GDP does not include production that is not monetized, or transacted in a market. Therefore, nature's ecological services such as cool air from large trees, or breathable air from forests, are not included in GDP. Actually, a dead tree is worth more in GDP than a living one, since it is sold as lumber and paper products.

What could we do to measure the importance of ecological services so that we don't cut all the trees who provide us with clean and cool air?