Lawn treatment in the form of pesticides and inorganic fertilizers poses a substantial threat to the environment . Homeowners in the United States use approximately three times more pesticides per acre than the average farmer, adding up to some 136 million pounds (61.7 kg)annually. Home lawns occupy more acreage in the United States than any agricultural crop, and a majority of the wildlife pesticide poisonings tracked by the Environmental Protection Agency (EPA) annually are attributed to chemicals used in lawn care. The use of grass fertilizer is also problematic when it runs off into nearby waterways. Lawn grass in almost all climates in the United States requires watering in the summer, accounting for some 40 to 60 percent of the average homeowner's water use annually. Much of the water sprinkled on lawns is lost as runoff . When this runoff carries fertilizer, it can cause excess growth of algae in downstream waterways, clogging the surface of the water and depleting the water of oxygen for other plants and animals. Herbicides and pesticides are also carried into downstream water, and some of these are toxic to fish, birds, and other wildlife.
Turf grass lawns are ubiquitous in all parts of the United States, regardless of the local climate . From Alaska to Arizona to Maine, homeowners surround their houses with grassy lawns, ideally clipped short, brilliantly green, and free of weeds. In almost all cases, the grass used is a hybrid of several species of grass from Northern Europe. These grasses thrive in cool, moist summers. In general, the United States experiences hotter, dryer summers than Northern Europe. Moving from east to west across the country, the climate becomes less and less like that the common turf grass evolved in. The ideal American lawn is based primarily on English landscaping principals, and it does not look like an English lawn unless it is heavily supported with water.
The prevalence of lawns is a relatively recent phenomenon in the United States, dating to the late nineteenth century. When European settlers first came to this country, they found indigenous grasses that were not as nutritious for livestock and died under the trampling feet of sheep and cows. Settlers replaced native grasses with English and European grasses as fodder for grazing animals. In the late eighteenth century, American landowners began surrounding their estates with lawn grass, a style made popular earlier in England. The English lawn fad was fueled by eighteenth century landscaper Lancelot "Capability" Brown, who removed whole villages and stands of mature trees and used sunken fences to achieve uninterrupted sweeps of green parkland. Both in England and the United States, such lawns and parks were mowed by hand, requiring many laborers, or they were kept cropped by sheep or even deer. Small landowners meanwhile used the land in front of their houses differently. The yard might be of stamped earth, which could be kept neatly swept, or it may have been devoted to a small garden, usually enclosed behind a fence. The trend for houses set back from the street behind a stretch of unfenced lawn took hold in the mid-nineteenth century with the growth of suburbs. Frederick Law Olmsted, the designer of New York City's Central Park, was a notable suburban planner, and he fueled the vision of the English manor for the suburban home. The unfenced lawns were supposed to flow from house to house, creating a common park for the suburb's residents. These lawns became easier to maintain with the invention of the lawn mower. This machine debuted in England as early as 1830, but became popular in the United States after the Civil War. The first patent for a lawn sprinkler was granted in the United States in 1871. These developments made it possible for middle class home owners to maintain lush lawns themselves.
Chemicals for lawn treatment came into common use after World War II. Herbicides such as 2,4-D were used against broadleaf weeds. The now-banned DDT was used against insect pests. Homeowners had previously fertilized their lawns with commercially available organic formulations like dried manure, but after World War II inorganic, chemical-based fertilizers became popular for both agriculture and lawns and gardens. Lawn care companies such as Chemlawn and Lawn Doctor originated in the 1960s, an era when homeowners were confronted with a bewildering array of chemicals deemed essential to a healthy lawn. Rachel Carson's 1962 book Silent Spring raised an alarm about the prevalence of lawn chemicals and their environmental costs. Carson explained how the insecticide DDT builds up in the food chain, passing from insects and worms to fish and small birds that feed on them, ultimately endangering large predators like the eagle. DDT was banned in 1972, and some lawn care chemicals were restricted. Nevertheless, the lawn care industry continued to prosper, offering services such as combined seeding, herbicide , and fertilizer at several intervals throughout the growing season. Lawn care had grown to a $25 billion industry in the United States by the 1990s. Even as the perils of particular lawn chemicals became clearer, it was difficult for homeowners to give them up. Statistics from the United States National Cancer Institute show that the incidence of childhood leukemia is 6.5% greater in familes that use lawn pesticides than in those who do not. In addition, 32 of the 34 most widely used lawn care pesticides have not been tested for health and environmental issues. Because some species of lawn grasses grow poorly in some areas of the United States, it does not thrive without extra water and fertilizer. It is vulnerable to insect pests, which can be controlled with pesticides, and if a weed-free lawn is the aim, herbicides are less labor-intensive than digging out dandelions one by one.
Some common pesticides used on lawns are acephate, bendiocarb, and diazinon . Acephate is an organophosphate insecticide which works by damaging the insect's nervous system. Bendiocarb is called a carbamate insecticide, sold under several brand names, which works in the same way. Both were first developed in the 1940s. These will kill many insects, not only pests such as leafminers, thrips, and cinch bugs, but also beneficial insects, such as bees. Bendiocarb is also toxic to earthworms, a major food source for some birds. Birds too can die from direct exposure to bendiocarb, as can fish. Both these chemicals can persist in the soil for weeks. Diazinon is another common pesticide used by homeowners on lawns and gardens. It is toxic to humans, birds, and other wildlife, and it has been banned for use on golf courses and turf farms. Nevertheless, homeowners may use it to kill pest insects such as fire ants . Harmful levels of diazinon and were found in metropolitan storm water systems in California in the early 1990s, leached there from orchard run-off. Diazinon is responsible for about half of all reported wildlife poisonings involving lawn and garden chemicals.
Common lawn and garden herbicides appear to be much less toxic to humans and animals than pesticides. The herbicide 2,4-D, one of the earliest herbicides used in this country, can cause skin and eye irritation to people who apply it, and it is somewhat toxic to birds. It can be toxic to fish in some formulations. Although contamination with 2,4-D has been found in some urban waterways, it has only been in trace amounts not thought to be harmful to humans. Glyphosate is another common herbicide, sold under several brand names, including the well-known Roundup. It is considered non-toxic to humans and other animals. Unike 2,4-D, which kills broadleaf plants, glyphosate is a broad spectrum herbicide used to control control a great variety of annual, biennial, and perennial grasses, sedges, broad leafed weeds and woody shrubs.
Common lawn and garden fertilizers are generally not toxic unless ingested in sufficient doses, yet they can have serious environmental effects. Run-off from lawns can carry fertilizer into nearby waterways. The nitrogen and phosphorus in the fertilizer stimulates plant growth, principally algae and microscopic plants. These tiny plants bloom, die, and decay. Bacteria that feed off plant decay then also undergo a surge in population. The overabundant bacteria consume oxygen, leading to oxygen-depleted water. This condition is called hypoxia. In some areas, fertilized run-off from lawns is as big a problem as run-off from agricultural fields. Lawn fertilizer is thought to be a major culprit in pollution of the Everglades in Florida. In 2001 the Minnesota legislature debated a bill to limit homeowners' use of phosphorus in fertilizers because of problems with algae blooms on the state's lakes.
There are several viable alternatives to the use of chemicals for lawn care. Lawn care companies often recommend multiple applications of pesticides, herbicides, and fertilizers, but an individual lawn may need such treatment on a reduced schedule. Some insects such as thrips and mites are suceptible to insecticidal soaps and oils, which are not long-lasting in the environment. These could be used in place of diazinon, acephate and other pesticides. Weeds can be pulled by hand, or left alone. Homeowners can have their lawn evaluated and their soil tested to determine how much fertilizer is needed. Slow-release fertilizers or organic fertilizers such as compost or seaweed emulsion do not give off such a large concentration of nutrients at once, so these are gentler on the environment. Another way to cut back on the excess water and chemicals used on lawns is to reduce the size of the lawn. The lawn can be bordered with shrubbery and perennial plants, leaving just enough open grass as needed for recreation . Another alternative is to replace non-native turf grass with a native grass. Some native grasses stay green all summer, can be mown short, and look very much like a typical lawn. Native buffalo grass (Buchloe dactyloides) has been used successfully for lawns in the South and Southwest. Other native grass species are adapted to other regions. Another example is blue grama grass (Bouteloua gracilis), native to the Great Plains. This grass is tolerant of extreme temperatures and very little rainfall. Some native grasses are best left unmowed, and in some regions homeowners have replaced their lawns with native grass prairies or meadows. In some cases, homeowners have done away with their lawns altogether, using stone or bark mulch in its place, or planting a groundcover plant like ivy or wild ginger. These plants might grow between trees, shrubs and perennials, creating a very different look than the traditional green carpet.
For areas with water shortages, or for those who are concerned about conserving natural resources , xeriscape landscaping should be considered. Xeriscape comes from the Greek word xeros, meaning dry. Xeriscaping takes advantage of using plants, such as cacti and grasses, such as Mexican feather grass and blue oat grass that thrive in desert conditions. Xeriscaping can also include rock gardening as part of the overall landscape plan.
[Angela Woodward ]
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