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National Wildlife Federation Releases Butterfly Research Findings

The monarch butterfly (Photo by Danaus plexippus)

The monarch butterfly (Photo by Danaus plexippus)

Monarch Populations Are Decreasing

The annual population status report for the monarch butterfly (Danaus plexippus) shows a 27 percent decrease from last year’s population.

Populations of this iconic black and orange butterfly have plummeted by approximately 90 percent in the last two decades. The threats to the species are the loss of habitat in the U.S. – both the lack of availability of milkweed, the only host food plant for monarch caterpillars, as well as nectar plants needed by adults – through conversion of habitat for agriculture, removal of native plants and the use of pesticides, and loss of habitat in Mexico from illegal logging around the monarchs’ overwintering habitat. The new population numbers stress the need to continue conservation measures to reverse this trend.


A Look At The Numbers

The population is evaluated by measuring the number of hectares occupied by the monarch butterflies in their overwintering habitat in Mexico. This year an estimated 109 million monarchs occupy just 2.91 hectares (7.2 acres), down from 150 million last year covering 4.01 hec­tares (9.9 acres).

The monarch population found west of the Rockies, which migrates to California rather than Mexico, has also severely declined but looks to have remained at the same level as last year.

Some reason exists to be cautiously optimistic. Shortly after last year’s population numbers were released, severe late-season storms hit monarch overwintering sites in Mexico, which scientists estimate killed anywhere from 7.4 percent of the population to as much as 50 percent of overwintering colonies. This mortality was not reflected in the official population number last year, meaning that far fewer monarchs actually survived to migrate north in the spring 2016.

In the best-case scenario of a 7.4 percent mortality, the monarch population that actually migrated north was 139 million, not 150 million, and so only decreased by 22 percent rather than the 27 percent based on pre-storm population numbers. In the worst-case scenario of 50 percent mortality from the storms, only 75 million monarchs would have survived to migrate north in 2016 but were able to build up their population to the current number of 109 million, showing a possible 45 percent increase in population.

Whether it was favorable weather conditions throughout the rest of 2016 or the restoration of habitat for monarchs across the U.S., or both, these scenarios show that if given the right conditions and habitat, the species has the potential to recover. For more information, visit nwf.org.



Immediate action is needed to protect and restore monarch habitat. On the local level, individuals can get involved by planting native milkweed and nectar plants right in their own yards.

The National Wildlife Federation (NWF) is a member of the Monarch Joint Venture, and has made monarch conservation a priority, working to recover the species in the following ways:

Mayors’ Monarch Pledge. The NWF has engaged over 260 mayors and community leaders in pledging to restore monarch habitat by planting milkweed for caterpillars, nectar plants for the adult monarchs, and eschewing pesticides and other actions. These municipalities in the monarchs’ main migratory flyway, from Austin, Texas to the Great Lakes, are committing to create habitat and educate citizens about how to make a difference.

Garden For Wildlife. This program educates millions of Americans each year on how to restore habitat for birds, butterflies, and other wildlife in their areas. The NWF recognizes such garden spaces as Certified Wildlife Habitats. Over 200,000 habitats have been designated in suburban yards, community gardens, schools, parks, and other public spaces. Entire communities, cities and counties have achieved the status.

National Pollinator Garden Network. The NWF and an unprecedented number of conservation and gardening organizations have launched the Million Pollinator Garden Challenge, a campaign to raise awareness on what Americans can do to help pollinators and register a million pollinator and monarch friendly gardens by the end of 2018.

Large Landscape Habitat Work. The NWF is working with the agriculture industry to establish monarch-friendly practices such as adding preserving native plant buffer zones around fields and riparian areas, adjusting mowing schedules and spraying practices to minimize impacts to pollinator habitat. The NWF is also working with the U.S. Fish and Wildlife Service, state affiliates, and state Wildlife Agencies to create state plans to conserve grasslands, establish power line right-of-way habitat, and promote roadside habitat planting along monarch’s migratory route.

Butterfly Heroes. This campaign engages kids and families in butterfly conservation. Participants pledge to plant butterfly gardens and receive a starter kit from the NWF that includes native milkweed or nectar plants for monarchs and information on creating a butterfly garden. This campaign kicks off on March 27 and goes through May 19, 2017.

National Wildlife Federation Releases Butterfly Research Findings

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