Positive impacts of introduced species on forests and forestry
The forest sector often depends on alien species to provide a variety of socio-economic, environmental and human health benefits to the forest sector and to the rural communities that depend upon forests.
With growing concerns about the degradation and loss of natural forests, planted forests and trees outside forests, composed most often of alien species, are becoming increasingly more important sources of products such as timber, fibre and fuelwood. They also provide non-wood forest products, such as fruits, leaves, roots, honey, fibres, oils, resins, cosmetics and medicines, either from the planted trees themselves or from other elements of the ecosystem that they help to create. Such products contribute to the livelihoods of rural communities by providing food and medicine as well as income from their sale or by providing employment.
Alien tree species planted in forest plantations and other areas help provide many vital ecosystem services such as:
- combating desertification;
- protecting soil and water;
- rehabilitating lands exhausted from other land uses;
- diversifying the rural landscape;
- maintaining biodiversity;
- enhancing carbon sequestration;
- amenity and shade.
Alien species can provide a diverse range of products and services. Clockwise from top left: A Prosopis plantation provides fuelwood for local communities, Cape Verde (FAO/14081/C. Errath); Borassus aethiopum fruits for sale by the roadside, Senegal (FAO/CFU000287/R. Faidutti); Prosopis spp. are used to stabilize sand dunes, Mauritania (FAO/CFU000381/ R. Faidutti); Tree seedlings are planted to reduce soil erosion, Myanmar (FAO/19748/G. Bizzarri).When planted in riparian areas, trees provide spawning beds for fish and molluscs and shade which aids in the reduction of eutrophication. Trees planted on farms helps to increase soil fertility by providing organic matter through litter decomposition at the soil surface or through atmospheric nitrogen fixation (nitrogen-fixing trees), both of which contribute to improvements in food production. Along roads and highways, trees and plants not only add beauty to cities and towns but also provide shade and control outdoor noise and traffic pollution. Trees also play a major role in preserving the social and cultural values attached to forests, particularly as natural forests decrease in size through deforestation or are designated for conservation or other purposes. The forest sector also employs introduced species in biological control programmes to help combat pest problems.
Positive impacts may be best achieved by careful management of introduced species in order to prevent them from becoming invasive.