Scale‐dependent effects of landscape composition and configuration on natural enemy diversity, crop herbivory, and yields

Abstract

(1) Land-use intensification in agricultural landscapes has led to changes in the way habitats and resources are distributed in space. Pests and their natural enemies are influenced by these changes, and by the farming intensity of crop fields. However, it is unknown whether the composition of landscapes (amount and diversity of land cover types) or their configuration (spatial arrangement of cover types) are more important for natural enemy diversity, and how they impact crop damage and yields. In addition, effects of interactions between local farming practices (organic vs. conventional) and landscape variables are unclear. (2) Here, we make use of a data set where landscape composition and configuration were uncorrelated across multiple spatial scales. Natural enemies, crop damage, and yields were sampled in 35 organic and conventional crop fields. Out of seven broad natural enemy taxa, five were positively affected by a complex landscape configuration. In contrast, only carabids were positively affected by the amount of seminatural habitat around fields. Increasing diversity of land cover types had positive effects on some, but negative effects on other taxa. Effect sizes varied among taxa but increased with increasing spatial scale, defined by circular areas of increasing radius around fields. (3) The diversity of aerial, but not of ground-dwelling enemies was higher in fields under organic than conventional management. Interactions of local and landscape variables were important for birds, but not other enemies. Bird richness was higher in organic fields in simple landscapes, but not in landscapes with complex configuration or high land cover diversity. (4) Crop damage decreased with landscape diversity, but increased in conventional fields with complex configuration. Yields increased with both parameters in conventional fields only, and were higher on average in organic compared to conventional fields. Enemy diversity was positively related to crop damage, indicating positive density-dependence of enemies on pests. However, the diversity of aerial enemies was also positively related to yields. (5) Our results suggest that the effectiveness of agrienvironmental schemes for managing natural enemy diversity, crop damage and yields could be enhanced by optimizing the effects of distinct landscape parameters, particularly landscape configuration and diversity, across scales.

Identifying the landscape drivers of agricultural insecticide use leveraging evidence from 100,000 fields

“…Crop and year fixed effects are included. noted elsewhere (27) and may reflect dispersal characteristics or patch use of different pests, although the existence and exact underlying causes of this pattern deserve further attention.…”

Cityscape quality and resource manipulation affect natural enemy biodiversity in and fidelity to urban agroecosystems

“…More simple landscapes with fewer resources, in contrast, are low quality landscapes and may contain high barriers to dispersal and may increase the fidelity of individuals to habitat fragments (Fahrig 2003). Resource availability in the landscape therefore determines landscape quality and drives dispersal and colonization patterns (Schellhorn et al 2015a), but interactions between landscape quality and local habitat management can influence populations, their dispersal, and service provisioning (Martin et al 2016). Local habitat manipulation (e.g., through plant resource additions) can increase habitat quality, better support biodiversity and thereby can enhance ecosystem services in simple, low quality landscapes (i.e., the intermediate landscape complexity hypothesis) (Tscharntke et al 2012).…”

Landscape processes underpinning bird persistence and avian-mediated pest control in fragmented landscapes

“…In coffee plantations in Costa Rica, Karp and colleagues showed that more forested landscapes had an increased abundance of avian consumers of the coffee borer beetle, as well as lower borer beetle infestation rates ). However, we also found evidences that these relationships between native habitat cover and ecosystem services are complex and may be context-dependent (Martin et al 2013, Martin et al 2016 (Martin et al 2013). …”

“…We found that increases in landscape heterogeneity were frequently positively correlated with avian-mediated pest suppression (e.g., Winqvist et al 2011, Martin et al 2016. A higher diversity of land-uses or land-covers can promote the persistence of avian predators through enhanced landscape complementation and supplementation processes (see below; Metzger and Brancalion 2016).…”

“…Similarly, pest suppression appears intensified in areas of higher edge density (Kross et al 2016), mainly due to the increase of bird richness and abundance at forest-farm field edges (Kross et al 2016, Martin et al 2016). …”