Plantation forests

The world's population is nearly 8 billion people, and the demand for products derived from wood for this number of people simply cannot be attained by harvesting from natural forests. To augment our needs, we have turned trees into a crop plant by creating plantation forests around the world. Plantation forests, also called “tree farms,” are grown on every continent except Antarctica and have been planted for many centuries. Plantations are grown almost exclusively for economic purposes, while benefits to wildlife and the environment are much less emphasized. As natural forests have shrunk in size, plantations forests have increased in area over time.

Plantation forests share many characteristics with more traditional agricultural crops in North America. Plantation forests are generally monocultures, consisting of a single genotype or species of tree. Occasionally, plantation forests have multiple genotypes of a single species, creating closely related polycultures. Tree species used are generally fast-growing, early successional species such as pine (Pinus spp.), poplars (Populus spp.), or eucalypts (Eucalyptus spp.). Regardless of the number of genotypes within a plantation forest, the treatment of these areas is generally the same. Trees are planted at uniform spacing, which is often determined by the size of the equipment and machines used to plant, apply pesticides, and harvest the stand. Trees almost always receive fertilization and receive irrigation in some drought-prone areas. Pest and weed control is often administered through the use of chemicals, but sometimes this can be accomplished through silvicultural and biological control methods.

Plantation forests contrast greatly with natural forests, which can have many different tree species. Natural forests often arise through succession, whereas plantation forests are planted, harvested after several years, and replanted, over and over again. Natural forests have many different-aged trees, while trees in plantation forests are all the same age. Natural forests have a diverse forest floor that supports woody vines and shrubs, herbaceous plants, many different arthropods, and even mammals. Plantation forests are generally kept weed- and insect-free, which in turn greatly reduces the attractiveness to most mammals, with the exception of deer, which may feed in plantation forests when the trees are young. To that end, however, most plantation forest managers implement deer-exclusion fences to eliminate deer browse damage. Natural forests do not receive irrigation or fertilization. Rather, they are dependent on nature to provide necessary water and nutrients for tree growth. Plantation forests, however, may be irrigated and fertilized in an effort to maximize tree growth and production.

Purpose and Land Area

Plantation forests are typically grown for industrial (48 percent in the year 2000) and nonindustrial purposes (26 percent), with another 26 percent as unspecified uses. In terms of industrial use, plantation forests focus on roundwood production that is classified as either industrial roundwood (e.g., sawlogs, veneer logs, plywood, and pulpwood) or wood fuel (e.g., wood used for cooking, heating, or power) production. Current worldwide harvests for industrial roundwood production are around 2.03 billion cubic meters (more than 71.6 billion cubic feet). Even though plantation forests constitute about 30 percent of total forests in the world, they may contribute up to two-thirds of wood production in some areas. In recent years, there has been a tremendous push to develop technology to make liquid biofuels (ethanol) using wood residues from plantation forests, as well as to use woody biomass along with coal in cofiring power plants. In the next decade, this technology may lead to widespread use of forest biomass for transportation and energy needs. Nonindustrial use of plantations includes providing ecological services such as wind protection, water and soil conservation, carbon sinks, and enhancement of barren and urban landscapes.

The area occupied by forest plantations varies considerably among continents. In North America, forest plantations cover an area over 72,587 square miles (188,000 square kilometers). Poplars (Populus spp. and hybrids) are grown primarily in the Pacific Northwest and the Great Lakes regions of the United States, with smaller areas in the northeast and southeast. Most plantations are grown on 8–12 year rotations, with the majority of wood going for pulp. However, some plantations in the Pacific Northwest are growing trees longer, with a targeted end use as lumber. Trees are generally planted at 2.5-by-3-meters (8.2-by-9.8-feet) spacing and are not thinned prior to harvest. When harvested, the entire site is clear-cut. Trees for the next rotation in the plantation forest are planted between the rows of harvested stumps, so by the time the second generation is ready to harvest, the old stumps have biodegraded. Willows (Salix spp.) are grown in the northeast, especially in New York State. These willow plantations are grown for 2–3 years and harvested up to four times before being replanted—a technique called “coppicing.” In this case, the biomass produced is used for energy, not pulp or lumber, and may be cut and made into large bales with modified agricultural equipment. In addition to hardwoods, several coniferous species, including pine and spruce (Picea spp.) trees are grown in the southeastern and northeastern United States and in parts of Canada. Conifer species are slower growing than poplars and require 1–2 thinning cuts after initial planting. Thinning cuts allow more space to grow for the trees that are left on site. Trees removed in the thinning are generally smaller and used for pulp, while the larger, older trees (up to 30 years old for Pinus spp. and older for Picea spp.) are used for lumber.

Plantation Forests in Asia

Asia has the greatest area of forest plantations in the world, with over 1.2 billion square miles (3.1 billion square kilometers) planted. This region, along with Australia, has the highest rate of forest plantation establishment in the world, with Japan, China, and India having the largest amount of forest plantation land area. Over 40 percent of Japan is classified as forest plantation, with trees such as Japanese cedar (Cryptomeria japonica), Japanese cypress (Chamaecyparis obtusa), Japanese larch (Larix leptolepis), and pine species. Japan uses its forest plantation trees for pulp and lumber products. Several pine and spruce species are grown in China, as well as hardwood species such as eucalyptus, paulownia (Paulownia spp.), birch (Betula spp.), locust (Robinia spp.), and poplars. Trees are harvested in as little as 6 years, and are given intensive nutrient, weed, and pest management. These trees are used for all types of wood products, including pulp for paper and lumber. China alone accounts for nearly three-fourths of the world's poplar production. India grows teak (Tectona spp.), eucalyptus, and poplar in its forest plantations. Teak is planted at wide spacing, with one thinning occurring when trees are around 33 feet (10 meters) tall, and another when trees are 99 feet (20 meters) tall. Branches are often removed on the lower portions of the stem, especially when teak trees are young. Teak is generally harvested by 30 years of age, but some plantations up to 60 years old do exist.

Plantation Forests in Europe

Europe as a whole has over 106,564 square miles (276,000 square kilometers) of forest plantations. Sweden, Finland, and other Nordic and Baltic countries have many acres of willow plantations. In these coppice systems, the trees are cut back after the first year to promote multiple sprouts. Biomass is harvested every 3–5 years thereafter for another 3–4 rotations. Plantations are fertilized, harvested during dormant periods, and treated much like traditional agricultural crops. Sweden is widely regarded as the world authority on willow coppice systems, as it has conducted extensive research and field trials on silviculture and harvesting methods. Pine and eucalypt plantation forests are found in Spain, while poplars are grown in France. Plantation forests in Europe are primarily used for biomass and energy, with a smaller portion going toward pulp and lumber.

Plantation Forests in Africa

Africa has about 3.8 million hectares (9.3 million acres) of forest plantations. They primarily consist of teak, pine, eucalypts, acacia (Acacia spp.), and types of rubber tree (Hevea spp.). As countries in Africa continue to develop, the demand for wood products is growing. A large portion of forest plantations are found in western Africa, where their primary uses are for fuelwood and environmental stability (e.g., preventing sand dunes). The eastern portion of Africa, unfortunately, has been one of the most unstable regions in the world in the last several decades, and likewise forest plantations in this region have been neglected and are impacted by pests and disease in addition to a general lack of silviculture. Central Africa has a low proportion of forest plantations, mostly pines and eucalypts. Here, the wood is used for fuel and lumber. The majority of forest plantations are in southern Africa, specifically South Africa. Eucalypts and pines are most often planted and used as fuelwood, pulp, or lumber for construction. South Africa is widely recognized as a world leader in forest plantation management and is able to supply the majority of the country's wood needs through its plantation forests.

Plantation Forests in South America

Eucalypts and pines are the most commonly grown tree species in South America, which has over 43,629 square miles (113,000 square kilometers) planted in forest plantations. Brazil, Chile, Argentina, and Uruguay have the most land area, while other countries have much less area in forest plantations. Brazil is one of the most active producers of pulpwood in the world. South American forest plantations are used for not only pulp and lumber but also for exports of wood chips and logs, as well as for biomass and cofiring plants. It is illegal to clear native forests in Chile, making the renewable wood from forest plantations even more valuable. In addition to pines and eucalypts, poplars and willows are grown on a smaller scale, especially in Argentina.

Plantation Forests in Australia

Australia (and Oceania) has over 1.5 million hectares (3.7 acres) of plantation forests. In Australia, plantation forests are mostly located in the southeastern area and Tasmania. The predominant tree species planted are pine, teak, mahogany (Sweitenia spp.), and eucalypts, with one native conifer, hoop pine (Araucaria cunninghamii) also used. These species are used for pulp and paper products, saw timber for building and furniture, and wood products such as particle board and plywood. Plantation forests are an important component of forestry in this region and account for a great deal of wood products. Forest plantations are managed very intensively, with pest and weed control. Australia and New Zealand are regarded as leaders in the development of plantation forest silviculture, and this is reflected in the high economic impact that this sector has on the local economy.

Criticisms of Plantation Forests

The main criticism of plantation forests is that they are monocultures that are even-aged with trees grown primarily for quick wood and fiber production. Hence, plantation forests have a much lower diversity of plant species and other biota that those of nonplantation forests. As monocultures, the trees may be more susceptible to outbreaks of insects and diseases because the trees may represent a single genetic stock and pests can move easily across the homogenous landscape. Plantation forests typically tend to be dominated by nonnative tree species that may have adverse ecological impacts. For example, eucalyptus trees that are widely used in plantation forests have a higher requirement for water than native species and show allelopathy where they produce compounds that inhibit the growth of other plants.

There have been cases where nonnative trees (e.g., pine trees planted in the Southern Hemisphere) have escaped plantations and have invaded natural ecosystems with significant alterations to native forest structure and composition. Nonnative forest pests have frequently been introduced to plantations, from where they can establish and spread into the natural forests. Because fertilizers and insecticides are often used in plantation forests, this may cause chemical pollution in the general area. Forests have been cleared to create plantations in areas where indigenous people used to live, thus causing their displacement. Further, there is a concern that if significant biofuel technology is developed, it could lead to large-scale replacement of natural forests by plantation forests, especially in tropical areas.

Benefits of Plantation Forests

There could be many ecological benefits to plantation forests, especially if plantations are managed with appropriate silvicultural methods and sustainable forest practices. Plantation forests have the maximum benefit when they are planted on degraded lands due to soil erosion after intensive agriculture and mining activities. In some instances, plantation trees have been used to competitively exclude nonnative weeds from landscapes, so that forests could be regenerated to a natural state over years. Planted trees that are hardier than native tree species may prevent further soil loss, rehabilitate the land, and assist with watershed protection. Afforestation of these areas has led to higher sequestration of carbon stocks, which is one of the reasons why many tropical countries are creating plantation forests. It is also argued that the use of existing plantation forests to the maximum capability may reduce the need to cut down natural forests for fiber production in the future. If managed properly, plantations can continue to provide a renewable source of wood for a long time. Since plantations are more productive than natural forests, more wood and fiber can be produced using less area. Sewage and industrial waste has been sprayed in plantations where trees break it down and absorb it, leading to a more environmentally friendly way of disposing waste. Certain types of trees in forest plantations, especially poplars, can also be used for phytoremediation, or removing pollutants from the soil by drawing them up through the roots and accumulating pollutants in tree tissues. Those trees can then be removed and disposed, taking the pollutants with them.

Plantation forests are excellent areas in which to conduct research. Because of the relatively sterile environment compared to natural forests (e.g., no ground vegetation, high survival of trees, low genetic diversity), plantation forests are well suited for experiments on tree physiology, tree growth and nutrient dynamics, and interactions with pests and diseases. By using plantation forests, scientists can isolate specific issues and adequately test them without lots of confounding effects that are often present in natural forests. Thus, plantation forests may not only produce a high amount of wood quickly on a small land area, but they also provide scientists with sites to conduct research to improve forest productivity. Research and production forest plantations contribute to the local economy, especially in the third world countries through providing livelihoods, poverty alleviation, and food security.

The World's “Wood-Baskets”

Overall, plantation forests that are present in most countries around the world are considered “wood-baskets.” The area occupied and the importance of plantation forests are increasing over time. Adverse effects of plantation forests include changes in the original forest structure, composition, and processes, with subsequent impacts on native species. The beneficial effects of plantation forests include production of wood and fiber that could be sustainable and renewable, some ecological values especially in degraded and urban areas, and a potential source of income to the local communities. A major challenge for plantation foresters is how to optimize production and efficiency with minimal impacts by insects and disease, while maintaining and enhancing local biodiversity. Management of plantation forests in the future is likely going to be heavily affected by changing technology, policy, and the value any society places on these highly modified habitats.