Imagine if the population of Missouri dropped by 90 percent. That would mean the only remaining residents live in Jackson County.
During the past 20 years, monarch populations have decreased significantly. Populations since the 1994 – 1995 overwintering have showed a downward trend, with 2015 – 2016 showing a modest increase that was not sustained in 2016-2017. In the 1990s, up to one billion monarchs made the migration. In 2013 to 2014, the population dropped to 33 million, representing a 90 percent decrease from the 20-year average.
Many factors have challenged monarch populations, including habitat loss in the United States and Mexico, recent droughts, climate change, land usage, poorly timed mowing and herbicide applications, and changes to production agriculture systems. A significant decline in nectar sources and milkweed in monarch breeding areas including Missouri are also a major threat. The decline in various milkweed species is particularly troublesome as they are essential for monarch survival. It is the only plant on which monarch butterflies lay eggs, and essentially the only plants monarch caterpillars eat. When the caterpillars and adults eat the perennial plant, they also ingest toxins that protect them from predators. However, milkweed is mainly pollinated by large bees and wasps. This shows how important biodiversity can be. Monarch Watch estimates that around 2.2 million acres of potential milkweed is lost in the United States each year. Without milkweed, there will be no monarchs.