Thoreau Followup

I’d like to respond to Brian’s post about the recent study on shifts in abundance of flowers in Concord over the past 150 years. One theme I’ve been trying to think through these past few months is how we think about conservation and biodiversity: what are we trying to save? How are we doing it? How are we feeling about the future, and what are the consequences?

As I read it, Brian’s really talking throughout about cultural memory: what we as humans highlight. From the Times’ predilection for climate change to the naturalist’s collecting strategy, we all have intuitive filters that preserve some memories while tossing off others. Maybe this is obvious, but the paper published in PNAS, “Phylogenetic patterns of species loss in Thoreau’s woods are driven by climate change” is about exactly that, but written in the world of climate and genes. The authors found that not only have plants in Concord experienced fairly dramatic shifts in abundance and phenology (timing of life cycles, e.g. flowering time), but that there was a significant genetic component to such effects. That is to say, if you find that one species of aster in Concord isn’t keeping up with climate change, it’s flowering later than it should and suffering the consequences, it’s likely that other asters are experiencing the very same problems. Just as the stories we tell are being shaped and categorized, so too is nature filtering the flowers we study.

Okay, it’s not a new idea. Richard Dawkins did a pretty nice job summing it all up in The Selfish Gene when he coined the whole “meme” idea — that cultural memory was shaped by evolutionary pressures, and that some ideas/arts/governments/&c. were better able to survive and reproduce than others.

We are about to experience, in the natural world, what amounts to a massive cultural revolution. Things that are now abundant may not be abundant in 100 years. Things that are rare may explode and thrive. And yet, I believe that historians and those who study the anthropology of science would say that by observing those processes, we (conservation biologists) are also influencing our understanding of those rapid changes. We as scientists suffer from an inability to say how rapidly nature changes under “normal” conditions. Paradoxically, we as humans also suffer from short attention spans and are easily confused by shifting baselines. That is to say: on a cultural level, I don’t think we’ve quite come to grips with how terrifying the next century could be, given the chance that current climate models are gross under-predictions of potential future change. But I also feel that on a scientific level, we don’t have a good grip on how biodiversity shifts over those time spans.

Imagine, if you will, the massive changes that have occurred in Brian’s current locale and mine. Just 13,000 years ago, Brian would be under 5 miles of ice; 13,000 years ago, I could walk from my home in Berkeley out to the Golden Gate and not get wet. And yet all those plants that Thoreau was writing about were somewhere in or around Concord, and they remain. Not to get all Crichton/Goldblum-y, but life really does find a way.

A final metaphor. In I think the first episode of Cosmos, Carl Sagan said that if he had a time machine, he would travel back to the Library of Alexandria. He wanted to know what the ancient world knew, to explore not just their science but also their culture. It’s thought that for every ancient epic we still have records of, 5, 10 or 100 may have been lost. But it doesn’t really matter whether there are fifty or a million copies of The Aeneid floating around — it still exists, and you can still read it. If you make bad enough decisions in high school, you may end up even translating parts of it from the original Latin. What we have saved, we have saved, and what we have lost is forgotten forever. Much like with biodiversity: it’s not the abundances that matter, it’s the binary: present or absent. Extant or extinct.

Willis, C. et al. Phylogenetic patterns of species loss in Thoreau’s woods are driven by climate change. PNAS, 105:44. (doi: 10.1072/pnas.0806446105)

[A related paper that I didn’t manage to work in but is worth checking out along the same lines, examining small mammal range shifts in Yosemite over the past 100 years was published in Science a few weeks ago: Mortiz, C. et al. Impact of a Century of Climate Change on Small-Mammal Communities in Yosemite National Park, USA. Science, 322:10. doi: 10.1126/science.1163428)

Posted by Tim on November 3rd, 2008 • • 1 comment

One Response to 'Thoreau Followup'

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  1. Ray said, on March 23rd, 2009 at 7:58 am

    Every time i come here I am not dissapointed, nice post