Forests contain the greatest assemblages of species found in any terrestrial ecosystem, and the status of biodiversity is, in itself, an indicator of forest condition. Forests encompass biodiversity at the ecosystem level, the species level, and the genetic level.
Numerous distinct types of forest ecosystem have been identified, occurring in:
- fresh and saltwater environments,
- moist lowlands and arid highlands,
- low and high latitudes.
Plant, animal and insect species in these forests directly supply the needs of forest-dwelling peoples. Wood products from thousands of tree species are used domestically and traded internationally. Nonwood forest products, including fruits, nuts, mushrooms, Christmas boughs, and floral decorations, are collected by individuals, traded in local markets and, in some cases, exported worldwide.
The genetic diversity of forest flora and fauna is a resource of great potential value to the agricultural and pharmaceutical biotechnology industries, though the process of winnowing valuable genes from millions of unrewarding species is proving time-consuming and expensive.
Use values aside, the biological richness and beauty of forest ecosystems are at the core of their appeal to environmentalists and the wider public today. Saving the rainforest is a passionate cause for many individuals who have no direct connection with, or use for, tropical forests. The rise of ecotourism testified to the need felt by (largely) urban-dwelling people to witness natural, as opposed to human-made, wonders. Forest-dwelling indigenous peoples are seen, by some, as safeguarding the cultural diversity and intimate knowledge of nature that are likely to be lost in an industrializing and homogenizing world.
Forest biodiversity is perceived as a good in itself, but perhaps no other ecosystem good is subject to so many different interpretations. The conservation, and exploitation, of biodiversity are variously supported on scientific, economic, spiritual, aesthetic, cultural, religious, and moral grounds.
Measuring forest biodiversity is beset by problems. Indicators of biodiversity status, at any level, are still controversial, and the data needed to support their development are incomplete:
- genetic diversity is still largely unmapped;
- many species remain unknown to science;
- baseline and trend data are largely lacking; and
- detailed systematic monitoring is beyond the resources of even the high-income countries.
Nevertheless, much work has been carried out in recent years, in particular by international non-governmental organizations (NGOs). Their efforts have improved our understandig of some aspects of forest biodiversity.
The following summarizes key findings regarding the condition and trends of biodiversity in forest ecosystems, as well as the quality and availability of data.
Conditions and trends
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WWF has identified more than 200 ecoregions as outstanding representatives of the world’s diverse ecoystems and, therefore, priority areas for conservation. Forest types account for two-thirds of all terrestrial ecoregions.
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Nearly three quarters of the world’s threatened bird species have restricted breeding ranges and remain confined to relatively small areas. Endemic bird areas (EBAs) encompass the range of the majority of these birds and more than 80 percent of EBAs are found in forests.
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Centers of plant diversity have been identified as conservation priority areas, rich in plant diversity or endemism. Nearly three quarters of the centers are found in forests.
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Less than 8 percent of global forest area is legally protected. Legal safeguards appear ineffective against logging, poaching, and other forms of development in many countries.
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Nearly 9 percent of trees globally are now at some risk of extinction. The leading threat is logging, followed by conversion to agriculture and expansion of human settlements.
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One quarter of the world’s threatened birds occur in the non-Caribbean neotropical region. BirdLife International has identified nearly 600 sites that are key to the survival of these species and more than 80 percent of the sites occur in forests.
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Forests near human settlement or transportation routes have high concentrations of non-native species, which have been introduced deliberately or accidentally. Most are benign, but some invasive plants and insect pests have done extensive damage to both production and amenity forests.
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Moderate estimates of future species extinction rates in tropical forests range from 1 to 5 percent per decade. However, such estimates have high and largely unknown levels of uncertainty, because of both the uncertainty of the underlying data and the assumptions on which they are based.
Information status and needs
- Information on biodiversity is not currently adequate as a basis for forest management planning decisions or land use decisions at the landscape level.
- Detailed field-based biodiversity surveying over wide areas is not economically feasible, even in high-income countries. There is an urgent need for local and regional biodiversity management tools that can be developed from remote sensing and GIS.
- Other priority needs include better baseline information at the level of ecosystem types, species, and genetic resources, and agreed indicators of biodiversity condition, including habitat heterogeneity monitored over time that can be used to assess the impacts of habitat loss and modification.
- More information is urgently needed on the current status of protected areas and the effectiveness of logging bans or other conservation measures within these areas.
Quality and availability of data
PAGE measures and indicators
Data sources and comments
Global 200 ecoregions Olson, D.M. and E. Dinerstein. 1998. “The Global 200: A Representation Approach to Conserving the Earth’s Most Biologically Valuable Ecoregions.” Conservation Biology 12 (3):502-515.
Categorization scheme based on broad environmental characteristics and expert opinion.
Endemic bird areas Stattersfield, A.J. et al. 1998. Endemic Bird Areas of the World: Priorities for Biodiversity Conservation. Cambridge: BirdLife International.
Global sites identified through field observation and expert judgment.
Centers of plant diversity Worldwide Fund for Nature and World Conservation Union. 1994. Centres of Plant Diversity: A Guide and Strategy for their Conservation. 3 volumes. Cambridge: IUCN Publications Unit.
Global sites identified through field observation and expert judgment.
Protected forest areas World Conservation Monitoring Centre (WCMC). 1999. Analysis of the Protection Status of the World’s Forests. CD-ROM, Version 2. Cambridge, United Kingdom: WCMC.
Global database, based on IUCN management categories I-V.
Threatened trees Oldfield, S., C. Lusty and A. MacKiven, eds. 1998. The World List of Threatened Trees. Cambridge: World Conservation Press.
Global list developed through field observation and expert judgment.
Threatened birds Wege, D.C. and A.J. Long. 1995. Key Areas for Threatened Birds in the Neotropics. Cambridge: BirdLife International.
Key Areas in Latin America mapped through field observation and expert judgment.
Non-native plant species
(% of total)Ricketts, T. et al. 1997. A Conservation Assessment of the Terrestrial Ecosystems of North America. Volume I: The United States and Canada. Washington D.C.: World Wildlife Fund (WWF-U.S.).
Data compiled from county level observation in North America. Data do not distinguish between benign non-natives and harmful invasives.
Projected extinction rates Various studies and theoretical estimates, most based on data from tropical rainforest areas and tropical islands.
