Reforestationtree cover to areas where woodlands or forest once existed but was destroyed; the destruction process is called deforestation. In many temperate zones such as the eastern United States, reforestation is seldom a critical issue because the native forests are so resilient that, given any opportunity, they will quickly re-establish themselves.
However, in many arid and tropical areas, forests are often unable to re-establish themselves without assistance due to a variety of environmental factors. One of these factors is that, once forest cover is destroyed in arid zones, the land quickly dries out and becomes inhospitable to new tree growth. Other critical factors include overgrazing by livestock, especially animals such as goats, and over-harvesting of forest resources by native populations or outside businesses. Together these may lead to desertification and the loss of topsoil; without soil, forests cannot grow until the very long process of soil creation has been completed - if erosion allows this. In some tropical areas, the removal of forest cover may result in a duricrust or duripan that effectively seal off the soil to water penetration and root growth. In many areas, reforestation is impossible above all because the land is in use by people.
In some areas, reforestation can easily be accomplished by the mass planting of tree seedlings. In other areas, mechanical breaking up of duripans or duricrusts is necessary, careful and continued watering may be essential, and special protection, such as fencing, may be required.
One great problem with reforestation is that, whereas the original forests often featured significant biodiversity, the replacement trees are often of only one or a few kinds, without the re-establishment of the other plants and animals that is required for a healthy ecosystem. When only one kind of tree (or other plant) is planted, the resulting system is called a monoculture.
Reforestation need not be used for recovery of accidentally destroyed forests. In some countries, such as Finland, the forests are managed by the pulp and paper industry. In such an arrangement, like other crops, trees are replanted wherever they are cut. In such circumstances, the cutting of trees can be carefully done to allow easier reforestation. In Canada, the pulp and paper industry systematically replaces many of the trees it cuts, employing large numbers of summer workers for treeplanting work.
The management of forest resources is called forestry.