A radical, underground movement is growing in the suburbs of the United States.

From coast to coast, eco-concerned homeowners are ripping out their manicured, chemically-treated lawns and replacing them with organic food gardens, native flowers and sometimes, just rocks.

"It's a growing endeavour. It gets bigger and bigger every year," said Steven Saffier, coordinator of the Audubon Society's At Home programme, which encourages people to let their lawns go wild to support birds and other wildlife.

The lawn, the one-third acre or more of trimmed grass outside the front door of so many U.S. homes, is getting an eco-makeover as people learn about the lawn's impact on the larger environment.

Groups as diverse as urban garden clubs, environmental groups and wildlife protection groups are spreading the word that a big, lush lawn harms biodiversity and is an eco- disaster.

"Lawns contribute to climate change," Saffier told IPS. "The fossil fuels used in fertiliser and pesticide production add CO2 to the environment."

Lawns in the U.S. are grown mostly from non-native grasses that require large amounts of water, pesticides and fertilisers. Many homeowners aim for perfection, considered a dark green mat of closely-mown grass without weeds, a look promoted by chemical and fertiliser manufacturers here.

But homeowners, corporations and schools are starting to catch on to the idea of creating a wild space where nature can thrive.

Last week, Saffier helped dig a garden with a native spice bush plant at a Pennsylvania school. The group had barely covered the roots of the plant with dirt when a swallowtail butterfly landed on a leaf and laid her eggs.

"That's the kind of thing we are going for, on a larger scale," Saffier said.

What happens on individual lawns is multiplied many times over, because more U.S. surface area is devoted to lawns than any other irrigated crop, according to an analysis by the National Aeronautics and Space Administration (NASA).

The Lawn Institute, which represents the 35-billion-dollar per year turf industry, estimates that 25 million acres of lawn are growing in the U.S. This land previously hosted native trees, shrubs and grasses and entire ecosystems, but not anymore.

"The nutrient, hydrology and nitrogen cycles that happen naturally in biodiverse ecosystems are completely absent in lawns," Saffier said.

These acres of contiguous lawn have contributed to the severe decline in the U.S. bird population, Saffier said.

"The lawn is a landscape that offers nothing to the bird," he said.

Ninety-six percent of birds eat mainly insects, like caterpillars and bugs, and these insects are highly specialised and eat just one, two or three types of native plants.

"The birds won't find insects on the lawn," Saffier said. Fewer caterpillars mean birds do not have enough food to feed their young.

Of the 800 major bird species in the U.S., 200 are in dangerous decline, Audubon says. Populations of meadow larks and other grassland species in the mid-western U.S. have plummeted 60 percent, while interior forest birds, like scarlet tanagers, have also seen a precipitous decline.

Shrub land bird species, like the Brown Thrasher and Eastern Towhee, have decreased 75 percent since 1966, according to the North American Breeding Bird Survey, of the U.S. Geological Survey and Environment Canada.

Bird populations are doubly harmed when lawns are sprayed with pesticides and herbicides.

"It only takes a trace amount of chemicals on insects or plants to impact birds. Birds have very sensitive nervous systems," Saffier said.

Of the 30 most common pesticides used on lawns, more than half are toxic to birds and fish, and linked to cancer and birth defects in humans, according to the environmental group, Beyond Pesticides. Eleven of the 30 are endocrine disrupters, chemicals that interfere with reproductive and other hormones in humans and animals.

Lawns and gardens are sprayed with more pesticides per acre than farmland, with weed killer the most used yard chemical, at 90 million pounds per year. About 78 million U.S. households spray pesticides on their yards each year, according to Beyond Pesticides.

Lawn grasses tend to shed rainwater, so the chemicals run off into surface and groundwater after a downpour, increasing the chance that animals as well as humans will be exposed to them, John Kepner, project director of Beyond Pesticides, told IPS.

"Children are the most vulnerable," he said.

Lawns were originally a flagrant display of European wealth, a sign that a household was rich enough to devote land to grass rather than food.

They remain a status symbol today, says Julian Agyeman, chair of Urban and Environmental Policy and Planning at Tufts University.

"The paradigm is that you should have a lawn at any cost, even if you can't afford it," Agyeman told IPS.

Millions of U.S. poor can't afford homes and lawns - and sometimes not even enough food - and are hired, often at low wages, to mow and spray chemicals on the lawns of the wealthy.

"Adding insult to injury, the poor can't afford a lawn and then end up caring for the lawns of those that can," Agyeman said.

Food Not Lawns, a group with chapters in many U.S. communities, works with people who are ready to completely let go of the lawn as status symbol.

"We call it lawn eradification," Steve Mann, co-founder of Food Not Lawns Kansas City, Missouri, told IPS.

Instead of turf, people are encouraged to grow fruit and nut trees, like pecans, walnuts and almonds, as well as vegetables. Since 2007, 250 people have consulted with the group.

The group is seeking zoning changes from the city so neighbours can sell their extra garden produce, and hire others to help them. They've encountered surprising opposition from local realtors.

"Just think, you could pick up some fresh lettuce and tomatoes for your dinner right down the street. What's wrong with that?" Mann said.

The opportunity for gardens in Kansas City is endless, given the amount of lawn space. "My god, people here have acres of it," Mann said.

Penny Lewis, executive director of the Ecological Landscaping Association, a group of professionals and homeowners, told IPS the lawn paradigm must change.

"Rather than the status symbol being the picture-perfect lawn, it becomes the eco-friendly lawn," she said.