Monarch butterflies have hit record lows in recent years. The loss of milkweed, the only food source for their caterpillars, the increase of pesticide use, the loss of protective forest for wintering habitat, and many other factors have reduced the number of butterflies making the epic migration across the North American continent to wintering grounds every year.
However, are the numbers really as bad as we think? Researchers suspect we might be making an error in calculations.
The Washington Post reports, "A study published today in the Annals of the Entomological Society of America complicates the commonly held notion that monarchs going missing by the hundreds of millions... By looking at a different set of data than the one most conservationists have always relied on, the researchers concluded that the yearly peak monarch population has not declined nearly as steeply as was previously believed."
This different set of data looks at monarchs at a different time of year. Normally, conservationists count the number of wintering monarchs, those individuals that make it to the annual wintering grounds in Mexico and parts of California. This is one single generation out of the four generations of butterflies it takes each year to complete the migration. By this count, the numbers have become frighteningly low. However, the researchers behind the new study are looking at monarch numbers during the other phases of the migration in the summer. It is during this season, say the researchers, that the monarch butterfly numbers seem to bounce back.
"Though the size of the summer population fluctuated wildly from
year-to-year, the results of these censuses showed no significant
downward trend, the researchers reported. What’s more, the size of the
wintering generation didn’t seem to affect the summer population’s
ability to bounce back."
What this study suggests is that the monarch butterfly species is not experiencing a severe decline -- but the migration is. Fewer monarchs are making it to the wintering grounds, but the overall population might not be in such a steep decline as feared.
This does not mean that conservation efforts can be sidelined. Other researchers disagree with the findings, and even the research team behind this study says that despite the more hopeful numbers, the future for monarchs is still something to worry about. There is still a good deal of study that needs to be done before a clear picture of what is happening to monarchs can be known. So please continue to plant milkweed and help out in any other way you can, since monarchs aren't out of the woods yet.
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