Big Questions Come in Little, Eight-Legged Packages
How spiders survive in the city brings up some uncomfortable questions about how we interact with nature.
There was a paper published late last year in the Journal of Urban Ecology, that I just read this week and I can’t stop thinking about. It is titled “Changes in Spider Comunity Composition are Associated with Urban Temperature, Not Herbivore Abundance” (I am writing this on a tablet and cannot figure out how to italicize in the Medium app. Forgive me.) The study is pretty straight forward. Cities are warm, many bugs seem to do well in warm cities. So, the researchers asked, is that because warmer temperatures boost their little metabolisms, or is it because higher temperatures control predators? Put another way: many insects do well in warm cities, but do spiders?
No. At least not a certain a certain family of spiders, Anyphaenidae (known as “ghost spiders”). After they picked 20 sites in Raleigh with trees and above a certain ambient temperature , the researchers looked at these arborial communites of insects and spiders (specifically ghost spiders) over two years. They found that higher tempertures were correlated with lower ghost spider abundance. Along with warmer temperatures, this may help explain why insect populations can boom in our built worlds. It’s not just warmer tempeatures, its a lack of predators.
This, it seems to me, is not unlike the voracious spread of deer after eliminating wolves, or the spread of rats, doves, and racoons in neighbrhoods that are flush with trash and lack any predator control. In many ways, these spiders represent common environmental questions, writ small. Are their predator-prey interactions still natual, or human influenced? Or both? Or is their a difference? Should we be concerned about how we have altered nature for bugs and spiders, or fasinated at how these microcosims of life and death can adapt? If we built the city, are we actors in this ecosystem?
But this is not a case like logging or overfishing — we didn’t build cities because we wanted to control ghost spider populations. We built, and the nature adapted. So are we responsible for this change in predator-prey dynamics, and if so how much?
“Look, it’s just spiders and bugs,” you might be saying. “Don’t make too big a deal out of somthing so small.” Sure, you’re not wrong. In the end, the deatils of how ghost spiders and insects interact is not, in any real sense, a big deal. But these questions of ecological responsibility — our place in natural communities and the boundry between the our world and the natural one — are important. They are key to addressing the concerns of climate change, pollution and mass extinction. If we can’t even answer them for a small spider in the trees of Raleigh, N.C., well… shit.