Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, CA 95616;
Natural Capital Project, Woods Institute for the Environment, Stanford University, Stanford, CA 94618.
Proc Natl Acad Sci U S A. 2018 Aug 14;115(33):E7863-E7870. doi: 10.1073/pnas.1800042115. Epub 2018 Aug 2.
The idea that noncrop habitat enhances pest control and represents a win-win opportunity to conserve biodiversity and bolster yields has emerged as an agroecological paradigm. However, while noncrop habitat in landscapes surrounding farms sometimes benefits pest predators, natural enemy responses remain heterogeneous across studies and effects on pests are inconclusive. The observed heterogeneity in species responses to noncrop habitat may be biological in origin or could result from variation in how habitat and biocontrol are measured. Here, we use a pest-control database encompassing 132 studies and 6,759 sites worldwide to model natural enemy and pest abundances, predation rates, and crop damage as a function of landscape composition. Our results showed that although landscape composition explained significant variation within studies, pest and enemy abundances, predation rates, crop damage, and yields each exhibited different responses across studies, sometimes increasing and sometimes decreasing in landscapes with more noncrop habitat but overall showing no consistent trend. Thus, models that used landscape-composition variables to predict pest-control dynamics demonstrated little potential to explain variation across studies, though prediction did improve when comparing studies with similar crop and landscape features. Overall, our work shows that surrounding noncrop habitat does not consistently improve pest management, meaning habitat conservation may bolster production in some systems and depress yields in others. Future efforts to develop tools that inform farmers when habitat conservation truly represents a win-win would benefit from increased understanding of how landscape effects are modulated by local farm management and the biology of pests and their enemies.
非作物生境有助于控制害虫,同时保护生物多样性和提高产量,这一观点已成为农业生态学的范例。然而,尽管农场周围景观中的非作物生境有时有利于害虫天敌,但在不同的研究中,天敌的反应仍然存在异质性,对害虫的影响也不确定。观察到的物种对非作物生境的反应异质性可能是起源于生物学的,也可能是由于对生境和生物防治的测量方式不同而导致的。在这里,我们使用一个包含 132 项研究和全球 6759 个地点的害虫防治数据库,来模拟天敌和害虫数量、捕食率以及作物损害作为景观组成的函数。我们的研究结果表明,尽管景观组成在研究内部解释了显著的差异,但害虫和天敌的数量、捕食率、作物损害和产量在不同的研究中都表现出不同的反应,在非作物生境较多的景观中有时增加,有时减少,但总体上没有一致的趋势。因此,使用景观组成变量来预测害虫控制动态的模型几乎没有潜力来解释研究之间的差异,尽管在比较具有相似作物和景观特征的研究时,预测会有所改善。总的来说,我们的研究表明,周围的非作物生境并不总是能改善害虫管理,这意味着在某些系统中,生境保护可能会提高产量,而在其他系统中则会降低产量。未来开发能够告知农民何时生境保护真正代表双赢的工具的努力,将受益于对景观效应如何受到当地农场管理和害虫及其天敌的生物学的调节有更深入的了解。