First, let me make very clear that to reduce the burning of fossil fuels and reduce your carbon footprint are paramount steps for slowing the rise of carbon dioxide in the atmosphere. Less greenhouse gasses will lessen the ravages of Climate Change.  My point is we should also be greatly concerned with a greater greenhouse gas.

The bad news is that carbon in the atmosphere has risen in hockey-stick fashion.  At first it was gradual and then at a relatively recent inflection point climbed rapidly to 400 parts per million carbon dioxide in the atmosphere.  The incontrovertible truth is that 400 parts per million is 0.04% of greenhouse gasses and 95% of greenhouse gasses is water vapor.

The reasons for all eyes on global carbon dioxide levels when concerned about climate change are that is easily measured, makes a most compelling graph, and has a simple elegance that publishers of scientific journals approve of. It’s neat and informative, like using the Dow Jones to follow the stock market.

Measuring water vapor is not as straight forward. Much as I like to deploy a sling psychrometer, one must track air masses, the motion of fronts and jet streams, distinguish onshore breezes from offshore, and measure other nearly chaotic events – manage many data points all at once. Besides, Charles David Keeling coming down from Mauna Loa with a hockey-stick scribed into the atmospheric CO2 graph is the stuff of legends.

Turns out, the green parts of your yard and the green places of your neighborhood can do a lot to reverse climate change, to restore the more favorable environmental conditions of yesteryear.  Your yard may be small, as mine is in Somerville.  Given the super-sized effects of water vapor in the climate change debacle, how you treat your land is not insignificant.

For starters, just say no to technological fixes for your lawn. Let it go natural. This will save you money. However, you’ll get push-back, “your lawn is going to die,” because this approach is not as good for the economy as is buying bags of fertilizer five times a year.

Nitrogen, the nutrient of fertilizers, is recommended by the fertilizer industry because it will cause the grass to green up quickly.  Like feeding children sugar for breakfast, the grass perks up and then needs more fertilizer.  With food on the surface the roots need not push down through the ground.  Plants spread thin on the surface exposing bare ground. Soil compacts and dies leaving open real estate for weeds.

A fertilized lawn needs much water because the ground absorbs little and nearly all runs off to pollute waterways and wetlands. Grass blades are thin and make easy eating for pests.  Lawn care companies offer “overseeding”, the spreading of more chemically treated seeds to “reinvigorate” your lawn.  Never mind that the application of fertilizer, synthetic or organic, caused the lawn to need reinvigorating in the first place.  Technology disrupts nature and we pay the consequences.

Blaming lawns for polluting and using lots of water is like blaming a car for hitting something.  The fault lies not in the grass or automobile; fault is found in how people managed.   We can restore healthy lawns by modifying our lawn care practices.  Instead of the recommended multiple applications of fertilizer of one pound per thousand square feet of lawn (any more will burn the lawn), apply one application of 100% slow-release fertilizer, one-half pound per thousand square feet of lawn.

Slow-release fertilizer is composed of round pellets of nitrogen each with a coating that feeds the grass over six months or more.  Most brands include nutrients for soil microbes. When the weather is cold or dry, the pellets stay intact.  When the grass is growing and in need of nutrients slow-release is there.  With slow-release there is no run off to pollute our waterways and cause harmful algal blooms.

A healthy lawn sends down roots, opening the soil to fungi, bacteria, microbes, and very small animals. We misunderstand plants when we think, as taught in science class, of seeds sprouting, plants growing with photosynthesis, followed by death and only then returning nutrients to the soil. That oversimplification leaves us ignorant to what is actually going on. Nature is a complicated system of moving parts.

Plants evolved in water. They were only able to come ashore after having established symbiotic relationship with fungi and bacteria. The fungi protected plants roots from desiccation enabling it to live away from water.  Bacteria fixed nitrogen and prepared minerals for the plant.  Recently seeds have been found to contain the genetic material of species-specific bacteria and fungi.  When the seed sprouts these bacteria and fungi go to work on both outside the plant and internally touching each plant cell with individual fungal hyphae. The boundaries between the three types of organisms are very permeable and chemical communications rampant across vast mycorrhizae networks.

Another myth of grass lawns held people who believe they have been informed by science is that lawns are monocultures, a single plant species.  Clearly such individuals do not practice the science of observing, questioning, recording and communicating. (Science is more an iterative process of discovery than a gospel of knowledge.) To call a lawn a monoculture is like calling a forest a monoculture because it’s just trees. Look at a square yard of lawn and you will find three to eight species of grass and nearly as many other plants including clover.

Beneath the turf of grass lawns is a world even less understood than the ocean, another place where few have looked beneath the surface.  The region of soil in the vicinity of plant roots is known as the rhizosphere. Here plants are the only primary producers feeding entire ecosystems of enormous diversity of life forms.

When grass takes 3.67 tons of carbon dioxide out of the atmosphere through the process of photosynthesis, it will use some for metabolism, some to produce plant fiber, and push out as root exudate 1 ton of liquid carbon.  As a result, the healthy turf you see above ground, all those blades of plant carbon may look significant.  Yet, in the soil below lies thirty times the carbon as above.

A healthy grass lawn can put down as much as one inch of soil a year. That is about 300 tons of carbon an acre. To do so, grass photosynthesizes more than 1,000 tons of CO2 out the air.

It gets better.  Stepping on grass, having a picnic, mowing or grazing grass stimulates it to grow. Plant cells send chemical signals along mycorrhizae highways of bundled hyphae.  Picked up by distant bacteria that specialize in the nutrient or mineral needed, the nutrient or mineral is sent back to the plant cell.  Powering the exchange is more liquid carbon pumped out by the grass plant. The soil thickens and grass plants become healthier, more robust, more drought tolerant, resistant to pests and denser, preventing weeds to take hold.

When grass plants add a cubic yard of black soil, 4.4 gallons of water is drawn in from air. Earthworm move about the soil opening passages for air as they eat through the soil. Swallowed dirt enters worm guts to be ground with small rocks adding minerals to the mash. This is passed to a lower gut where bacteria go to work further refining minerals and increasing nutrition.  What comes out is called vermicast and is much sought after by gardeners. Earthworms add to it a sticky substance that increases nutrient retention, improves soil texture and adds water retention to the soil.  Comparing adjacent fields with and without worms, the field with worms was found to absorb water 35 times greater.

A healthy lawn protects the land from the loss of water by evaporation.  An extreme example was recorded at a farm in Texas experiencing a heat dome effect.  The air temperature was 105 F. A tilled field exposing bare dirt had a soil surface temperature of 155 F. Here there was much radiant solar heat and much drying. In an adjacent field, soil beneath a cover crop was a relatively cool 77 F.

Green areas and particularly lawns with deep soils retain water during extreme weather events to protect homes from flooding and erosion.  Conversely, increases in impervious surfaces cause more run off, loss of water from the watershed that scours and scores out sediments. Impervious surfaces heat up quickly, warming the air and causing it to draw more moisture through evaporation, drying the landscape.

Research indicates that increases in impervious surfaces, the pumping of ground water and the flushing waste water (combined sewer overflows) into the sea is responsible for about 25% of sea level rise.  Don’t just fret over melting ice in Greenland, increase carbon capture and improve the green water cycle at home.

If you have a patio with an impervious surface, consider replacing it with lawn grass.  This will cool where you are sitting when its hot out. Retain more water during heavy rains.  Perhaps better protect your home while taking more carbon out of the atmosphere and storing carbon as productive soil supporting local wildlife. Go green.

Modifying your lawn care practices will do more to reduce greenhouse gasses and abate climate change than will exchanging a gas-powered car for a hybrid.  These yard actions will save you money, improve the quality of your yard, if not your family’s life, and also improve conditions for us all living on planet Earth.