to contribute to global warming. (Sustainable organic techniques have been shown to help reduce global warming.) A hectare of lawn in Nashville, Tennessee, produces greenhouse gases equivalent to 697 to 2,443 kg of carbon dioxide a year. The higher figure is equivalent to a flight more than halfway around the world. Lawn mowing is one element of lawn culture that causes a great amount of emissions. Water conservation Maintaining a green lawn sometimes requires large amounts of water. While natural rainfall is usually sufficient to maintain a lawn's health in the temperate British Isles- the birthplace of the concept of the lawn- in times of drought hosepipe bans may be implemented by the water suppliers. Conversely, exportation of the lawn ideal to more arid regions (e.g. U.S. Southwest and Australia) strains water supply systems when water supplies are already scarce. This necessitates upgrades to larger, more environmentally invasive equipment to deal with increased demand due to lawn watering. Grass typically goes dormant during periods of cold or heat outside of its preferred temperature ranges; dormancy reduces the grasses' water demand. Most grasses typically recover quite well from a drought, but many property owners become concerned about the brown appearance and increase watering during the summer months. Water in Australia observed 1995 data that up to 90% of the water used in Canberra during summer drought periods was used for watering lawns. In the United States, 50 to 70% of residential water is used for landscaping, with most used to water lawns. A 2005 NASA study estimated conservatively of irrigated lawn in the US, three times the area of irrigated corn. That translates to about of drinking-quality fresh water per person per day is required to keep up United States' lawn surface area. Chemicals An increased concern from the general public over pesticide and fertilizer use and their associated health risks, combined with the implementation of the legislation, such as the US Food Quality Protection Act, has resulted in the reduced presence of synthetic chemicals, namely pesticides, in urban landscapes such as lawns in the late 20th century. Many of these concerns over the safety and environmental impact of some of the synthetic fertilizers and pesticides has led to their ban by the United States Environmental Protection Agency and many local governments. The use of pesticides and other chemicals to care for lawns has also led to the death of nearly