While the monarch butterfly is not endangered, the North American migration is considered
an endangered biological phenomenon. The monarchs’ habitat and overwintering
sites span the continent. Because of this, conservation efforts need to be addressed
on a trinational level. (Canada, Mexico, as well as the U.S.)
During the breeding phase of the monarch annual life cycle, habitat loss and degradation
are a conservation concern. Expanding suburbanization and other activities are leading
to the loss of 2400 or more hectares of land per day in the United States,
according to the American Farmland Trust. In agriculture, plant pests reduce yield,
costing farmers. To eliminate insects like European corn borers, pesticides are
applied. Unfortunately, these pesticides have non-target effects on monarchs that
can be lethal. Another pesticide concern is the use of herbicide tolerant crops
like soybeans, which allow herbicide applications after the crop has emerged. Increased
use of these crops has reduced the amount of weeds, including milkweed, in agricultural
fields. While the crops can withstand multiple herbicide applications, the milkweed
Mowing roadsides is another contributor of monarch habitat loss, reducing the number
of plant species. It’s unfortunate that the monarch host plant has the word
‘weed’ in its name, as there are some cities and counties that consider
it a noxious weed, and actively remove the plant.
Illegal logging in the overwintering sites of Mexico is also a concern. Removing
trees from protected areas breaks up the forest, resulting in more edges, which
make roosting monarchs more vulnerable to the elements. One study from Mexico published
in 2006 used satellite imagery from 1986 to 2006 to determine the amount of forest
that has been lost or disturbed. The analysis of the images concluded that 10,500
hectares of Monarch Butterfly Biosphere Reserve land have been affected, equivalent
to one fifth of the total protected land.
An obstacle facing the preservation of the overwintering sites is that they are
privately owned, even though they are federally protected. One way to encourage
land owners to protect the trees the monarchs need is to pay them to relinquish
their logging rights and/or for their conservation efforts. This approach allows
the land owners to earn a living while at the same time protecting the monarchs.
For a detailed summary of monarch needs, threats to these needs, and actions that
are being taken to address these threats, see the North American Monarch Conservation Plan. Development of this
plan was supported by government agencies from Canada, Mexico and the
US, as well as the trinational Commission on Environmental Cooperation.
Its primary author is Karen Oberhauser.