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Recycling the urban forest.

Following the rural forest's example, people and cities are beginning to take the "waste" out of "yard waste" by putting yard trimmings back into the urban forest ecosystem.

CONSIDER, for example, the pride that the homeowner takes in the lawn he maintains in front of his house, whether a bungalow or a mansion. Although his lawn appears to him as a tranquil and beautiful piece of "nature," it is in fact a monstrosity when considered from the point of view of scientific ecology. Almost everywhere, and especially in the temperate zone, the creation and maintenance of a lawn involves the expenditure of much energy and other resources to destroy and control the weeds, brush, and trees that would naturally grow on it and that indeed reestablish themselves as soon as the lawn is neglected.--Rene's Dubos, at a Princeton University lecture on Earth Day, April 22, 1980.

America is a nation of cities, and our urban environments are under increasing attack from traffic, air pollution, and the loss of open space. Municipalities from Maine to California are seeking solutions by returning, in growing numbers, to the rhythms and ecologies of nature.

Nowhere is this salutary trend more pronounced than in the appearance over the last decade of what has come to be known as the urban forest. From the perspective of those involved with the growing art and science of urban forestry, cities are no longer merely a collection of houses and streets with a few trees scattered across parks and yards. On the contrary--urban areas are now viewed as a very specific ecosystem: a fully functioning forest in its own right.

These urban forests have their own natural cycles and, just like their rural cousins, exert powerful changes on their environment, changing wind patterns, pumping vast amounts of water, storing carbon dioxide, and cooling down their asphalt and concrete surroundings.

City dwellers are rapidly discovering that nurturing and promoting these natural processes of the urban forest often have unexpected beneficial results. In Oakland, for instance, the devastating fire of 1991 left 5,000 homes destroyed or damaged, plus tens of thousands of yard trees blackened and hundreds of acres of underbrush charred. Measures must be taken to prevent a replay of this disaster.

In the wake of the burn, city crews have been busy chipping up the debris, but they no longer haul it away. Faced with the problem of dealing with all those damaged trees, brush, and debris, city managers and urban foresters chose to pattern their approach after nature's "removal" system. Oakland now requires residents to recycle the byproducts of trees and brush on their own land.

Of course, there is no better place for this mulch than the floor of the forest, even if that floor happens to be the backyard of a suburban house. But the lesson is clear: The same process of ecological recycling can work just as well in the heart of the urban forest as it does in our larger natural forests.

For the expanding cities of America, this important ecological lesson could not have come at a more opportune time. Landfills everywhere are reaching their capacity. We are, quite simply, running out of space for our garbage. Borrowing processes from nature to recycle natural products--that is, "waste" from the urban forest--will help relieve much of the pressure on our overcrowded municipal landfills--and improve the urban environment.


The shocking facts are the same in every corner of the country. Twenty years ago, New Jersey had 331 landfills; today there are 13, and half the state's refuse is transported to Pennsylvania and Ohio. Chicago will run out of landfill space in 1994, Los Angeles in 1995. Florida's landfills will be brimming within five years.

Even Fresh Kills Landfill on Staten Island--which receives 13,000 tons of garbage every day, making it the largest dumpsite in the world--is rapidly reaching its capacity. By the year 2000, this modern monument to solid waste will be able to accommodate only 20 percent of New York City's garbage. By that time, Fresh Kills will reach, 1,505 feet and overtake Maine's Cadillac Mountain as the highest point on the Eastern Seaboard.

In an effort to stem this waste tide, both the Environmental Protection Agency and state agencies have mandated reductions in the solid-waste stream by up to 50 percent within the coming decade. Governing agencies nationwide have been forced into a race against the clock, devising plans to drastically reduce the millions of tons of garbage homeowners produce every day.

Surprisingly, this is not the first garbage crisis. In the early 1960s, a government study revealed that only 6 percent of the nation's landfills were "sanitary." The others were small, private dumps where anything and everything was tossed and often burned, with no regard for public health and safety.

"Out of sight, out of mind" was the operating philosophy; little thought was given to any leaching from the dumpsites (read: toxic cesspools) into the underground water reserves. Many cities are now paying the price for this lack of foresight. Los Angeles, for example, has seen one-third of its aquifers--the crucial underground source of drinking water--contaminated by plumes of rugged solvents from wartime factories and unregulated toxic dumpsites. (Not to mention casual home and industrial dumping, such as spilling oil in a driveway or on the ground.)

The Solid Waste Disposal Act, passed in 1965, forced cities to adhere to stricter landfill requirements. Following that landmark legislation, larger and more modern landfills were built throughout the nation.

Less than three decades later, these newer landfills are reaching their capacity. And no wonder: Americans produce more garbage than any other nation on earth. In Orange County, California--the world record holder--every man, woman, and child contributes 2.2 tons of garbage to the waste stream each year. That's 12 pounds per person per day! And the rest of the country is not far behind.

The roots of the present crisis lie in our attitude and approach to both consumption and trash: We are still operating under the pretense that we have unlimited resources--and unlimited space for the discarded items. Clearly, that is no longer the case. We have no choice now but to reduce the total amount of our waste flow that is destined for burial in our landfills. As William Rathje, head of the University of Arizona's research project on garbage, wrote in The Atlantic (December 1989), "Source reduction is to garbage what preventive medicine is to health."

We can, of course, reduce our overall consumption, demand more efficient packaging, and simply make everything last longer. While we work on these things, the most immediate way to lessen our present landfill crisis by recycling.

When we hear the word "recycling" we immediately think of aluminum cans, newspaper, and glass bottles. Recycling these items can reduce the garbage going into landfills by 15 to 25 percent, but there is another component of the waste stream that should be recycled: yard trimmings and lawn clippings.

On average, this so-called "green waste"--including some kitchen scraps--constitutes between 20 and 30 percent of the total weight of a city's garbage. But "green waste" is also bulky, quickly filling up landfills. As an early response to the landfill dilemma, many municipalities are phasing it our of their trash collections. Homeowners now must find ways to dispose of the remnants of their yard work.

For millions of homeowners, this refusal to pick up their clippings, leaves, and cuttings actually is the best possible news. They now have a chance to recycle their organic materials, and in so doing, return a more natural balance to the urban forest.


Like its urban cousin, the rural forest also produces masses of dead organic material. In nature, however, these materials are not considered waste. Instead, they are a necessary part of the larger ecological cycle.

Leaves on the forest floor slowly decompose into a rich layer of humus (the organic portion of soil formed from decomposing plant or animal matter), returning important elements--carbon, nitrogen, and phosphorous--back into the soil in just the right proportions. Living trees and vegetation then take in these elements to build trunks, branches, and new leaves.

The cycle in a forest community is smooth and efficient. Powered by water and sunlight, the forest is in a constant and ever-changing cycle of life.

By contrast, every part of the urban forest community's life cycle is short-circuited through human intervention. Limbs, leaves, and grass clippings are considered "waste" and assiduously removed from the urban ecological system. Artificial fertilizers are brought in to replace lost nutrients. Insects that otherwise would help break down excess material are considered pests and eradicated. To the casual observer, the urban forest appears neat and trim, but when yard trimmings are removed entirely from the natural cycle, the urban forest becomes a drastically truncated ecosystem.

One culprit in the disruption of the urban forest's natural cycle is the typical suburban lawn. No American dream house is complete without a manicured lawn, but this verdant perfection comes at a steep price.

With all cut organic material removed, powerful fertilizers supplant the natural process of nutrient replacement. Many pesticides deal indiscriminately with all insects, including those beneficial to the process of decomposition. Residues from these artificial chemicals--fertilizers and pesticides--seep into the ground, damaging trees and often entering the water supply.

In fact, grass is inimical to the trees in the urban forest. "Forest Lawn" may be an evocative name for a cemetery, but it is an arboreal oxy-moron: There are no lawns in a forest. Lawns in cities compete with trees for available nitrogen. In addition, the chemicals applied to lawns often are absorbed by trees' delicate feeder-root systems, causing a wide range of health problems.

For cities, lawns also create a logistical nightmare: an endless stream of bagged grass clippings. Now that cities are refusing to remove such clippings, many homeowners have turned to the simplest of solutions: the mulching mower.

Mulching mowers reduce the size of clippings and spread them back on the grass where they rapidly decompose and return to the soil. After a generation of using mowers that virtually vacuum the lawn clean, many homeowners are skeptical. For that reason, municipalities have engaged in educational techniques such as the "Just Say Mow!" program in Milwaukee, and Texas' "Don't Bag It!"

The benefits of these programs are clear. Cities enjoy a massively reduced garbage load, and homeowners are elated with the surprising results--healthier lawns, trees, and shrubs, as well as less yard work.


Refusing to collect grass clippings is only the beginning of the trend of recycling the urban forest. In the near future, several cities will refuse to collect all yard clippings, including leaves, branches, and bush clippings. Many homeowners have gladly taken on this challenge by composting yard waste. Composting allows cut organic material to reduce in weight and volume through the natural process of decomposition.

"You've got to study how nature decomposes," says Malcolm Beck, a horticulturist in Austin, Texas, and a lifelong composter. Beck points out that "recipes" for compost abound, but they all need four crucial elements: moisture, oxygen, and a proper ratio of carbon and nitrogen. "Composting is an art," says Beck. "Nature provides the science." Depending on the method and the mixture, composting yard trimmings of all kinds can be completed in as little as a month.

Properly executed, the process is odor-free--and surprisingly rewarding. Homeowners who start composting are excited to learn they can create an abundant supply of rich, moist humus that can be used to bed flowers and vegetables, as potting soil, or as a natural soil amendment.

"Composting empowers people," says Bob Skiera, former city forester of Milwaukee, Wisconsin. "It allows them to do something positive with their environment." (See Growing Greener Cities for instructions on composting. Another excellent handbook is Backyard Composting, from Harmonious Technologies, Ojai, California. A more comprehensive resource is The Rodale Book of Composting, from Rodale Press, Emmaus, Pennsylvania.)

When landfill tipping fees rise above $30 a ton, cities also get enthusiastic about composting. In many cases, municipalities' involvement in recycling yard and lawn trimmings is, appropriately, a grass-roots operation.

In Cuyahoga County, Ohio, concerned citizens established a composting operation that included 14 communities. The Greater Cleveland Ecology Association took over day-to-day management of the process, and today five centers handle 180,000 tons of leaves each year. The result? More than 6,500 cubic yards of leaf humus is for sale to local gardeners.

Many communities have been recycling their urban forest excess for years. Milwaukee, hard hit by Dutch elm disease, lost more than 130,000 city trees, but the experience taught them a lot about recycling the urban forest. "We have been composting since 1936," says former city forester Skiera. Early recycling efforts involved wood chips from the lost elms and yard trees. But when the landfill crisis hit Wisconsin, Milwaukee looked into methods of recycling yard waste, too.

Early experiments indicated that composting such yard trimmings was feasible. Grass clippings, however, presented a problem. At 95 percent water, they tend to be heavy. And since they are enclosed in plastic bags, lawn clippings rot anaerobically (without access to air). "Our concern about grass clippings," Skiera says, "was downwind."

The urban forest needs mulch, and Skiera notes that compost constitutes an excellent product for this use, but not on its own. "By itself, compost is a perfect planting bed for weeds." Skiera recommends a two-inch blanket of compost covered with two inches of wood chips; then "It replicates the natural forest bed."

Austin, Texas, has a successful operation in which "source-separated organic waste"--yard trimmings, wood chips, leaves, and the like--is added to sewage sludge and alchemically transformed into "Dillo Dirt" (as in "armadillo"). "People pay us $5 a cubic yard to haul it off," says Jim Doersam, the engineer in charge of the innovative process. "Previously, we had to pay someone to take it away."

A two-year program introduced the public to Dillo Dirt. "There's a lot of pride there," says Doersam. "People know where it comes from and what it is. But the bottom line is, does it make their gardens look better?" The answer is a clear "Yes!" Enthusiastic residents of Austin now gladly pay up to $20 a cubic yard at garden retail outlets to buy back their own recycled--and composted--"green waste."

If there is a silver lining to the current landfill crisis, it is decidedly an earthy one. Whether involved in backyard composting, costly large-scale municipal operations, or low-tech, innovative regional compost and recycling solutions, Americans are starting to deal, one way or another, with the more than 30 million tons of cut organic material we previously dumped into landfills each year.

By recycling leaves, limbs, and clippings we can renew our association with the natural process at work throughout the urban forest. Taking responsibility for our yard trimmings and lawns clippings means further integrating ourselves into the natural cycle of the urban forest. And it means preventing this ecosystem from becoming short-circuited and shattered.

Stanley Young writes regularly on the environment for such publications as People magazine, Los Angeles Magazine, and Whole Earth Review.


1. Lawns must be mowed more frequently. Once a week is recommended.

2. Do not remove more than one inch or one-third of the lawn's height.

3. You should rake the clippings twice a year: after the first spring mowing (to green up the grass); and after the last fall mowing (to reduce the threat of disease).


There are almost as many ways to compost as there are possible ingredients. From leaves (dead or live) to kitchen scraps to lawn clippings to sawdust, virtually everything organic in the urban forest ecosystem can be composted.

How do you do it? The simplest way is to make a pile in your backyard of leaves, kitchen scraps, lawn clippings, and tree and shrub trimmings. You should turn the pile every seven days; within five weeks, depending on the mixture and the amount, you should have rich, fresh compost for everything from flower beds to trees--old and new. You don't need a lot of space, but keep your compost pile ventilated to avoid any smell. Don't use your compost before it's done. You'll know when your organic stew is ready because it looks like the rich brown forest floor.


Many municipal composting operations are often expensive to set up. In Seguin, Texas (pop. 20,000), Larry McCarthy has come up with a decidedly low-tech, low-cost approach. Citizens in Seguin rake their leaves to the curb where trucks vacuum them up. A tree chipper follows, reducing limbs and small logs to chips, which it spews into a waiting 10-cubic-yard "brush truck." At the composting site--43 acres of poor soil--thin layers of the leaf and chip mixture are covered with a thin layer of sewage sludge.

"It's not a composting operation according to a purist," says McCarthy. "The process is lower, and mimics what goes on in a forest." The material reduces slowly to a fraction of its former bulk, all the while enriching the soil beneath it. In a few years, the plot will be rich enough to use for farming or ranching.

This simple approach to recycling yard trimmings--and sewage-- has earned Seguin several environmental awards, including one last year for the region's best integrated solid-waste system. "Every aspect of it saves us money," says McCarthy. Residents don't have to buy bags or cut up limbs, the brush truck costs half what a garbage truck would, and the recycling site is closer than the nearest landfill, which cuts down on transportation costs.
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Author:Young, Stanley
Publication:American Forests
Date:Nov 1, 1992
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