7 million birds each year, a topic that was central to the novel Silent Spring by the conservationist Rachel Carson. The use of lawn chemicals made its first appearance in the 18th century through the introduction of “English garden” fads. These types of lawns put precise hedging, clean cut grass, and extravagant plants on display. Following the initial introduction of lawn chemicals, they have still been continually used throughout North America. Because many of the turf-grass species in North America are not native to our ecosystems, they require extensive maintenance. According to the United States Geological Survey, 99% of the urban water samples that were tested contained one or more types of pesticides. In addition to water contamination, chemicals are making their way into houses which can lead to chronic exposure. Currently, standards for pesticide management practices have been put in place through the Food Quality Protection Act. Decreasing environmental impact In the United States, lawn heights are generally maintained by gasoline-powered lawnmowers, which contribute to urban smog during the summer months. The EPA found, in some urban areas, up to 5% of smog was due to small gasoline engines made before 1997, such as are typically used on lawnmowers. Since 1997, the EPA has mandated emissions controls on newer engines in an effort to reduce smog. A 2010 study seemed to show lawn care inputs were balanced by the carbon sequestration benefits of lawns, and they may not be contributors to anthropogenic global warming. Lawns with high maintenance (mowing, irrigation, and leaf blowing) and high fertilization rates have a net emission of carbon dioxide and nitrous oxide that have large global warming potential. Lawns that are fertilized, irrigated, and mowed weekly have a lower species diversity. Replacing turf grass with low-maintenance groundcovers or employing a variety of low-maintenance perennials, trees and shrubs can be a good alternative to traditional lawn spaces, especially in hard-to-grow or hard-to-mow areas, as it can reduce maintenance requirements, associated pollution and offers higher aesthetic and wildlife value. Non-productive space Lawns take up space that could otherwise be used more productively, such as for urban agriculture or home gardening. This is the case in many cities and suburbs in the United States, where open or unused spaces are "not generally a result of a positive decision to leave room for some use, but rather is an expression of a pastoral aesthetic norm that prizes spacious