Agricultural landscape simplification does not consistently drive insecticide use

Abstract

The increase in agricultural production over the past 40 y has greatly altered land-use patterns, often resulting in simplified landscapes composed of large swaths of monocultures separated by small fragments of natural lands. These simplified landscapes may be more susceptible to insect pest pressure because of the loss of natural enemies and the increased size and connectivity of crop resources, and a recent analysis from a single year (2007) suggests this increased susceptibility results in increased insecticide use. I broaden the temporal analysis of this connection between landscape simplification and insecticide use by examining cross-sectional and panel data models from multiple decades (US Department of Agriculture Census of Agriculture years 2007, 2002, 1997, 1992, 1987) for seven Midwestern states composed of over 560 counties. I find that although the proportion of county in cropland-my metric for landscape simplification-was positively correlated with insecticide use in 2007, this relationship is absent or reversed in prior census years and when all years are analyzed together. This broader temporal perspective suggests that landscape simplification has inconsistent effects on insecticide use and that multiyear studies will be key to unlocking the true drivers of variation in insecticide application.pesticides | ecosystem services | land-use policy | longitudinal data

Reduction of Crop Diversity Does Not Drive Insecticide Use

“…Data used in this study includes 1997, 2002, 2007, and 2012 census years, and includes the following county-level variables: land area treated with insecticides, market value of all crops, total land area, total agricultural land area, total harvested area, and harvested acres of specific crops. All are in acres, as given the the COA, except for crop value which were converted to US dollars/hectare to be consistent with previous studies (Larsen, 2013;Meehan et al, 2011).…”

“…Two recent studies that applied different statistical methods on the same variable sets have drawn controversial conclusions regarding the effect of landscape simplification on insecticide use intensity, using the proportion of cropland treated with insecticides as a proxy for "use intensity" (Larsen, 2013;Meehan et al, 2011). While Larsen (2013) used ordinary least squares and Meehan et al (2011) used spatial error models, they both found that in 7 Midwest states, i.e. Illinois, Indiana, Iowa, Michigan, Minnesota, Ohio, and Wisconsin, 1) the proportion of corn acreage and 2) the proportion of fruits and vegetables in total harvested cropland of a county both significantly correlated to increased insecticide use in recent years.…”

“…Current methods for investigating insecticide usage on crops typically use either pounds of insecticide applied per acre of cropland (Vialou et al, 2008), or percentage of cropland treated with insecticide (Fausti et al, 2012;Larsen, 2013;Meehan et al, 2011;Tscharntke et al, 2007). National Agricultural Statistics Service (NASS) conducts an annual agricultural survey each June based on random sampling of growers and a Census of Agriculture (COA) every five years based on a comprehensive survey of all farm and ranch operators.…”

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

“…Data-driven approaches have proven useful in elucidating the larger scale patterns in the relationship between landscape-level agricultural intensification and insecticide use (18,19). However, these studies have been limited in spatial resolution of both crop (20) and insecticide data (21).…”

Intersection between biodiversity conservation, agroecology, and ecosystem services

“…Moreover, effects of insecticide input on bio-control can go beyond farm level (Bianchi, Ives, and Schellhorn 2013). For example, crop pest abundance increases with the proportion of harvested cropland treated with insecticides in Midwestern United States (Meehan et al 2011), although this relationship can vary greatly between years (Larsen 2013).…”