全球入侵物種數量在上升

一個國際研究團隊，包括倫敦大學學院的研究人員發現，在全球範圍內外來物種的數量正在上升，並沒有顯示出任何飽和的跡象。

由德國森肯堡研究中心和奧地利維也納大學科學家領導的研究團隊發現，世界範圍內，在過去200年裡，新確定的外來物種數量在持續增長，所有的首次入侵記錄，超過三分之一發生在1970到2014年。

這項發表在今天出版的《自然通訊》上的研究表明，個體趨勢與生物分類群有所不同，這可以歸因於人類活動，但總體而言，對所有生物群體來說，外來物種的數量正在增加。

「我們觀察到的首個明顯增長的入侵率記錄是19世紀的維管束植物、鳥類和哺乳動物，這可能是歐洲殖民擴張時期，園藝的傳播而且認為這種引入是有益的所導致的。其它生物如藻類、軟體動物或昆蟲的新入侵率是在1950年之後急劇增加的，這極有可能是貿易全球化因素所導致，」論文的共同作者提姆 布萊克本教授解釋說（倫敦大學學院遺傳學、進化和環境科學）。

雖然我們已經知道外來物種的數量在過去的50年裡一直在增加，但仍不清楚外來物種的積累是否已經達到了峰值，出現減速的情況。

論文的第一作者，德國森肯堡研究中心的Hanno Seebens博士說：「所有大陸上的所有生物群體，在過去200年間，外來物種的數量都在持續上升。對大多數生物群體來說，在最近幾年，入侵率達到最高值。除了哺乳動物和魚類之外，沒有跡象表明外來物種入侵出現減速跡象，在不遠的將來，我們會看到更多的新入侵物種。」

這一結論是由來自世界各地的45名科學家進行的一項大型合作研究得出的，他們建立了一個資料庫，數據是在該物種的本土範圍以外的區域首次被發現的日期。利用超過4萬5千個記錄（超過1萬6千個外來物種），研究人員分析了過去幾個世紀外來物種的積累。

科學家們發現有記錄的37%的外來物種都是在1970-2014年和最近入侵的。峰值出現在1996年，當時世界上有585個新外來物種被記錄下來，或每天1.5個新外來物種。「對於大多數外來物種來說，首次入侵日期的數據獲取不到，因此，我們公布的入侵日期記錄顯然低估了外來物種入侵的程度，」 高級研究作者Franz Essl博士說（奧地利，維也納大學）。

該團隊稱，外來物種的數量空前的增加可以導致區域物種丰度的增加，也導致對原生生態系統的各種負面影響，包括植物群和動物群的全球同質化，以及本地物種的滅絕。

出於這個原因，目前，世界各地正在建立各種法律法規，以減少新的外來物種的引入。「但是，我們的研究結果表明，過去的努力還不夠有效以跟上正在進行的全球化。我們迫切需要實施更加有效預防政策，」 Essl博士總結道。 （張微編譯）

以下為英文原文：

Invasive species on the rise globally

The number of alien species is increasing globally, and does not show any sign of saturation, finds an international team involving UCL researchers.

Led by scientists from Senckenberg, Germany, and the University of Vienna, Austria, the team found that during the last 200 years, the number of new established alien species has grown continuously worldwide, with more than a third of all first introductions recorded between 1970 and 2014.

The study, published today in Nature Communications, shows that individual trends differ among taxonomic groups, which can be attributed to human activities, but overall, alien species numbers are increasing for all groups of organisms.

"We observe distinct increases in first record rates of vascular plants, birds and mammals in the 19th century, probably as a result of the spread of horticulture and attempts at supposedly beneficial introductions during the period of European colonial expansion. The rates of new introductions of other organisms such as algae, molluscs or insects increased steeply after 1950, most likely because of the ongoing globalisation of trade," explained study co-author Professor Tim Blackburn (UCL Genetics, Evolution & Environment).

Although it was already known that the number of alien species has increased during the last 50 years, it remained unclear whether or not the accumulation of alien species has already reached a point of slow-down.

Dr Hanno Seebens (Senckenberg, Germany), first author of the study, said: "For all groups of organisms on all continents, the number of alien species has increased continuously during the last 200 years. For most groups, the rate of introduction is highest in recent years. Barring mammals and fishes, there are no signs of a slow-down in the arrival of aliens, and we have to expect more new invasions in the near future."

This conclusion results from of a large collaborative effort by 45 scientists from all over the world, who established a database of the date an alien species was first detected in a region outside the species' native range. Using more than 45,000 of these first records of more than 16,000 alien species, they analysed the accumulation of alien species over the last few centuries.

The scientists found that 37% of all recorded alien species were introduced between 1970-2014 and thus recently. The peak came in 1996, when 585 new alien species were recorded worldwide, or more than 1.5 new alien species per day. "As the date of first record is not available for most alien species, these numbers are clearly underestimating the full extent of alien species introductions", said senior study author Dr Franz Essl (University of Vienna, Austria).

The team say the unprecedented increase in alien species numbers can lead to an increase in regional species richness but also lead to a variety of negative impacts on native ecosystems, including the global homogenisation of floras and faunas, and the global extinction of native species.

For this reason, various laws are currently in force globally attempting to mitigate the introduction of new alien species. "However our results show that the past efforts have not been effective enough to keep up with ongoing globalisation. There is an urgent need to implement more effective prevention policies at all scales," concluded Dr Essl.