4 years ago



cannot be overstated

cannot be overstated (Wassenaar and Hobson 1998, Oberhauser et al. 2001, Brower et al. 2012a, b; Flockhart et al. 2013, 2014; Pleasants and Oberhauser 2013, Pleasants in press). The dramatic loss of milkweed from the monarch’s summer breeding grounds thus puts the monarch at risk of extinction (Flockhart et al. 2014), and this risk is magnified by other ongoing threat factors such as climate change, severe weather events, and habitat loss to development (Brower et al. 2011, 2012a, b; Saenz Romero et al. 2012, Vidal et al. 2013). Loss of Monarch Habitat in Croplands Due to Increased Use of Glyphosate With Roundup Ready Crops First introduced by the Monsanto Company in 1974, glyphosate is an extremely effective herbicide that kills a broader range of plants than most weed-killers (Duke and Powles 2008). This is because glyphosate inhibits a critical enzyme—5-enolpyruvyl-shikimate-3-phosphate synthase (EPSPS) —that is found in virtually all green plants, and which helps the plant synthesize various compounds it requires for growth and survival. Glyphosate is thought to kill plants by inducing shortages of these essential compounds (Henderson et al. 2010), though other potentially complementary mechanisms have been proposed (Lorentz et al. 2011, Johal and Rahe 1984, Duke et al. 2007). Glyphosate is a systemic herbicide that has unparalleled effectiveness on perennial weeds—such as common milkweed—that most other herbicides fail to kill (Franz et al. 1997). When glyphosate is sprayed on a weed, it is absorbed by the leaves and stems and then translocated (moved) inside the plant to concentrate in actively growing meristematic tissues, including the plant’s roots and developing buds (Duke and Powles 2008). By killing common milkweed at the root, regrowth the following year is largely prevented (Bhowmik 1994). In 1996 Monsanto introduced the first of a series of Roundup Ready crops, which are genetically engineered to survive direct broadcast application of glyphosate, sold under the brand name of Roundup, but also in many generic versions produced by other firms. Roundup Ready crops enable glyphosate to be used post-emergence (to the growing crop) to kill weeds through much of the growing season without crop injury. Glyphosate is particularly lethal to milkweed when used in conjunction with Roundup Ready crops because it is applied more frequently, at higher rates, and later in the season—during milkweed’s most vulnerable flowering stage of growth— than when used with traditional crops. The increasingly common practice of growing Roundup Ready crops continuously and sequentially (corn, soybean, corn, and so on) on the same fields means that milkweed is exposed to glyphosate every year, with no opportunity to recover. Prior to the Roundup Ready crop era, glyphosate was little used in corn and soybean production. From 1990 to 1995, glyphosate was applied to only 5-20 percent of national soybean acres and from 1-6 percent of corn acres each year [U.S. Department of Agriculture National Agricultural Statistics Service (USDA NASS) 1991-2008]. Monsanto introduced Roundup Ready soybeans in 1996 and Roundup Ready corn in 1998. Herbicide-resistant varieties (nearly all Roundup Ready) comprised 93 percent of soybeans and 85 percent of all corn grown in the United States in 2013 (USDA ERS 2014a). Monarch ESA Petition 46

Pesticide usage figures from USDA’s National Agricultural Statistics Service (NASS) and the U.S. Geological Survey (USGS) show the dramatically increasing use of glyphosate in American agriculture triggered by Roundup Ready corn and soybeans. The glyphosate data discussed below are based primarily on NASS, which surveys thousands of farmers to arrive at the best available estimates of pesticide use in American agriculture (USDA NASS Advisory 2006). NASS reports pesticide use by crop—including percent of total crop acres treated, application rate, number of applications, and total amount used—for the “Program States” where most of the crop (corn or soybeans) is grown in the survey year. Several operations were required to derive the figures reported below. First, use figures for different types (salts) of glyphosate (these include “sulfosate,” which is the trimethylsulfonium salt of glyphosate, see: as reported by NASS were combined: total amounts and percent area treated of different types were summed, while weighted averages were calculated for application rates and frequencies. Second, because NASS figures on total amount of glyphosate reflect usage only in those Program States surveyed in a given year, the totals are normalized to estimate national usage, and to enable valid comparisons from year to year. On average, NASS surveyed pesticide use on 88 percent of corn acres and 88 percent of soybean acres for the reported time period (USDA NASS 2013, 2011, 1991-2008). Thus, for example, if total glyphosate use as reported by NASS is 50.00 million pounds on corn in a year in which 90 percent of corn acres were surveyed, national glyphosate use on corn is 55.56 million pounds (50.00 million lbs./0.90). Third, because NASS did not survey pesticide use on corn and soybeans every year (particularly after 2005), glyphosate figures are interpolated or extrapolated for un-surveyed years. USGS also reports use of pesticides, including glyphosate, based primarily on proprietary data from GfK Kynetec, Inc. (Thelin and Stone 2012), and these data corroborate our NASS-derived figures. Between 1995, the year before Roundup Ready soybeans were introduced, and 2013, total glyphosate use on corn and soybeans rose from 10 million to 205 million pounds per year, a 20- fold increase (see Figure 17). USGS figures on national glyphosate use on corn and soybeans agree closely with those derived from NASS data (see Figures 17 and 18). This dramatic increase is attributable to increased acreage treated, more glyphosate being applied per acre, and increasingly frequent applications in a single year and over the course of years. Each of these factors and its relevance to common milkweed is discussed below. From 1995 to 2013, combined corn and soybean acreage treated with glyphosate increased from 17 to 157 million acres, a nine-fold increase (see Figure 19), tracking the rising adoption of Roundup Ready varieties (see Figure 20). For perspective, these 157 million glyphosate-treated acres represent half of all harvested cropland in the entire country in 2012 (315 million acres), an area nearly the size of Texas (USDA Census 2012, Table 8). Monarch ESA Petition 47

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