Brazil’s Urban Ants May Predict Reaction To Warming Trends


Wall Street Journal – April 27, 2007

Interesting article that discusses how ants have adapted to the heat caused by our large urban cities.  The study is important because it can compare insects that live in a city (where it is warmer) than in the rural parts of the country.  Insects can be gathered from both locations and tests can proceed giving a very stable comparative reference.  The IPCC is predicting mass extinctions due to the increase of global temperatures, this study suggests that our fellow inhabitants on this planet may be more resistant than some think.

It’s getting hotter in the human hive, and in some ant colonies, but the ants are learning to live with it.

In São Paulo, Brazil, leafcutter ants are thriving in temperatures up to 20° F higher than in the countryside, biologist Michael J. Angilletta Jr. and his colleagues at Indiana State University reported last month. The urban ants acclimated to heat that, in recent experiments, all but killed their rural relatives.

Every city is a man-made microclimate. Asphalt, glass and other building materials absorb and reflect the energy of sunlight, sometimes in surprising ways. The temperature of artificial playground turf can reach 150°. These higher temperatures mean hotter days, warmer nights, less frost, longer growing seasons, altered rainfall patterns and more smog.

Such islands of heat are the Galápagos of global warming — a natural laboratory of selective pressure and adaptation.

When the heat is its most severe, the ants “wobble when they are walking. They will crouch down and not get up. Eventually, they will lose complete mobility,” Dr. Angilletta said.

To compare the heat tolerance of urban and rural ants of the same species, the researchers exposed hundreds of ants to 108° temperatures inside a walk-in test chamber, keeping the city ants and country ants in separate petri dishes. They then timed how long it took for the insects to be overcome by the heat — what researchers called the “knockdown time.”

In the end, the urban ants took 20% longer to drop from the heat than their country cousins. (The scientists sweltering inside the chamber, meanwhile, barely made it through four hours of observation.) No one knows yet whether ants survive higher heat through changes in behavior, or whether urban warming has modified their genetic code.

As temperatures continue to rise, however, humans keep cool in ways that intensify urban warming. Scientists led by Yukitaka Ohashi at Okayama University of Science in Japan reported in January that on a warm day, Tokyo’s office air conditioners generate enough waste heat to raise the city’s temperature almost 3°. All told, cities consume 75% of the world’s energy and produce 80% of its greenhouse gas emissions.

This month, U.N. climate experts warned that as many as a quarter of the world’s plants and animals may become extinct as temperatures soar in coming decades. Since Aesop, though, the smart money has been on ants.

I know that many of you may have a hard time reading this source article because it may require a subscription but here is the link to read the entire article.

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