So what exactly is the "presettlement equilibrium" to which some folks want the forests of the western U.S. returned?  And why would they prefer the equilibrium of a bygone era to that of the present?  Indeed, why would one want equilibrium at all?

Taking the first question first, Kloor cites Wallace Covington of Northern Arizona University in Flagstaff, Arizona as saying that the pine forests of that part of the country supported an average of 57 trees per hectare back in 1876, when the first Europeans settled in the area, but that they now support as many as 2100 trees per hectare in some places.  Which brings up a couple of other questions.  How did the forests grow so populous?  And is that bad?

Some answers to the first of this second set of questions are grazing, fire suppression and even global warming, the first two of which are clearly man-induced but the last of which is not-so-easily thus categorized.  As for the second more value-oriented inquiry, greater quantities of forest materials are normally prized.  In this case, however, the tightly packed stands of Arizona trees are reported by Kloor to be prone to disease and catastrophic wildfires.  But this negative consequence could readily be turned into a positive one by selective logging, which would benefit man and nature alike.  And this conclusion pretty much answers the second of our original three questions.  Why would one prefer the equilibrium of 1876, when the new one would be so much more beneficial to all concerned if managed intelligently?

As for wanting equilibrium at all, one who seeks such a situation desires that which never was and never will be; for transition is the name of the game in everything involving biology.  Nothing that lives is ever static.  It is either growing or dying, progressing or retrogressing, on one time scale or another.  And we would be much better served, as would the biosphere, if we would acknowledge that fact and learn to live with it.

So what is the ultimate driving force behind the great explosion of forest growth that has been occurring for the past two centuries or so on every continent of the globe where trees are found?  In his seminal publication "CO2 and the Biosphere: The Incredible Legacy of the Industrial Revolution," Idso (1995) identifies three ubiquitous influences, in addition to various local factors, that are likely responsible: global warming, enhanced atmospheric nitrogen deposition, and the rising CO2 content of earth's atmosphere.

The last two of these three promoters of forest growth are clearly of anthropogenic origin, while the first is often argued to be as well.  Hence, on this accidental or unanticipated level, man is proving to be a boon to the planet's trees and the wealth of animal life for which they provide habitat.  Acting intelligently, as by selective logging, for example, humanity can also be a positive factor.  Clearly, however, the consequences of some of man's activities have not been so beneficial, such as the clear-cutting of forests that leads to permanent habitat destruction; and it is activities such as this latter example that need to be curtailed, not those that help.

History provides many valuable lessons.  It shows us our successes and failures; and fortunate we are that the unanticipated effects of anthropogenic CO2 emissions have been of immense benefit to plant life, and trees in particular.  So why fight nature?  If one of the consequences of our industrial activities has been the aerial fertilization of the world's forests, let's give thanks and not rant and rave and "yearn" for the biological paucity of the past.  As Dixy Lee Ray used to say, "I lived in the good old days; and they weren't that good."  Now it seems that the trees themselves are echoing her sentiments.  We would do well to listen to them.