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Carbon Footprint

Evaluating and designing landscapes to reduce global warming


  • Globally, terrestrial plants capture more carbon dioxide (CO2) than all the oceans combined.
  • The amount of carbon sequestered from plants and stored in the soil is twice that in found in the atmosphere
  • In the US, 48 percent of greenhouse gas emissions come from buildings, according to Architecture 2030
  • Changes in landscape design, construction and maintenance can increase the amount of carbon removed from the atmosphere

Concerns about climate change have greatly increased interest in sustainable building design. In the United States, buildings, industry and transportation all contribute to greenhouse gas emissions. To reverse this trend we need to:

  • reduce emissions from our activities
  • find ways to capture CO2 from the atmosphere and store it indefinitely.

Plants capture carbon dioxide through photosynthesis and store it below ground. This organic carbon "sequestered" in the soil is a vital part of the carbon cycle and represents a carbon store that is twice as large as that is in the atmosphere. If we manage the soil and vegetation to maximize carbon sequestration we can have a positive impact on greenhouse gas emissions and climate change. Some ecosystems are very effective at storing carbon below ground. For example, wetlands are excellent carbon stores as the saturated conditions do not allow breakdown of dead plant material. Similarly, grassland soils contain much carbon, because grasses put more biomass below ground than above - this material gets bound up in soil and can be stored there for hundreds of years. Conserving and restoring these landscapes is clearly a high priority task. If we fail to design and manage our landscapes carefully, it can negatively affect global climate change.

The Lady Bird Johnson Wildflower Center and Mithun, a multidisciplinary design practice, (www.mithun.com), have joined forces to expand our current understanding of the construction industry's role in global warming and our ability to effect positive change. The carbon calculator at www.buildcarbonneutral.com generates a uniquely integrated perspective for use in the first phase of design - reviewing the amount of CO2 released not during the lifetime of a completed building, but by its materials and site during the construction process. Although most carbon calculators estimate the amount of carbon dioxide released during the day-to-day operation of buildings, designers have lacked an important tool - one that calculates the total amount of carbon dioxide produced as a direct result of the energy required to manufacture, transport, and assemble construction materials.

Existing calculators also fail to account for landscapes which can hold carbon in vegetation and soil for long periods of time--up to hundreds of years. This first version of the BuildCarbonNeutral calculator incorporates the amount of carbon dioxide sequestered or released as a result of restoration or destruction of natural landscapes, such as prairies and forests. However, future versions will calculate the amount captured by other urban landscapes, such as lawns and gardens. Designers armed with this information can engineer the entire site - building and landscape - to reduce its carbon footprint.

© 2016 Lady Bird Johnson Wildflower Center