沒有人類，整個世界也許看起來就像塞倫蓋蒂(Serengeti)般的生機盎然

原網址：www.sciencedaily.com/releases/2015/08/150820212652.htm

Without humans, the whole world could look like Serengeti

沒有人類，整個世界也許看起來就像塞倫蓋蒂(Serengeti)般的生機盎然

New study shows what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts

新的研究顯示出若沒有過去與現在的人類影響，自然世界中哺乳類的多樣性應該如何分佈

The fact that the greatest diversity of large mammals is found in Africa reflects past human activities -- and not climatic or other environmental constraints. This is determined in a new study, which presents what the world map of mammals would look like if modern man (Homo sapiens) had never existed.

在這篇新研究中，研究人員呈現出若現代人(Homo sapiens)從未出現，哺乳類在這個世界上應是如何分佈。他們的結果顯示非洲擁有最高的大型哺乳類多樣性，反映出來的是過往人類活動的影響，而非氣候或其他環境限制導致。

In a world without humans, most of northern Europe would probably now be home to not only wolves, Eurasian elk (moose) and bears, but also animals such as elephants and rhinoceroses.

在沒有人類的世界，現今北歐大部分的地區可能不只是狼、歐亞駝鹿(麋鹿)與熊的家園，也會有其它動物生活於此，像是大象與犀牛。

This is demonstrated in a new study conducted by researchers from Aarhus University, Denmark. In a previous analysis, they have shown that the mass extinction of large mammals during the Last Ice Age and in subsequent millennia (the late-Quaternary megafauna extinction) is largely explainable from the expansion of modern man (Homo sapiens) across the world. In this follow-up study, they investigate what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts, based on estimates of the natural distribution of each species according to its ecology, biogeography and the current natural environmental template. They provide the first estimate of how the mammal diversity world map would have appeared without the impact of modern man.

此幅景象呈現於丹麥奧胡斯大學(Aarhus University)的研究人員新進行的研究結果之中。在先前的分析當中，他們已經顯示在上次冰河期以及之後數千年間，發生的大型哺乳類滅絕事件(晚第四紀巨型動物群滅絕事件，the late-Quaternary megafauna extinction)絕大部分要歸咎於現代人(Homo sapiens)往世界各地遷徙。在這篇後續研究當中，他們根據不同種哺乳類各自的生態、生物地理分佈以及在自然條件下，各地環境應有的樣貌為何，來預測牠們的自然分佈模式，並總和所有結果得出若沒有過去及現今的人類影響，在自然情形下哺乳類多樣性在全世界的分佈模式。他們的結果呈現了首幅在沒有現代人的影響下，哺乳類多樣性會如何分佈的世界地圖。

"Northern Europe is far from the only place in which humans have reduced the diversity of mammals -- it's a worldwide phenomenon. And, in most places, there's a very large deficit in mammal diversity relative to what it would naturally have been," says Professor Jens-Christian Svenning, Department of Bioscience, Aarhus University, who is one of the researchers behind the study.

「北歐絕不是唯一人類導致哺乳類多樣性下降的地區─這是一個在全世界都相當普及的現象。而且在多數地區，哺乳類多樣性跟在自然背景下應有的相比，都下降了非常多。」此篇研究的作者之一，奧胡斯大學生命科學系的教授Jens-Christian Svenning說。

Africa is the last refuge

非洲─最後的淨土

The current world map of mammal diversity shows that Africa is virtually the only place with a high diversity of large mammals. However, the world map constructed by the researchers of the natural diversity of large mammals shows far greater distribution of high large-mammal diversity across most of the world, with particularly high levels in North and South America, areas that are currently relatively poor in large mammals.

現今的哺乳類多樣性世界地圖顯示出非洲為僅存大型哺乳類仍具有高度多樣性的地區。然而，由研究人員建立的世界地圖卻顯示在自然情況下，具有高度大型哺乳類多樣性的地區廣泛分佈於世界各地。其中又以南北美洲為特別高的地區，儘管目前這些地方的大型哺乳類相對來說相當罕見。

"Most safaris today take place in Africa, but under natural circumstances, as many or even more large animals would no doubt have existed in other places, e.g., notably parts of the New World such as Texas and neighboring areas and the region around northern Argentina-Southern Brazil. The reason that many safaris target Africa is not because the continent is naturally abnormally rich in species of mammals. Instead it reflects that it's one of the only places where human activities have not yet wiped out most of the large animals," says Postdoctoral Fellow Soren Faurby, Department of Bioscience, Aarhus University, who is the lead author on the study.

「現今的遊獵(safari，原本意指以狩獵大型動物為主的遠行活動，現在多已轉變成觀光性質)多半僅見於非洲，但在自然條件下，毫無疑問地會有同樣多數量，甚至更大批的大型動物生存在其他地區，譬如說目前新世界的都會區，如德州與其鄰近區域，以及阿根廷部北部至巴西南部地區。許多遊獵選在非洲並非因為當地本來就擁有特別多種的哺乳類，而是反應出非洲為人類活動尚未殲滅大部分大型哺乳類的僅存地區之一。」本篇研究的第一作者，奧胡斯大學生命科學系的博士後研究員Soren Faurby說。

The existence of Africa's many species of mammals is thus not due to an optimal climate and environment, but rather because it is the only place where they have not yet been eradicated by humans. The underlying reason includes evolutionary adaptation of large mammals to humans as well as greater pest pressure on human populations in long-inhabited Africa in the past.

因此非洲擁有許多種哺乳類的原因並非是其擁有特別宜人的氣候以及環境，而是因為它是尚未遭人類染指的最後淨土。這背後的原因包括了當地的大型哺乳類演化出對人類有較高的適應能力，以及長久以來非洲的住人地區因為寄生蟲肆虐，而大幅限制了人口增長。

Better understanding helps nature preservation

瞭解更多有助於生態保育

The study's openly accessible data set of natural range maps for all late-Quatenary mammals provides researchers with the first opportunity to analyse the natural patterns in the species diversity and composition of mammals worldwide. Hereby, it can be used to provide a better understanding of the natural factors that determine the biodiversity in a specific area.

此篇研究提供了所有晚第四紀以來的哺乳動物，在自然條件下應會如何分佈的公開地圖資料，有了這些資料，研究人員首度有機會分析世界各地的哺乳動物多樣性及組成，在僅考慮自然條件下的分佈模式。而這可以讓我們對特定地區的自然因子如何影響當地的生物多樣性有更深入的瞭解。

Today, there is a particularly large number of mammal species in mountainous areas. This is often interpreted as a consequence of environmental variation, where different species have evolved in deep valleys and high mountains. According to the new study, however, this trend is much weaker when the natural patterns are considered.

現今的山區環境有特別多樣的哺乳類。這通常被視作山區能提供各式各樣的環境而造成的結果。生物在高山與深谷中會往不同的方向演化，因而創造出特別高的多樣性。然而根據此篇新研究，在僅考慮自然因素的生物多樣性分佈模式中，這種趨勢並不特別明顯。

"The current high level of biodiversity in mountainous areas is partly due to the fact that the mountains have acted as a refuge for species in relation to hunting and habitat destruction, rather than being a purely natural pattern. An example in Europe is the brown bear, which now virtually only live in mountainous regions because it has been exterminated from the more accessible and most often more densely populated lowland areas," explains Soren Faurby.

「現今的山區擁有相當高的生物多樣性，部分原因來自於高山對生物來說，是躲避人類狩獵以及棲地破壞的避難所，而非純粹由自然因素造成。在歐洲一個很好的例子便是棕熊。棕熊現在僅生存於深山地區，這是因為牠們已難以生活在對人類而言易於抵達且人口密集的平地。」

Hereby, this new study can provide an important base-line for nature restoration and conservation.

此新研究能夠提供未來自然保育與復育的研究上重要的基準點。

The study has been published in the scientific journal Diversity and Distributions.

本研究刊登於科學期刊《生物多樣性與分佈》(Diversity and Distributions)。

The natural diversity of large mammals is shown as it would appear without the impact of modern man (Homo sapiens). The figure shows the variation in the number of large mammals (45 kg or larger) that would have occurred per 100 x 100 kilometer grid cell. The numbers on the scale indicate the number of species.

上圖為在沒有現代人類(Homo sapiens)的影響下，大型哺乳類多樣性的自然分佈模式。將地圖分成100 x 100 公里的網格後，計算每一格當中有多少種大型哺乳類(45公斤以上)而得到此圖。右方刻度代表物種數目。

Credit: Illustration: Soren Faurby

引用自：Aarhus University. "Without humans, the whole world could look like Serengeti: New study shows what the natural worldwide diversity patterns of mammals would be like in the absence of past and present human impacts." ScienceDaily. ScienceDaily, 20 August 2015.