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Lessons from a Sugar Maple

Paul Kando

We, humans, seem to be the only species on Earth incapable of living within our natural energy budget. We use more energy than any other species, yet remain less than satisfied. It was in 1988 that NASA’s James Hansen testified in Congress about the Earth overheating because of the atmospheric buildup of human-caused greenhouse gases, Addressing this problem would have been easier back then, yet not much was done. Last November 196 nations have finally agreed in Paris to limit our collective carbon emissions and keep the global average temperature within 2ºC above the preindustrial level. We have passed that benchmark briefly last week.

Bucket on a tree
Tapping a Maple tree at Goranson Farm
photo credit: Lincoln Academy

How do other living things manage to thrive, without austerity measures to keep them on their energy budget? Perhaps we could learn something from the rest of nature.

Take sugar maples. The leaves absorb radiated solar energy in tiny “energy factories” within their cells, called chloroplasts . Using chlorophyll and other pigments arrayed to capture light, plants convert the sun's energy into storable form. This photosynthesis combines molecules of carbon dioxide from the air and water from the soil and airborne vapor into sugar molecules. A mature sugar maple may have 500 pounds of green leaves with a surface area of several hundred square meters, and produces some 2 metric tons of sugar each year.

Some of that sugar is glucose, the most important sugar in human metabolism. It is a simple sugar or monosaccharide, so called because it has one of the smallest molecules with the characteristics of its class of carbohydrates. Glucose is one of the primary molecules that serve as energy banks for plants and animals. It is found in the sap of plants, and in the animal bloodstream where it is known as "blood sugar".

The normal concentration of glucose in human blood is about 0.1%, but it is much higher in persons suffering from diabetes. As a primary energy source in the body, glucose requires no digestion and is often provided, in lieu of food, intravenously to persons in hospitals. Glucose is sometimes called dextrose. Corn syrup is mostly dextrose.

Other plant sugars are more complex. Cellulose provides structure, such as the wood of trees. Among animals only ruminants can digest cellulose, with help from a second stomach full of microorganisms. Starches are sugar-like energy sources for living cells, including those of humans. Glycogen is a starch-like sugar, found primarily in animal muscles where it serves as a ready source of stored energy.

Sugars are carbohydrates — molecular chains of carbon with hydroxyl (-OH) groups attached. They are relatives of the hydrocarbons of oil, coal and natural gas – fossils with the oxygen squeezed out.

Here is a lesson to ponder: A tree is a complex system, yet it has no hierarchic management layer, only system-wide collaboration. Each leaf is an autonomous energy factory and each of the tree’s millions of cells carries the tree’s complete genetic code. Some management structure! There is much more to emulate but let this suffice for today.