I can't resist the soap box

[woobat]

So, we're having a plague of tent caterpillars around here, and yeah, they're really gross. I have a high tolerance for a lot of "gross" things in the outdoors, but these freak even me out. Sylvantechie and I went on a hike yesterday, and had to walk along swinging a stick in front of us, knocking down the 'pillars and their webs in order to not

Comments

[woobat]

I think this discussion of the normal cycles of tent caterpillars has some interesting things in common with the discussions about the cycles in climate. Yes, normal cycles have occured in the past in both caterpillar populations and climate. Abnormal cycling is difficult at best to differentiate from normal cycling, and both timing of cycles and magnitude need to be teased out, and it's nearly impossible to do controlled experiments on large scale environmental systems.

We have two species of tent caterpillars causing problems right now: the eastern tent caterpillar (creates the tents that we're all familiar with), and the forest tent caterpillar, which is likely to be the bigger problem. The eastern tent caterpillar primarily chows down on cherries and apples (that's why you see them a lot on ornamental crabapples). The forest tent caterpillars find a lot of the more traditional forest trees (oak and maple) to be very tasty, and lead to massive deforestation.

True, both species tend to have natural cycles. The reasons for the cycling haven’t been really well studied, from what I can tell, but it appears that a variety of factors lead to the population crash that ends the typically 1-3 year cycles: low spring temperatures, late frosts, parasites, diseases, and increase in predator populations. The lag time between outbreak and population crash seems to be attributed to several factors, including the ramp-up time for predator species to increase their population (birds have longer life cycles than insects, for example) and needed population density for parasites and diseases to do their job.

So I think we have two problems: first, the outbreaks seem to be worse (one UMass Extension official said that the forest tent caterpillar outbreak in southern massachusetts last year was the worst in 100 years, and our tent caterpillars are already larger than would be expected at this time of year), and second, a lot of those factors that bring outbreaks to an end are potentially screwed up by climate change. Low spring temperatures? Late frosts? Ha! And if the migratory bird populations continue to lag behind the caterpillar hatchings, it seems likely that they'll have less of an ability to shut down the outbreaks. Some of the more effective fungal parasites thrive under cool, moist weather conditions, and again, those conditions are less and less common.

[woobat]

(cont.)

And then there's the issue of what degree of proof of causality one needs before taking action. I think it's wise to lean more towards the precautionary principle when dealing with climate change, and less towards the traditional need for rigorous proof of causality. We're all in the middle of a long term, large scale experiment on the impacts of our various activities on our environment. We only have one lab specimen, and it's critical to our own survival. In many cases, by the time we have even a preponderance of data pointing towards the need for action (let along rigorous proof of causality), the time for that action has passed. We're in the middle of that with the larger question of climate change. Really, we needed to have been limiting emissions of greenhouse gases fifteen to twenty years ago, and we're just now finally getting to the point of large scale public belief in climate change and the need for action. We need to be quicker on our feet in responding to the affects of climate change than is generally allowed for with proof of causality.

Forests seem to recover (albiet with reduced diameter growth) from tent caterpillar outbreaks that last only a few years. If they last for more than a few years, or if there are significant secondary stressors (like, say, drought or other pests, both of which are more likely as a result of climate change), then there’s often wide spread mortality. So if we require proof of causality to take action, and we start doing the necessary research now to determine whether increased average temperature affects the severity or length of tent caterpillar outbreaks, do you think that research will be done in time to take any action to decrease the severity of the effects?