Abstract
Greenhouse gas emissions associated with pesticide applications against invasive species constitute an environmental cost of species invasions that has remained largely unrecognized. Here we calculate greenhouse gas emissions associated with the invasion of an agricultural pest from Asia to North America. The soybean aphid, Aphis glycines, was first discovered in North America in 2000, and has led to a substantial increase in insecticide use in soybeans. We estimate that the manufacture, transport, and application of insecticides against soybean aphid results in approximately 10.6 kg of carbon dioxide (CO2) equivalent greenhouse gasses being emitted per hectare of soybeans treated. Given the acreage sprayed, this has led to annual emissions of between 6 and 40 million kg of CO2 equivalent greenhouse gasses in the United States since the invasion of soybean aphid, depending on pest population size. Emissions would be higher were it not for the development of a threshold aphid density below which farmers are advised not to spray. Without a threshold, farmers tend to spray preemptively and the threshold allows farmers to take advantage of naturally occurring biological control of the soybean aphid, which can be substantial. We find that adoption of the soybean aphid economic threshold can lead to emission reductions of approximately 300 million kg of CO2 equivalent greenhouse gases per year in the United States. Previous studies have documented that biological control agents such as lady beetles are capable of suppressing aphid densities below this threshold in over half of the soybean acreage in the U.S. Given the acreages involved this suggests that biological control results in annual emission reductions of over 200 million kg of CO2 equivalents. These analyses show how interactions between invasive species and organisms that suppress them can interact to affect greenhouse gas emissions.
Highlights
Many pest organisms reach their most damaging levels away from their native geographic range
We focus on greenhouse gas emissions associated with insecticide use to control the soybean aphid, Aphis glycines, a recent invasive agricultural pest in North America
We use estimates of insecticide application associated with soybean aphid control from the United States Department of Agriculture National Agricultural Statistics Service (USDA NASS) Agricultural Chemical Usage Field Crops Summary databases
Summary
Many pest organisms reach their most damaging levels away from their native geographic range This general pattern has been documented for weeds [1], insect pests [2], and pathogens [3,4] among others. Our goal is to estimate the actual emission costs incurred by the invasion as well as the hypothetical emissions that would occur in the absence of biotic resistance in the form of naturally occurring biological control. This allows an estimation of the role of biological control in attenuating greenhouse gas emissions of an invasive pest
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