“Negative emissions” are a good thing. For the environment and for your health. Scientists don’t always think like marketers when they name these things. We wish that negative emissions sounded more positive. Cause they are.
Negative emissions — the removal of pollutants from the atmosphere — have always been a byproduct of plant life. They are becoming ever more important as we confront global climate change. So important that there are technologies being developed to artificially mimic what plants have been doing all along.
But we’re plant people, and some plants produce negative emissions more efficiently than others. Let’s talk about maximizing our negative emissions, as gardeners.
The Heavy Lifting
Forests have been called the ‘lungs of the earth’, as trees take in carbon dioxide, and pump out oxygen. It is true that all plants absorb carbon dioxide, but trees really are the most effective due to their size and extensive root structures. However, not all trees are created equal. According to the U.S. Department of Energy (DOE), the most effective species at generating negative emissions are trees which grow quickly and live a long time. The challenge is that these two traits are generally mutually exclusive.
Right Tree/Right Place
The answer is to plant the right tree in the right place to ensure that it can live a long, healthy life. The biggest issues to consider are soil quality, site selection, and species selection. Thankfully, researchers at the Vineland Research and Innovation Centre have launched Greening the Canadian Landscape Program (http://www.greeningcanadianlandscape.ca/). Based on their research, the program digs into soil remediation and species selection to make recommendations that maximize the odds of choosing the right tree for your location.
In the Garden
As garden plants go, a native perennial garden is more sustainable by virtually every measure when compared to a planting of annuals. Not only do perennial plants come back every year, which eliminates the energy-intensive process of replacing them, but they have deeper roots. The roots allow them to sequester more carbon in the soil by passing it along to mycorrhizae in exchange for nutrients. The mycorrhizae store the carbon in the soil as glomalin, which forms humus. No, not the kind you dip crackers in, but a soil component that is mostly carbon.
Around the Garden
The larger shrubs and evergreens you place around your yard also play a role in negative emissions, especially for filtering particulate matter that contributes to human health concerns such as asthma.
Royal Horticulture Society (RHS) research in the U.K. found that shrubs such as yew and cotoneaster, are remarkably well suited for filtering particulate pollutants from nearby traffic.
To maximize the benefit, they should be planted as a hedge, separating people from the source of pollution. Regular pruning produces a denser hedge with a greater filtering capacity.
The added benefit of a hedgerow rather than a fence is that it will cool warm air in the summer, provide a habitat for birds and bugs to improve the overall biodiversity in your garden.
In the Home
This is a wonderful time of year to add to your indoor plant collection. The NASA Clean Air Study was a joint project between the National Aeronautics and Space Administration (NASA) and the Associated Landscape Contractors of America (ALCA) in 1989, and it remains the authoritative list for common indoor plants with maximum negative emissions. These plants were identified not only for their ability to absorb carbon dioxide, but also toxins such as benzene, formaldehyde, and ammonia among others. Here are three:
Spider Plant (Chlorophytum Comosum “Vittatum”) Hands-down one of the easiest plants to grow and is just as easy to propagate by the little ‘baby spider-plants’ it produces. Give it bright, indirect sunlight. Removes formaldehyde and xylene.
Dracaena (Draecena sp.) Available in over 40 different varieties, which means you should have no problem finding one you like. Be mindful of pets, however, as dracaena can be harmful if consumed. Removes benzene, formaldehyde, trichloroethylene, and xylene.
Peace Lily (Spathiphyllum sp.) They not only tolerate low light, they also produce a unique flower while purifying the air. Soil should be moist, without overwatering. Removes ammonia, benzene, formaldehyde, and trichloroethylene.
Many of the choices we make have an impact on the environment, from the cars we buy to the food we eat. When making decisions about the plants in our lives, we have the benefit of choosing the greater of benefits. This is the positive magic of negative emissions.
Mark Cullen is an expert gardener, author, broadcaster, tree advocate and holds the Order of Canada. His son Ben is a fourth-generation urban gardener and graduate of University of Guelph and Dalhousie University in Halifax. Follow them at markcullen.com, @markcullengardening, on Facebook and bi-weekly on Global TV’s National Morning Show.