Colorful California Landscape: A Water-Friendly Garden
Colorful California Landscape:  A Water-Friendly Garden

Clean Air

Air pollution is a serious health threat that causes asthma, coughing, headaches, respiratory and heart disease, and cancer.  Over 150 million people live in areas where ozone levels violate federal air quality standards; more than 100 million people are impacted when dust and other particulate levels are considered "unhealthy."

When I was in elementary school, I remember being taught that plants make oxygen.  We were told that carbon dioxide (CO2) gets into the air from us exhaling and through other ways such as industrial and car emissions.  Plants through a process called photosynthesis, take CO2 out of the air, absorb the carbon and release oxygen back into the air.  We were told that plants were very important for providing us oxygen and therefore we should have as many plants as possible.

Our level of understanding has now expanded tremendously.  Not only is the release of oxygen into the air important, but it is also very important to capture (sequester) carbon.  The carbon that is in the air is called carbon dioxide (CO2).  We breath in oxygen and breath out CO2.  Therefore, it is not a good thing to be increasing the amount of CO2 in the air.  We need to be finding ways to reduce the amount of CO2 in the air.  This can be done globally by decreasing pollutants such as car emissions.  This can also be done locally - right in your own yard.  You can have a direct impact on the quality of the air by the way you garden and your selection of plants.  Some plants are better than others for sequestering carbon.

Carbon Sequestration

Carbon storage (sequestration) occurs in plants and soils primarily through the natural process of photosynthesis.  Carbon dioxide in the air is taken up through tiny openings in leaves and incorporated as carbon into plants.  Some of this carbon makes its way into soils through the roots and fallen leaves.  Carbon in plants and soils can return to the atmosphere as CO2 when, for example, agricultural tillage practices stir up soils or when biomass (tree trunks, branches, foliage, and roots) burns.  Plants and soils can either capture OR release carbon.

The figure below from the US Environmental Protection Agency (EPA) shows how carbon is captured (sequestered) by biomass (trees and plants) and soil and how it is released back into the air.

One unit of CO2 released from a car's tailpipe has the same effect as one unit of CO2 released from a burning forest.  Likewise, CO2 removed from the atmosphere through planting a tree can have the same benefit as avoiding an equivalent amount of CO2 released from a factory.

Trees sequester ("lock up") CO2 in their roots, trunks, stems and leaves while they grow, and in wood products after they are harvested.  Trees near buildings can reduce heating and air conditioning demands, thereby reducing emissions associated with power production.

Measuring Sequestored Carbon in Your Yard

You can sequestor carbon in your yard and therefore help improve the quality of the air.  This can be done very easily by your choice of plants and how you care for your soil.  We now know that the urban forest (for example, the trees YOU plant) can mitigate the negative health effects of pollution by:

  • Absorbing pollutants like ozone, nitrogen dioxide and sulfur dioxide through leaves
  • Intercepting particulate matter like dust, ash and smoke
  • Releasing oxygen through photosynthesis
  • Lowering air temperatures which reduces the production of ozone
  • Reducing energy use and subsequent pollutant emissions from power plants

Using the National Tree Benefit Calculator, you can see data on the impact of planting just one tree.  Our 6" diameter Coastal Oak reduces atmosphere carbon by 49 pounds per year.  In comparison, a flight from New York to Los Angeles adds 1,400 pounds of CO2 per passenger.

There are ways to measure the amount of carbon in your soil and track how well you are doing with carbon sequestration.  Our landscape architect, Guy Stivers, performed the soil sampling and provided us with the report.  He calculated that our total landscape area is 3,367 square feet (or 3,367 cubic feet of soil).  Since the remodel in June of 2009, our landscape soils now sequester 1.7 pounds of carbon per the top 12" of soil. According to Mr. Stivers, there is a potential for us to increase this from 1.7 to 5 pounds per cubic foot  through our current practics of soil rejunvenation!  Compare this to a typical home landscape which sequestors only 1.0 to 1.2 pounds of carbon per cubic foot.

In 2010 we had an estimated 5,724 pounds (3,367 cu. ft. x 1.7 lbs.) of sequestered carbon in our soils.  This is equivalent to emissions from 295 gallons of gasoline.  That is enough gas to drive a 2008 Toyota Prius 14,750 miles!

See our Living Soils page to see how we are rejuvenating our soil to improve the soil biology and carbon sequestration.
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Stewardship requires the recognition that we are all caretakers of the environment and economy for the benefit of present and future generations. We must balance the impacts of today's decisions with the needs of future generations. - The Minnesota Round Table on Sustainable Development (1998)