Some authorities in Jefferson Parish, Louisiana, are upset that they didn't get a permit to build rock dykes between barrier islands to keep the BP oil spill out of fragile estuaries. The permits were denied because, as local scientists such as Kerry St. Pé of the Barataria-Terrebonne National Estuary Program pointed out, the plan wouldn't work.
In fact, it would have made things worse: Storms are going to drive water towards the coast and drop rain onto it that will run back towards the sea. If the normal channels for this water are blocked with rock, then the water will simply shoot through any cracks at high velocity (pushing oil further into the estuary), or eat away at the barrier islands, which are made of sand.
I think part of the problem here is that people are too fond of a territorial metaphor: Keep bad things out. It's partly a parallel to the boundaries of one's own body, where it often makes sense: Watch what you eat. "Don't put that in your mouth," we tell children. "You don't know where it's been." Have a low tolerance for lead in the drinking water. Avoid unnecessary exposure to mosquitoes, germs, and sharp things on the ground. And, as I always say about cigarettes, if anything is on fire, you should not stick it into any opening of your body.
Like many things that appeal to our intuition, however, the boundaries metaphor can steer us into a denial of reality. You can't build a rock wall that will stop the interaction of hurricanes and the coastal ecosystem. You can't build a technological umbrella that will deflect an incoming nuclear attack (at least, we sure can't in the near future, even if suitcases weren't the new ICBM). You can't build an effective wall across a 2,000-mile border, especially if your national economy encourages and depends on people finding a way around it.
For that matter, you can't stop breathing. So let's take a deep breath, and keep working out how to interact with the messy, complicated, and dangerous world which we are called to be, not of, but in.