Good Walls Make Bad Neighbors
Don’t contribute to habitat fragmentation.
Let’s indulge in a thought experiment.
For as long as you can remember, your family has lived in the same house. Generations and generations. Not only do you know this house and neighborhood inside and out; you rely on that knowledge to survive. All your neighbors similarly do.
Your water and electricity arrive reliably. The single grocery store in your area provides sustenance. The dance hall is where everyone meets their mate. There’s always another bed available for a new baby.
One day, you leave home as you always do to go to the grocery store, but what is this?! Access to one side of the street has been blocked with a high wall—no space even for a person on foot to squeeze through. Oh, well, you’ll just have to go the long way around, but you find the other side cut off by a wall too. You try your backyard and the one across the street. No go. You’re completely walled in.
You wonder whether you could scale the wall, but you’re no climber and the wall is sheer and high. Maybe slither underneath? Nope. Its foundation penetrates the ground. It’s a well-built wall by the standards of masons. Not so much by the standards of survival.
You stomp home, where the cupboard is bare. Maybe you’ll drink some water, slake your thirst while you think, at least. Uh oh. Your neighbor informs you that all utilities have been cut off. You can’ even shower now for that hot date you had planned at the dance hall. Wait! There’s no way to get to the dance hall anyway since those damn walls went up.
How’s this going to work out? Well, you’ll starve if you don’t die of thirst first. No humans in your neighborhood will be able to procreate. (Death tends to have that effect on a species.) Or even if they can survive, they can’t meet new mates. You’re all doomed.
Now imagine you’re a desert tortoise and you’re met with this:
This is a portion of the wall around our house in the Coachella Valley. Most houses are completely walled in and the perimeter wall encloses the entire neighborhood except at the gated entrances, probably two linear miles in all. It is not an aberration. In fact, it’s pretty much the norm in these parts. Nearly every gated community has a wall around it. If you’re a critter that can’t jump six feet, your feeding and mating grounds may be compressed. If you’re fleeing a predator, you may get trapped against the wall and become easy pickings. If you manage to mate but your species relies on freedom of movement to establish new territories, you may lose vitality due to unsustainable competition for resources or reduced genetic diversity.
A study in Science Advances entitled “Habitat fragmentation and its lasting impact on Earth’s ecosystems” reported the following:
A synthesis of fragmentation experiments spanning multiple biomes and scales, five continents, and 35 years demonstrates that habitat fragmentation reduces biodiversity by 13 to 75% and impairs key ecosystem functions by decreasing biomass and altering nutrient cycles. Effects are greatest in the smallest and most isolated fragments, and they magnify with the passage of time. These findings indicate an urgent need for conservation and restoration measures to improve landscape connectivity, which will reduce extinction rates and help maintain ecosystem services.
The wall around our neighborhood appeared in the 1970s. The study was reported in 2015. Since then, I very much doubt that anything has improved. In fact, developers just broke ground on a Disney-branded community near us that will eliminate one square mile of blow desert and undoubtedly have a wall around it (likely four linear miles), disrupting the lives of whatever mammals survive the construction.
Many actions we take as humans have the unintended effect of corralling wildlife into unsustainable spaces or driving animals into unfriendly habitat. We build on the best land and leave only steep slopes or wet areas for the wild things, despite the fact that these conditions, while they support some species, create obstacles for others. We pave roads that become death traps. We reroute rivers or starve them of flow or constrain their natural flood plains. We suppress fires that many species rely upon for renewal. (Certain trees in the New Jersey Pine Barrens and other places require fire for their seeds to germinate.) We build walls and fences that further fragment territories.
I wrote about the harm fencing does to wildlife in a prior newsletter. At Puddock Hill, circumstances have forced us to erect deer fencing, but we endeavor to provide gaps for critters as large as foxes to work their way through. Walls that are an inherent part of the neighborhood, as they are at our house in the Coachella Valley, present a more difficult challenge. Furthermore, I have little control of our walls, which fall under the purview of the homeowners association.
Years ago, when I served on a Nature Conservancy board, I learned of efforts to promote wildlife corridors. In some places, civic forces have even built wildlife bridges over highways. As vital as these projects may prove to be, they are mere threads in the complex web of habitats.
What is a backyard steward to do given our limited resources and other constraints? For birds and insect pollinators, which of course can overcome barriers more easily than terrestrial species, planting a variety of natives helps join the tapestry together. Even small parcels, if there are enough of them and they are well distributed, can have an impact, as Mary Reynolds emphasizes in her We Are the Ark philosophy of “restorative kindness.”
When it comes to fences and especially walls, the challenge becomes more formidable. First, don’t wall in large swaths of land. Use fences judiciously and provide access for all but the creatures you must fence out. If you inherit a fence or wall, seek ways to breach it here and there if the authorities allow. Plant natives on both sides if you can, so at least the flying things will have continuity.
Good fences only really make good neighbors when our neighbors are people. Put yourself in the mind of a creature that evolved without walls—which is to say all creatures—and refresh your imagination on how impossible life would be if you could never again reach the supermarket.
The bareness of the wall shown above resulted from removal of some water-hungry fruit trees. We replaced them with three native Blue Palo Verde trees (Parkinsonia florida), among the most beautiful trees in the desert and requiring little irrigation. These trees host five species of native butterflies and moths. Here’s what two looked like a day after planting:
