有机农业成功控制土豆害虫 Why ecological evenness is as important as relative richness.
为什么生态平衡与物种相对丰富同等重要。 Daniel Cressey
A study suggesting that organic agriculture gives better pest control and larger plants than conventional farming is sure to reignite longstanding debates about the merits of organic versus conventional agriculture. It also highlights an often-neglected aspect of biodiversity.
\"Organic agriculture promotes more balanced communities of predators,\" says David Crowder, author of the new study published today in Nature.
“有机农业推动肉食动物群体更加平衡。”大卫·克劳德（David Crowder）说，他的研究发表在《自然》杂志上。 \"Our study does not tell farmers they should shift to organic agriculture. What our study suggests is that organic agriculture is promoting these more balanced natural enemy communities and they may have better, organic pest control.\"
“我们的研究并不是要告诉农民转变到有机农业。我们的研究只是表明有机农业可以使农业害虫的天敌群落更加平衡，可以更好控制农业害虫。” Much focus is put on species numbers or \'richness\'. But the research by Crowder, an insect ecologist at Washington State University in Pullman, and his colleagues, shows the importance of \'evenness\' — the relative abundance of different species. Evenness quantifies not just the presence of different species, but whether one is dominant or whether there is an equal distribution of numbers between species.
通常人们把关注点放在物种数量或者丰富程度上。但是华盛顿州立大学的昆虫生态学家克劳德的研究显示平衡的重要性——各种物种相对充盈。平衡不仅仅是指不同物种存在，还包括是否某种占优势，物种间的数量是否均等分布。 The team looked at the bugs, nematodes and fungi that attack the hated Colorado potato beetle (Leptinotarsa decemlineata).
科罗拉多土豆甲虫(Leptinotarsa decemlineata)是一种很讨厌的害虫，研究团队观察了可以攻击甲虫的昆虫、线虫和真菌。 They conducted a meta-analysis of data collected on these denizens of Washington potato fields and found that although organic and conventional farms did not differ markedly in the richness of beetle eaters, the evenness of predators differed \"drastically\". Organic fields — where only a limited number of man-made chemicals can be used — had far greater evenness than those where pesticides were applied regularly.
Furthermore, the team set up an experimental field in which they manipulated the evenness of predators. Increasing the evenness led to what the researchers call a \"powerful trophic cascade\", resulting in fewer potato-munching beetles and larger potato plants.
此外，研究团队还设置了一块实验田，操控里面甲虫天敌的平衡。他们发现增加平衡度会产生他们称之为“强力营养级串联”的现象，会使吃土豆的甲虫的数量减少，同时会使土豆更高大强壮。 Although the work of Crowder and his group does not address the issue of yields from organic versus conventional farms, their study found that the increased evenness of organic farms compared with that of conventional farms led to 18% lower pest densities and 35% larger plants. Bigger plants generally mean greater potato yields.
尽管克劳德和他的研究团队没有解决有机农业和传统农业到底那个更好的问题，但是他们的研究发现增加有机农田的平衡相对于传统的农田甲虫密度会减少18%，土豆植株高大35%。更高大的植株通常意味着更高的产量。 Even richer
甚至更丰富 At least as important as what the research says about organic farming is what it says about species evenness.
就像研究所说的物种平衡至少与有机农业同等重要。 \"Almost all the studies that have been done have looked at the number of species in an ecosystem,\" says Crowder. \"Very few studies have looked at the relative abundance. We think our study is really one of the first to highlight that evenness is also important.\"
“几乎所做的所有研究都只注重生态系统的绝对物种数量，”克劳德说。“很少有研究关注相对丰富度。我们认为我们研究是第一次真正的强调平衡是同等重要的。” Understanding evenness can be extremely useful to those studying biodiversity, agrees Marc Cadotte, a community ecologist at the University of Toronto at Scarborough. This knowledge can shed light on, for example, the processes maintaining species abundance, and can also be crucial for determining how ecosystems will respond to challenges, such as those posed by climate change.
多伦多大学的群落生态学家马克·卡多特（Marc Cadotte）对此表示同意：“理解平衡对研究生物多样性极其有用。”例如，这个可以显示出主要物种丰富程度的情况，并且对决定生态系统如何应对类似于气候改变引起的挑战至关重要， This paper, says Cadotte, demonstrates that different agricultural practices have distinct effects on evenness, and that manipulating evenness leads to the cascading reactions identified by Crowder and his team.
卡多特说，克劳德团队的这篇论文说明不同的农业形式对生态平衡有着截然不同的影响，操纵平衡会导致级联效应。 \"Evenness is a critical component of biodiversity,\" says Cadotte. \"Much research has emphasized species richness, maybe at the detriment of studying evenness.\"
“平衡是生态多样性至关重要的元素，”卡多特说，“大量研究强调物种的丰富程度，可能对生态平衡研究不利。” Meanwhile, Crowder says that the next step is to discover what it is about organic agriculture that promotes evenness, and to determine whether this finding also applies in systems other than potato fields.