The value of the American lawn

Parwinder Grewal, Ph.D.
Urban Landscape Ecology Program, The Ohio State University, Wooster, OH 44691, USA

Introduction
Lawns are a central part of landscapes throughout North America, and have emerged as the dominant land use in rapidly expanding urbanized areas (Robbins and Birkenholtz, 2003).  Lawns were cultivated in ancient China and Persia, and historians agree that the precursor to the modern American lawn was the "grassy meades" that surrounded British estates.  Originally kept short by browsing sheep, as the city parks of Auckland, New Zealand are today, these formal lawns were later maintained by gardeners using scythes.  American aristocrats copied this "manor house" aesthetic, but the invention of the push mower in 1830 placed lawn maintenance within the reach of average people, and lawns spread quickly in the American landscape.  As early as 1880, state agricultural colleges began breeding improved grass cultivars for lawns.  The next major change began during World War II, when chemical research led to the development of the first selective herbicides.  Together, the development of synthetic fertilizers and the rise of the suburban dream among the growing middle-class, led to the rapid growth of the lawn care industry. 

    Although the original lawns in the British estates were composed of a diverse variety of plants, today's preferred American lawns contain only one or 2 to 3 grass species.  The simultaneous development of the golf course and lawn care industries have led to the perfection of monospecific, weed-free lawns which are referred to as turfgrass lawns.  The word turfgrass originated from the Sanskrit word, darbha, meaning tuft of grass.  Turfgrass lawns are easy to establish from seed or from the readily available sod, making turfgrass the cheapest ground cover to install. 

    Lawns of turfgrass provide a low-cost surface ideal for many outdoor sports and recreational activities.  Lawns are used for playing sports including archery, badminton, baseball, cricket, croquet, field hockey, football, golf, hiking, horse racing, horse-shoes, lawn bowling, lawn tennis, lacrosse, polo, rugby, shooing, skiing, soccer, softball, track and field, and volleyball.  Both the enjoyment and the benefits of improved physical and mental health derived from recreation and leisure activities on lawns of turfgrass are vital to the contemporary society, especially in densely populated urban areas.  Homeowners derive benefits of outdoor recreation, physical exercise and therapeutic relaxation from the care and grooming of lawns.  Apart from these obvious uses, the American lawn contributes hugely to the national economy and provides numerous benefits to the environment, human health, and the society that are difficult to quantify.  These benefits of the American lawn are explored in this article.   

Promoting economic development
The modern lawn care industry in the U.S.A. has grown rapidly in the past four decades.  It now contributes substantially to the national economy with numerous employment opportunities.  According a survey by the Professional Lawn Care Association of America, more than 26.4 million households spent $17.4 billion on professional lawn care, landscape, and tree care services in 1999.  The total annual revenue for turfgrass industry which includes the maintenance of home lawns, sports fields, golf courses, and cemeteries, is estimated at astounding $45
billion. 

    A survey of middle-class, midwestern home-owning families (n = 325) living in suburban and rural communities reveals an almost unanimous (98%) consensus on the value of a lawn as the primary component of the residential landscape (M. Quigley, personal communication).  Regardless of recognized cost, constant maintenance, and striving for a "perfect lawn" look, lawns are considered both "part of nature" and essential to the value of the property.  A 1991 study estimated that an attractive landscape can increase the value of a home by an average of 7.5 percent, and reduces the time on the market by 5-6 weeks.  It has also been reported that the landscape investments are recovered fully, and sometimes doubled, by the increased home values (The Wall Street Journal).  Good lawn and landscaping increases community appeal.  Parks and streets with lawns and trees have been found to be second only to education in resident's perceived value of municipal services.  Well-landscaped grounds and places for taking walks are among the most important factors considered when individuals choose a place to live. 

    Cities can be very dismal without green lawns in parks, besides boulevards, and surrounding homes, schools, businesses, and the workplace.  Lawns are the unifying element amidst the miscellany of building architecture.  Unmanaged landscapes can result in loss of productivity and increase in susceptibility to anxieties and mental diseases.  Landscaped lawns in business districts convey the "we-care" message leading to lowering of perceived job stress and improvements in worker productivity.  Employees with an outside view of plants and green space experience less job pressure and greater job satisfaction than workers viewing man-made objects or having no outside view (Kaplan and Kaplan, 1989).  They also report fewer headaches and other ailments than workers without the view.  Psychologists have found that plants and green spaces provide a sense of rest that allows workers with access to plants and nature to be more productive (Kaplan and Kaplan, 1989).  Greening of business districts increases community pride and positive perception of an area, drawing customers to the businesses.   

Enhancing and protecting the environment
Lawns protect and significantly improve our natural resources including the soil, water and the air.  The many ways in which lawns protect and enhance the earth's natural resources are described below.

Lawns mitigate global warming by capturing carbon dioxide
Lawns have significant mitigating effect on global warming due to their tremendous capacity to sequester (store) atmospheric carbon.  In fact, a recent report from Colorado indicates that carbon sequestration in turf soil occurs at a rate comparable to the land that is placed in the Conservation Reserve Program in the USA (Qian and Follett, 2002).  In this report, the scientists analyzed historic soil data from many turfgrass sites.  The data show that carbon sequestration continued for up to 31 years in golf course fairways after their initial establishment.  
    Well maintained lawns capture more carbon dioxide than the poorly maintained lawns with bare ground patches.  Plants capture atmospheric carbon dioxide to make their food (carbohydrates) with the help of the sunlight.  These carbohydrates are stored in plant tissues including leaves, stems, and roots.  This carbon along with nitrogen (in the form of proteins) stored in plant parts serves as the main source of food for numerous soil microorganisms and invertebrates that perform important functions such as nutrient release for plant growth and fighting plant diseases.  To a considerable extent, returning the grass clippings to the soil actually reduces the amount of fertilizer needed for the lawn.  
    Capturing excess carbon dioxide from the air is one of the main arguments used for saving the tropical "rain forest".  The homeowners, sports turf mangers, and commercial turfgrass area owners with well-maintained lawns are contributing their share to the reduction in global warming by capturing and storing the excess carbon dioxide from the environment into the soil.

Lawns reduce urban heat island effect through cooling
"Heat islands" occurs when developed urban areas have significantly higher average temperatures than the surrounding countryside.  On hot summer days, urban air can be 2-10oF hotter than the surrounding rural areas.  Heat islands form as vegetation is replaced by roads (asphalt and concrete), buildings, and other structures necessary to accommodate growing populations.  These surfaces absorb rather than reflect, the sun's heat, causing surface temperatures and overall ambient temperatures to rise.  One of the most extreme examples of this phenomenon is the city of Los Angeles, where the average high temperature in summer has increased by nearly one degree per decade.  Among other things, this has contributed to the city's legendary smog problem, since ozone forms more readily at higher temperatures. 

Heat island effects should not be confused with global warming.  Heat islands and global warming are two distinct phenomena, and the presence of elevated urban temperatures does not imply that the global climate is changing.  Indeed, increased air temperatures associated with heat islands are primarily a result of urban paving, not global warming.  However, hotter local temperatures can contribute to global climate change by increasing energy demand.  As temperatures increase due to the heat island effect, more electricity is required for indoor air conditioning and other cooling purposes.  As fossil fuels are burned to produce this cooling energy, power plant pollution, which includes ozone precursors and greenhouse gasses, increases.  Thus, local temperature increases resulting from the heat island effect can have an indirect impact on global climate.

Heat islands raise urban temperatures in the summertime, adversely affecting human health and the environment.  Additionally, heat islands reduce livability by decreasing urban ventilation, increasing air pollution levels, and increasing the risk of heat-related illness and death.  In fact, heat islands increase ground-level ozone pollution.  Ozone is an odorless, colorless gas that has been referred to as good or bad depending on its location in the atmosphere.  The good ozone occurs naturally in the stratosphere, approximately 4-15 miles above the earth's surface, where it forms a protective layer that shields us from harmful ultra-violet radiation.  Stratospheric ozone forms what is known as the ozone layer.  The bad ozone exists in the troposphere, close to the earth's surface.  It is formed by a chemical reaction between nitrogen oxides and volatile organic compounds in the presence of heat and sunlight.  Ground-level ozone is a harmful pollutant and is the main constituent of atmospheric smog.  Because heat and sunlight increase the formation of ground-level ozone and its precursor compounds, the heat island effect can increase ozone pollution to levels that threaten human health; especially that of children, the elderly, asthmatics, and other vulnerable groups.  
What do lawns have to do with the heat island effect?  All vegetation, including trees, shrubs, and grasses produce natural cooling effects through a process called evapotranspiration.  In evapotranspiration, water transpires from a leaf's surface and evaporates into the atmosphere, reducing ambient temperature.  Although trees and shrubs are generally appreciated for producing significant cooling due to their visible shade effects, lawns substantially contribute to this phenomenon.  A study has shown that the average size front lawns of eight homes have the cooling effect of about 70 tons of air conditioning, while the average home has an air-conditioner with only 3 or 4 ton capacity (Johns and Beard, 1985).  For this reason, the lawns are referred to as the natural air-conditioners.
 
Thus, well-maintained lawns have a dual effect on the urban heat island effect.  First the lawns reduce the negative impacts of the heat islands by lowering the actual ambient temperature.  Second, by reducing energy demand for air conditioning, the cooling effect of lawns reduces the production of climate altering emissions which exacerbate concerns about global warming.

Lawns protect, restore, and improve soil
Soil is a basic part of any ecosystem and is practically non-renewable.  It takes virtually millions of years to build biologically and chemically active topsoil that can support plant growth.  Therefore, protection of the topsoil must be a prime objective for any landscape activity.  Turfgrass can protect this invaluable resource by controlling erosion caused by wind and water run-off.  The dense leaves, thatch, and roots of turfgrass provide an excellent cover that tremendously reduces soil erosion, even on severe slopes.  With well-established and well-maintained lawns, almost no soil will be lost even in heavy rainstorms.  To the surrounding environment, this means less mud and dust.  On a larger viewpoint, it means conservation of topsoil and less sediment pollution of our rivers and lakes.  A study concluded that a 30 minutes storm producing a 76 mm per hour rainfall could cause a soil loss of 223 kg per hectare from bare ground compared to only 10-60 kg from a healthy turfgrass cover (Gross et al., 1991). 

How does turfgrass reduces soil erosion?  A healthy turfgass lawn absorbs rainfall six times more effectively than a wheat field and four times better than a hay field.  Turfgrass stabilizes the soil surface with its numerous roots and shoots.  A hectare of turfgrass will typically possess 75 million to >20 billion shoots (Beard, 1973; Lush, 1990).  Regular mowing of turfgrass increases shoots compared to an ungrazed grassland.  Thus, turfgrass offers a cost-effective means of controlling water and wind erosion of soil and is called the "bandage for the earth".   
  
 Turfgrasses substantially contribute to soil quality.  Soil scientists agree that the best soils are ones that contain organic matter in various states, from green organic matter to mineralized compounds.  Organic matter helps separate clay particles, improves water infiltration rates, helps retain essential nutrients, and helps supports the microbes essential to cycling nutrients and maintaining habitats necessary to support beneficial organisms.  Turfgrasses add significant amounts of organic matter to soils over time through root, stolon and rhizome formation and decay.  Grass clippings also reach soils through the actions of microbes and invertebrates, especially earthworms.   Due to the tremendous amount of organic matter additions from the turnover of roots and other plant tissues, turfgrass improves and restores soils rapidly.  In fact a high proportion of the world's most fertile agricultural soils have developed under a vegetative cover of grasses (Gould, 1968).  Turfgrass roots may grow from 0.5 to 3 m deep depending upon turfgrass species, extent of mowing, and soil conditions.  It has been reported that the root biomass of a Kentucky bluegrass lawn is in the range of 11,000 to 16,000 kg per hectare (Boeker, 1974; Falk, 1976).  In the upper 150 mm of the soil there are about 122,000 roots and 6.1 x 107 root hairs per liter of soil, with a combined length of >74 km and a surface area of about 2.6 m2 (Dittmer, 1938).  A study has estimated that the annual root system turnover rate is about 42% for a lawn (Falk, 1976).  Considering this estimate, 6761 kg of root biomass would be turned over into the soil per hectare each year (Beard and Green, 1994).  This estimate is low because it does not account for root secretions, death and decay of fine roots and root hairs, and consumption of roots by soil animals.  The amount of root biomass annually produced and turned over into the soil, or root net productivity, for a defoliated grassland is higher than the amount reported for ungrazed prairie ecosystems.  This is why accelerated soil restoration of environmentally damaged areas by planting perennial grasses is employed effectively on highly eroded rural landscapes, burned-over lands, garbage dumps, mining operations, and steep timber harvest areas.       

Lawns enhance ground water recharge
Ground water is the principal resource of fresh water for many homes and municipalities and represents much of the potential future water supply.  It is also the source of much of the water used for irrigation and is a major contributor to flow in many streams and rivers.  Underground aquifers (or ground water) supply drinking water to about 50% of the US population.  In fact, drinking water is a scarce resource.  Shortages of water plaque hundreds of cities worldwide especially during the summer months, resulting in bans on the use of water for irrigation of lawns and landscapes.  Sub-optimal ground water recharge can cause drying of underground aquifers and reduce summer base flows, leaving streams shallower and warmer thus threatening the aquatic life.  Therefore, capturing of storm water run-off and ground water recharge should be a goal of new developments, existing developments, and production agriculture.  In this regard, turfgrass offers the most cost-effective means of storm water capture and ground water recharge.  Studies in Maryland have shown that surface-water runoff losses from a cultivated tobacco site averaged 6.7 mm per ha per 4 weeks during the growing season (May - September); whereas, the surface-water runoff loss from perennial turfgrass averaged only 0.6 mm per ha per 4 weeks (Gross et al., 1990; 1991).  

The exceptional water absorption capacity of turfgrass is mainly due to its ability to trap and hold runoff, enabling more water infiltrating through the soil-turfgrass ecosystem.  A mowed turfgrass lawn possesses a leaf and stem biomass ranging from 1,000 to 30,000 kg per ha, depending on the grass species, season, and cultural regime (Lush, 1990).  This biomass is composed of a matrix of fine-textured stems and narrow leaves with numerous, random open spaces.  This canopy matrix is highly porous, allowing water infiltration, and a resistance to lateral surface water flow.  The water absorption capacity of turfgrass lawns is further enhanced by the activity of earthworms supported by this organic matter rich ecosystem.  Populations in the range of 200-300 earthworms per m2 are common in lawns (Potter, 1998).  Earthworm activity increases the amount of macropore space within the soil that results in high soil water infiltration rates and water-retention capacity.   
  
However, in new developments, topsoil is often removed and soil beneath is compacted, significantly reducing water infiltration.  Impervious surfaces like roads, pavements, and roofs detain no water at all.  This leads to extremely fast run-off during storms, which erodes surface soil and stream banks and carries urban pollutants into streams.  Therefore, in new developments, the retention and reuse of native topsoil, reduction of the construction footprint, minimizing of soil compaction, and restoration of soil infiltration capacity should be the goal.  One way to restore water infiltration capacity of the native soil in urbanized areas is to restore soils by incorporating compost and other organic matter.  About 2-4 inches of compost tilled into the upper 8-12 inches of soil, depending upon soil types can provide effective restoration of many soil functions including the water infiltration.  One study in Washington demonstrated up to 50% reduction in winter storm runoff from plots of glacial till soil amended with compost, as compared to non-amended till soil.  Tilling in compost when re-landscaping and top-dressing turfgrass with compost can retrofit existing landscapes, restoring their water infiltration capacity.

Lawns accelerate organic chemical decomposition
Lawn soil food web offers one of the most active biological system for the degradation or sequestering of pollutants such as heavy metals, hydrocarbons from oil, grease and fuels, waste oils, paint thinners, preservatives, and solvents in the run-off water and sediment from impervious surfaces (Schuyler, 1987).  Lawn soils support diverse community of microbes and non-pest invertebrates.  The bacterial population in the moist litter, grass, clippings, and thatch of a lawn commonly is in the order of 109/cm2 of litter surface (Clark and Paul, 1970).  A New Jersey Kentucky bluegrass/red fescue lawn supported 83 invertebrate taxa including insects, mites, nematodes, annelids, and gastropods (Streu, 1973).  Dozens of beneficial species of rove beetles, ground beetles, ants, spiders, collembolans, and earthworms, are found in lawn soils (Potter, 1998).  The average microbial biomass pool in grasslands is 1090 kg carbon per ha compared to only 700 in arable crops and 850 in forest systems (Smith and Paul, 1990).  We have found that microbial biomass in lawn soils exceed 1140 kg carbon per ha in the Wayne County, Ohio (Singh and Grewal, unpublished data).  Our preliminary studies reveal that lawn soil food web is also highly resilient to the impact of chemical inputs such as pesticides and fertilizers (Cheng and Grewal, unpublished).    
 
Lawns reduce air pollution
Lawns improve air quality by stabilizing dust (soil erosion through wind) emanating from nearby roads, agricultural, and other non-turfed areas and removing carbon dioxide, smoke, and other air pollutants including allergy-related pollens (Beard and Green, 1994).  A study also suggests that tall fescue a common lawn grass can capture even carbon monoxide, a major pollutant from the vehicle emission (Gladon et al., 1993).  This area deserves more attention from the scientific community.    

Lawns abate noise
Noise pollution is an environmental factor that has gained much attention in recent years.  Studies on the acoustic properties of plants indicate that turfgrass is much more effective at absorbing sound than the trees which mainly act as scatters of sound.  It has been found that the absorption coefficient, i.e., the fraction of incident sound which is totally absorbed at each single reflection, was superior for turfgrass than a heavy carpet on a felt pad (Robinette, 1972). 

Lawns reduce glare
The reflection from the paved surfaces can cause uncomfortable levels of glare on a bright sunny day. Buildings, concrete pavements, and glass reflect more light than turfgrass.  The surface characteristics of turfgrass reduce multidirectional light reflection that reduces glare. While turfgrass is usually effective at reducing secondary glare, trees and shrubs are effective at reducing primary glare directly from the source (Robinette, 1972).  However, studies on the effectiveness of integrated landscapes of lawns, shrubs, and trees on the management of uncomfortable levels of glare are not yet available.   


Improving human health and public safety
 
Lawns improve physical and mental health
Physical exercise and mental diversion from work place stress are the two most often cited reasons for people's engagement in lawn care activities.  Mowing grass with a push-type, reel lawn mower and routine gardening tasks such as shoveling, weeding, and rototilling can measure up to the exertion rates of jogging, bicycling or aerobics.  Studies have shown that one hour of weeding can burn up to 300 calories - the same as walking or bicycling at a moderate pace.  Engaging in care and grooming of lawns and landscapes also releases tension and frustration of every day life.

    In fact, the idea of well-mowed and tidy lawn is now well entrenched in our psychology and have profound effect on mental and physical health of the urban population.  A study conducted in Peoria, Illinois on a random sample of people from suburban communities designed to measure the effects of untended lawns on their homeowners revealed that homeowners that were not allowed to maintain their lawns experienced many symptoms of psychological abnormality, including depression, suicidal tendencies, child abuse and other forms of violence, anorexia, bulimia, societal withdrawal, and poor sexual function, as well as such physical symptoms as increased ulcer formation and blood pressure, and more susceptibility to cancer (Smeldgas, 1999). 

    Well-managed lawns and landscapes improve mental health through therapeutic impact.  According to the E. O. Wilson's "biophilia" hypothesis, humans are innately attracted to other living organisms, thus bond with nature (Wilson, 1984).  Thus contact with nature and well-managed lawns and landscapes have healing effect.  Restorative gardens offer an environment for people who are sick, injured, and under stress to recover and regain vigor and confidence.  Such landscapes are currently used by long-term care facilities in treatment of Alzheimer and AIDS patients in Ireland and England (Ousset et al., 1998; Milligan et al., 2004).  A study has shown that hospital patients whose rooms overlooked vegetation recovered faster and required less pain medication than did patients without a view of nature (Ulrich, 1984; 1986).  In fact, horticulture is considered therapeutic.
 
Lawns promote neighborhood cohesion
The well-maintained wide-open, American boulevards and residential lawns that lack fences promote a sense of neighborhood cohesion that is usually lacking in many parts of the world.  These highly maintained lawns and landscapes can be both aesthetically pleasing and inviting to the visitors.  The sense of pride taken by homeowners in displaying their lawn management skills creates an environment for neighborliness.  In fact, this display ethic creates a social pressure to "fit in" and encourages the adoption of lawn management practices that produce tidy, green, and weed-free lawns.  Community pride and interest is often derived from quality sports fields and parks.  Recreation and leisure activities on lawns are vital to the contemporary society, especially in densely populated urban areas. 

    In fact, a unique phenomenon often occurs related to lawns - residents will mow their neighbor's lawns during periods that the neighbor is on vacation or ill.  Neighbors often see and talk to each other while undertaking their weekly lawn maintenance tasks.

Lawns reduce crime
Well-maintained lawns and landscapes reduce crime.  In a California study, landscape areas were relatively graffiti-free, while open, non-landscaped areas were graffiti-targets.  Well-planned and maintained landscapes are seen as safer than unmaintained plantings.  Lawns in particular provide a sense of security by enhancing visibility zones that discourage unwanted intruders and vandals. 

Lawns reduce physical injuries to players
Lawns provide a unique, low-cost cushioning effect that reduces injuries to the players when compared with nonturfed soils, particularly in the more active contact sports like football, rugby, and soccer.  Surface hardness measurements illustrate the substantial benefit of a properly managed, quality turf in reducing the hardness of sports fields (Beard and Green, 1994).  The resiliency of turf lawns helps to protect the legs while running or walking.  Artificial turf installed in many stadiums has been replaced with natural turfgrass due to injuries and player preference. 

Lawns reduce fire hazard
Green, growing lawns serve as effective fire breaks that significantly reduce fire hazard (Beard and Green, 1994).  This attribute is especially important for homes and buildings adjacent to extensive woodlands or brush areas and also in dry arid environments.  

Lawns reduce noxious pests and human disease exposure
Close mowed residential lawns reduce the invasion of unwanted animals into the house.  In fact, it is often suggested that the idea of close-mowed lawn around the house was invented to reduce the invasion of undesired small animals such as rodents, snakes, chiggers, ticks, and mosquitoes that seek heaven in taller grasses, flowers, and shrubs. 

    Allergy related pollens can cause human discomfort and potentially serious health concerns to susceptible individuals.  Dense lawns typically are void of the many weedy species that often produce allergy-related pollens.   Furthermore, lawns that are mowed regularly tend to remain vegetative with minimal floral development, and thus have reduced pollen production.  The incidence of human diseases, particularly those facilitated by vectors such as insects and ticks, is substantially reduced in well-mowed lawns.  For example, the tick that spreads the Lyme disease is commonly found in unmowed tall grass and woodland-shrub habitats as opposed to well-mowed turfgrass lawns. 

Conclusions and Contemporary issues
Turfgrass lawns have become the dominant land use in most urbanized areas in the United States.  Residential lawns are considered both a "part of nature" and essential for the value of the property.  Lawn maintenance has become a big business and the lawn care industry has grown to an impressive $17 billion in annual revenues providing numerous employment opportunities.  Besides their contribution to the national economy, the lawns provide many additional benefits to the society both locally and globally.  Lawns protect and enhance our natural resources including water, soil, and the air.  Well-maintained lawns mitigate the effects of global warming and heat islands, protect, restore, and build topsoil, enhance ground water recharge, purify the air and water via removing pollutants and solvents, and abate noise and glare.  The lawns promote neighborhood cohesion, improve physical and mental health of people, reduce crime, enhance public safety, and increase business productivity, and are a source of community pride.  In fact lawns remedy many of the problems arising from paving of the cities and villages.

    The maintenance of turfgrass lawns at the current aesthetic standards is however costly.  The high dependence on the use of synthetic fertilizers, pesticides, and petrochemicals is of concern to the contemporary society.  Another concern is the potential health and non-target effects of chemical pesticides which is often associated with their overuse and miss use.  This can be rectified through proper public education.  Low-input and safer alternatives for lawn management are needed. 

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