monarch-esa-petition-final_61585

application period later into the growing season when milkweed is more susceptible to
glyphosate.
Additional monarch habitat is being lost due to the rapid conversion of grasslands and other
milkweed-containing land types to corn and soybean fields to produce biofuels. Most remaining
monarch habitat in the Midwest is on Conservation Reserve Program (CRP) lands. This habitat is
threatened by ongoing conversion of these lands to corn and soybean production, a change
driven by federal biofuels policy. Nationally, CRP acreage has shrunk by 11.2 million acres (30
percent) since 2007, with more than half of this decline occurring in the Midwest, which has lost
6.2 million CRP acres. This land-use change has resulted in the widespread elimination of
milkweed from these habitats due to glyphosate use.
Glyphosate used in conjunction with Roundup Ready crops has nearly eliminated milkweed from
cropland throughout the monarch’s vital Midwest breeding range. It is estimated that in Iowa, for
example, cropland lost 98.7 percent of its milkweed from 1999 to 2012. In just the 13 years from
1999 to 2012, it is estimated there was a 64 percent decline in overall milkweed in the Midwest,
most of which was from croplands. Because cropland milkweed produces nearly four times as
many monarchs as plants in other settings, milkweed loss in corn and soybean fields has had a
disproportionate impact on monarch numbers. It is estimated that in 2012, the Midwest produced
88 percent fewer monarchs than it did in 1999.
Monarch habitat is further threatened by the imminent introduction of new herbicide-resistant
crops that are genetically engineered to now be resistant to multiple herbicides including for the
first time 2,4-D and dicamba, which will be used in addition to glyphosate. Herbicides frequently
drift beyond the boundaries of crop fields to affect wild plants growing nearby. These new
genetically engineered crops will lead to sharply increased herbicide use, continued elimination
of common milkweed from cropland, and reduction via herbicide drift of flowering plants that
provide monarch adults with nectar, thereby threatening monarch nectaring habitat. Remnant
monarch habitat outside of croplands is also being lost and degraded.
Monarch breeding, nectaring, and wintering habitats have also been lost to development, and this
threat is ongoing. Between 1982 and 2010, 43 million acres of land in the United States were
newly developed, representing a 58 percent increase in developed land over a roughly 30-year
period. Of note, more than 37 percent of developed land in the United States was developed
during the last 28 years. East of the Rockies, it has been very roughly estimated that
approximately 167 million acres of monarch habitat, an area about the size of Texas, may have
been lost since the mid-1990s due to agricultural changes and development including nearly onethird
of the monarch’s total summer breeding range.
Monarch breeding habitat west of the Continental Divide is being lost due to urban and rural
development, aggressive roadside management, herbicides, intensification of agriculture, and
long-term drought. Glyphosate is also heavily used in the western portion of the monarch’s
range, and may be degrading habitat there as well.
The monarch is also threatened in its winter range. Monarch wintering habitat in California is
threatened by development and natural senescence. Monarch wintering habitat in Mexico is
Monarch ESA Petition 8