Green fences and animal highways


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Robert Frost famously wrote about how “Good fences make good neighbors,” but the type of fence that pioneers built in the American West can be a drain on the environment. Picket fences block animal migration routes and are often painted with toxic chemicals. Building a wooden fence kills trees and fossil fuels are burned transporting lumber. These fences can also cause erosion by transferring the force of the wind into the soil, and they take constant maintenance.

Centuries old techniques offer a green alternative. Just as the Normans used hedgerows and Native Americans used Osage-Orange, botanists are exploring new ways to use living plants to regulate property lines. For example, Phung Tuu Boi is building a green fence to keep people from areas contaminated with Agent Orange. As the director of the Center for Assistance in Nature Conservation and Community Development in Hanoi, he’s developed a fence that keeps animals from foraging in contaminated sites while also restoring the soil and growing a cash crop:

Mr. Boi has developed a low-tech solution to overcome these problems: a fence made of trees covered with cactus-sharp needles to deter humans and animals alike. Mr. Boi hopes this so-called green fence will not only discourage trespassers, but also provide them with an economic incentive to leave the barrier intact. Once mature, the trees he has chosen to make up the fence, Gleditschia australis, produce a fruit that residents can sell to make soaps and medicinals. Gleditschia, a type of honey locust, is disease and insect resistant, and its thorns and soft wood should deter residents from cutting it down for firewood.

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Another advantage of living fences is that they offer habitat for wildlife. These slices of greenery often act as highways for wild animals on the move and dense tree lines are just as effective at controlling domestic animals.