In last month's installment of this two-part series, you heard about the origins of hedgerows and how they could save the farm. But you don't have to be a head of lettuce to appreciate the hedgerow: Part 2 focuses on hedgerows around homes and in urban communities improving children's health, feeding you, and ultimately save the world! Enter our superhero in green: the hedgerow!
Again, What is a Hedgerow?
If you still think a hedgerow is just a boring row of plants, you need to talk to Zach, Viviana, Galen, Emery, Alan and Raul — students in the GreenWorks class at Liberty Continuation High School in Paso Robles. Not only will they give you an eloquent definition of the hedgerow (essentially a linear planting of trees, shrubs, forbs and grasses), they will wax scientific about "nitrogen fixers" before they spill out Latin names of native hedgerow plants and rattle off the etymological connections to Greek mythology of Achilleas millefolium. These students participate in the school's "GreenWorks" class, a class devoted to environmentally themed topics. They are excited about hedgerows; they have planted their own on school grounds. A project in partnership with One Cool Earth, funded by the U.S. Fish and Wildlife Service's School Yard Habitat program, their hedgerow is part of a pollinator garden and indigenous peoples' plant garden on ½ acre of the school grounds. Students plant and observe the garden while learning about our region's natural history and ecology. Add one more talent to the hedgerow's repertoire — it can be a classroom!
Sacrificial Lungs
A hedgerow is a great teaching tool, but what else is it doing at a school? Everyone can appreciate the metaphor that trees and plants 'are' the earth's lungs, producing oxygen and taking up carbon dioxide and water in a critical gas exchange. Let's take parallels a step further. What if we could use plants to do some of the work of our our own lungs, the really dirty work — filter polluted air? Shrubs and trees, like lungs, have immense surface area. This is especially true for trees with needles. Both plants and lungs need lots of surface area to make their life-giving gas exchanges possible — more surface area means more exposure of cells to the air. However, both of these surfaces are very reactive with air-borne pollution, such as noxious gases and tiny particulate matter from vehicle exhaust. While exhaust from a passing car on the average suburban street dissipates rapidly, diluted by the large volumes of 'fresh' air, the exhaust from a steady stream of cars on an interstate like Highway 101 can grow concentrated and become a serious health hazard, harming our respiratory systems.
Sulphur Butterfly
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The most vulnerable human respiratory systems belong to kids. Their developing respiratory systems can be affected early on by tiny particulate matter from vehicle exhaust, resulting in childhood asthma and chronic respiratory infections. A California state law forbids the construction of schools within 500 feet of major sources of air pollution, such as a freeway. This law is raising problems in cities like Los Angeles freeways in every direction. Also, many schools were built before the law existed, even many schools within the relatively depopulated San Luis Obispo County. School ventilation systems are often not equipped to filter out the tiniest, most hazardous particles. Hedgerows to the rescue! A strategically placed row of evergreen trees and shrubs, say around a sports field or between a classroom and a freeway, can filter a significant amount of these small particles. Evergreen trees with needles work best because of their surface area, and also because they offer year-round filtration unlike deciduous trees which lose their leaves. In fact, air pollution can be at its worst in winter when inversion layers hold contaminated air to the ground. Particles sequestered by needles or leaves are washed benignly to the ground in the next rain. It is for exactly this reason that Cal Trans bothers to spend some of your tax money on landscaping freeways. More than just looking good, those shrubs along the highway are taking the hard part out of breathing.
Of course, plants create small particles themselves (pollen), and even volatile organic compounds, so careful consideration must be taken when choosing plants in such a setting.
Rest Your AC in the Shade
If you live in the milder climes of the coast, air conditioning and central heating might be words foreign to your ears. But north of the grade, or more than 20 miles from the coast, temperatures swing from hot to cold. Winds anywhere, but especially the incessant coastal breezes push and pull warmth from homes. Too much sun exposure in the summer can turn homes into oven, exhausting the AC. Energy costs to heat and cool under these condition can run up to hundreds of dollars a year.
Sue Reed has devoted a portion of her excellent book, "Energy-Wise Landscape Design" to the fundamentals principles of using hedgerows to counteract these energy-draining elements of nature. Her book outlines how you can situate a multi-level hedgerow of trees and shrubs around a house to cut wind. Especially for older houses, the main loss of heat is from wind pushing air out of a house through cracks and gaps, air that you just paid to have warmed! Therefore, slowing wind speed around a house can result in direct energy and cost savings. In the summer, the sun can beat on roofs, glare through even curtained windows, and raise home temperatures. A deciduous tree or row of them on the south and west face of a home can block sun in the summer, while allowing it to shine through when it's wanted in the winter.
While you're working less thanks to all the money the hedgerow is saving on heating and cooling, you might consider its other merits: cheaper and last longer than a wooden fence (better looking too!); doesn't consume natural resources; the birds love it; it can be grown from fire-resistant plants, forming a protective buffer around your home; you can make it from edible plants such as feijoa, apples, plums, blackberries, gooseberries, currants, figs, pomegranates, olives, and grapes; incorporate drought tolerant and nitrogen fixing natives and you won't have water or fertilizer costs. Heck, with a good enough hedgerow, you can quit your day job!
Hedgerows Save the World
Honey Bee
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Like an apocalyptic weapon of the most nefarious villain, the greatest threat to the planet Earth today is invisible, odorless, tasteless, and everywhere. No, it is not a biological disease or poison gas, it's carbon dioxide! Without freaking out too much about climate change, suffice it to say that it's happening — right now — with glaciers melting like ice cubes in a politician's glass of whiskey. Enough said.
The solution to climate change is simply formulated: 1. reduce emissions; 2. take back the what we've already emitted. The first, most crucial step is in the domain of energy efficiency and conservation — we need to rethink our technologies! The second step falls within the skillset of the hedgerow. While engineers are busy tinkering with expensive and uncertain carbon capture technologies, they seem to have overlooked this Neolithic invention (see The Golden Age of Hedgerows: Part 1), our humble hedgerow, the superhero that will save the world. I may be accused of exaggerated claims of the hedgerow's abilities hitherto, but now I'm getting serious. To back me up, the United States Forest Service has come out of the woods and proven their mastery of Excel. Behold, the Carbon Calculator! See the references below to download this amazing tool yourself, but here are the basics.
This calculator is used to estimate just how much carbon one can save by planting a single tree near a home. By entering a number of parameters defining: your geographic region, the age of your home, your heating/cooling equipment, the type of tree you're planting, and its orientation to your home, the beautifully formatted Excel spreadsheet spits out numbers: in pounds and kilograms, it tells how much carbon the tree takes up in its growth per year, and the total after a given number of years. Even more exciting, the calculator tells you how much carbon you will avoid emitting, from avoided energy use in heating and cooling due to factors discussed in the previous section. I played around with the inputs and found that a coast live oak tree takes up nearly a ton of carbon dioxide over its first 20 years. It also saved 300 lbs./year of carbon emissions by shading the south side of a pre-1950's house! Given that the per-capita carbon emissions in the US are around 20 tons/year, we've got a ways to go with reductions, but his is a good start, especially for folks with land. If we were to plant hedgerows with trees near our homes and on just a small fraction of the 1,200,000 acres of agriculture land in the county, especially emphasizing carbon-storing trees, we could make a real impact.
Back to School
We still have a lot of experimenting to do with the hedgerow to prove its superpowers. We have many questions now. What plants make the best ones in our area? How should we situate it around our homes and schools to maximize its effects? What are the surest methods of planting? We can answer some of these questions by looking to existing landscapes. But to some extent, the truly sophisticated hedgerow is a new, untested device in the New World. An appropriate place to begin answering some of these questions: back where we started with Zach, Gaelen, Alan, Eric, Raul and Viviana at Liberty Continuation High School. I mentioned that these students have planted their own hedgerow on school grounds. They are also purveyors of hedgerows, and in February of this year made their first sale of a simple 100' hedgerow to D'Anbino Vineyard to the east of Paso Robles. In slightly over an hour, these students installed more than a hundred of the native plants they had grown themselves over the previous year. Kathy D'Andrea and her colleagues at the vineyard chose to install the hedgerow for many reasons: beautification, displace gophers and weeds in the vineyard's margins, attract beneficial insects, provide wildlife habitat, and to furnish herbs for their biodynamic applications. But more than anything, Kathy's purchase of plants from the students represented an investment in the development of the hedgerow in San Luis Obispo County. We are taking the hedgerow back to school and we are going to get results.
Cottonwood Tree
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References
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Photos by Shelley Ellis
