A forestation

Afforestation is the process of establishing a forest on land that is not a forest, or has not been a forest for a long time by planting trees or their seeds. The term may also be applied to the legal conversion of land into the status of royal forest.
The term reforestation generally refers to the reestablishment of the forest after its removal, or planting more trees for example from a timber harvest. Since the industrial revolution many countries have experienced centuries of deforestation, and some governments and non-governmental organisations directly engage in programs of afforestation to restore forests and assist in preservation of biodiversity.
The United States and northwestern Europe have more forest cover than at the beginning of the twentieth century. However, significant deforestation in South and Central America and in South Asia still continues.
In various arid, tropical, or sensitive areas, forests cannot 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. 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.