The big picture of forest health
Oftentimes, we fail to see the bigger picture regarding forest health and condition. Despite some challenging issues, the forests of Michigan and much of the nation are in reasonably good shape.
Recently, I was asked to collaborate with a journalist to describe how our nation’s forests are in decline. I suppose that the journalist, like many, had been influenced by media coverage of such phenomena as huge western fires, mountain pine beetle mortality and the increase in exotic species invasions. I did not agree with her premise of decline and forwarded some internet links about a few key research-based publications.
Knowing a bit about our forest history will help appreciate where we are today. The U.S. eastern forests took a major hit during the nation’s expansion and settlement period, with dramatic losses in both forest area and volume. That history was colorful and rich with traditional lore and iconic tales.
The forests of the western USA were far less affected in terms of acreage.
Since the curve bottomed-out in the early 1900s, the forests have rebounded somewhat, especially in our northern forests. Acreages, volumes, tree diameters and other measures have steadily increased since then.
Specific regions will vary from national trends. Within many states, including Michigan, the balance between growth, removals and mortality will vary across the landscape. However, it is sometimes useful to look away from the magnifying glass and take a look around at the bigger picture.
Projections from the U.S. Forest Service, and others, over the next several decades are for slower increases in area and volume. Eventually, the tables are expected to turn and the forest area is predicted to decline, mostly due to human encroachment. The reversal of the forest growth trend over a century’s time will have a number of important implications; socially, environmentally and economically.
In deliberating forest conditions, here are a few facts and trends:
- About three-fourths of the U.S. forest lies in the eastern states.
- Partial harvesting methods are, by far, the most common.
- Clearcutting is least often employed in northern forests.
- The major timber producing region is the South, followed by the North.
- Less than 1.5 percent of forest acres are harvested each year, around ten million acres.
- There are about 750 million acres of forest in the United States, or 33 percent of our land cover and about two-thirds of the area occupied by forest in 1600.
- Americans use between 3 and 5 pounds of wood per day.
- The majority of forest land is privately-owned and most of the harvest comes from private forest.
- Forest growth far exceeds removals, although the U.S. is a net wood importer.
- Volumes per acre are higher on public forest than private forest.
- Average volume per acre on private forest is about 17.5 cords.
- There are about 300 billion trees in the U.S.
- The steepest increase of forest volume was in the 1960s and 1970s.
- Over the last decade, growth and mortality have increased, while removals have decreased.
- Western forests have higher proportions of large trees.
The role of forests in the carbon equation has attracted increasing interest over the past decade or so. Forests annually accumulate massive amounts of carbon. Forest products, especially solid wood products also hold large amounts of carbon. Together, forests and forest products store enough carbon to offset 12-19 percent of the U.S. annual fossil fuel carbon emissions. Managed forests absorb more carbon than unmanaged forests. The use of wood for raw material and energy has great environmental advantages over the use of other raw materials and fossil fuels.
While the young journalist’s view of our forest resource seemed premature, there are, indeed, some substantial threats to the future benefits of forests. Why might century-old forest trends begin to reverse?
The answers are based on collateral trends and generally all linked to each other.
Private land will be undergoing one of the largest ownership change phases in our national history. Much of the forest will be broken into smaller parcels and subsequently developed, resulting in further forest fragmentation. Values of the new owners and the small parcel sizes will have important consequences.
A growing number of forest exotic species and their impact will accelerate. Beetles, borers, adelgids, wilts, cankers and other damaging agents will challenge forest managers and society. In some cases, a well-managed forest may help reduce the negative impacts.
The loss of wood-using industries will hamper abilities to manage a forest. An unmanaged forest, due either to lack of markets or benign neglect on the behalf of forest owners, will provide fewer goods and services. A robust forest industry sector will be better able to consume the variety of timber products that can be manufactured from a forest.
According to Michigan State University Extension, changing weather patterns are framing many of these threats. Altered precipitation and temperature cycles, seasonal timing, ecological dynamics, and other variables are shifting the physical environment within which forests live. A managed forest is a more resilient forest but resiliency has its limits. With little doubt, communities will need to adapt to these evolving conditions.