因為無法形成新群落而滅絕,而這兩種狀態很可能同時發生。因此作者認為,對鳥的生存而言,森林面積大小遠比森林完整性更為重要。
Conservation of extensive Amazon forest reserves is even more important than previously thought, according to a new study by an international scientific team. The research, to be published in tomorrow's issue of the journal "Science," spotlights the importance of protecting the Amazon from fragmentation.
The article summarizes bird survey results from the world's largest and longest running experimental study of forest fragmentation - the Biological Dynamics of Forest Fragments Project at the National Institute for Amazonian Research.
Between May 2000 and August 2006, Brazil lost nearly 150,000 square kilometers (57,915 square miles) of forest - an area larger than Greece. Across the entire Amazon since 1970, an area four times that size has been destroyed. Every year, land clearing for agriculture, ranching and logging - both legal and illegal - shrinks the Amazon forest by thousands of square kilometers, leaving small forest fragments isolated from one another by cleared land.
Many species that occur in intact forests prior to destruction will not be present in a small fragment. But the scientists wanted to learn if these same species would be found in an equally small plot surrounded by untouched forest. They say the answer to this question has profound management implications because it weights the relative importance of area and isolation in the design of forest reserves. The scientists found that conservation of large areas is important because the forest is diverse.
"What might look like a vast mantle of homogeneous green is actually a multicolored mosaic," said Lovejoy, who is president of the The H. John Heinz III Center for Science, Economics and the Environment. "Species that occur throughout the forest at the large scale actually may have very specific requirements at the fine scale," he said.
This detailed look at the dynamics of 55 bird species allowed an unprecedented test of theories about the effects of reserve size and isolation on the local extinction and colonization of species. The study shows that some species vanish because they do not survive in a given site, others because they do not colonize new sites that become available. The two processes may also act in combination. The effects of area size on the occurrence of bird species are much stronger than the effects of isolation, the scientists concluded.