What is a residential landscape?

    A typical residential landscape contains basic components: a building or two, a driveway, a sidewalk, a lawn area, a garden -- which are all connected to a neighbor hood with similar sites consisting of similar components.   In relationship to a creekshed or a watershed, one home site is actually quite a small component of that larger landscape, but when we investigate the cumulative effects of how each residential landscape is managed, we start to realize that these small, human tended sites do have an impact on the overall urban ecosystem.  Thus, if we begin to look at our home site micro-ecosystems as parts of a larger pattern in a larger ecosystem, we can investigate how we might better create and manage our home sites so that they complement the larger ecosystems rather than work against them.

    For instance, we can look at our green space -- our lawns.  Before our lawns are lawns, they are many other things.  They are pioneer prairies, they are oak hickory savannas, they are marshlands, or any other number of naturally-occuring ecosystems that succeed throughout time.  However, during the construction process, the ecosystem that our houses, apartments, condominiums were built on, were reinvented.  Maybe some earth moving took place, maybe a few trees (or many) were removed and then replaced with new species, or maybe the area needed to be drained of swamp water before we planted the land with seeds of Kentucky Bluegrass or Perennial rye grass and called it "lawn".  There is not much inherently wrong with the lawn.  In fact, it has provides us with many benefits, such as providing a soft space to play or a neat, trimmed piece of the earth that we can tend and make into our own outdoor space.  However, now that there are more and more houses being created and residential land uses are becoming a high percentage of many urban watersheds, resource and urban planners have started thinking about how this land use effects certain natural systems. People are also beginning to consider alternatives to the "conventional turf" lawn and landscape that offer many aggregate as well as site specific benefits including water quality protection, runoff reduction, and wildlife habitat.  In addition to the green areas on our residential landscapes, people are beginning to reconsider impervious areas, like driveways, paths and sidewalks, and how they can be altered or re-created to reduce the detrimental effects that a highly impervious landscape has on water resources and other ecological functions in the urban ecosystem.
 

    Impervious surfaces are those surfaces in the landscape that do not permit water to infiltrate into the ground.  When rainfall, water from a sprinkler, or suds from washing a car hit these surfaces, they normally run off, untreated, into the stormwater conveyance system that travels directly into a stream.  In the urban landscape, these impervious areas include rooftops, driveways, sidewalk, cement pathways, carports, and streets.  Increased impervious surface area is perhaps the most damaging aspect of urbanization in terms of its impact on the watershed.  When "natural vegetation covers a site, approximately 10% of all of its stormwater flows off of the land, however, this volume is doubled when pavement and buildings cover 10-20% of a site, which is typical for residential development" (Davis, 1994). Encouraging the velocities and volumes of water produced from these areas in a storm event are "efficient" drainage facilities, such as catch basins and pipes through which many urban streams, including Malletts Creek, travel extensively.  All of these conveyors of stormwater combine to increase the flow fluctuations downstream, causing stream bank erosion and disruption habitat, reducing the diversity of aquatic species regardless of water quality.  In addition to conveying more water, then, these surfaces are culprits of stream pollution.  A great quantity of pollutants -- oil, grease, phosphorous, nitrogen, metals and others -- accumulate on impervious surfaces and subsequently are washed into the stream with the stormwater flowing rapidly over pavement.

Most Americans irrigate their lawn excessively.

    Often, these areas can be calculated for and entire watershed, or subwatershed to determine the effective impervious area (EIA) which is the portion of the mapped impervious areas (MIA) within a basin that is directly connected to the drainage collection system.  In a watershed, or creekshed, the EIA is the area that watershed planners have directed much attention to over the past few decades. Many cities and counties across the U.S. are incorporating Geographic Information Systems into their planning activities to assist in making analytically based decisions with watershed modeling techniques.  Incorporating impervious values into these analysis has been an invaluable tool for mitigating the impacts of future land use plans and have helped planners and political decision makers more astute in thinking along "new" environmental boundaries.  To see how impervious surfaces can be calculated from digitizing an aerial photograph at a large scale, click here.  Some planning techniques that are followed in site plan review by the City of Ann Arbor to minimize the impact of impervious surfaces are:

• preserving groundwater recharge areas and permeable soils
• minimizing impervious areas and making efficient use of paved areas
• encouraging permeable building and ground cover materials including open block and brick work, modular pavers, gravel
• using grassed swales, versus paved curb and gutter systems which trap and transport pollutants more effectively
• directing all stormwater discharges to open, grassed areas such as swales and lawns

    Since this land cover is a considerable proportion of our urban landscapes, it is important that we understand how it works with the larger ecosystems of that landscape.  Studies of the typical high-input lawn (those that receive regular treatments of fertilizers, pesticides and irrigation) have shown that these pervious may not be concrete, but they do not function naturally.  The greatest stressor that these areas deal with is the local disturbance of native soils that happens before we even move into a home.  When a residential site is under construction, the site is graded, topsoil is removed, there is often severe erosion and heavy compaction of the soils  by heavy equipment, and depressions where wetlands or swamps once collected water are filled in.  Most soil surveys, therefore, usually rename the soil for urban areas "urban soils" after a site is developed.  These soils are generally highly compacted, low in permeability, and poor in structure and as a result, produce more runoff than before they were disturbed.

    Lawn management factors have also contributed to the poor contribution of lawns to the larger ecosystem. The term "high-input", a category under which more than half of the typical U.S. lawn falls, receives excess irrigation, fertilization and pesticides leading to a detrimental impact on the larger watershed.  Although a direct, causal link between these residential lawn inputs and their effect on stream health has not been quantified, research shows that this "over management" of the lawn by the homeowner or a lawn service creates more runoff that contains higher concentrations of nutrients and pesticides than if these nutrients were only received through "free" sources like from atmospheric deposition.  Researchers in Wisconsin found that phosphorous concentrations in residential yards were higher than any other urban source area.  The impact of pesticides applied to lawns and their link to stream health is currently unresolved as well, but the bioaccumulative effects of these chemicals have been discovered in mass goose deaths in the Midwest in particular.  Although the area of research about the larger impacts of residential pervious areas on watershed health is young, it is clear that alternative lawns have the potential to decrease runoff, decrease pollutant loading, and increase wildlife habitat across the larger watershed landscape and thus, should be further investigated as an opportunity for change.
 
 

The Importance of Involving People: preference and motivation

    If we, as an urban community, decide that rethinking the residential landscape is a good idea for all of the above reasons, then why, when one travels through a residential neighborhood, do lawns -- on old developments and young -- remain the same?  Researches in the fields of environmental education, environmental psychology and landscape architecture have been collaborating in their work to better understand the culture of the urban residential landscape and why it is that people are resistant to changing their yard management behaviors.  As is evident in the literature that although a critical mass of homeowners consider themselves to be "ecologically-mided", these same home owners have not generally converted their piece of the larger ecosystem into native or more ecologically sound landscapes.  Factors that have been cited with regard to this phenomenon have been people's preferences: do these ecological landscapes look good?, and certain barriers to implementation such as the pressure to conform to social norms, the lack of skills, and lack of the right incentives or motivators.

    As an example of how strongly people feel about their lawns, some communities even have ordinances against "natural" landscaping.   Why is this?  Lawns, for decades, have been considered "sources of community pride" (Talbot, et al, 1987) and have been designed for communicating social consensus to the community.  Indeed, the norm of the conventional lawn is a part of U.S. social norms, "the expectation that I represent myself as a citizen in the landscape of my home is etched deeply into popular culture" (Nassauer, 1995), .If these two main barriers -- preference and lack of motivation for implementation -- are standing between high-input, monoculture lawns that harm the watershed and low-input diversely native lawns that can benefit the watershed, what can be offered to offset these barriers and make change possible?
 

Many people enjoy mowing their lawn.  It shows that they care.

    Researchers have investigated the preferences of people in different watersheds across the country in order to determine any universal characteristics that can be applied.  A very important finding has been that people, in general, seem to prefer neat and tidy looking lawns.  This is not suprising due to our previous assertion that people expect others to judge them by the appearance of their lawns.  If a resident wishes to communicate to the passerby and the community that he/she cares about the property and thus, the community at large, it is predictable that the homeowner will conform to some socially accepted standard of "care".  These "cues to care" (Nassauer, 1988a, 1988b, 1992) in the residential landscape include management techniques such as well-mown turf, bright green vegetation, and orderly patterns created with hedging, fencing, and possibly the strategic placement of certain plants.  Since it has been found that in general, many native ecosystems tend to be described as messy-looking, not attractive, and not well-cared for, getting people to implement these more natural lawns has been a challenge.  Knowing that one can frame these "messy" ecosystems, however, to create a neat and cared-for look, may open doors to people's acceptance of these landscape in their neighborhoods and in their own yards.

    So, if we can figure out what people will like on their residential landscapes and what will be socially and culturally acceptable, why has it been difficult to get people to adapt to these alternative behaviors?  Researchers have been looking at how various motivators can be helpful with this roadblock.  Two main categories of motivators exist.  First, and best known, is the extrinsic motivator. These motivators come from outside of the person and can be any form of monetary incentive, reward, recognition, or compensation.  Implementing local ordinances or providing tax breaks for voluntary compliance with a desired community behavior are examples of extrinsic motivators.  These motivators have been studied extensively, especially in trying to understand participation levels in community recycling programs.  Interventions in these studies usually produce positive results, yet the incentives do not seem to result in durable, or lasting, behavior changes.  Research is still needed in this area.  Secondly, intrinsic motivators are becoming an area of great interest in the field of conservation behavior and are gaining recognition as a way to create durable change in a community.  Intrinsic motivators include factors such as an increase in someone's sense of ownership, sense of pride, or a sense that they are contributing to something positive.  Due to their very personal nature, these motivators are less easy to instill and are more difficult to measure.  Interventions that have been found to have some promise include having a person sign a commitment to do that behavior for a certain amount of time, having a person join a group of other practitioners and give periodic feedback to those people to let them know the results of their efforts, and to establish ongoing education so that people's knowledge can be built upon incrementally and give the participant a sense of skill mastery.  To read more about studies on motivators and their effects, please click here!
 

Looking Ahead:

    Change has never been an easy process, but one that goes through many iterations of research, discovery, confusion, rejection, acceptance, adoption, ridicule, adoption, confusion, and so on.  Thus, in this stage of a new research area on the effects of the residential landscape on a watershed ecosystem, we are progressing.  We are still asking questions like:  is turf really all that bad and what dies the best alternative consist of?, and how do pollutant loads in streams change with changes in lawn vegetation and/or lawn stormwater retention?, and how can we get people to think that alternative lawns are healthy for an ailing urban ecosystem and are worthwhile of a behavior modification?  -- but these are important and timely questions and are worth our attention.  As we enter into a new century that predicts only growth in residential land use, it is important that we consider how individual homeowners -- caretakers of a small, but important pattern on the landscape -- can adapt behaviors that instead of compromising the larger ecosystem, can complement the larger ecosystem.
 
 
 
 
 

• Bannerman, R.T., D.W. Owens, R. dodds, and P. Hughes.  1992.  Sources of pollutants in Wisconsin Stormwater, WI DNR, Madison, WI.
• Davis, F., 1994. Non point Source Pollutions and Stormwater Management: Issues and Activities in the Middle Huron River Watershed, Janis A. Bobrin, Washtenaw County Drain Commissioner.
• Nassauer, J.I.  1995.  Messy ecosystems, orderly frames.  Landscape Journal, 14 (2): 161-170.
• Nassauer, J.I.  1988a.  The aesthetics of horticulture:Neatness as a form of care.  HortSci (23): 973-977.
• Nassauer, J.I.  1988b.  Landscape care: Perceptions of local people in landscape ecology and sustainable development. Landscape and Land Use Plannning,(8): 27-41.
• Nassauer, J.I.  1992.  The appearance of ecological systems as a matter of policy.  Landscape Ecology, (6):239-250.
• Pitt, R. 1992.  Small Storm Hydrology.
• Schuler, T. 1995.  The Peculiarities of Perviousness,
• Sutherland, R.. 1995.  Methodology for Estimating the Effective Impervious Area of Urban Watersheds, Watershed Protection Techniques, 2 (1):282-283.
• Talbot, et al. 1987.  The functions of urban nature: Uses and values of different types of urban nature settings.  In R. Kaplan and S. Kaplan (Eds.). The Experience of Nature.  New York: Cambridge University Press.
• Terrene Institute.  1994.  Urbanization and Water Quality, A Guide to Protecting the Urban Environment.  Washington, D.C.
• Rappaport, B. 1993.  Weed Laws.  The John Marshall Law Review, 26(4), 873-930.
• Roberts, E and B. Roberts.  1989.  Lawn and Sports Turf Benefits.  The Lawn Institute.  Pleasant Hill, TN. 31pp.