Tipping points…for moths and men

“The best laid schemes o’ mice an’ men / Gang aft agley.” – Robert Burns, in To a Mouse“.

Perhaps you know Of Mice and Men. It’s a 1937 novella written by John Steinbeck. Like his book The Grapes of Wrath, it deals with the plight of Depression-era migrant workers. Steinbeck borrowed the title from the Robert Burns poem, which notes that events don’t always turn out as mice and men might plan.

Burns could just as easily drawn a comparison between moths and men…


You can make a career studying the moth thought process.

One of the world’s most distinguished biologists, John G. Hildebrand, a neurobiologist and chair of the Department of Neuroscience at the University of Arizona in Tucson, has done just that…for forty years.  Some time back, I heard him give a lecture on the olfactory system of the giant sphinx moth, Manduca sexta, native to those parts, that was utterly fascinating, both with regard to the intricacy and broad-ranging consequences of the findings and the laboratory technique required to produce such insights.

To cut to the chase, it turns out that the antennae of this moth include carbon-dioxide sensors. As near as Dr. Hildebrand and his colleagues could find out, Manduca uses the sensors to help guide it to flowers that are particularly nectar-rich. Here’s the abstract of the 2004 paper in the Journal of Chemical Ecology by Thom et al. describing the work:

“The hawkmoth Manduca sexta (Lepidoptera: Sphingidae), an experimentally favorable Lepidopteran that is highly sensitive to carbon dioxide (CO2), feeds on the nectar of a range of flowering plants, such as Datura wrightii (Solanaceae). Newly opened Datura flowers give off dramatically elevated levels of CO2 and offer ample nectar. Thus, floral CO2 emission could indicate food-source profitability. This study documents that foraging Manduca moths prefer surrogate flowers that emit high levels of CO2, characteristic of newly opened Datura flowers. We show for the first time that CO2 may play an important role in the foraging behavior of nectar-feeding insects.”

But Hildebrand mentioned in a side conversation to his talk that the moth’s sensors work within only a limited range of ambient CO2 levels. This meant, he said, that as background levels rise, to say, double or triple current levels, they might reach a tipping point where the moth’s foraging skills would deteriorate.  [Interested? You can find more here.]

Not a lepidopterist? Thinking that at CO2 levels 2-3 times current values, the fate of Manduca might be the least of our problems?

Then it’s a good thing that you can also make a career studying the human thought process, as manifested in individuals and in groups. Amateurs can play as well. In that connection, it’s been interesting to watch the reactions to recent publications from NOAA such as the State of the National Climate Overview for June. The public has reacted strongly to such recent reports. In part this almost certainly stems from the substance of the scientific studies, which taken together, suggest that a global warming trend is visible in the (noisy) temperature record.

However, another dimension may play in as well…the reports are being issued not simply at a time when oppressive heat prevails over much of the United States, but also when our plans “gang aft aglay,” when power outages, covering wide regions and lasting for days, have reminded us that as human beings we share a tipping point:

98.60 Fahrenheit.

Turns out that our bodies’ thermoregulation system doesn’t work so well at temperatures in this range and above. We used to know that. But today, under normal circumstances, for many living and working at desk jobs in the United States, in a virtual climate maintained by A/C (at considerable energy cost), this vulnerability seems remote – more-or-less removed from direct experience. That blast of hot air we encounter when we walk between buildings or from work to the bus or Metro? It’s almost fun for short periods.

But not day after day. Not night after night. All of us in the region quickly became aware of our physiological limitations. We shared a visceral reaction, not just a cursory attention triggered by news pictures of kids playing in the water gushing from fire hydrants. We experienced what folks in the hazards world refer to as a “teachable moment.” We suddenly got our heads around “tipping points” in a way that no amount of media coverage of melting glaciers or Arctic ice pack or diagrams of shifting ocean circulations or warnings of permafrost thermal runaway would ever produce, except for the few who study such processes. We felt our productivity decline, our focus evaporate.

Some say this public concern will fade come the first cool weather in the fall. Certainly true enough. But in its train will emerge some other weather concern.

And hopefully some small number of economic researchers have already set to the task of assessing the cost of this summer’s heat; the crop loss and the decline in productivity of those who work outside, the increase in cooling costs, the stress on the electrical power infrastructure, the increased water consumption for all sorts of activity, the added healthcare load…and all the other factors that play in. It’s shaping up to be a big part of the 2012 weather story.

And it’ll make for interesting reading along about the time of next year’s heat waves.

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One Response to Tipping points…for moths and men

  1. Michael Cunningham says:

    “as background levels rise, to say, double or triple current levels, they might reach a tipping point where the moth’s foraging skills would deteriorate” … and natural selection would be likely to come into play long before that point was reached.

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