"Trees are America's Renewable Resource"

... say the bumper stickers.

New England
Forests are impressive


Yes, at 500 watts/acre

... that's 1/8 watt per sq. meter
Forests in southern and central New England were almost entirely non-existent at the turn of the century, because they had been cleared for farming.  But it is hard to farm the rocky New England soil.  Starting with the completion of the Erie Canal, continuing with railroads in the 1800s, and finally with trucking on highways in the 1900s, transportation to the fertile Ohio River valley made it increasingly hard for New England farms to compete.

Thus began an unplanned --- and on-going --- reforestation.  (That's a polite way of saying that the trees are taking over.)

As impressive as the forests are, the rate at which the forests turn sunlight into wood energy averages (around the clock) a mere 500 watts per acre.  That is, an acre of land (about 44,000 square feet, 4400 square meters) of prime forest land stores solar energy at the same rate as five couch-potatoes burn calories just by being there.

SI equivalence: about 1/8 watt per square meter, or close to 0.07% efficiency at converting average sunlight (160 watts per square meter in southern New England) into wood energy.

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