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

Abstract

Agricultural landscape intensification has enabled food production to meet growing demand. However, there are concerns that more simplified cropland with lower crop diversity, less noncrop habitat, and larger fields results in increased use of pesticides due to a lack of natural pest control and more homogeneous crop resources. Here, we use data on crop production and insecticide use from over 100,000 field-level observations from Kern County, California, encompassing the years 2005-2013 to test if crop diversity, field size, and cropland extent affect insecticide use in practice. Overall, we find that higher crop diversity does reduce insecticide use, but the relationship is strongly influenced by the differences in crop types between diverse and less diverse landscapes. Further, we find insecticide use increases with increasing field size. The effect of cropland extent is distance-dependent, with nearby cropland decreasing insecticide use, whereas cropland further away increases insecticide use. This refined spatial perspective provides unique understanding of how different components of landscape simplification influence insecticide use over space and for different crops. Our results indicate that neither the traditionally conceived "simplified" nor "complex" agricultural landscape is most beneficial to reducing insecticide inputs; reality is far more complex.pesticides | biological control | landscape simplification | landscape complexity | crop diversity

Combined effect of matrix quality and spatial heterogeneity on biodiversity decline

“…Nevertheless, further analysis would require setting species-specific survival thresholds to reflect that the minimum viable population highly depends on species attributes and environmental conditions. See Larsen and Noack (2017) for an example where responses to agricultural practices depend more on individual attributes (of both crops and pests) than on landscape characteristics.…”

The influence of risk preferences, knowledge, land consolidation, and landscape diversification on pesticide use

“…As land consolidation in China proceeds, there is a need to examine the effects of land consolidation on pesticide use. Ecological theory predicts that simplified agricultural landscapes will increase pest severity because fewer natural enemies and concentrated host plants will further increase pesticide use (Larsen & Noack, 2017). However, the role of the landscape in pesticide applications has not been adequately supported by empirical studies, partially due to the lack of high spatial resolution crop and insecticide data (Larsen & Noack, 2017).…”

“…Ecologists have argued that landscape patterns influence pesticides because simplified landscapes often lead to increased pest severity, which leads to higher pesticide demand (Larsen, 2013; Larsen & Noack, 2017; Meehan, Werling, Landis, & Gratton, 2011). Agricultural intensification has caused landscape simplification due to the expansion of agricultural land, enlargement of field size, and removal of noncrop habitat.…”

Mixed effects of landscape complexity and insecticide use on ladybeetle abundance in wheat fields

“…A landscape dominated by non‐crop habitats is usually characterized by a higher abundance of natural enemies, and different non‐crop habitats in a landscape may serve varied functions for natural enemies at one or several times of the year . In recent decades, natural habitats in agricultural ecosystems have been degraded worldwide, with a corresponding reduction in the biological control services provided by natural enemies, leading to the need for increased agricultural input to control pests …”

“…10,11,14,15 In recent decades, natural habitats in agricultural ecosystems have been degraded worldwide, with a corresponding reduction in the biological control services provided by natural enemies, leading to the need for increased agricultural input to control pests. [16][17][18][19][20][21] Recent studies have suggested that the positive effects provided for natural enemies by non-crop habitats in a landscape can sometimes be affected (and even overridden) by agricultural practices. 9,15,[22][23][24][25][26] The use of chemical insecticides is one common agricultural practice that plays a crucial role in the regulation of pest insect densities, and often has lethal or sublethal effects on the natural enemies of key pests.…”