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The Earth has many diverse ecosystems and ecologicalsystem diversity. These are NASA composite images of the Earth: 2001 (left), 2002 (right), titled The Blue Marble. Ecosystem diversity deals with the variations in ecosystems within a geographical location and its overall impact on human existence and the environment.
An ecosystem (or ecological system) is a system formed by organisms in interaction with their environment. [2]: 458 The biotic and abiotic components are linked together through nutrient cycles and energy flows. Ecosystems are controlled by external and internal factors.
Coral reefs form complex marine ecosystems with tremendous biodiversity. Marine ecosystems are the largest of Earth 's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems , which have a lower salt content.
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Ecosystem services are ecologically mediated functional processes essential to sustaining healthy human societies. [6] Water provision and filtration, production of biomass in forestry, agriculture, and fisheries, and removal of greenhouse gases such as carbon dioxide (CO 2) from the atmosphere are examples of ecosystem services essential to public health and economic opportunity.
Forests harbour most of Earth's terrestrial biodiversity. The conservation of the world's biodiversity is thus utterly dependent on the way in which we interact with and use the world's forests. [78] A new method used in 2011, put the total number of species on Earth at 8.7 million, of which 2.1 million were estimated to live in the ocean. [79]
They form some of the most productive and dynamic ecosystems on Earth. [45] Smaller areas of anchored kelp are called kelp beds. Kelp forests occur worldwide throughout temperate and polar coastal oceans. [45] Kelp forests provide a unique three-dimensional habitat for marine organisms and are a source for understanding many ecological processes.
In 2011 a study published in PLoS Biology estimated there to be 8.7 million ± 1.3 million eukaryotic species on Earth. [11] By 2017, most estimates projected there to be around 11 million species or fewer on Earth. [4] A 2017 study estimated there are around at least 1 to 6 billion species, 70-90% of which are bacteria. [4]