Can you mitigate climate change while you garden?? (part 1)

By: Jessica Lehr, Director, Pollinate Collingwood

Climate change is a hot topic these days, and we can easily become overwhelmed with how to play a part in reducing our impact.  

Did you know that gardening with native plants helps lower our carbon footprint, also known as our carbon dioxide (CO2) emissions into the atmosphere?  CO2 is one of several greenhouse gases that contribute to climate change and is humanity’s greatest contribution to the greenhouse effect.  Other important greenhouse gases are methane, ozone, nitrous oxide, and water vapour. 

The International Panel on Climate Change’s (IPCC) most recent report acknowledges the value of both forests and grasslands in carbon sequestration.  Sequestration is the ability to put away or hold something, which in this case is carbon.  Carbon sequestration is considered to be an ecosystem service as it is a service provided by our environment that gives back to other living things and the functioning of the planet. In forests, carbon sequestration can be more easily seen aboveground, as carbon is held in the trunks of trees. For native grasslands, this sequestration is through the plant root systems, which often grow several feet down into the soil, capturing and holding onto carbon deep underground.  

Recognizing this, the US recently created the Rangelands Soil Carbon Management Offsets Program, which offers financial incentives for ranchers to increase the amount of carbon dioxide that is absorbed by their lands.  To do this, ranchers must leave areas of their ranchland in their natural state.  Within the rangelands of the Western US, it is estimated that land with native plants can absorb 190 million tons of CO2 per year!  We can convert this as a ton of CO2 is equal to 2,204.6 pounds and a pound of CO2 measures 8.7 cubic feet (246.3L). Considering that a medium-sized chest freezer measures about 8-9 cubic feet, that means that these native rangelands are sequestering over 418 billion chest freezers worth of carbon dioxide each year! 

That sounds like a lot, but what does that really mean? Well, it might be easier if we directly compare two grass species. An acre of turfgrass (usually mainly Kentucky bluegrass, Poa pratensis), seen on golf courses, some parks, and on private property lawns, holds about 3,600 pounds of greenhouse gas per year while switchgrass (Panicum virgatum), a native grass found on rangelands, holds 10,000 pounds!  

But this is just one grass species – Here in Ontario, we have many native grasses that can be planted, including Big Bluestem, Little Bluestem, Indian Grass, Switchgrass, Canada wild rye, and Prairie dropseed. To find out more about different native Ontario grasses, check out https://www.inournature.ca/native-grasses-for-ontario-gardens.  

Many native flowering plants outside of the grass family also have longer roots than the cultivated plants.  Some examples of native plants in Central Ontario with extensive root systems include Pale purple coneflower, Black-eyed Susan, Wild bergamot, Evening primrose, New England aster, and Stiff goldenrod.  These long root systems are an adaptation that allows for plants to draw from water deep in the ground through drought periods. In addition, these deep root systems also help prevent soil erosion and aid in water filtration into the soil.   

Science Alert!  To understand how roots play such an important role in carbon sequestration, we must look into the role of the microscopic arbuscular mycorrhizal fungi that cover the root systems of these plants and their extended hyphae that reach out into the soil.

There can be hundreds of miles of fungal hyphae in a pound of soil.  While stands of hyphae may only live for a few days, sloughed off glomalin can last in the soil. Sloughed off glomalin forms clumps of soil granules called aggregates which add structure to soil and keep other stored soil carbon from escaping.

In addition to drawing attention to the value of forests and grasslands for carbon sequestration, the IPCC document discussed the value of conserving green (land)  and blue (aquatic) spaces in cities.  Through the protection of these natural spaces, a community is also protecting places of carbon storage and sequestration, as well as protecting biodiversity.   Biodiversity is the variety of life found within a region, including animals, insects, plants, fungi, and microorganisms.  A greater diversity of plants provides a strong foundation for a larger variety of insects, including our essential native pollinators and other animals. In turn, the complex series of interactions between the living organisms ensure resilient functioning of the ecosystem and the continuation of the ecosystem services (such as oxygen production, water filtration, and soil formation, amongst many others)…   

2020-2030 has been declared the “Decade of Restoration” by the United Nations (UN), which recognizes the value of green assets.  Restoration can include the rewilding of roadsides, marginal areas, and sections of parkland, as well as on personal property.  We can all play a part in this!  

Want a deeper dive into this? Check out these resources:

• A gallon of gas = 20 pounds of CO₂!
• Glomalin: Hiding Place for a Third of the World’s Stored Soil Carbon
• IPCC: Sixth Assessment Report – Climate Change 2022: Mitigation of Climate Change
• Meet the Magical Glomalin: Perhaps the most important glue in the world!
• The Carbon Footprint of a Lawn
• Carbon-Offset Cowboys Let Their Grass Grow
• Tallgrass Prairie and Carbon Sequestration