"Sprawl" is one of the most common terms used to describe the "unrestricted and rapid expansion of development" at the periphery of a community. It maintains a low-density character that neither maximizes land use efficiency nor protects natural resources. Rather, sprawling development encroaches on natural habitats and expends natural resources at a rate much higher than compact development patterns. Whether it be on the outskirts of a large metropolitan area, on the edge of a small rural town, or encroaching into a historically agricultural area, sprawl is characterized by:
Low-Density Development
The density of development typically refers to the number of residential or non-residential units per acre of land. Unless a parcel serves multiple uses, low-density development uses land inefficiently and expends natural resources at a higher rate than mid or high density. For example, one single-family residence on an acre parcel with ornamental landscaping (low-density housing) typically uses much more water than an attached, multi-family unit with little no landscaping (higher-density housing). Concentrating development in a compact form maintains the opportunity to conserve habits and improve the ecological functions of open space, such as wetlands, floodplains, and riparian corridors.
Sprawling development jeopardizes conservation opportunities, and inefficiently accommodates the market for new development. Smart growth would preserve open space while concentrating growth in more compact, walkable, transit-oriented centers, with more housing, business, and recreation closer together. If a large parcel contains a single-family home, agricultural fields, and perhaps a small light industrial use (e.g. a commercial welder's shop) – that is not sprawl. The lot mixes multiple uses on one parcel and its higher-density development contributes to more efficient land use of the area.
Separated Land Uses
Separated land uses are also referred to as single-use zoning districts. When land uses are separated or segmented, grocery stores and other commercial amenities are far away from residential neighborhoods and generate more car travel. The longer a trip distance, the more likely people are to rely on car travel – increasing emissions, traffic congestion, complicating road safety, and reducing the vitality in downtown cores. While mixed-use zoning (i.e., allowing residential, commercial, and/or industrial uses within a single area) can lead to higher-density development and more efficient land use, separated land uses lead to sprawl.
Car-Centric Transportation Design
In areas with low-density development or sprawling development, public transit and active transportation modes become less feasible. When people live further from the places they need to access – across longer distances and separated land uses – car travel is more common.
A community planned for car travel tends to use land less efficiently. Per square foot, single occupancy vehicles or cars take up more space than transit vehicles and active transportation infrastructure. Car-centric transportation design tends to include wide multi-lane roads, faster speed limits, and large surface parking lots. Multi-modal transportation planning supports mobility for vulnerable road users, in addition to the conservation benefits of compact community design.
Car-centric planning de-prioritizes modes of travel that use land more efficiently – like walking, biking or using the bus – which compounds the problem. When the built environment discourages or obstructs more sustainable modes of transportation, people become even more dependent on cars and supportive of sprawling, car-centric development patterns.
Human-environment systems are dynamic, people’s behavior responds to the built environment while planning and development is affected by people’s habits and preferences. Such systems can self-perpetuate in directions that positively or negatively affect the conservation of habitats or natural resources.
The negative effects of sprawling development include:
Expending Natural Resources
A characteristic of sprawl is poor or low land use efficiency. Inefficient land use fails to maximise the benefit of natural resources consumed on site and land area occupied by the uses. space and to minimize wastage and other negative impacts.
For example, spread-out or sprawling development uses more water, both in terms of daily use per capita but also due to decreased groundwater absorption and higher runoff. Low-density, dispersed developments on large lots have “higher onsite water use… than more compact developments do.” In fact, increasing housing density from two units per acre to five units per acre has been shown to cut the daily per capita water demand in half. In addition to lowering per-household water consumption, smaller residential lot sizes and clustering of smaller homes on lots reduce the size of lawns and the water consumption needed to maintain them.
In addition to using more water, sprawling development can lead to more water loss and contamination through run-off. When undisturbed land, such as forests and meadows, are developed into buildings, lawns, and roads, it impairs the land’s ecosystem function and disturbs watershed health. Development compacts soil and removes topsoil – leading to erosion, a loss of soil biodiversity, a reduction in the capacity for the soil to act as a carbon sink, and a loss of water permeability. Studies find that highly compacted lawns generate almost as much run-off as paved surfaces.
Inefficient land use expends more natural resources like water through higher household consumption, loss of soil absorption and groundwater recharging, and greater run-off into watersheds. This is a significant way sprawl can affect the long-term sustainability of communities with increasingly limited water resources.
Encroaching on Wildlife Habitats
When a community develops outwardly, human activities – and impacts – encroach on the natural areas that are key to the health of wildlife habitats. Sprawl reduces natural habitats and disrupts ecosystems, putting the healthy and vitality of wild species at real risk. In addition to wildlife habitat encroachment, inefficient land use can create significant soil and water impacts. Development often stresses ecosystems and wildlife through noise, air, and water pollution.
Sprawling development and car-centric transportation systems create more impervious cover – human-made surfaces that don’t absorb rainfall, such as roads, buildings, driveways, parking lots, or pools– which accumulate pollutants that are then washed off into watershed systems during storms, in high-volume run-off rather than gradual soil absorption. This can exacerbate drought and flooding conditions as well. EPA studies find that low-density development produces more run-off and affects the watershed more than high-density development. For example, one acre developed at low-density with one house produces almost four times more run-off per unit in a year than if that acre was developed at higher density with eight houses on it.
Habitat reduction, riverbank erosion, and decreases in water quality and stream biodiversity all affect the ecosystems and water resources necessary for both animals and humans.
Compromising People’s Health
In addition to impacts on open spaces and natural resources, segmented and separated land uses can also have ripple effects on the local economy and residents’ health and well-being. When land uses are separated into segmented zoning districts, where housing developments may not be within walkable or bikeable distances from commercial areas, people must travel further – often in cars – to get to school, work, shopping, and entertainment. Did you know that people are more likely to connect with their community – i.e. by engaging with a small local business, or interact with another human being – if they are walking and not driving? Car travel over longer distances also intensifies traffic congestion and generates air pollution, degrading air quality and compromising roadway safety.
The more spread out and isolated a community is, the more sedentary its residents often are, which can contribute to health impacts such as rising obesity rates and cardiovascular risks. Long distances between land uses or destinations, plus time spent driving, is also found to negatively impact social connectedness and cohesion. Car-centric transportation planning creates barriers for those unable to drive, including delays seeking healthcare due to lack of transportation. Increased access to multi-use public spaces, mixed-use and walkable neighborhoods, affordable and reliable public transportation, and natural environments and open spaces have been found to improve social cohesion and engagement, a sense of community, and feelings of place and belonging – all of which are key to the mental health of a community.
Sprawl has major impacts related to the physical qualities of environments, as well as people’s lived experience in the community. From increased GHG emissions that cause climate change to air, water, and noise pollution, sprawling development encourages behaviors – or creates a human-environment system – that negatively impacts the quality of life for individuals and communities as a whole.
The Community Planning program at the Land Trust is committed to combating sprawl and employing smart land use planning for a sustainable, livable future. Increasing density and mixed-use zoning can improve land use efficiency. Managing and minimizing additional spread-out, low-density development can be facilitated by improving public transit systems and pedestrian and bike infrastructure, so we can protect the open spaces and natural resources that Wood River Valley residents so value.