Karen Oberhauser, University of Minnesota
Monarch numbers are declining; this decline is statistically significant (Brower et al. 2012) and readily apparent from data on the area occupied by monarchs on the overwintering roost in Mexico (see graph at http://www.monarchbutterflyfund.org ). While we saw more monarchs during the summer of 2014 than we did last year or the year before, and will thus hopefully see more in Mexico this winter, it’s unlikely that the population will be anywhere near as large as it was a decade ago. For many of us, this is incredibly sad. Like me, I’m guessing that you feel a strong connection to these amazing insects.
What caused this problem? In short, we did, with our insatiable usurpation of more and more of the earth to grow our food, build our dwellings and roads and shopping centers, and produce our energy. In the short term, changes in the way we control weeds in agricultural fields has meant that a huge swath of land that until very recently was available to monarchs – “corn belt” land that harbored monarchs’ milkweed host plants between rows of corn and soybeans – is no longer available. Previous weed control methods included cultivation, but milkweed often grew back after the cultivator went through a field. Now, thanks to crops that are genetically modified to be able to withstand the herbicide Round-up (and soon, other herbicides), farmers can spray a field to kill weeds even after the crop has sprouted. But really, that land was gone to hundreds of species of plants, insects, birds, and mammals when we plowed up the prairies over a century ago (see blog posting by Robert Krulwich). The organisms that depended on these rich and diverse ecosystems were pushed into the margins – the roadsides, hedgerows, and less desirable land that couldn’t be easily farmed. In a way, monarchs were lucky because they used a host plant that grew well not only in these margins, but, because it could often tolerate “old-fashioned” weed control methods, in the fields themselves. Unfortunately, monarchs’ luck has run out, at least with respect to row crop fields.
While I can wish that milkweed still grew between those rows of Midwestern row corn and soybeans, we can’t really expect farmers not to use a new, easier, and more efficient means of controlling weeds. Agricultural practices in the U.S. are the result of societal decisions. Personally, I think that these decisions are ill-considered. For example, every summer we grow corn on 80 to 90 million acres of land*, an area about the size of Germany. While people argue that we are feeding the world with this corn, a little over a third of the corn we grow is used as animal feed. If we wanted to use land to most efficiently to feed people, we would grow food that people eat directly, not food that gets transferred through animals. About 35-40% of it is diverted from food to fuel, and used to produce ethanol, which isn’t feeding anyone. About 11% is exported (so perhaps feeding the world), and 11% is used for food products in the U.S. A large portion of the last 11% is used to make high fructose corn syrup, something that we would arguably be better off eating less of. Thus, while herbicide-tolerant GM (genetically modified) corn and soybeans may provide an efficient way to control weeds, the argument that they are being used to feed the world more efficiently is far-fetched (see also Foley 2013).
However, we can’t change the U.S. agricultural system in time to save monarchs or many other species. All of the arguing about Round-up is not going to solve the problem for monarchs, at least in the short term, even if it is a big part of the problem. We need to look at other solutions, at land that is more readily available. We need to be creative, to look at roadsides, utility and railroad rights-of-way, Conservation Reserve Program (CRP) land, and yards. In reality, vast expanses of lawns are monocultures of grass not unlike corn fields, albeit on a smaller scale. And lawns are basically wasted land (we don’t even get ethanol, cattle feed, or high fructose corn syrup from them) that many of us can do something about.
In a single year, a Midwestern lawn can be converted to a habitat that resembles the prairie that was here before, harboring dozens of species of the birds and insects that used to live here, including, if we plant milkweed, monarchs.
The good news is that so many people are motivated to help monarchs, and that monarchs can live in small pieces of good habitat (and even some not-so-good habitat; I’ve found them on milkweed plants growing in cracks in the sidewalk). You can help, right in your own backyard, to save a familiar butterfly that you’re probably seeing less of lately. If you make some space for that familiar butterfly, your backyard habitat can act as a bridge to other habitats, creating a habitat corridor. Neighbor after neighbor, planting milkweed and linking nature preserves and neighborhood parks, can help to create habitat corridors that can help all pollinators.
The Monarch Joint Venture is a partnership of organizations dedicated to conserving and protecting monarchs in the U.S., through a combination of habitat conservation, enhancement and restoration; education; and research and monitoring. Just as a small garden for monarchs and pollinators can become a part of something much bigger, small donations can make a big difference in supporting the work of this national partnership to protect monarchs.
The opinions expressed in this article are the author’s. I thank Wendy Caldwell, Elizabeth Howard, and Candy Sarikonda for helpful input.
* Statistics on land in corn production and uses vary from year to year, depending on the price of corn futures and many other factors. The data used in this paragraph came from the USDA ERS http://www.ers.usda.gov/topics/crops/corn/.aspx#.VBmb6bSczjs and Foley 2013
References
Brower, L.P., O.R. Taylor, E.H. Williams, D.A. Slayback, R.R. Zubieta, and M.I. Ramírez. 2012. Decline of monarch butterflies overwintering in Mexico: is the migratory phenomenon at risk? Insect Conserv. Diver. 5:95-100.
Foley, J. 2013. It’s time to rethink America’s corn system. Scientific American. http://www.scientificamerican.com/article/time-to-rethink-corn/ Accessed September 2014
Krulwich, R. 2012. Cornstalks Everywhere But Nothing Else, Not Even A Bee. http://www.npr.org/blogs/krulwich/2012/11/29/166156242/cornstalks-everywhere-but-nothing-else-not-even-a-bee Accessed September 2014