Monarch decline in Mexico cause for alarm

By: 
Rob Zimmer
Columnist

With the recent release of data from monarch colonies on their Mexican overwintering grounds, once again, monarch lovers were hit hard with bad news. From population estimates, monarch numbers overwintering in Mexico last winter decreased once again, this time by 22%.

Monarch lovers here in Wisconsin, therefore, must be more diligent than ever when it comes to planting host plants and nectar plants to help build numbers over the summer season.

Each winter, on the cool mountain slopes of interior Mexico, monarchs are counted by researchers as they cling to the trees in large, mostly dormant clusters. Estimates of both population of these amazing insects, as well as winter habitat size in acreage and hectares are made.

Both population and amount of acreage available for monarchs decreased over the past winter.

Habitat loss in Mexico is one of the biggest factors in monarch population declines. Each year, more and more of this valuable habitat, located in the mountains of central Mexico, is lost due to development and illegal logging. Combined with the loss of monarchs locally here in Wisconsin and other states due to habitat loss, development, pesticide use, changes in agricultural practices and other factors, the butterflies are in decline once again.

As gardeners and plant lovers, we can do much to help sustain monarch numbers, at least here in our area. By helping to build strong monarch populations here in the Midwest during the summer season, we give the overwintering population a better chance. The more monarchs that make the journey, the more monarchs that hopefully will overwinter successfully and return to the southern states in spring where the population cycle begins again.

Planting native wildflowers is, of course, a benefit to monarchs, as well as many other pollinators. Providing monarchs with a rich supply of fresh, native milkweed throughout the season is also vital.

As you likely know, monarch caterpillars will only host upon species of native milkweed. Therefore, the more milkweed we can provide, the stronger the population will be when migration time comes in August and September.

Some of the best host plants for monarchs include swamp milkweed, orange milkweed, common milkweed and whorled milkweed.

In addition to these host plants, it is important to provide nectar plants, especially for late in the season, August into October, when monarchs are on the move.

Late season native nectar plants include New England aster, ironweed, joe-pye weed, black eyed Susan, purple coneflower, goldenrod, as well as annual flowers such as cosmos, zinnia, Mexican sunflower, salvias, heliotrope, tall verbena, lantana and others.

By incorporating all of these plants, and others, in your landscape, you give monarchs a fighting chance.


Rob Zimmer is a nature and garden author, public speaker and radio show host on WHBY. Readers can find him on Facebook at www.facebook.com/RobZimmerOutdoors.