Most people I talk to think that logging a mature forest has to start with clear-cutting. As a result, my friends feel that the few remaining areas of old growth in the US and Canada are to be held sacrosanct. When I point out that old growth is carbon-neutral, they are first puzzled and then, when the implications have sunk in, they are angry. They are puzzled because "carbon-neutral" is redolent of PR-speak by multinational corporations.
"Carbon-neutral" has gotten a bad name because companies like Dell, Google, HSBC, ING Group, PepsiCo, Sky, Tesco, Toronto-Dominion Bank, Asos, and Bank of Montreal have at various times declared themselves carbon-neutral. Carbon-neutrality is a concept that arose in connection with the Kyoto protocol and means that the organization concerned offsets their CO2 emissions by activities that absorb carbon from the atmosphere or by buying such activities from other organizations that, as one may hope, have the required net negative carbon emissions and have not also sold it someone else. "Carbon-neutral" is a term that reeks of PR shenanigans and it's mean of me to tar the sacred cause of preserving Old Growth with that brush.
Yet, although the term is rarely used in this context, it is a fact that a tract of old growth is carbon-neutral. The very definition of old growth is that this forest has reached its maximum biomass. Sure, its magnificent canopy absorbs CO2 from the atmosphere, lots of it. But, by definition, its biomass does not increase. Therefore, it produces the same amount of CO2 as it aborbs by photosynthesis. This may seem surprising, but it becomes obvious when you realize that the great mass of decaying trunks and the thick layer of humus is not increasing in mass (total biomass remains constant, remember?) which means that the carbon in the humus and dead trunks is turned into CO2 at the same rate as its capture by photosynthesis.
If you are looking for opportunities to diminish the decrease the disastrously high carbon dioxide content of the atmosphere (400 parts per million, more than it has been in the past half million years), then don't look to old growth.
Clear-cutting old growth is of course not an answer either. It messes up the streams, causes erosion, leaves us with an eyesore for decades, and it continues the carbon-dioxide production while it has eliminated the carbon-dioxide absorption of the canopy.
In spite of what commercial corporations seem to think, there are other methods of logging than clear-cutting. An alternative was developed in Germany under the name "Dauerwald" in the first half of the last century. Currently it is known as CCF, "continuous cover forestry". The term covers a variety of management systems that have in common that the trees have a variety of ages with the oldest trees between a hundred and two hundred years old.
The age distribution should be such that it can be maintained over the centuries. Without human intervention biomass would increase so that the forest as a whole captures more carbon than it produces. Logging prevents increase of biomass. By selective logging one can aim at an age distribution that maximizes carbon capture. The carbon captured from the atmosphere is removed in the form of timber. One way of slowing the return of this carbon to the atmosphere is to replace as much as possible concrete in construction by lumber. This has the added advantage that making cement releases large amounts of CO2.
But what about diversity, both in plant and in animal life? An old growth forest with all its decaying trunks, standing and fallen, accommodates a great variety of animal life. A rigorous application of the CCF idea would result in the elimination of this. Thus the true art of forestry is to leave just enough dead trees so as to support a high degree of diversity in animal and plant life.
A carbon-capturing forest can be as beautiful as any.