Hot Outside? Plant some Bean Seeds!

The author of this post is Michael Chmielewski, a junior Biology major at the University of St. Thomas.

When I was in grade school, I remember growing beans in small amounts of soil contained in Dixie cups. Add the right amount of soil, water, place the germinating plant in the sun, and voila—up came a tiny sprout, which eventually matured into a full-grown bean plant. I remember being captivated by this seemingly miraculous process of lifelessness giving way to life in a matter of a few short weeks. Yet, as we grow older, to where does this awe recede? Many urbanites buy food at giant supermarkets, largely without knowing (or maybe even caring) where such bounty originated and how it was produced.

Green bean sprouts

Green bean sprouts

Growing produce for consumption is certainly no trivial process. Just like the bean plants, agricultural products require the right formula of nutrients, light, soil, and temperature to thrive and make it onto our plates. And in a world progressively compromised by issues such as environmental degradation, biodiversity loss, greenhouse gas emissions, unprecedented human population increase, and the necessity for doubling global food production in just 35 years (Foley et al., 2011), employing sustainable agricultural methods has become all the more difficult—and necessary.

But before we throw up our hands in despair, consider this: steps are being taken globally to ameliorate these seemingly insurmountable issues; there is hope amidst the bleakness. Take urban agriculture— it reconnects the producer and consumer by contributing to local food markets, and may hold profound implications for the sustainable agriculture movement (Ladner, 2011). Let’s focus on a specific aspect of urban agriculture that may especially flourish in city environments: season extension due to the urban heat island effect.

Urban agriculture

Urban agriculture

The urban heat island effect, or the warming of a city environment as a result of anthropogenic activity, is commonly viewed as a deleterious impact of city life. The temperature in a city of 1 million inhabitants will have an average temperature 2°C warmer than adjacent rural areas, which can have compromising effects on human health, including heat stroke, hyperthermia, and increased mortality rates (U.S. EPA).

Minneapolis, MN

Minneapolis, MN

But while such warming may bring about injurious effects to city-dwellers, studies have shown that urban agriculture may benefit from the urban heat island effect.  Growing seasons may be increased by approximately 7-8 days in urban environments due to elevated temperature and higher atmospheric carbon concentrations (Roetzer et al., 2000; White et al., 2002; Ziska et al., 2003; Zhang et al., 2004). And where there is a longer growing season, there is also more produce, higher profitability (Galinato and Miles, 2011), and potentially greater carbon fixation—all of which could contribute to enhanced agricultural sustainability.

Sure, these benefits are appealing, but what about ameliorating the urban heat island effect? Even more, what if we could use this excess heat to prolong the growing season, while simultaneously cooling the adjacent urban environment? While it may sound too good to be true, studies inform that this may indeed be plausible. Urban greening has been cited as a means by which surrounding temperatures may be decreased in a city (Bowler et al., 2010), and if this is true, urban agriculture may also contribute to this phenomenon. Just think—we may be able to benefit from a problem while concurrently contributing to its solution!

As I was captivated by the bean seeds giving way to flourishing life in elementary school, so might this realization contribute to again instilling an appreciation for agriculture—especially when it may contribute to the greater well-being of urbanites.  As innovative humans, we can optimize environments (man-made or not) to meet our food production needs while minimizing the deleterious effects of current global agriculture. In this case, using the seemingly detrimental, anthropogenic urban heat island effect to augment temperature regulation may serve to enhance urban agricultural production, and garner newfound appreciation for the food that ends up on our plates. In a world faced with unprecedented global sustainability issues, urban agriculture may contribute to part of the sustainable solution—one bean sprout at a time.


About Adam Kay

I study urban ecology and urban agriculture
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