Quite frankly, this field of inquiry is so complicated that it takes a lifetime to begin to understand it, and I still can't claim that I understand it fully after almost 40 years in the field.
Non-declining even flow is a human construct. Forest plans are based on some of the most sophisticated mathematical calculations that you could imagine. At its simplest, you think of it as a rule that allows you to cut a year's growth produced by your entire forest, plus the amount of 'inventory' in your entire forest, divided by the number of years in the chosen rotation period.
Growth + Inventory/(rotation period) = amount you can cut forever, non declining.
The length of the rotation period is determined by other factors, and is usually the point at which one more year's growth is less than the average annual growth so far. This is because trees grow faster and faster for a while, but then they slow down. For a while each year's growth is more than the previous year's growth and more than the average so far. Then the annual growth peaks and starts to decline. When the annual growth falls below the accumulated average, that's the year you should rotate your crop. If you don't you'll get less and less growth every year from then on, and eventually the whole thing will start negative growth and if you wait too long it will go to pieces, although you'll probably be dead by then.
Every year you recalculate: growth + inventory, divided by rotation length. Growth occurs over the entire forest, but it is much faster in the new forests that you started after you cut the diseased old forests. Each year's growth is added to the inventory, but the formula basically remains the same. You never run out because by the time you get to the last acres in your forest the first acres you cut decades ago are ready again, just like a crop of corn.
Departure from non-declining flow is a controversial strategy that results in higher cut now and a higher total yield after adding up all the annual harvests over a fairly long period of usually at least a few decades, but it only works where there is a 'surplus' of senescent forests, what some people call old growth.
In a managed forest, or a healthy one, Departure from Non-Declining Even Flow makes no sense and has no beneficial effect, unless you just want to convert your forest land to another use, like housing developments or something.
You have look at old growth as a commodity, not a subjectively defined value, in order to understand it. If you saw "Ferngully, the Last Rain Forest" and make your judgments based on that, you can't possibly how understand how departure from non-declining even flow works.
The idea of a 'surplus' of old growth might seem offensive to some people, but in this context it is simply a mathematical concept. From a purely emotional point of view, there is no such thing as a surplus of old growth, but in the objective mathematical sense, there is.
Departure from non-declining even flow is a strategy to increase the total yield added up over decades. It short, you cut more now (departure), knowing that you have to cut less later (decline), because the total added up over the decades (and the annual rate that you eventually stabilize at) is greater than if you had not 'departed' from the concept of non-declining even flow.
Biologically, you are capturing the wood that would be lost to disease, rot, and old age by cutting old diseased forests faster now, knowing that you can't keep it up forever even though the new forests are growing four times faster than the old ones you cut.
Let's say you inherit a fortune that is drawing 1% interest per year. Your benefactor set up rules that say you can take out 2% of the balance every year because he expects you to live fifty years and he wants the fortune to last as long as you do. Every year you take out 2%, and whatever is left continues to grow at 1%. But your benefactor forgot about inflation, and pretty soon instead of growing at 1% per year your fortune is losing 1%, and every year it gets worse. You still take out 2%, but you get poorer and poorer every year.
Then you get the idea that if you take out 5% every year instead of 2%, you can reinvest the extra 3% in the stock market and protect yourself from inflation. If you do that, you would depart from the non-declining even flow rules set up for your inheritance, and the original account would be drained in only twenty years instead of fifty. But that's OK, because you are earning 5% in the stock market by reinvesting, and beating inflation to boot, so you'll NEVER run out of money.
That's a gross over simplification, but the concept is basically the same.
Selective harvesting has its place, but selective harvesting in some forests is risky because if you cut the trees that have value the ones that are left can't use the extra space you have given them the way a healthy forest could if you selectively cut in it. You end up with a very expensive operation, and no residual value in the remaining trees because they are misshapen, sick or dying.
In order to make a judgment about whether clearcuts are healthy or not, you have to look at them 20, 30, 40 and more years later. They all look bad for the first ten years or so, but after that, unless a severe mistake was made, the new forest should be growing faster and faster. I can show you some clearcuts that are growing so fast they are exceeding our highest expectations. They look nothing like a clearcut now; they look like a forest.
Clearcutting is nothing more than harvesting a crop that takes generations to grow, and restarting a new crop immediately afterward.
Almost anybody can find horror stories where they turned out badly, and the ones I found are the principal reason I decided to get into the finer points of forestry so I could help make things go better.
However, there's nothing intrinsically bad about clearcutting, and in many places it is the BEST forest regeneration system available. Most of the so-called ill effects are the result of other factors like erosion on poorly designed roads, not clearcutting itself.
I operated under rules that required much justification for creating a clearcut larger than 40 acres, so it didn't happen very often. I also had to consider every other forest value, and there are a great many, before deciding how to harvest a given stand of trees. Wildlife, birdlife, plantlife, watershed values, and so forth. Every single value was factored in to my recommendations, and I'm proud of the way I went about it, along with my many fine professional colleagues.
Private forest companies can make their clearcuts as large as they want, and they often do that because it's much easier. They get a lot more yield overall, because that is their singular objective. However, it looks like hell to most people, including me. They have the right to do it, in the same sense that you have the right to mow your lawn, or not.
Loggers and forest people are some of the finest people around. Anybody who thinks he knows what hard work is can't compare to a logger in full swing. |
