Data from: Organic farming enhances parasitoid diversity at the local and landscape scale

1. The magnitude of the benefits derived from organic farming within contrasting managed landscapes remains unclear and, in particular, the potential scale-dependent response of insect parasitoids is relatively unexplored. Identifying the scale at which parasitoids are affected by organic farming will be an important step to enhance their conservation. 2. We sampled tachinid parasitoids at the centre and margin of arable and grassland fields on paired organic and conventional farms located in landscapes with different proportions of organic land. A total of 192 fields were sampled in two biogeographical regions of the UK. 3. We found that the positive effect of organic farming on tachinid parasitoid diversity can be observed at multiple spatial scales. At the local scale, we found higher abundance and species richness of tachinid parasitoids on organic than on conventional farms and on field margins than on field centres. At the landscape scale, the diversity of tachinids was higher in landscapes with higher proportions of organic land. At both scales, the positive effect of organic farming was clear for arable fields, while it was almost neutral for grasslands. 4. Synthesis and applications. Any attempt to enhance parasitoid diversity in agricultural landscapes needs to consider the local management in relation to the habitat type, location within the field and agricultural management in the surrounding landscape. To restore parasitoid diversity, the promotion of organic agriculture should aim to increase both the total extent of organic farming and the connectivity of individual farms. As the benefits of organic farming to biodiversity clearly spread beyond individual farm boundaries, any assessment of organic farming should consider these positive externalities.

1. 不同管理模式的农业景观中，有机农业所能带来的生态效益规模仍不明朗，而昆虫寄生性天敌（insect parasitoids）对景观尺度的潜在响应机制更是鲜有研究。明确有机农业影响寄生性天敌的作用尺度，将是加强其生物多样性保育的关键一环。2. 本研究在英国两个生物地理区域内，选取成对设置的有机农场与常规农场，针对有机用地占比各异的景观，于农田与草地的田块中心及边缘采样寄蝇类寄生性天敌（tachinid parasitoids），共完成192个田块的采样工作。3. 研究结果表明，有机农业对寄蝇类寄生性天敌多样性的积极影响可在多个空间尺度上显现：在局地尺度上，有机农场的寄蝇类寄生性天敌个体丰度与物种丰富度均高于常规农场，且田块边缘的天敌丰度与物种丰富度亦高于田块中心；在景观尺度上，有机用地占比更高的景观中，寄蝇类天敌的多样性更为丰富。无论上述哪种尺度，有机农业的积极效应仅在农田中显著，而对草地则几乎无影响。4. 综合与应用。任何旨在提升农业景观中寄生性天敌多样性的举措，都需要综合考量生境类型、田块内区位以及周边景观的农业管理模式等因素。若要恢复寄生性天敌的多样性，推广有机农业的目标应同时兼顾提升有机农业的总覆盖范围与个体农场间的连通性。鉴于有机农业对生物多样性的利好效应明显超出单个农场的边界，任何有机农业的评估都应将这类正向外部性纳入考量。