Monarch Butterflies and Other Pollinators Are Declining – But We Can Help

As we could tell from their scarcity in our area last year, monarch butterflies are declining across their range. In early February, 2014, news reports from Mexico stated that the number of monarchs in the wintering area was the lowest ever recorded. The population of wintering migrants is measured by the number of acres of forest that the monarchs occupy. This winter there are only 1.65 acres with monarchs, a 44% decline over 2012-2013.

Researchers have identified several possible reasons for this alarming reduction in the number of monarchs. Climate change and resulting weather that makes reproduction difficult is one. Deforestation in the Mexican wintering areas is another. A third is the use of genetically engineered crops on which glyphosate herbicides can be sprayed. The herbicides are wiping out milkweed, the only plant on which monarch larvae feed.

Monarch butterfly on common milkweed.

As individuals, we cannot do much about climate change or deforestation in Mexico, but we can about the milkweed that monarchs need to survive. Planting milkweed in our gardens and encouraging our friends and neighbors to do the same can help alleviate the larval food problem.

Also troubling is the alarming drop in the number and biodiversity of native pollinators — bees and wasps, flies, butterflies and moths, and beetles. For example, a 2011 study reports that four species of North American bumble bees have had population declines of as much as 96% in the last 100 years and their ranges have restricted significantly (goo.gl/cmXf5Y). The Xerces Society Red List identifies the rusty patch bumble bee as Imperiled (at high risk of extinction) and the yellow banded bumble bee as Critically Imperiled (at very high risk of extinction). 

One of the primary reasons for the low pollinator numbers is loss of habitat. Here again we can do something to help. Pollinators have two requirements, food and nest sites. Native flowering shrubs and perennials will provide the nectar and pollen that they need from spring through fall. Nest sites can be patches of bare ground, brush piles, bundles of hollow reeds, or a nest block.

Pollinators will also be helped by avoiding the use of pesticides which either kill insects directly or impair their ability to reproduce.

Menunkatuck’s Plant Sale for the Birds is offering pollinator-friendly perennials as well as bird- and pollinator-friendly shrubs. Start your pollinator garden this spring. See the Plant Sale brochure in this newsletter or visit menunkatuck.org.

(For more about the decline in the monarch butterfly and wild bee populations, see Yale Environment 360 - goo.gl/kGHR86 and  goo.gl/HW97zI.)

(From the March, 2014 newsletter.)