• biodiversity
    Coral reefs are among the most biodiverse ecosystems on the planet.

    Species by the Numbers
    Scientists have identified about 1.75 million different species. That includes 950,000 species of insects, 270,000 species of plants, 19,000 species of fish, 9,000 species of birds, and 4,000 species of mammals. This is only a small portion of the total number of species on Earth. There are millions more species yet to be discovered and named.

    Powerful Pollinators
    Bees, birds, and other creatures pollinate 75 percent of the world's major crops. In areas with lots of biodiversity, insects and other creatures pollinate plants naturally. But when biodiversity is reduced, this is impossible. There are not enough insects to pollinate large fields of single crops, so farmers must truck in honeybees to do the job.

    California almond farmers need about 1.5 million hives of honeybees to pollinate their crops. That's more than half of all the commercial beehives in the country.

    Medicine from Nature
    About 25 percent of the medicines used today are taken from or modeled on chemicals found in plants, animals, or other living things.

    Biodiversity refers to all the different kinds of living organisms within a given area. Biodiversity includes plants, animals, fungi, and other living things. Biodiversity can include everything from towering redwood trees to tiny, single-cell algae that are impossible to see without a microscope.

    Kinds of Biodiversity

    A common way to measure biodiversity is to count the total number of species living within a particular area. Tropical regions, areas that are warm year-round, have the most biodiversity. Temperate regions, which have warm summers and cold winters, have less biodiversity. Regions with cold or dry conditions, such as mountaintops and deserts, have even less.

    Generally, the closer a region is to the Equator, the greater the biodiversity. At least 40,000 different plant species live in the Amazon rain forest of South America, one of the most biologically diverse regions on the planet. Only about 2,800 live in Canada’s Quebec province.

    The warm waters of the western Pacific and Indian Oceans tend to be the most diverse marine environments. The Bird’s Head Seascape in Indonesia is home to more than 1,200 species of fish and 600 species of coral. Many of the corals build coral reefs, which are home to hundreds more species, from tiny seaweeds to large sharks.

    Some places in the world have a large number of endemic species—species that exist only in that place. The Cape Floristic Region in South Africa is home to about 6,200 plant species found nowhere else in the world. Areas with high numbers of endemic species are called biodiversity hotspots. Scientists and communities are making a special effort to preserve biodiversity in these regions.

    Biodiversity can also refer to the variety of ecosystems—communities of living things and their environments. Ecosystems include deserts, grasslands, and rain forests. The continent of Africa is home to tropical rain forests, alpine mountains, and dry deserts. It enjoys a high level of biodiversity. Antarctica, covered almost entirely by an ice sheet, has low biodiversity.

    Another way to measure biodiversity is genetic diversity. Genes are the basic units of biological information passed on when living things reproduce. Some species have as many as 400,000 genes. (Human beings have about 25,000 genes, while rice has more than 56,000.) Some of these genes are the same for all individuals within a species—they’re what make a daisy a daisy and a dog a dog. But some genes within a species are different. This genetic variation is why some dogs are poodles and some are pit bulls. It’s why some people have brown eyes and some people have blue eyes.

    Greater genetic diversity in species can make plants and animals more resistant to diseases. Genetic diversity also allows species to better adapt to a changing environment.

    Importance of Biodiversity

    All species are interconnected. They depend on one another. Forests provide homes for animals. Animals eat plants. The plants need healthy soil to grow. Fungi help decompose organisms to fertilize the soil. Bees and other insects carry pollen from one plant to another, which enables the plants to reproduce. With less biodiversity, these connections weaken and sometimes break, harming all the species in the ecosystem.

    Ecosystems with a lot of biodiversity are generally stronger and more resistant to disaster than those with fewer species. For instance, some diseases kill only one kind of tree. In the early 1900s, American chestnut blight killed most of the chestnut trees in the eastern forests of North America. The forest ecosystem survived because other kinds of trees also grew there.

    Biodiversity is important to people in many ways. Plants, for instance, help humans by giving off oxygen. They also provide food, shade, construction material, medicines, and fiber for clothing and paper. The root system of plants helps prevent flooding. Plants, fungi, and animals such as worms keep soil fertile and water clean. As biodiversity decreases, these systems break down.

    Hundreds of industries rely on plant biodiversity. Agriculture, construction, medical and pharmaceutical, fashion, tourism, and hospitality all depend on plants for their success. When the biodiversity of an ecosystem is interrupted or destroyed, the economic impact on the local community could be enormous.

    Biodiversity is especially important to the medical and pharmaceutical industries. Scientists have discovered many chemicals in rain forest plants that are now used in helpful drugs. One of the most popular and safe pain relievers, aspirin, was originally made from the bark of willow trees. Medicines that treat some forms of cancer have been made from the rosy periwinkle, a flower that grows on the African island of Madagascar. Scientists have studied only a small percentage of rain forest species in their search for cures. But every year, thousands of species go extinct, or die out entirely, before scientists can determine whether they might be useful in medicines.

    Decreasing Biodiversity

    In the past hundred years, biodiversity around the world has decreased dramatically. Many species have gone extinct. Extinction is a natural process; some species naturally die out while new species evolve. But human activity has changed the natural processes of extinction and evolution. Scientists estimate that species are dying out at hundreds of times the natural rate.

    A major reason for the loss of biodiversity is that natural habitats are being destroyed. The fields, forests, and wetlands where wild plants and animals live are disappearing. Land is cleared to plant crops or build houses and factories. Forests are cut for lumber and firewood. Between 1990 and 2005, the amount of forested land in Honduras, for instance, dropped 37 percent.

    As habitats shrink, fewer individuals can live there. The creatures that survive have fewer breeding partners, so genetic diversity declines.

    Pollution, overfishing, and overhunting have also caused a drop in biodiversity. Global climate change—the latest rise in the average temperature around the globe, linked to human activity—is also a factor. Warmer ocean temperatures damage fragile ecosystems such as coral reefs. A single coral reef can shelter 3,000 species of fish and other sea creatures such as clams and sea stars.

    Biodiversity can also be harmed by introduced species. When people introduce species from one part of the world to another, they often have no natural predators. These non-native species thrive in their new habitat, often destroying native species in the process. Brown tree snakes, for instance, were accidentally brought into Guam, an island in the South Pacific, in the 1950s. Because brown tree snakes have no predators on Guam, they quickly multiplied. The snakes, which hunt birds, have caused the extinction of nine of the island’s 11 native forest-dwelling bird species. 

    People all over the world are working to maintain the planet’s biodiversity. In the United States, the Endangered Species Act protects about 2,000 organisms that are in danger of becoming extinct. Animals and plants are the most familiar types of endangered species, but a fungus, such as the white ferula mushroom can also be threatened. The white ferula mushroom, a delicacy that only grows on the Italian island of Sicily, helps decompose organic compounds such as plants. Some environmental groups are working to create a sustainable mushroom population to satisfy consumers as well as the local ecosystem.

    Around the globe, thousands of wilderness areas have been set up to conserve plants, animals, and ecosystems. Local, national, and international organizations are cooperating to preserve the biodiversity of regions threatened by development or natural disasters. UNESCO’s World Heritage Site program recognizes areas of global importance, such as the enormous wetland region of the Pantanal in South America. Many national parks, such as Glacier National Park in the U.S. state of Montana, protect biodiversity within the park by restricting extractive activities, such as mining and drilling.

    Marine protected areas (MPAs) have been established to preserve sea life. In the marine protected area around Australia’s Great Barrier Reef, no-fishing zones have helped fish populations thrive. People are also working to limit pollution and restore coral reef ecosystems in the area. As ecosystems become healthier, their biodiversity increases.

  • Term Part of Speech Definition Encyclopedic Entry
    adapt Verb

    to adjust to new surroundings or a new situation.

    agriculture Noun

    the art and science of cultivating the land for growing crops (farming) or raising livestock (ranching).

    Encyclopedic Entry: agriculture
    algae Plural Noun

    (singular: alga) diverse group of aquatic organisms, the largest of which are seaweeds.

    alpine Adjective

    having to do with mountains.

    animal Noun

    organisms that have a well-defined shape and limited growth, can move voluntarily, acquire food and digest it internally, and can respond rapidly to stimuli.

    aspirin Noun

    drug for relieving pain and reducing inflammation, or swelling.

    biodiversity Noun

    all the different kinds of living organisms within a given area.

    Encyclopedic Entry: biodiversity
    breed Verb

    to produce offspring.

    brown tree snake Noun

    reptile native to Australia and Papua New Guinea.

    cancer Noun

    growth of abnormal cells in the body.

    chemical Noun

    molecular properties of a substance.

    chestnut blight Noun

    disease, caused by a fungus, that can be fatal to chestnut trees.

    climate change Noun

    gradual changes in all the interconnected weather elements on our planet.

    Encyclopedic Entry: climate change
    conserve Verb

    to save or use wisely.

    coral Noun

    tiny ocean animal, some of which secrete calcium carbonate to form reefs.

    coral reef Noun

    rocky ocean features made up of millions of coral skeletons.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    decompose Verb

    to decay or break down.

    decrease Verb

    to lower.

    delicacy Noun

    food or dish notable for its rarity or cost.

    desert Noun

    area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.

    Encyclopedic Entry: desert
    disease Noun

    a harmful condition of a body part or organ.

    drill Verb

    to make a hole using a rotating digging tool.

    drug Noun

    chemical substance used to change the physical or mental state of an organism.

    dwelling Noun

    a place to live.

    economic Adjective

    having to do with money.

    ecosystem Noun

    community and interactions of living and nonliving things in an area.

    Encyclopedic Entry: ecosystem
    Endangered Species Act Noun

    (1973) U.S. legislation that protects endangered species when they are threatened by human activity.

    endemic species Noun

    species that naturally occurs in only one area or region.

    environment Noun

    conditions that surround and influence an organism or community.

    Equator Noun

    imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude.

    Encyclopedic Entry: equator
    evolve Verb

    to develop new characteristics based on adaptation and natural selection.

    extinct Adjective

    no longer existing.

    extractive activity Noun

    process that removes, or extracts, any natural or cultural resource from an area.

    fertile Adjective

    able to produce crops or sustain agriculture.

    fertilize Verb

    to make productive or fertile.

    fiber Noun

    long, thin, threadlike material produced by plants that aids digestive motion when consumed.

    fragile Noun

    delicate or easily broken.

    fungus Noun

    (plural: fungi) type of organism that survives by decomposing and absorbing the material in which it grows.

    gene Noun

    part of DNA that is the basic unit of heredity.

    genetic diversity Noun

    difference or variety of units of inheritance (genes) in a species.

    genetic variation Noun

    differences in the genes among individual members of a species.

    grassland Noun

    ecosystem with large, flat areas of grasses.

    Great Barrier Reef Noun

    large coral reef off the northeast coast of Australia.

    habitat Noun

    environment where an organism lives throughout the year or for shorter periods of time.

    Encyclopedic Entry: habitat
    hospitality Noun

    the treatment of guests.

    ice sheet Noun

    thick layer of glacial ice that covers a large area of land.

    Encyclopedic Entry: ice sheet
    international organization Noun

    unit made up of governments or groups in different countries, usually for a specific purpose.

    Encyclopedic Entry: international organization
    introduced species Noun

    a species that does not naturally occur in an area. Also called alien, exotic, or non-native species.

    marine Adjective

    having to do with the ocean.

    mining Noun

    process of extracting ore from the Earth.

    MPA Noun

    (marine protected area) area of the ocean where a government has placed limits on human activity.

    overfish Verb

    to harvest aquatic life to the point where species become rare in the area.

    overhunt Verb

    to capture and kill enough animals to reduce their breeding population below sustainable levels.

    Pantanal Noun

    largest wetland area in the world, in western Brazil, Bolivia, and Paraguay (more than 150,000 square kilometers/58,000 square miles).

    pharmaceutical Noun

    drug or having to do with drugs and medications.

    plant Noun

    organism that produces its own food through photosynthesis and whose cells have walls.

    pole Noun

    extreme north or south point of the Earth's axis.

    pollen Noun

    powdery material produced by plants, each grain of which contains a male gamete capable of fertilizing a female ovule.

    pollinate Verb

    to transfer pollen from one part of a flower (the anther) to another (the stigma).

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    predator Noun

    animal that hunts other animals for food.

    province Noun

    division of a country larger than a town or county.

    Encyclopedic Entry: province
    rain forest Noun

    area of tall, mostly evergreen trees and a high amount of rainfall.

    Encyclopedic Entry: rain forest
    root system Noun

    all of a plant's roots.

    rosy periwinkle Noun

    flowering plant native to the African island of Madagascar, used in medicines.

    seaweed Noun

    marine algae. Seaweed can be composed of brown, green, or red algae, as well as "blue-green algae," which is actually bacteria.

    sustainable Adjective

    able to be continued at the same rate for a long period of time.

    temperate Adjective

    moderate.

    temperature Noun

    degree of hotness or coldness measured by a thermometer with a numerical scale.

    Encyclopedic Entry: temperature
    thrive Verb

    to develop and be successful.

    tropical Adjective

    existing in the tropics, the latitudes between the Tropic of Cancer in the north and the Tropic of Capricorn in the south.

    UNESCO Noun

    the United Nations Educational, Scientific, and Cultural Organization.

    Encyclopedic Entry: UNESCO
    wetland Noun

    area of land covered by shallow water or saturated by water.

    Encyclopedic Entry: wetland
    white ferula mushroom Noun

    fungus native to the Italian island of Sicily, used in cooking.

    wilderness Noun

    environment that has remained essentially undisturbed by human activity.

    Encyclopedic Entry: wilderness
    World Heritage Site Noun

    location recognized by the United Nations as important to the cultural or natural heritage of humanity.