農(nóng)作物病蟲害正在以同變暖的溫度相同的步伐朝著地球的兩極邁進(jìn)。這一發(fā)現(xiàn)表明,，氣候變化正在驅(qū)動病蟲害的遷移，同時對糧食安全問題提出了更大的挑戰(zhàn),。
氣候變化被認(rèn)為將導(dǎo)致物種在世界各地的分布變化,，即整體遠(yuǎn)離赤道并向兩極平移。生態(tài)學(xué)家已經(jīng)在許多野生物種中證實(shí)了這樣的一種轉(zhuǎn)移,，包括一些鳥類和昆蟲,。
在許多國家，氣候變化已經(jīng)引發(fā)了關(guān)于糧食安全的強(qiáng)烈關(guān)注,，而害蟲或許會讓情況變得更糟,。主持這項(xiàng)新研究的英國?？速愄卮髮W(xué)的生態(tài)學(xué)家Dan Bebber表示：“我們的防御工事，從殺蟲劑到殺菌劑都被要求能夠?qū)Ω对絹碓蕉嗟暮οx和疾病,，但后者卻正在進(jìn)化出針對前者的抗性,。”而害蟲種群擴(kuò)張到新的領(lǐng)土無疑增加了這些生物體逃脫人類控制后造成的風(fēng)險。
而其中最大的威脅來自于真菌和卵菌,，它們是相似但分屬不同種類的微生物,，能夠?qū)е轮参锏牟『Α讉€高毒性的真菌菌株近年來出現(xiàn)在世界各地,，而即便在導(dǎo)致愛爾蘭大饑荒168年以后,，卵菌綱的致病疫霉(Phytophthorainfestans)仍然是各國需要面對的一個永恒問題。
農(nóng)作物病蟲害的全球活動從未得到全面的分析,。為了填補(bǔ)這一空白,，Bebber及其同事采用了CABI(原名農(nóng)業(yè)生物科學(xué)國際中心)提供的歷史記錄——它們記載了從1822年至今發(fā)生在全世界的農(nóng)作物病蟲害。該研究的合作者之一,、?？速愄卮髮W(xué)的植物病理學(xué)家Sarah Gurr指出：“沒有人曾著眼于任何一個這樣的數(shù)據(jù)庫。這是第一個此類分析,。”
另一位合作者M(jìn)ark Ramotowski將CABI的樣本從8萬個記錄縮小至26776個記錄——研究人員主要聚焦于上世紀(jì)60年代之后的時間段,，因?yàn)檫@些記錄往往是最可靠的。對于612種不同的害蟲,，研究人員確定了每一種害蟲在一個新的國家(或者一個大國的某一地區(qū))被首次發(fā)現(xiàn)的年份,，并把這作為害蟲到達(dá)該國或該地區(qū)平均緯度的時間。
這項(xiàng)研究的主要弱點(diǎn)在于數(shù)據(jù)的偏差,。研究人員假設(shè),，如果沒有任何現(xiàn)實(shí)趨勢，害蟲似乎應(yīng)該朝著赤道運(yùn)動,，而不是兩極方向,。這是因?yàn)榕c其他國家相比，發(fā)達(dá)國家擁有的科學(xué)資源能夠比前者更早地監(jiān)測到害蟲,，而發(fā)達(dá)國家往往位于高緯度地區(qū),。隨著各國的發(fā)展以及對害蟲更多的了解，害蟲的范圍似乎開始向熱帶地區(qū)遷移,。
事實(shí)上,，研究人員發(fā)現(xiàn)，農(nóng)作物害蟲以平均每年2.7公里的速度向兩極方向遷移,，這與全球氣候變化的速度非常接近,。然而，這一速度在不同的物種乃至同一物種之中也存在巨大變化。真菌,、甲蟲,、蝽、螨蟲,、蝴蝶以及蛾子表現(xiàn)出了向高緯度地區(qū)的明顯遷移,，而病毒和線蟲動物門則向低緯度地區(qū)遷移。其他物種沒有表現(xiàn)出任何可察覺的改變,。
Gurr表示：“許多研究表明,，氣候變化正在影響野生物種種群的分布規(guī)律。而這是第一個表明類似過程正在害蟲種群中發(fā)生的研究,。”她還強(qiáng)調(diào)了一個令人擔(dān)憂的發(fā)現(xiàn),，即真菌和卵菌正在以非常快的速度前進(jìn)——分別為每年7公里和6公里,。研究人員在9月1日的《自然—氣候變化》雜志上報告了這一研究成果,。
英國約克大學(xué)生物學(xué)家Chris Thomas強(qiáng)調(diào)，農(nóng)作物病蟲害整體的運(yùn)動速度非常近似于由他主持的一項(xiàng)有關(guān)野生物種遷徙的薈萃分析的研究結(jié)果,。他說：“我的第一印象為這是一項(xiàng)非常徹底的研究,。”Thomas指出，就像作者所說的,，那些看起來向赤道前進(jìn)的害蟲種群——大部分是線蟲動物門和病毒——往往是了解最少的,，因此它們隨后更有可能在發(fā)展中國家被發(fā)現(xiàn)。（生物谷 Bioon.com）
生物谷推薦的英文摘要
Nature doi:10.1038/nature.2013.13644
Crop pests advancing with global warming
Eliot Barford
Crop pests and diseases are moving towards the poles at about the same speed as warmer temperatures. The finding suggests that climate change is driving their relocation, and raises major concerns about food security.
Climate change is expected to cause changes in the distributions of species around the world, with an overall shift away from the equator and towards the poles. Ecologists have already documented such a shift in many wild species, including some birds and insects1, 2, 3.
The changing climate is raising major concerns about food security in many countries, and pests may contribute to making matters worse. “Our defences, pesticides and fungicides, are being asked to deal with larger and larger numbers of pests and diseases, each of which can evolve fungicide or pesticide resistance,” says ecologist Dan Bebber of the University of Exeter, UK, who led the new study. Expansion of pest populations into new territories increases the risk that these organisms will escape our control.
Among the biggest threats are fungi and oomycetes, similar but distinct groups of microbes, which cause plant diseases. Several highly virulent strains of fungi have emerged in recent years around the world, and the oomycete Phytophthora infestans remains a persistent problem even 168 years after causing the great Irish potato famine4.
Global movement of crop pests had never been comprehensively analysed. To fill this gap, Bebber and his colleagues made use of historical records held by CABI (formerly known as the Centre for Agricultural Bioscience International), which document crop pests and diseases around the world from 1822 to the present. “No one has looked at any of these datasets. This is the first such analysis,” says co-author Sarah Gurr, a plant pathologist also at Exeter.
Co-author Mark Ramotowski, who did his work as a student at the University of Oxford, UK, narrowed the CABI sample down from over 80,000 records to 26,776, focusing on the period since 1960, when they are ilkely most reliable. For 612 different pest species, the researchers identified the first year in which each was observed in a new country (or region for larger countries) and took that to be the date at which the pest reached that country or region’s average latitude.
The main vulnerability of their study was biases in the data. The group hypothesised that, in the absence of any real trend, pests would appear to be moving towards the equator rather than the poles. This is because wealthier countries have the scientific resources to detect pests earlier than others, and wealthier countries tend to be at higher latitudes. As countries develop and study their pests better, the pests’ range could appear to move into the tropics.
Instead, the team found that, on average, crop pests have been moving towards the poles at 2.7 kilometres per year, which is very close to the rate of climate change5. However, the rate of shift varied significantly for different groups and among individual species. Fungi, beetles, true bugs, mites, butterflies and moths showed clear movements to higher latitudes, whereas viruses and nematode worms shifted to lower latitudes. Other groups showed no detectable change.
“Many studies have shown that climate change is affecting the distribution of wild species populations. This is the first one to show that a similar process is happening in pest species,” says Gurr. She highlights the worrying finding that fungi and oomycetes are moving particularly quickly, at 7 and 6 km per year respectively. Her team's study is published today in Nature Climate Change6.
Chris Thomas, a biologist at the University of York, UK, notes that the overall rate of movement is quite similar to that found in a meta-analysis he led on the movement of wild species1. “My first impression is that it looks like a thorough study.” He notes, as do the authors, that those pest groups seen moving towards the equator — largely nematode worms and viruses are the most poorly understood, and therefore the ones most likely to be discovered later in developing countries.
