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Terrestrial ecosystems occupy 55,660,000 mi 2 (144,150,000 km 2), or 28.26% of Earth's surface. [5] Major plant taxa in terrestrial ecosystems are members of the division Magnoliophyta (flowering plants), of which there are about 275,000 species, and the division Pinophyta (conifers), of which there are about 500 species.
The terrestrial scheme divides the Earth's land surface into 8 biogeographic realms, containing 867 smaller ecoregions. Each ecoregion is classified into one of 14 major habitat types, or biomes. In 2017 the WWF team revised ecosystem names and boundaries in the Arabian Peninsula, drier African regions, and Southeastern United States. [1]
Ecoregions may be identified by similarities in geology, physiography, vegetation, climate, soils, land use, wildlife distributions, and hydrology. The classification system has four levels, but only Levels I and III are on this list. Level I divides North America into 15 broad ecoregions; of these, 12 lie partly or wholly within the United States.
According to Richard Forman and Michel Godron, [22] a landscape is a heterogeneous land area composed of a cluster of interacting ecosystems that is repeated in similar form throughout, whereby they list woods, meadows, marshes and villages as examples of a landscape's ecosystems, and state that a landscape is an area at least a few kilometres ...
Land-cover definitions define forests based upon the density of trees, area of tree canopy cover, or area of the land occupied by the cross-section of tree trunks meeting a particular threshold. [21] This type of definition depends upon the presence of trees sufficient to meet the threshold, or at least of immature trees that are expected to ...
For example, ecosystems can be quite different if situated in a small depression on the landscape, versus one present on an adjacent steep hillside. [ 9 ] : 39 [ 10 ] : 66 Other external factors that play an important role in ecosystem functioning include time and potential biota , the organisms that are present in a region and could ...
A marine coastal ecosystem is a marine ecosystem which occurs where the land meets the ocean. Worldwide there is about 620,000 kilometres (390,000 mi) of coastline. Coastal habitats extend to the margins of the continental shelves, occupying about 7 percent of the ocean surface area.
The intensive land-use biome comprises five distinct terrestrial ecosystem functional groups: pastures, crops, plantations, urban and semi-natural ecosystem functional group. The artificial wetlands biome in the freshwater realm includes large reservoirs and other constructed wetlands , rice paddies , aquafarms and networks of canals and ditches.