Melanie Lenart, Ph.D.: Environmental Scientist and Writer

When Litter Is Good

(Walking on Earth column published in Tucson Green Times/The New Southwest, August 2010)

By Melanie Lenart


Soil often travels in the Southwest. Dust forms clouds that block highways. Sand dunes creep around the landscape, consuming back yards in northern Arizona. Finding a way to hold it down would save lives and land.

Plants are the key to keeping soil locked in place, as I was reminded during a summer visit to South Carolina’s Lowcountry.

Along the Edisto Beach shoreline, high tide already comes within a couple dozen feet of the first row of houses. People can’t afford to see their soil taking flight or their sand drifting out from under them. As a result, residents appreciate their ground cover, even when it takes the form of dead leaves.

Clumps of grass held down the sandy soil in the back yard of our rental house, a gray-blue wooden structure. Where the grasses didn’t take root, sand showed through in foot-sized patches sporting ant hills.

Like the other homes in the neighborhood, this house stood about a dozen feet off the ground on six-inch wide wooden stilts. Clearly the floods that can erode soil come fairly often to these hurricane-prone lands.

Maybe that’s why people here seemed a bit more willing to let the leaves fall where they may.

In many parts of the world, including the Southwest, residents typically treat “leaf litter,” as it’s known in scientific circles, like so much garbage. They rake it up and throw it away, as if it belongs next to discarded yogurt containers and old candy wrappers. It doesn’t.

Organic matter from decaying leaves helps soil particles stick together, making them harder to erode. A natural fertilizer, it supports the growth of plants that help keep soil in place. It helps soil hold moisture. Even the weight of the leaves themselves helps protect soil from erosive winds and rain.

In South Carolina’s Edisto Beach, the classic yellow-beige sand was darker where the leaves from the backyard oaks and pines dotted the ground – a sign that organic matter was at work.

In the arid Southwest, we can’t count on having enough rain to support plant growth. But we can let the leaf litter build up where it falls.

My back yard in central Tucson serves as an example of how this can work, given that it was a blank slate when we bought it. The yard was completely covered in concrete, which we removed in 2004 with the help of a dozen hearty friends.

Since then, a palo verde tree has been dropping its leaves in a corner of the yard – onto a soil slightly darker and less sandy than the Edisto Beach variety. In the six years since this would-be dust bed was again exposed to air and wind, the leaf litter has built up enough to hold down the soil even where no plants grow.

Instead of forming dust or shifting sands, the backyard soil is staying in place here and in Edisto Beach. It’s a lovely arrangement, in that avoiding the work of raking up leaves also reduces the need for dusting the furniture. It’s a practice that warms the heart of anyone who loves the environment more than housework.

Ironically, sometimes the most environmentally friendly practice is to leave litter on the ground.

Author: Melanie Lenart is an environmental scientist and writer, and the author of Life in the Hothouse: How a Living Planet Survives Climate Change.






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