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Biological diversityâ??or biodiversityâ??refers to the variety of life on earth and the natural patterns it forms. The biodiversity we see today is the result of billions of years of evolution. It forms the web of life of which we all are an integral part and upon which we so fully depend. Biodiversity refers to the diversity between species, within species and the diversity of ecosystems.

Species diversity: The diversity between species

Species diversity refers to the variety of different types of plants and animals, including bacteria, fungi, insects, mammals, plants and everything in between. Species diversity ensures that ecosystems run smoothly and survive. For example, a giraffe cannot do the same pollination job as a bee, nor could a bee play the same role in a savanna ecosystem as a giraffe. So far, about 1.75 million species have been identified, mostly small creatures such as insects. Scientists reckon that there are actually about 13 million species, though estimates range from 3 to 100 million.

Photo of a mountain lion.
Photo of a silverhaired bat.
Silverhaired Bat
Learn more about bats
Picture: Species diversity The mountain lion (left) and the silverhaired bat (right) are only two of the estimated 13 million species. As all living components of an ecosystem, the lion and the bat play a very important role in their ecosystems. (Learn more the mountain lion,learn more about bats.) Mountain Lion picture courtesy of Desert USA. Bat image courtesy of the Organization for Bat Conservation.
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Genetic diversity: The diversity within species

Biodiversity also refers to the genetic differences within each species. Chromosomes, genes, and DNA are the building blocks of life and determine the uniqueness of each individual and each species. Think of the seedlings that grow from a packet of new seedsâ??or the variety of people within your own family. No two plantsâ??and no two peopleâ??are exactly alike! Genetic diversity ensures that parents pass on the traits (such as disease resistance, physical form, etc.) that their offspring need to survive. When small populations are isolated from other populations of their species, there may be forced inbreeding, possibly leading to a loss of genetic diversity and to the extinction of the population.

Ecosystem diversity: The diversity of ecosystems

Yet another aspect of biodiversity is the variety of ecosystems such as those that occur in deserts, forests, wetlands, mountains, lakes, rivers, and agricultural landscapes. In each ecosystem, living creatures, including humans, form a community, interacting with one another and with the air, water, and soil around them. Ecosystem diversity refers to the variety of habitats and climates on earth.

Photo of the shale barrens in Sideling Hill Creek.

Photo of fish above a coral reef.
Shale Barrens of Sideling Hill Creek, Maryland.
Tropical Reef at Palau Islands, Western Caroline Islands.
Picture: Ecosystem diversity. The shale barrens of Sideling Hill Creek (left) and a coral reef at the Palau Islands (right) only represent two of the many ecosystems that all together enable life on earth. Shale Barrens picture courtesy of Anand Mishra/ The Nature Conservancy; coral reef picture courtesy of Dr. James P. McVey, NOAA Sea Grant Program.

Why care about biodiversity?

Life on earth is made possible by the diversity of ecosystems and the species that live in them. Think about all the products and services that the ecosystems provide us with:

  • Food like fruits, vegetables, and other plants and animals.
  • Shelter, including homes for many species of plants and animals.
  • Timber, fuel, resins, gums and other useful products.
  • Medicines.
  • Natural beauty and inspiration.
  • Ecological services, such as keeping our air and water clean, regulating our climate, pollinating our crops, and keeping our soils healthy and productive. For example, species like bees, flies, butterflies, moths, birds, bats and others help pollinate flowers so fruits like apples or strawberries can grow. And an ecosystem like the rainforest acts as a filter for the earth's air, absorbing carbon dioxide and releasing oxygen.

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What are the threats to biodiversity?

Many of the threats to biodiversity stem from a growing human population on earth: There are 6 billion humans on this planet today, and that number may reach 9 to 12 billion in the next 50 to 100 years. In addition, humans are using more energy, land, water and natural resources (like trees, fossil fuels, minerals, plants and animals) than ever before. Overharvesting, fragmentation and degradation of natural habitats, global climate change, pollution, and the introduction of species are al threats to biodiversity and undermine the health of the ecosystem of which we are part and upon which we depend.What can you do? No need to sit around and wonder what is happening to the biodiversity. This is what you can do:

  • Learn more! Visit museums, botanical gardens, nature centers, parks, zoos and aquariums. Read library books and magazines and explore the links on this page. The more you learn about biodiversity, the more you can do to help protect it.
  • Donate you time and money to environmental organizations doing biodiversity conservation work.
  • Buy eco-friendly products, such as paper made from recycled materials. Buy products that don't use fossil fuels or toxic chemicals. Buy locally-grown, organic foods. Buy wood products from sustainably grown, not endangered, tree species. Don't buy exotic, non-native pets or products made from endangered species.
  • Drive less! Use eco-friendly transportation like subways, bikes and carpools.
  • Be energy efficient. Use energy efficient appliances and computers. Use compact fluorescent light bulbs.
  • Use less pesticides, fertilizers and other chemicals on your lawn. Plant native vegetation and flowers that bees, butterflies, hummingbirds and other pollinators will like.

References and further reading

An excellent resource to get your questions about biodiversity answered is the Smithsonian Institution Frequently Asked Questions about Biodiversityoutside link.

The outside linkConvention on Biological Diversity, established in 1992 after the convention has created a guide that discusses biodiversity and how the Convention promotes nature and human well-being. The guide is available as an outside linkhtml file and in outside linkpdf.

A outside linkTeacher resource about endangered and threatened species created by the U.S. Fish and Wildlife Service.

outside linkSierra Club Population and Biodiversity Factsheet. outside linkNatureServeoutside linkVirtual Library of Ecology and Biodiversity, an online resource to ecology and biodiversity information.

outside linkSmithsonian Institution's MAB Biodiversity program. Created in 1986, MAB's mission is to promote the conservation of biodiversity.