Humans have relied on forest products for thousands of years. During the Pleistocene Epoch, about 1.5 million years ago, humans began using wood as a fuel to make fire. Today, wood remains the primary fuel for cooking and heating in many developing countries. This isn't the case in industrialized nations, which rely more heavily on fossil fuels.
In the United States, fuelwood accounts for only 7 percent of all timber consumption. Nearly all the rest falls under three categories:
- Lumber is responsible for 53 percent of U.S. timber consumption.
- Pulp and paper products consume another 32 percent.
- Wood-based composites, such as plywood and veneer, use another 7 percent.
Let's take a closer look at each category.
The word "lumber" refers to wood material that is finished square or rectangular in shape. That means it doesn't include roundwood, which is wood set in either a round or half-round shape, such as pilings, poles and posts. It does, however, encompass boards and planks, such as those typically used in construction -- two-by-fours, two-by-sixes, two-by-eights and so on. In fact, the construction industry uses about 50 percent of all the lumber produced in the United States [source: Bowyear]. The rest goes to make products such as crates, pallets and furniture.
National Geographic/Getty ImagesDouglas firs are in demand not only at Christmastime but constantly. The construction industry prizes their timber.
Furniture makers are especially fond of hardwood lumber. Hardwoods, such as oak, maple, walnut and mahogany, feature grain patterns that most people find pleasing. They're also very durable, making them ideal for cabinets and flooring. The furniture industry is the second-largest market for hardwood timber [source: USDA Forest Service]. Only the pallet industry uses more hardwood, primarily oak, which delivers extra strong wood to support heavy loads.
Very little hardwood goes into construction lumber. Softwoods, which include pine, larch, fir, Douglas fir, cedar, cypress and redwood, are preferred instead because they provide long, straight timber.
Pulp and Paper Products
Like all living things, wood is made up of cells. The cells function like rigid boxes that, collectively, make a tree strong. The walls of each box are made of two chemicals: cellulose and lignin. Cellulose is a tough but fairly flexible molecule. Lignin acts like glue to harden the cellulose and keep it from bending.
Humans discovered long ago that if they could separate the cellulose fibers from the lignin, they could make several useful products. The most important product based on wood fibers is paper. That material we write, draw and doodle on is made from a mass of softened fibers -- pulp -- that are formed into a mat, pressed and dried (we'll talk more about this in the Processing Timber section). Fiberboard is also made of cellulose fibers, but the fibers are bonded with an adhesive to make a dense product that can be used as a tabletop. Hardboard is even stronger. It's derived from pulp that has been pressed together under extremely high pressure.
Composites combine wood with at least one other material. Plywood and particleboard are two common composites. Plywood begins as several thin pieces of wood known as veneers. The veneers are glued and pressed together to make a material that shrinks and swells less than lumber. Particleboard is similar to fiberboard in that wood products are mixed with an adhesive and then pressed together. However, the starting point of particleboard isn't pulp but rather sawdust or wood shavings. Oriented strand board, or OSB, is a type of particleboard that rivals plywood in strength and durability, making it a popular alternative in the construction industry.
By now, it should be clear that no part of a tree is wasted, except for maybe a few stray leaves. But before wood can be transformed into a sheet of paper or the frame of a house, the timber must be harvested. That's the topic of the next section.