Lawns and Landscaping

Environmental Impact of Conventional Lawn and Landscape Practices

In many regions of the United States, over 50 percent of residential water consumption is used for the irrigation of lawns and gardens. In the United States, rainwater harvesting for domestic use is only just creeping back into the public consciousness in all but the most drought-stricken regions. In addition, building codes in many communities actually make low-tech rainwater harvesting—even for irrigation—illegal or overly complicated by requiring the use of engineered systems. As such, almost all water used for irrigation in suburban America is potable water, meaning that it has been treated and is fit for human consumption. In addition to creating or exacerbating water scarcity issues, the allocation of such a high proportion of potable water to irrigation represents a great inefficiency because the treatment and distribution of potable water require expensive infrastructure that is resource- and energy-intensive to run and maintain.

[Page 266]Lawn care and landscaping are multibillion dollar industries built largely around chemical products and resource-intensive practices aimed at supporting ornamental species that are grown out of their native context. Because of the accessibility of chemical fertilizers and pest control agents, their overuse in domestic applications is rampant. Nitrogen, phosphorus, and potassium are the three main components of most fertilizers. Nitrogen, in the form of water-soluble ammonium nitrate and ammonium sulfate, is typically the largest constituent in inorganic fertilizers. Nitrates become available to plants as soon as water is applied but may leach through the root zone to contaminate groundwater. In contrast, nitrogen from manure and other natural organic sources tends to remain in place but is not biologically available until it is broken down by natural microbial activity in the soil. Nitrogen is the limiting nutrient in most estuarine and marine systems, and unabsorbed ammonium nitrates and sulfates, which are carried to these water bodies in storm water runoff, can cause algal blooms that eventually lead to low dissolved oxygen, with grave consequences for fish and other aquatic organisms. Phosphorus is the limiting nutrient in rivers, lakes, and other freshwater systems, so phosphorus from excessive fertilizing can be similarly detrimental to these habitats. Phosphates—phosphorous combined with oxygen—are immobilized in soil and are thus of little threat to groundwater supplies, although phosphorus from organic sources may be less tightly bound to soil and therefore be more prone to leaching or runoff.

...