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The natural world. Looking pretty for 3.5b years.

Best of Intentions

Author: Hugh Bollinger/Thursday, January 29, 2015/Categories: wildlife conservation, sustainability, environment

Everyone loves monarch butterflies. Everyone wants to help them.

The iconic orange insects make a yearly, long-distance, migration from their Canadian breeding grounds to wintering rousts in pine forests of central Mexico. A shorter trek happens in California. However, their routes through the mid-western states have been disrupted by removal of natural habitats and the use of agricultural chemicals to control weedy plants in planted fields.

        Monarch Butterfly Migration Map  (credit: Monarch

The butterfly's primary food source is the milkweed plant ( Asclepias ), represented by several species native to states in mid-west, south, Texas, and California. To help the butterflies, school kids, organic farmers, and home gardeners here and elsewhere have been encouraged to plant milkweeds to help the butterflies along the way to their wintering pine rousts.

Monarch on native milkweed (credit: Wikipedia)           Caterpillar on tropical milkweed (AAAS, Sonia Altizer)

Unfortunately, many of these plantings have proved to create a significant problem themselves. A new report published in  Science Magazine  shows that the lack of suitable sources for native milkweed plant materials, has proved a dual disaster for the butterfly's due to the species used, the Tropical Milkweed (Asclepias curassavica). This non-native species turns out to be ecologically inappropriate for the butterflies even though their caterpillars can feed on it. The tropical milkweed doesn't die-back in winter so the monarchs halt their migration in Texas and Louisiana. The South American species also harbors a parasitic microbe that Infects feeding caterpillars making the resulting butterflies much weaker and unable to migrate the long distance to Mexico. Monarch populations and their migrations continue to decline.

To help concerned planters the Xerces Society, the insect conservation organization, has developed a Milkweed Seed Finder  for appropriate planting sources. Hopefully, home gardeners and others will support these suppliers who know what is best for individuals to understand and help monarch conservation.


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