Other causes for monarch’s decline

Mark S. Edwards' June 12 opinion piece 'Valuing monarchs good start” attributes the decline of the monarch butterfly to conventional farming, or more precisely, herbicides applied to GMO crops.

Edwards explains the correlation between the lack of available milkweed, the only food source for the monarch caterpillar, and this recent downward trend.

Interestingly, however, farmers like us have always cleared cropland of weeds to save water and soil nutrients for the crops themselves. Pre-emergent herbicides (far more toxic than Roundup/glyphosate) were applied long before GMOs were introduced more than 15 years ago and intensive cultivation (still used in organic production) kept weeds in check for the remainder of the year. Roundup kills milkweed only if it is sprayed directly, thus, it is no surprise to see milkweed growing in our grasslands, waterways, filter/buffer/turn strips, fence rows and ditches.

Indeed, entomologists have recognized many factors contributing to the dearth of milkweed. It is true farmers, on average, have fewer acres in pasture/rangeland. U.S. farm ground suitable for both milkweed and crops is also lost daily through urbanization.

Other important causes include, but may not be limited to, recent weather extremes causing severe drought and record cold winters, deforestation due to logging in Mexico (where monarchs migrate annually) and ecotourism.

Unfortunately, the natural concentration of monarch populations make this beautiful butterfly more vulnerable to any one catastrophic event, but Edwards is not alone in hoping for the monarch's return to its former glory.

Brent and Deb Donohoe

West Branch