Concern over repairing damages caused by humans to ecosystems is not recent. Forest plantations have been established since the 19th century in Brazil with different objectives. However, it was only in the 1980s, with the development of restoration ecology as a science, that the term ecological restoration was defined more clearly, with more comprehensive objectives. It has been the most used concept in the world in recent years (Engel & Parrotta 2003). The history of this stage, in Brazil, began in 1862. One of the first projects of forest restoration took place in the current National Forest of Tijuca, in the city of Rio de Janeiro. The goal was to conserve springs and regularize public water supply (See: Pacto para Restauração Ecológica da Mata Atlântica [Pact for Ecological Restoration of the Atlantic Forest], 2007).
Areas that have the following “symptoms” are considered degraded: mining, erosive processes, absence or reduction of vegetation cover, waste disposal, and mirrored surface, among others (SMA 2004). In 2004, the Society for Ecological Restoration (SER) published “SER International Primer on Ecological Restoration”. This guide defines ecological restoration as an intentional activity that initiates or accelerates the recovery of an ecosystem concerning its health, integrity, and sustainability. Ecosystems that require restoration have been degraded, damaged, transformed or entirely destroyed as a direct and indirect result of human activities.
Additionally, it describes several steps that must be taken to develop and manage ecological restoration projects. A few of them are: identifying the location and type of ecosystem to be restored; identifying the agent causing the degradation; and identifying whether restoration requires direct interventions.
Within these principles, several models were developed to restore degraded areas, including:
Driving natural regeneration: restoring by secondary succession. All it takes is to abandon the area to be restored so that it naturally develops by natural regeneration (Engel and Parrotta, 2003). However, to allow it to happen, it is necessary to overcome barriers for natural regeneration, such as the absence or low availability of propagules (seeds) for site colonization, failure to recruit seedlings and saplings (seed and seedling predation and/or lack of a favorable microclimate), lack of symbionts (mycorrhizas and rhizobacteria), pollinators, and dispersers. Today, this is one of the methods the National Council of the Environment recommends for forest restoration in areas of permanent protection (See: http://www.mma.gov.br/port/conama/).
Planting seeds: this technique overcomes one of the natural regeneration barriers since the propagules would be directly thrown into the place to be restored. When this technique is applied, success depends on minimal conditions to allow seedlings and saplings recruitment and maintenance of interactions to keep the ecosystem operating. In Mato Grosso, some initiatives show that the direct sowing method proved to be viable, despite unsatisfactory performance for some species. It is recommended as an economical alternative for forest restoration (see: www.socioambiental.org).
Planting of seedlings: Planting seedlings is a more expensive way of restoring degraded areas. However, planting seedlings of fast-growing native species is a highly efficient process because it increases the chances of seedling development and decreases the loss of seeds. In time, it stimulates the development of vegetable specimens in other levels of succession and attracts frugivore animals that disperse seeds. Due to the high success rate of this technique, by using fast-growing species, it takes about one to two years after planting for tree species to overcome competition with herbaceous and grass species through shading (Cavalheiro et al., 2002).
It is possible to reduce the costs of restoration activities by planting “islands” of seedlings. It is possible to plant seedlings as suggested by Kageyama and Gandara (2000). High diversity islands are small nuclei formations where plants of different life forms are placed (herbs, shrubs, lianas, and trees). With high diversity and densities of tree species, these islands would give “momentum” to restore connectivity between the fragments and assist the restoration process of native forests (Kageyama et al., 2003). Another option is to plant isolated trees or groups of species that attract the fauna, which would act as seed dispersers (SMA 2004).
Content by Roberta Cury.