Department of Entomology and Nematology, University of California, Davis, CA 95616.
Environmental Resources Analysis Research Group, Department of Plant Biology, Ecology and Earth Sciences, Universidad de Extremadura, Badajoz 06006, Spain.
Proc Natl Acad Sci U S A. 2022 Sep 13;119(37):e2208813119. doi: 10.1073/pnas.2208813119. Epub 2022 Sep 6.
Increasing diversity on farms can enhance many key ecosystem services to and from agriculture, and natural control of arthropod pests is often presumed to be among them. The expectation that increasing the size of monocultural crop plantings exacerbates the impact of pests is common throughout the agroecological literature. However, the theoretical basis for this expectation is uncertain; mechanistic mathematical models suggest instead that increasing field size can have positive, negative, neutral, or even nonlinear effects on arthropod pest densities. Here, we report a broad survey of crop field-size effects: across 14 pest species, 5 crops, and 20,000 field years of observations, we quantify the impact of field size on pest densities, pesticide applications, and crop yield. We find no evidence that larger fields cause consistently worse pest impacts. The most common outcome (9 of 14 species) was for pest severity to be independent of field size; larger fields resulted in less severe pest problems for four species, and only one species exhibited the expected trend of larger fields worsening pest severity. Importantly, pest responses to field size strongly correlated with their responses to the fraction of the surrounding landscape planted to the focal crop, suggesting that shared ecological processes produce parallel responses to crop simplification across spatial scales. We conclude that the idea that larger field sizes consistently disrupt natural pest control services is without foundation in either the theoretical or empirical record.
在农场增加多样性可以增强许多对农业有益的关键生态系统服务，而对节肢动物害虫的自然控制通常被认为是其中之一。在整个农业生态学文献中，普遍认为增加单一栽培作物种植的规模会加剧害虫的影响。然而，这种预期的理论基础并不确定；机制数学模型反而表明，增加田间面积对节肢动物害虫密度可能具有积极、消极、中性甚至非线性的影响。在这里，我们报告了一项广泛的作物田块大小效应调查：在 14 种害虫、5 种作物和 20000 年的田间观测中，我们量化了田块大小对害虫密度、农药施用和作物产量的影响。我们没有证据表明更大的田块会导致持续恶化的害虫影响。最常见的结果（14 种物种中的 9 种）是害虫严重程度与田块大小无关；对于 4 种物种来说，更大的田块导致了更轻微的害虫问题，只有一种物种表现出了预期的趋势，即更大的田块会使害虫严重程度恶化。重要的是，害虫对田块大小的反应与它们对周围种植的作物面积的反应强烈相关，这表明共享的生态过程在空间尺度上产生了对作物简化的平行反应。我们的结论是，认为更大的田块大小会持续破坏自然害虫控制服务的观点在理论或经验记录中都没有依据。
