《经济学人》：蚯蚓是纯粹的益虫吗？

原文标题：Invasive speciesNews from the undergroundWorms are changing North America’s ecologyEcological scienceThe soil ecology of North America is being turned over[Paragraph 1] EARTHWORMS’ BENIGN image as aerators, drainers and fertilisers of field and garden belies a darker secret. They are actually fierce competitors with other invertebrates, voraciously consuming rotting plant matter and tiny organisms such as protists, nematodes, bacteria and fungi, all of which might otherwise sustain a wide variety of soil dwellers.

[Paragraph 2] That much is well known, not least from research conducted in northern North America. Here, worms were wiped out during the last ice age, which ended 12,000 years ago. They started returning, in the form of European interlopers, only a few centuries in the past. What have not been investigated much until now are the consequences of this subterranean carnage for surface-dwelling critters. But that has just been corrected by Malte Jochum of Leipzig University, in Germany, and his colleagues, in a study just published in Biology Letters.[Paragraph 3] Dr Jochum and his team worked in a forest overlooking Barrier Lake, in Alberta, Canada, where the earthworm invasion has been tracked for three decades. That has permitted the identification of areas with low (four worms per square metre, on average), medium (43 worms per square metre) and high (106 per square metre) populations.[Paragraph 4] Within each zone of abundance the researchers marked 20 plots with individual areas of two square metres. They identified all of the plants therein and used vacuum-suction collecting devices to “hoover” up as many as possible of the above-surface arthropods (mostly insects and spiders) in each plot. They then sorted, identified and measured these animals to calculate their abundance, biomass and species richness.[Paragraph 5]Altogether, the collectors picked up 13,037 individual arthropods—and discrepancies between plots were quickly obvious. Those with abundant earthworms were depauperised of arthropods compared with ones where worms were rare. Plots with the most worms in them had 61% fewer individual arthropods, 18% fewer arthropod species and a 27% diminution in total arthropod biomass, compared with those with the fewest.[Paragraph 6] So-called detritivores—which compete directly with worms for food—suffered worst. There were 80% less of them in areas of worm abundance, compared with those of worm scarcity. But herbivores and omnivores suffered, too. Only for carnivorous arthropods, such as spiders, was there good news. Their numbers were up 41% in worm-rich plots, compared with worm-poor ones.[Paragraph 7] Why predators did well is unclear. Some, perhaps, were eating worms directly. Others may have taken advantage of the stripping of cover for their prey caused by worms pulling the leaf-litter underground for later consumption.[Paragraph 8] The knock-on effects of this carnage further up the food chain, among invertebrate-eating amphibians, reptiles, birds and mammals, remain obscure. Species that like to consume worms are presumably doing better, while those that prefer their meals crunchy, rather than squishy, will be doing worse. Whether this matters in the grand scheme of things is debatable. But for those who prefer their ecosystems pristine, this work confirms that earthworms are certainly not the unalloyed good which some people make them out to be.（恭喜读完，本篇英语词汇量522左右）原文出自：2022年4月2日《经济学人》Science & technology版块精读笔记来源于：自由英语之路本文翻译整理：Irene本文编辑校对: Irene仅供个人英语学习交流使用。

【补充资料】

冰河时期（Ice Age）又称冰川期，指地球在某些年代里陆地和海洋都被冰层覆盖的时期。这些冰封地带比现在受冰封的地域广阔得多。在冰河时期，冰层覆盖了世界上大片土地，这些地区的气候非常寒冷；海洋里有很多冰块，地面也凝结了厚厚的冰。同时，由于较多水分储在冰块中，各地的海平面便较低了。冰河时期时间可以维持超过一百万年，地球形成以来冰河时期曾出现过十一次，上一个冰河时期称为“大冰河时代”，发生于距今一万八千年前，结束于一万年前，当时地球约三分之一的陆地被覆盖在240米厚的冰层下。冰河时期期间，温度下降，改变了地球表面的植物相和生物的生存环境，许多生物因此面临灭亡或被迫迁移，只有能够适应环境的物种，才能幸存下来。堰塞湖(Barrier lake ）是由火山熔岩流或由地震活动等原因引起山崩滑坡体等堵截河谷或河床后贮水而形成的湖泊。由火山熔岩流堵截而形成的湖泊又称为熔岩堰塞湖。堰塞湖的形成有四个过程，一是原有的水系；二是原有水系被堵塞物堵住。三是河谷、河床被堵塞后，流水聚集并且往四周漫溢。四是储水到一定程度便形成堰塞湖。堰塞湖一旦决口会对下游形成洪峰，处置不当会引发重大灾害。

【重点句子】（3个）

But herbivores and omnivores suffered, too.The knock-on effects of this carnage further up the food chain, among invertebrate-eating amphibians, reptiles, birds and mammals, remain obscure.Earthworms are certainly not the unalloyed good.

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