Predicting Landscape Configuration Effects on Agricultural Pest Suppression

Abstract

Arthropod predators and parasitoids attack crop pests, providing a valuable ecosystem service. The amount of noncrop habitat surrounding crop fields influences pest suppression, but synthesis of new studies suggests that the spatial configuration of crops and other habitats is similarly important. Natural enemies are often more abundant in fine-grained agricultural landscapes comprising smaller patches and can increase or decrease with the connectivity of crop fields to other habitats. Partitioning organisms by traits has emerged as a promising way to predict the strength and direction of these effects. Furthermore, our ability to predict configurational effects will depend on understanding the potential for indirect effects among trophic levels and the relationship between arthropod dispersal capability and the spatial scale of underlying landscape structure. Landscape Structure Influences Pest Suppression in Crop FieldsIn agricultural landscapes, predatory and parasitic arthropods suppress herbivorous arthropod populations, providing an essential ecosystem service valued at billions of dollars annually [1]. In recent decades researchers have begun to identify factors driving the abundance of natural enemies (see Glossary), pests, and the effectiveness of pest suppression in crop fields, with the aim of designing and managing agricultural landscapes to maximize this and other services [2][3][4][5]. Positive outcomes from enhanced pest suppression could include greater crop yields, reduced pesticide use, and increased arthropod diversity in agricultural landscapes. Arthropod communities in crop fields are influenced by the landscape that surrounds them: on their own, crop fields are unsuitable for some beneficial insects because they are usually monocultures and undergo frequent disturbance. This means that other nearby habitats may be especially important for determining which arthropods colonize farm fields. Most research on how landscape structure influences pest suppression has focused on effects of landscape composition (i.e., amounts of habitat). In general, seminatural habitats can provide natural enemies with resources including food, overwintering habitat, nest sites, and refuge from agricultural disturbance, allowing them to survive and then colonize crop fields to exploit the herbivores that accumulate there [3]. Pest suppression is generally thought to increase when crop fields are surrounded by more noncrop or seminatural habitat. However, while this occurs in some circumstances, the effects of landscape composition on pest suppression overall are inconsistent, varying among systems and organisms [4].Beyond composition, there is also variation in landscape configuration [6]. Multiple lines of reasoning suggest that configurational aspects of landscape structure should affect pest suppression. First, since there is spillover of beneficial organisms along interfaces between habitat patches [7], configurational variables such as patch size, shape, amount of shared edge, and connectivity should influence...

The influence of landscape composition and configuration on crop yield resilience

“…These were as follows: percentage area, mean edge:area index and mean distance to the nearest patch. These were drawn from a variety of composition and configuration metrics widely used in assessments of landscape impacts on ecological processes (Chaplin‐Kramer et al., 2011; Cushman, McGarigal, & Neel, 2008; Haan et al., 2019; Martin et al., 2019) explored in preliminary analyses (Appendix ). Mean edge:area index and distance to the nearest patch were transformed to indices of ‘connectivity’ and ‘proximity’ (Appendix ) to aid interpretation of regression coefficients.…”

“…However, natural enemies comprise a great diversity of organisms, each with their own, complex relationships with landscape structure and with one another (Chaplin-Kramer et al, 2011;Karp et al, 2018;Martin, Reineking, Seo, & Steffan-Dewenter, 2013;Martin et al, 2016;Plantegenest, Le May, & Fabre, 2007). These relationships are often highly context-dependent (Haan et al, 2019).…”

“…spatial arrangement of those land cover types), after Fahrig et al (2011). While many studies have demonstrated relationships between landscape structure and service indicators such as beneficial invertebrate communities or crop pest populations (Bianchi, Booij, & Tscharntke, 2006;Chaplin-Kramer, O'Rourke, Blitzer, & Kremen, 2011;Haan, Zhang, & Landis, 2019;Rusch, Bommarco, Jonsson, Smith, & Ekbom, 2013), few have directly examined effects on crop yield (Holland et al, 2016(Holland et al, , 2017Karp et al, 2018). Those that do (e.g.…”

Temporal Resource (Dis)continuity for Conservation Biological Control: From Field to Landscape Scales

“…In addition to habitat amount, landscape configuration strongly affects pests, enemies, and crop yield, though temporal dimensions remain largely under-explored (Haan et al, 2020). One robust finding across temperate agricultural landscapes is that habitat edges tend to support more diverse, abundant ground beetle (Roume et al, 2013;Duflot et al, 2017;Ng et al, 2018;Knapp et al, 2019) and spider communities (Öberg et al, 2007Royauté and Buddle, 2012;Mestre et al, 2018) in and around cereal fields, particularly early in the growing season.…”

“…The challenge for agroecologists is to improve the scientific basis for habitat management while accounting for the context-dependency of pest and natural enemy dynamics (Settele and Settle, 2018). Temporal resource patterns are increasingly recognized as a crucial aspect of agroecosystem context, with many calling for more rigorous consideration in CBC research (Welch and Harwood, 2014;Schellhorn et al, 2015;Haan et al, 2020;Spiesman et al, 2020).…”