The Global 200 is the list of ecoregions identified by the World Wide Fund for Nature (WWF), the global conservation organization, as priorities for conservation. According to WWF, an ecoregion is defined as a "relatively large unit of land or water containing a characteristic set of natural communities that share a large majority of their species dynamics, and environmental conditions". [1] [2] [3] For example, based on their levels of endemism, Madagascar gets multiple listings, ancient Lake Baikal gets one, and the North American Great Lakes get none.
The WWF assigns a conservation status to each ecoregion in the Global 200: critical or endangered; vulnerable; and relatively stable or intact. Over half of the ecoregions in the Global 200 are rated endangered.
The WWF has identified 867 terrestrial ecoregions across the Earth's land surface, as well as freshwater and marine ecoregions. The goal of this classification system is to ensure that the full range of ecosystems will be represented in regional conservation and development strategies. Of these ecoregions, the WWF selected the Global 200 as the ecoregions most crucial to the conservation of global biodiversity. The Global 200 list actually contains 238 ecoregions, made up of 142 terrestrial, 53 freshwater, and 43 marine ecoregions.
Conservationists interested in preserving biodiversity have generally focused on the preservation of tropical moist broadleaf forests (commonly known as tropical rainforests) because it is estimated that they harbor one half of Earth's species. On the other hand, the WWF determined that a more comprehensive strategy for conserving global biodiversity should also consider the other half of species, as well as the ecosystems that support them.
Several habitats, such as Mediterranean forests, woodlands, and scrub biome, were determined to be more threatened than tropical rain forests, and therefore require concerted conservation action. WWF maintains that "although conservation action typically takes place at the country level, patterns of biodiversity and ecological processes (e.g., migration) do not conform to political boundaries", which is why ecoregion-based conservation strategies are deemed essential.
Historically, zoologists and botanists have developed various classification systems that take into account the world's plant and animal communities. Two of the worldwide classification systems most commonly used today were summarized by Miklos Udvardy in 1975.
The Earth's land surface can be divided into eight biogeographic realms (formerly called kingdoms, and which the BBC calls ecozones) that represent the major terrestrial communities of animals and plants, and are a synthesis of previous systems of floristic provinces and faunal regions. The biome system classifies the world into ecosystem types (i.e. forests, grasslands, etc.) based on climate and vegetation. Each biogeographical realm contains multiple biomes, and biomes occur across several biogeographical realms. A system of biogeographical provinces was developed to identify specific geographic areas in each biogeographical realm that were of a consistent biome type, and shared distinct plant and animal communities. The WWF system represents a further refinement of the system of biomes (which the WWF calls "major habitat types"), biogeographical realms, and biogeographical provinces (the WWF scheme divides most biogeographical provinces into multiple smaller ecoregions).
Based on a comprehensive list of ecoregions, The Global 200 includes all major habitat types (biomes), all ecosystem types, and species from every major habitat type. It focuses on each major habitat type of every continent (such as tropical forests or coral reefs). It uses ecoregions as the unit of scale for comparison. WWF say ecoregions could be considered as conservation units at regional scale because they meet similar biological communities.
Some ecoregions were selected over other ecoregions of the same major habitat type (biome) or realm. Selection of the Global 200 relied on extensive studies of 19 terrestrial, freshwater, and marine major habitat types. Selection of the ecoregions was based on analyses of species richness, species endemism, unique higher taxa, unusual ecological or evolutionary phenomena, and global rarity of major habitat type.
Global 200 ecoregion list is most helpful to conservation efforts at a regional scale: local deforestation, destruction of swamp habitats, degradation of soils, etc. However, certain phenomena, such as bird or whale migration, depend on more complex parameters not used to define the current database, such as atmospheric currents and dynamic pelagic ecosystems. These would require gathering more information, and co-ordination of efforts between multiple ecoregions. However, the Global 200 ecoregions can help these efforts by identifying habitat sites and resting sites for migratory animals. It may also help identify the origin of invasive species, and offer insights for slowing down or stopping their intrusion.
WWF has identified 35 global priority places around the world (terrestrial, freshwater and marine) as either being home to irreplaceable and threatened biodiversity, or representing an opportunity to conserve the largest and most intact representative of their ecosystem. [5]
A biome is a distinct geographical region with specific climate, vegetation, and animal life. It consists of a biological community that has formed in response to its physical environment and regional climate. Biomes may span more than one continent. A biome encompasses multiple ecosystems within its boundaries. It can also comprise a variety of habitats.
The Afrotropical realm is one of the Earth's eight biogeographic realms. It includes Sub-Saharan Africa, the southern Arabian Peninsula, the island of Madagascar, and the islands of the western Indian Ocean. It was formerly known as the Ethiopian Zone or Ethiopian Region.
The Madagascar subhumid forests are a tropical moist broadleaf forest ecoregion that covers most of the Central Highlands of the island of Madagascar. They are included in the WWF's Global 200 list of outstanding ecoregions. Most of the original habitats have been lost due to human pressure.
The Upper Guinean forests is a tropical seasonal forest region of West Africa. The Upper Guinean forests extend from Guinea and Sierra Leone in the west through Liberia, Côte d'Ivoire and Ghana to Togo in the east, and a few hundred kilometers inland from the Atlantic coast. A few enclaves of montane forest lie further inland in the mountains of central Guinea and central Togo and Benin.
Forest–savanna mosaic is a transitory ecotone between the tropical moist broadleaf forests of Equatorial Africa and the drier savannas and open woodlands to the north and south of the forest belt. The forest–savanna mosaic consists of drier forests, often gallery forest, interspersed with savannas and open grasslands.
The Northern Congolian forest–savanna mosaic is a forest and savanna ecoregion of central Africa. It extends east and west across central Africa, covering parts of Cameroon, Central African Republic, Democratic Republic of the Congo, South Sudan, and Uganda. It is part of the belt of transitional forest-savanna mosaic that lie between Africa's moist equatorial Guineo-Congolian forests and the tropical dry forests, savannas, and grasslands to the north and south.
The Coastal forests of eastern Africa, also known as the East African Coastal Forests or Zanzibar–Inhambane forests, is a tropical moist forest region along the east coast of Africa. The region was designated a biodiversity hotspot by Conservation International.
The Southern Zanzibar–Inhambane coastal forest mosaic, also known as the Southern Swahili coastal forests and woodlands, is a tropical moist broadleaf forest ecoregion of eastern Africa. It is a southern variation of Northern Zanzibar-Inhambane coastal forest mosaic. The ecoregion supports habitats of forest, savanna and swamps. The southern portion of the ecoregion is not as well studied due to the 1977-1992 civil war in Mozambique.
Northern Zanzibar–Inhambane coastal forest mosaic, also known as the Northern Swahili coastal forests and woodlands, is a tropical moist broadleaf forest ecoregion of coastal East Africa. The ecoregion includes a variety of habitats, including forest, savanna and swamps.
The southern Congolian forest–savanna mosaic is an ecoregion that covers a large area of the southern Democratic Republic of the Congo and northeastern Angola. Its rich blend of habitats provides key insights into the biogeography of central Africa with the extensive climatic variation that it has been experiencing for the last 10 million years. The human population is not high.
The Apure–Villavicencio dry forests (NT0201) is an ecoregion in Venezuela and Colombia to the east of the eastern cordillera of the Andes. The ecoregion covers the transition zone between montane forests in the Andes and the llanos, or lowland grasslands. It has been severely degraded by deforestation, farming and ranching. The remnants are poorly protected.
The Western Congolian forest–savanna mosaic is an ecoregion of Angola, Democratic Republic of the Congo, Republic of the Congo, and Gabon.