A recent report from the United Nations Inter-governmental Panel on Climate Change (IPCC) states that “warming of the climate system is unequivocal.” The IPCC reports that the average global temperature is increasing at an alarming rate. In just the past 50 years, Northern Hemisphere temperatures were higher than during any other 50-year period in the last 500 years, perhaps even the past 1,300 years. The IPCC projects that the Earth’s surface temperature could rise by as much as 4°C in the next century.
The primary cause of the warming trend is an increasing concentration of greenhouse gases (GHGs), especially carbon dioxide (CO2) in the atmosphere. The 2007 Assessment Report by the IPCC indicates that GHG emissions increased by 70 percent between 1970 and 2004. These gases are primarily emitted through human behavior, such as the burning of fossil fuels, with nearly half of worldwide CO2 emissions produced by buildings.
Left unchecked, the increase in the Earth’s temperature is expected to have devastating effects. Global warming could cause: melting ice shelves and rising coastal waters, the spread of airborne diseases, extensive species extinction, drought and wildfires, mass human migrations, and wars over shrinking amounts of potable water. According to the IPCC, the projected sea level rise could reach 19-23 inches by the year 2100. There are a range of landscape architecture-related mitigation strategies that, if employed at mass scale, can help reduce GHG emissions.
Site Planning
By properly positioning a building, providing for more open space and planting appropriate vegetation, site planning techniques can significantly reduce CO2 emissions. Site planning is the art and science of arranging the uses of portions of land. Proper site planning can lead to substantial reductions in energy use and sequester sizeable amounts of carbon emissions. Through an assessment of a site's environment, the landscape architect can purposefully site buildings, provide open space, and specify appropriate vegetative density.
In order to develop a site plan that includes comprehensive environmental mitigation solutions, the landscape architect must perform a thorough site investigation. Site reconnaissance includes a careful evaluation of the site’s ecosystem, including solar access, open space, drainage, vegetation, growing potential, and other important environmental characteristics of the site’s region. Information collected through this process provides a guide for subsequent design decisions.
A building should be situated in a way that maximizes the insulating and buffering capabilities of trees. The site plan can orient structures within a site to take advantage of trees and passive solar energy, as well as minimize the impact of development on existing environmental site conditions.
Land-Use
Climate Protection Plan – Land Use, City Government of Cambridge, Massachusetts
Land Use Planning and Climate Change in the West, Lincoln Institute of Land Policy Working Paper
Mainstreaming Adaptation to Climate Change (MACC): Climate Change Impact on Land Use Planning and Coastal Infrastructure, National Oceanic and Atmospheric Administration’s National Ocean Service
Planning and Climate Change Policy Statement and impact assessments, Communities and Local Government, UK Government
Promoting Smart Land Use, UBCM and Province of British Columbia
Sustainable Site Planning
Optimize Site Potential, Whole Building Design Guide
Sustainable Site Design, National Park Service
Sustainable Sites Initiative
Open Spaces
Open green spaces such as parks, meadows, and fields can be a reliable source of carbon sequestration. Open spaces absorb heat and cool an area through evapotranspiration (evaporation and plant transpiration from the land’s surface to the atmosphere). Clustering buildings and structures allows for more open space, and reduces removal of existing vegetation.
How Cities Use Parks for Climate Change Management, American Planning Association
Local Action Plan for Climate Change, Philadelphia City Government, Pennsylvania
Open Space, Room to Breathe, Department of Environmental Conservation, New York State
Plant Selection
Plant selection plays a critical role in creating sustainable sites. Trees absorb CO2, emit oxygen, and provide energy-saving insulation to buildings in the area. The U.S. Department of Energy has shown that a canopy of 100 ten-year-old trees can sequester up to one ton of carbon each year. Trees have a powerful impact when configured near parking lots and other paved spaces. By shading vehicles and pavement, the trees mitigate the urban heat island effect (UHIE). According to a study by the USDA Forest Service, a tree canopy may even absorb vehicle emissions.
Chart of Water Conserving Plants, California Water Company
Climate Smart Greenhouse Gas Emission Reduction Projects, Urban Forest Economic Institute
Green Landscaping: Natural Landscaping for Public Officials, U.S. Environmental Protection Agency
Hardy Plants for Waterwise Landscapes, Washington State University
Reducing Urban Heat Islands: Trees and Vegetation, U.S. Environmental Protection Agency
U.S. Botanic Garden
Water Conservation and Plants, Stopwaste.org
Stormwater Management
Stormwater runoff carries pollutants, overwhelms urban infrastructure, erodes stream channels, and degrades aquatic habitats. In the United States, 772 cities and 40 million people live where storm drainage and sewer systems are combined. When the drainage system is overwhelmed by stormwater, combined wastewater may surface, producing detrimental environmental conditions. Even when working under regular conditions, wastewater feeds into a treatment system that draws upon energy resources.
As climate patterns change, some regions will confront scarce water resources, making it much more critical to provide for the conservation, reuse, and recycling of water. A variety of innovative techniques are available to retain and recycle stormwater, as well as filter water that reaches conventional drainage systems. Porous pavements, in place of impervious surfaces, can increase infiltration of stormwater into the soil. Strategies to create collection points for stormwater runoff should include bioretention areas, stormwater planters and tree boxes. These areas can be designed to be periodically saturated with stormwater, providing another layer of protection against excessive runoff.
Green surfaces can also mitigate the urban heat island effect (UHIE), which is primarily caused by the expanse of hard and reflective surfaces, such as roads, parking lots, and conventional roofs (which absorb solar radiation and re-radiate it as heat). According to the US Environmental Protection Agency, peak utility loads increase 1.5-2.0 percent for every 1°F increase in summertime temperature. Over the past several decades, the UHIE temperature increases have translated to a 3-8 percent increase in community-wide demand for electricity. Just as open green space can alleviate the UHIE, green stormwater technologies such as bio swales, rain gardens, and green roofs can minimize reflective surfaces.
Harvest H20
Low Impact Development Center
Stormwater Knowledge Resources, Water Environment Research Foundation
Green Roofs
Green roofs are increasingly recognized across the nation for their environmental benefits. A green roof is a roof that is either partially or completely covered with plants. By cooling the surface of the roofs, green roofs can help a region mitigate global warming by reducing energy use and GHG emissions. Green roofs mitigate the UHIE effect through the process of evapotranspiration, releasing cooling water into the atmosphere, and lowering ambient temperatures. Plants also convert CO2, water and sunlight into oxygen and glucose through photosynthesis. This cyclical process supplies animals and humans with oxygen and food and reduces the concentration of CO2 in the atmosphere.
Green roofs regulate roof temperatures and protect them from the wide temperature swings that boost energy consumption. With decreased heating and cooling needs, buildings with green roofs use less energy. Situation models found that a typical one-story building with a growing medium of about 3-4 inches would result in a 25 percent reduction in energy consumption for summer cooling.
ASLA Green Roof
Green Roofs for Healthy Cities
Reducing Environmental Heat Islands: Green Roofs, U.S. Environmental Protection Agency
Reducing the Urban Heat Island Effect, City of Chicago Government
Report on the Environmental Benefits and Costs of Green Roof Technology, City of Toronto Government, Canada
Urban Heat Island Mitigation Strategies Can Improve New York City’s Environment: Research on the Impact of Mitigation Strategies, Sustainable South Bronx / Columbia University Earth Institute
Urban Heat Island Mitigation Strategies, U.S. Environmental Protection Agency
Smart Growth Communities
The U.S. contains five percent of the world’s population, but emits one-fifth of global CO2 emissions from fossil fuels. One-third of U.S. GHG emissions come from the transportation sector. Smart growth communities feature more compact, pedestrian- and transit-oriented communities with a mix of residential and commercial uses. In contrast, sparsely populated communities that are isolated from reliable transportation systems and commercial businesses require increased vehicle usage, resulting in significant GHG emissions. The principles of smart growth design can assist in reducing vehicle use, and thus, fossil fuel dependence.
A study by the National Resources Defense Council (NRDC) found that, if all conditions that accompany densely populated communities were present, such as good transit, proximity to shopping, and recreational activities and a walkable environment, families in that community would reduce vehicle use by 25-30 percent. As a result, comprehensive transportation planning must incorporate community-based accessibility strategies. Walkable and bikeable communities inspire residents to use non-motorized transportation significantly more than traditional communities.
Climate Smart Communities, Department of Environmental Conservation, New York State
Smart Communities Network
Smart Communities Network's Smart Growth Resource Library on Climate Change
Complete Streets
A set of design options known as "Complete Streets" can help maximize alternative transportation opportunities, thereby decreasing GHG emissions. Complete Streets strategies provide for the design of efficient sidewalks, crosswalks, wide shoulders, medians, exclusive bus lanes, raised crosswalks, bike lanes, and other transportation corridors that provide safe access for all users. One study showed that each 1 percent of automobile travel replaced by walking or cycling will decrease motor vehicle emissions by 2 to 4 percent.
These smart growth design principles also provide safe and fun opportunities for recreational activities. Creating neighborhood open space for recreational purposes reduces vehicle use when families are searching for entertainment outlets. The open spaces also support plants, trees, and other vegetation that convert CO2 into oxygen, which can assist in mitigating global climate change.
Complete Streets.org
LivableStreets Streets Wiki
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