The grass growing outside our windows may hold the largest overlooked means to meeting our goal of net zero carbon emissions. Treated right, lawns will pick up where the revised climate bill that Gov. Baker recently approved leaves off. Lawns carpet our landscape. We’ve got plenty, more than 2,000 square miles in Massachusetts. Let’s put them to work, naturally.
Lawns are blamed for polluting and requiring too much water. Actually, we are at fault for spreading quick-release fertilizer and toxic chemicals. Don’t be fooled by the directions printed on bags instructing us to spread one pound per thousand square feet of lawn on Easter, Memorial Day, Fourth of July, Labor Day and in the fall.
You don’t need a specialist looking under the turf to recommend what your lawn needs. It’s not an automobile in need of a tune up. Lawns don’t work like that. Just leaving the grass clippings is about the same amount of nitrogen in a year as one application of fertilizer.
When fertilizer is applied, grass “greens up quick.” The grass blades are thin. Roots sprawl on the surface in need of frequent watering. Plants are spread apart. The bare spots in between, called “sunspills,” bake, compact, and the soil dies to become dirt. Such soils can only be penetrated by the most pioneering of weeds. Pests find easy munching here for the forage lacks fiber. The recommended response is to “overseed” and apply toxic chemicals. One application of Roundup will kill about a quarter of the good mycorrhizal fungal network in the soil.
There’s always the option of spreading one-half pound of 100% slow-release fertilizer in the spring. This consists of small coated pellets that grass takes up slowly over many weeks. There is no polluting runoff to feed harmful algal blooms.
The use of fertilizer on lawns was banned in Falmouth after 16 striped bass fish were found dead on a shore of Little Pond. Seven years later, the lawns of Falmouth appear no less healthy than the lawns of nearby towns where liberal applications of fertilizers are the norm (at yours and lawn critters expense).
The roots of healthy grass reach deep into the soil. Liquid carbon, as carbohydrates, is pumped out as root exudate to build soil. For every ton of carbon put into the ground, grass plants pull from the air 3.67 tons of carbon dioxide. An acre of one-inch deep new soil requires about 1,000 tons of carbon dioxide from the air. With photosynthesis some carbon goes to metabolism, some to plant biomass, and a surprising amount goes to creating soil. Meanwhile, bacteria fix all the nitrogen needed. They provide other nutrients in usable forms that are moved across vast mycorrhizae networks.
A grass cell in need of something is in touch with individual strands of fungal hyphae. A signal, an enzyme, is put into the network and picked up by only the bacteria that specializes in that particular nutrient. Walking on the grass results in more carbon dioxide pulled from the air.
A healthy lawn can build an inch of soil in a year. Intricate natural processes are involved in turning dirt and compost into humus. Humus binds carbon for thousands of years and forms the heart and bone of healthy soils. Worms and ants move about, aerating the soil. They and smaller organisms including nematodes, mites, springtails, and tardigrades break up, ingest, grind, mix and excrete materials that improve the soil. The sticky substance that holds it all together, glomalin made by worms, was only recently discovered by Sara F. Wright.
With more soil, more water is held. With every cubic yard of new soil, 4.4 gallons of water is added. Gained from water vapor in the air. Soil four inches deep with a good tunneling worm population, will hold seven inches of rainfall.
Adding an inch of soil beneath the lawn every year or two is significantly beneficial, not only for the flowers, trees and wildlife. Lawns with healthy soils retain water and arrest runoff to protect property from erosion and flood damage. Replacing impervious surfaces, for example, a patio with grass, increases both water retention and carbon capture out of the air. Research indicates with more soil protected by plants and less discharging of water into sewers and storm drains, sea level rise could be reduced by 25%.
Volunteer to help green lawns build healthy soils by not spreading quick-release fertilizer and not applying harmful chemicals. You will be taking steps to restore the land, stop harmful algal blooms in waterways, retain more water in place-based water cycles, achieve net zero carbon emissions and reverse climate change. By acting in concert, together at no expense, we may enjoy healthier yards, greener neighborhoods, more verdant landscapes, and a cooler Commonwealth.
Rob Moir is the president and executive director of Ocean River Institute.