• conservation
    Drip irrigation conserves water, soil, and energy.

    Photograph by James L. Stanfield

    Tree Huggers
    The Chipko Movement, which is dedicated to saving trees, was started by villagers in Uttar Pradesh, India. Chipko means hold fast or embrace. The villagers flung their arms around trees to keep loggers from cutting them down. The villagers won, and Uttar Pradesh banned the felling of trees in the Himalayan foothills. The movement has since expanded to other parts of India.

    Thirsty Food
    People require about 2 to 4 liters of drinking water each day. However, a day's worth of food requires 2,000 to 5,000 liters of water to produce. It takes more water to produce meat than to produce plant-based foods.

    Tiger, Tiger
    Tigers are dangerous animals, but they have more to fear from us than we have to fear from them. Today there are only about 3,200 tigers living in the wild. Three tiger subspecies the Bali, Caspian, and Javan tigers have gone extinct in the past century. Many organizations are working hard to protect the remaining tigers from illegal hunting and habitat loss.

    The Earth’s natural resources include air, water, soil, minerals, fuels, plants, and animals. Conservation is the practice of caring for these resources so all living things can benefit from them now and in the future.

    All the things we need to survive, such as food, water, air, and shelter, come from natural resources. Some of these resources, like small plants, can be replaced quickly after they are used. Others, like large trees, take a long time to replace. These are renewable resources.

    Other resources, such as fossil fuels, cannot be replaced at all. Once they are used up, they are gone forever. These are nonrenewable resources.

    People often waste natural resources. Animals are overhunted. Forests are cleared, exposing land to wind and water damage. Fertile soil is exhausted and lost to erosion because of poor farming practices. Fuel supplies are depleted. Water and air are polluted.

    If resources are carelessly managed, many will be used up. If used wisely and efficiently, however, renewable resources will last much longer. Through conservation, people can reduce waste and manage natural resources wisely.

    The population of human beings has grown enormously in the past two centuries. Billions of people use up resources quickly as they eat food, build houses, produce goods, and burn fuel for transportation and electricity. The continuation of life as we know it depends on the careful use of natural resources.

    The need to conserve resources often conflicts with other needs. For some people, a wooded area may be a good place to put a farm. A timber company may want to harvest the area’s trees for construction materials. A business may want to build a factory or shopping mall on the land.

    All these needs are valid, but sometimes the plants and animals that live in the area are forgotten. The benefits of development need to be weighed against the harm to animals that may be forced to find new habitats, the depletion of resources we may want in the future (such as water or timber), or damage to resources we use today.

    Development and conservation can coexist in harmony. When we use the environment in ways that ensure we have resources for the future, it is called sustainable development. There are many different resources we need to conserve in order to live sustainably.

    Forests

    A forest is a large area covered with trees grouped so their foliage shades the ground. Every continent except Antarctica has forests, from the evergreen-filled boreal forests of the north to mangrove forests in tropical wetlands. Forests are home to more than two-thirds of all known land species. Tropical rain forests are especially rich in biodiversity.

    Forests provide habitats for animals and plants. They store carbon, helping reduce global warming. They protect soil by reducing runoff. They add nutrients to the soil through leaf litter. They provide people with lumber and firewood.


    Deforestation is the process of clearing away forests by cutting them down or burning them. People clear forests to use the wood, or to make way for farming or development. Each year, the Earth loses about 14.6 million hectares (36 million acres) of forest to deforestation—an area about the size of the U.S. state of New York.

    Deforestation destroys wildlife habitats and increases soil erosion. It also releases greenhouse gases into the atmosphere, contributing to global warming. Deforestation accounts for 15 percent of the world’s greenhouse gas emissions. Deforestation also harms the people who rely on forests for their survival, hunting and gathering, harvesting forest products, or using the timber for firewood.

    About half of all the forests on Earth are in the tropics—an area that circles the globe near the Equator. Although tropical forests cover fewer than 6 percent of the world’s land area, they are home to about 80 percent of the world’s documented species. For example, more than 500 different species of trees live in the forests on the small island of Puerto Rico in the Caribbean Sea.

    Tropical forests give us many valuable products, including woods like mahogany and teak, rubber, fruits, nuts, and flowers. Many of the medicines we use today come from plants found only in tropical rain forests. These include quinine, a malaria drug; curare, an anesthetic used in surgery; and rosy periwinkle, which is used to treat certain types of cancer.

    Sustainable forestry practices are critical for ensuring we have these resources well into the future. One of these practices is leaving some trees to die and decay naturally in the forest. This “deadwood” builds up soil. Other sustainable forestry methods include using low-impact logging practices, harvesting with natural regeneration in mind, and avoiding certain logging techniques, such as removing all the high-value trees or all the largest trees from a forest.

    Trees can also be conserved if consumers recycle. People in China and Mexico, for example, reuse much of their wastepaper, including writing paper, wrapping paper, and cardboard. If half the world’s paper were recycled, much of the worldwide demand for new paper would be fulfilled, saving many of the Earth’s trees. We can also replace some wood products with alternatives like bamboo, which is actually a type of grass.

    Soil

    Soil is vital to food production. We need high-quality soil to grow the crops that we eat and feed to livestock. Soil is also important to plants that grow in the wild. Many other types of conservation efforts, such as plant conservation and animal conservation, depend on soil conservation.

    Poor farming methods, such as repeatedly planting the same crop in the same place, called monoculture, deplete nutrients in the soil. Soil erosion by water and wind increases when farmers plow up and down hills.

    One soil conservation method is called contour strip cropping. Several crops, such as corn, wheat, and clover, are planted in alternating strips across a slope or across the path of the prevailing wind. Different crops, with different root systems and leaves, help slow erosion.


    Harvesting all the trees from a large area, a practice called clearcutting, increases the chances of losing productive topsoil to wind and water erosion. Selective harvesting—the practice of removing individual trees or small groups of trees—leaves other trees standing to anchor the soil.

    Biodiversity

    Biodiversity is the variety of living things that populate the Earth. The products and benefits we get from nature rely on biodiversity. We need a rich mixture of living things to provide foods, building materials, and medicines, as well as to maintain a clean and healthy landscape.

    When a species becomes extinct, it is lost to the world forever. Scientists estimate that the current rate of extinction is 1,000 times the natural rate. Through hunting, pollution, habitat destruction, and contribution to global warming, people are speeding up the loss of biodiversity at an alarming rate.

    It’s hard to know how many species are going extinct because the total number of species is unknown. Scientists discover thousands of new species every year. For example, after looking at just 19 trees in Panama, scientists found 1,200 different species of beetles—80 percent of them unknown to science at the time. Based on various estimates of the number of species on Earth, we could be losing anywhere from 200 to 100,000 species each year.

    We need to protect biodiversity to ensure we have plentiful and varied food sources. This is true even if we don’t eat a species threatened with extinction because something we do eat may depend on that species for survival. Some predators are useful for keeping the populations of other animals at manageable levels. The extinction of a major predator might mean there are more herbivores looking for food in people’s gardens and farms.

    Biodiversity is important for more than just food. For instance, we use between 50,000 to 70,000 plant species for medicines worldwide. The Great Barrier Reef, a coral reef off the coast of northeastern Australia, contributes about $6 billion to the nation’s economy through commercial fishing, tourism, and other recreational activities. If the coral reef dies, many of the fish, shellfish, marine mammals, and plants will die, too.

    Some governments have established parks and preserves to protect wildlife and their habitats. They are also working to abolish hunting and fishing practices that may cause the extinction of some species.

    Fossil Fuels

    Fossil fuels are fuels produced from the remains of ancient plants and animals. They include coal, petroleum (oil), and natural gas. People rely on fossil fuels to power vehicles like cars and airplanes, to produce electricity, and to cook and provide heat.

    In addition, many of the products we use today are made from petroleum. These include plastics, synthetic rubber, fabrics like nylon, medicines, cosmetics, waxes, cleaning products, medical devices, and even bubblegum.


    Fossil fuels formed over millions of years. Once we use them up, we cannot replace them. Fossil fuels are a nonrenewable resource.

    We need to conserve fossil fuels so we don’t run out. However, there are other good reasons to limit our fossil fuel use. These fuels pollute the air when they are burned. Burning fossil fuels also releases carbon dioxide into the atmosphere, contributing to global warming. Global warming is changing ecosystems. The oceans are becoming warmer and more acidic, which threatens sea life. Sea levels are rising, posing risks to coastal communities. Many areas are experiencing more droughts, while others suffer from flooding.

    Scientists are exploring alternatives to fossil fuels. They are trying to produce renewable biofuels to power cars and trucks. They are looking to produce electricity using the sun, wind, water, and geothermal energy—the Earth’s natural heat.

    Everyone can help conserve fossil fuels by using them carefully. Turn off lights and other electronics when you are not using them. Purchase energy-efficient appliances and weatherproof your home. Walk, ride a bike, carpool, and use public transportation whenever possible.

    Minerals

    Earth’s supply of raw mineral resources is in danger. Many mineral deposits that have been located and mapped have been depleted. As the ores for minerals like aluminum and iron become harder to find and extract, their prices skyrocket. This makes tools and machinery more expensive to purchase and operate.

    Many mining methods, such as mountaintop removal mining (MTR), devastate the environment. They destroy soil, plants, and animal habitats. Many mining methods also pollute water and air, as toxic chemicals leak into the surrounding ecosystem. Conservation efforts in areas like Chile and the Appalachian Mountains in the eastern United States often promote more sustainable mining methods.

    Less wasteful mining methods and the recycling of materials will help conserve mineral resources. In Japan, for example, car manufacturers recycle many raw materials used in making automobiles. In the United States, nearly one-third of the iron produced comes from recycled automobiles.

    Electronic devices present a big problem for conservation because technology changes so quickly. For example, consumers typically replace their cell phones every 18 months. Computers, televisions, and mp3 players are other products contributing to “e-waste.” The U.S. Environmental Protection Agency (EPA) estimates that Americans generated more than 3 million tons of e-waste in 2007.

    Electronic products contain minerals as well as petroleum-based plastics. Many of them also contain hazardous materials that can leach out of landfills into the soil and water supply.

    Many governments are passing laws requiring manufacturers to recycle used electronics. Recycling not only keeps materials out of landfills, but it also reduces the energy used to produce new products. For instance, recycling aluminum saves 90 percent of the energy that would be required to mine new aluminum.


    Water

    Water is a renewable resource. We will not run out of water the way we might run out of fossil fuels. The amount of water on Earth always remains the same. However, most of the planet’s water is unavailable for human use. While more than 70 percent of the Earth’s surface is covered by water, only 2.5 percent of it is freshwater. Out of that freshwater, almost 70 percent is permanently frozen in the ice caps covering Antarctica and Greenland. Only about 1 percent of the freshwater on Earth is available for people to use for drinking, bathing, and irrigating crops.

    People in many regions of the world suffer water shortages. These are caused by depletion of underground water sources known as aquifers, a lack of rainfall due to drought, or pollution of water supplies. The World Health Organization (WHO) estimates that 2.6 billion people lack adequate water sanitation. More than 5 million people die each year from diseases caused by using polluted water for drinking, cooking, or washing.

    About one-third of Earth’s population lives in areas that are experiencing water stress. Most of these areas are in developing countries.

    Polluted water hurts the environment as well as people. For instance, agricultural runoff—the water that runs off of farmland—can contain fertilizers and pesticides. When this water gets into streams, rivers, and oceans, it can harm the organisms that live in or drink from those water sources.

    People can conserve and protect water supplies in many ways. Individuals can limit water use by fixing leaky faucets, taking shorter showers, planting drought-resistant plants, and buying low-water-use appliances. Governments, businesses, and nonprofit organizations can help developing countries build sanitation facilities.

    Farmers can change some of their practices to reduce polluted runoff. This includes limiting overgrazing, avoiding over-irrigation, and using alternatives to chemical pesticides whenever possible.

    Conservation Groups


    Businesses, international organizations, and some governments are involved in conservation efforts. The United Nations (UN) encourages the creation of national parks around the world. The UN also established World Water Day, an event to raise awareness and promote water conservation.

    Governments enact laws defining how land should be used and which areas should be set aside as parks and wildlife preserves. Governments also enforce laws designed to protect the environment from pollution, such as requiring factories to install pollution-control devices. Finally, governments often provide incentives for conserving resources, using clean technologies, and recycling used goods.

    Many international organizations are dedicated to conservation. Members support causes such as saving rain forests, protecting threatened animals, and cleaning up the air. The International Union for the Conservation of Nature (IUCN) is an alliance of governments and private groups founded in 1948. The IUCN works to protect wildlife and habitats. In 1980, the group proposed a world conservation strategy. Many governments have used the IUCN model to develop their own conservation plans. In addition, the IUCN monitors the status of endangered wildlife, threatened national parks and preserves, and other environments around the world.

    Zoos and botanical gardens also work to protect wildlife. Many zoos raise and breed endangered animals to increase their populations. They conduct research and help educate the public about endangered species. For instance, the San Diego Zoo in the U.S. state of California runs a variety of research programs on topics ranging from disease control in amphibians to heart-healthy diets for gorillas.

    Scientists at the Royal Botanic Gardens, Kew, in London, England, work to protect plant life around the world. Kew’s Millennium Seed Bank, for example, works with partners in 54 countries to protect biodiversity through seed collection. Kew researchers are also exploring how DNA technology can help restore damaged habitats.

    Individuals can do many things to help conserve resources. Turning off lights, repairing leaky faucets, and recycling paper, aluminum cans, glass, and plastic are just a few examples. Riding bikes, walking, carpooling, and using public transportation all help conserve fuel and reduce the amount of pollutants released into the environment. Individuals can plant trees to create homes for birds and squirrels. At grocery stores, people can bring their own reusable bags. And people can carry reusable water bottles and coffee mugs rather than using disposable containers. If each of us would conserve in small ways, the result would be a major conservation effort.

  • Term Part of Speech Definition Encyclopedic Entry
    abolish Verb

    to wipe out or get rid of.

    acid Noun

    chemical compound that reacts with a base to form a salt. Acids can corrode some natural materials. Acids have pH levels lower than 7.

    adequate Adjective

    suitable or good enough.

    air Noun

    the layer of gases surrounding Earth.

    Encyclopedic Entry: air
    alarming Adjective

    shocking or very surprising.

    alliance Noun

    people or groups united for a specific purpose.

    aluminum Noun

    silvery, reflective metallic element with the symbol Al.

    amphibian Noun

    an animal able to live both on land and in water.

    anchor Verb

    to hold firmly in place.

    ancient Adjective

    very old.

    anesthetic Noun

    substance that reduces the awareness of physical sensation.

    appliance Noun

    tool used to carry out a specific task.

    aquifer Noun

    an underground layer of rock or earth which holds groundwater.

    Encyclopedic Entry: aquifer
    atmosphere Noun

    layers of gases surrounding a planet or other celestial body.

    Encyclopedic Entry: atmosphere
    bamboo Noun

    type of huge, woody grass.

    benefit Verb

    to be helpful or useful.

    biodiversity Noun

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

    Encyclopedic Entry: biodiversity
    biofuel Noun

    energy source derived directly from organic matter, such as plants.

    boreal forest Noun

    land covered by evergreen trees in cool, northern latitudes. Also called taiga.

    botanical garden Noun

    place where plants and flowers are grown and displayed for education and study.

    breed Verb

    to produce offspring.

    cancer Noun

    growth of abnormal cells in the body.

    carbon Noun

    chemical element with the symbol C, which forms the basis of all known life.

    carbon dioxide Noun

    greenhouse gas produced by animals during respiration and used by plants during photosynthesis. Carbon dioxide is also the byproduct of burning fossil fuels.

    carpool Noun

    system of transportation where one car transports several riders.

    cell phone Noun

    device that uses radio signals to transmit and receive voice and other data.

    clearcutting Noun

    process of cutting down all the vegetation in an area, usually as part of an economic industry.

    clover Noun

    type of plant (legume) often cultivated as forage or feed for livestock.

    coal Noun

    dark, solid fossil fuel mined from the earth.

    coexist Verb

    to live at the same time or in the same place.

    commercial Adjective

    having to do with the buying and selling of goods and services.

    commercial fishing Noun

    industry responsible for catching and selling fish.

    conflict Noun

    a disagreement or fight, usually over ideas or procedures.

    conservation Noun

    management of a natural resource to prevent exploitation, destruction, or neglect.

    Encyclopedic Entry: conservation
    construct Verb

    to build or erect.

    consumer Noun

    person who uses a good or service.

    continent Noun

    one of the seven main land masses on Earth.

    Encyclopedic Entry: continent
    contour strip cropping Noun

    form of crop rotation where wide bands of different crops are planted across slopes or hills.

    coral reef Noun

    rocky ocean features made up of millions of coral skeletons.

    cosmetics Noun

    substances applied to the body to make it appear more attractive.

    critical Adjective

    very important.

    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    curare Noun

    resin obtained from South American trees, often dried and used as an ingredient in muscle relaxants.

    deadwood Noun

    dead and decaying trees or branches.

    decay Verb

    to rot or decompose.

    deforestation Noun

    destruction or removal of forests and their undergrowth.

    deplete Verb

    to use up.

    devastate Verb

    to destroy.

    development Noun

    construction or preparation of land for housing, industry, or agriculture.

    diet Noun

    foods eaten by a specific group of people or other organisms.

    Encyclopedic Entry: diet
    disease Noun

    a harmful condition of a body part or organ.

    DNA Noun

    (deoxyribonucleic acid) molecule in every living organism that contains specific genetic information on that organism.

    drought Noun

    period of greatly reduced precipitation.

    Encyclopedic Entry: drought
    drought-resistant Adjective

    plant able to survive on little water.

    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    Encyclopedic Entry: Earth
    economy Noun

    system of production, distribution, and consumption of goods and services.

    ecosystem Noun

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

    Encyclopedic Entry: ecosystem
    efficient Adjective

    performing a task with skill and minimal waste.

    electricity Noun

    set of physical phenomena associated with the presence and flow of electric charge.

    electronics Noun

    devices or tools that use electricity to work.

    endangered species Noun

    organism threatened with extinction.

    Encyclopedic Entry: endangered species
    enormous Adjective

    very large.

    ensure Verb

    to guarantee.

    environment Noun

    conditions that surround and influence an organism or community.

    Environmental Protection Agency (EPA) Noun

    U.S. government organization whose mission is to "protect human health and the environment."

    Equator Noun

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

    Encyclopedic Entry: equator
    erosion Noun

    act in which earth is worn away, often by water, wind, or ice.

    Encyclopedic Entry: erosion
    estimate Verb

    to guess based on knowledge of the situation or object.

    evergreen Noun

    tree that does not lose its leaves.

    e-waste Noun

    electronic devices or their parts that have been thrown away.

    extinct Adjective

    no longer existing.

    extract Verb

    to pull out.

    fabric Noun

    cloth.

    factory Noun

    one or more buildings used for the manufacture of a product.

    farming Noun

    the art, science, and business of cultivating the land for growing crops.

    fertile Adjective

    able to produce crops or sustain agriculture.

    fertilizer Noun

    nutrient-rich chemical substance (natural or manmade) applied to soil to encourage plant growth.

    flood Noun

    overflow of a body of water onto land.

    Encyclopedic Entry: flood
    foliage Noun

    leaves of a plant, or the leaves and branches of a tree or shrub.

    food Noun

    material, usually of plant or animal origin, that living organisms use to obtain nutrients.

    Encyclopedic Entry: food
    forest Noun

    ecosystem filled with trees and underbrush.

    forestry Noun

    management, cultivation, and harvesting of trees and other vegetation in forests.

    fossil fuel Noun

    coal, oil, or natural gas. Fossil fuels formed from the remains of ancient plants and animals.

    freshwater Noun

    water that is not salty.

    fuel Noun

    material that provides power or energy.

    geothermal energy Noun

    heat energy generated within the Earth.

    global warming Noun

    increase in the average temperature of the Earth's air and oceans.

    Encyclopedic Entry: global warming
    government Noun

    system or order of a nation, state, or other political unit.

    Great Barrier Reef Noun

    large coral reef off the northeast coast of Australia.

    greenhouse gas Noun

    gas in the atmosphere, such as carbon dioxide, methane, water vapor, and ozone, that absorbs solar heat reflected by the surface of the Earth, warming the atmosphere.

    habitat Noun

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

    Encyclopedic Entry: habitat
    harvest Noun

    the gathering and collection of crops, including both plants and animals.

    hazard Noun

    danger or risk.

    herbivore Noun

    organism that eats mainly plants.

    Encyclopedic Entry: herbivore
    hunt Verb

    to pursue and kill an animal, usually for food.

    ice cap Noun

    area of fewer than 50,000 square kilometers (19,000 square miles) covered by ice.

    Encyclopedic Entry: ice cap
    incentive Noun

    offer or encouragement to complete a task.

    international organization Noun

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

    Encyclopedic Entry: international organization
    International Union for the Conservation of Nature (IUCN) Noun

    environmental organization concerned with preserving natural ecosystems and habitats.

    iron Noun

    chemical element with the symbol Fe.

    irrigate Verb

    to water.

    landfill Noun

    site where garbage is layered with dirt and other absorbing material to prevent contamination of the surrounding land or water.

    landscape Noun

    the geographic features of a region.

    Encyclopedic Entry: landscape
    leach Verb

    to separate materials by running water or another liquid through them.

    leaf litter Noun

    dead plant material such as leaves, twigs, pine needles, and bark that accumulates on the ground. Also known as plant litter and tree litter.

    livestock noun, plural noun

    animals raised for sale and profit.

    logging Noun

    industry engaged in cutting down trees and moving the wood to sawmills.

    lumber Noun

    precisely cut pieces of wood such as boards or planks.

    mahogany Noun

    type of tree with reddish-brown wood.

    malaria Noun

    infectious disease caused by a parasite carried by mosquitoes.

    mangrove Noun

    type of tree or shrub with long, thick roots that grows in salty water.

    marine mammal Noun

    an animal that lives most of its life in the ocean but breathes air and gives birth to live young, such as whales and seals.

    medicine Noun

    substance used for treating illness or disease.

    mine Verb

    to extract minerals from the Earth.

    mineral Noun

    inorganic material that has a characteristic chemical composition and specific crystal structure.

    mining Noun

    process of extracting ore from the Earth.

    monitor Verb

    to observe and record behavior or data.

    monoculture Noun

    the system of growing one type of crop.

    mountaintop removal mining (MTR) Noun

    method of coal mining where the peak of a mountain is removed to get at the coal beneath.

    national park Noun

    geographic area protected by the national government of a country.

    natural gas Noun

    type of fossil fuel made up mostly of the gas methane.

    Encyclopedic Entry: natural gas
    nonprofit organization Noun

    business that uses surplus funds to pursue its goals, not to make money.

    nonrenewable resource Noun

    natural resource that exists in a limited supply.

    nutrient Noun

    substance an organism needs for energy, growth, and life.

    Encyclopedic Entry: nutrient
    nylon Noun

    type of plastic (polymer) that can be made into fabric.

    ocean Noun

    large body of salt water that covers most of the Earth.

    Encyclopedic Entry: ocean
    ore Noun

    deposit in the Earth of minerals containing valuable metal.

    Encyclopedic Entry: ore
    overgrazing Noun

    process of too many animals feeding on one area of pasture or grassland.

    overhunt Verb

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

    pesticide Noun

    natural or manufactured substance used to kill organisms that threaten agriculture or are undesirable. Pesticides can be fungicides (which kill harmful fungi), insecticides (which kill harmful insects), herbicides (which kill harmful plants), or rodenticides (which kill harmful rodents.)

    petroleum Noun

    fossil fuel formed from the remains of ancient organisms. Also called crude oil.

    plastic Noun

    chemical material that can be easily shaped when heated to a high temperature.

    plow noun, verb

    tool used for cutting, lifting, and turning the soil in preparation for planting.

    pollute Verb

    to introduce harmful materials into a natural environment.

    pollution Noun

    introduction of harmful materials into the environment.

    Encyclopedic Entry: pollution
    population Noun

    total number of people or organisms in a particular area.

    predator Noun

    animal that hunts other animals for food.

    prevailing wind Noun

    wind that blows from one direction.

    public transportation Noun

    methods of movement that are available to all community members for a fee, and which follow a fixed route and schedule: buses, subways, trains and ferries.

    purchase Verb

    to buy.

    quinine Noun

    drug used to treat malaria.

    rainfall Noun

    amount of precipitation that falls in a specific area during a specific time.

    rain forest Noun

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

    raw material Noun

    matter that needs to be processed into a product to use or sell.

    recycle Verb

    to clean or process in order to make suitable for reuse.

    reduce Verb

    to lower or lessen.

    region Noun

    any area on the Earth with one or more common characteristics. Regions are the basic units of geography.

    Encyclopedic Entry: region
    remains Noun

    materials left from a dead or absent organism.

    renewable resource Noun

    resource that can replenish itself at a similar rate to its use by people.

    resource Noun

    available supply of materials, goods, or services. Resources can be natural or human.

    reuse Verb

    to use again.

    river Noun

    large stream of flowing fresh water.

    Encyclopedic Entry: river
    root system Noun

    all of a plant's roots.

    rosy periwinkle Noun

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

    rubber Noun

    natural or man-made chemical substance that is tough, elastic and can resist moisture.

    runoff Noun

    overflow of fluid from a farm or industrial factory.

    Encyclopedic Entry: runoff
    sanitation Noun

    promotion of hygiene, health, and cleanliness.

    sea level Noun

    base level for measuring elevations. Sea level is determined by measurements taken over a 19-year cycle.

    Encyclopedic Entry: sea level
    seed Noun

    part of a plant from which a new plant grows.

    seed bank Noun

    collection of seeds, preserved in case other specimens are destroyed.

    selective harvesting Noun

    forestry practice of cutting some of the trees in an area of land, while allowing others to grow. Also called selection cutting.

    shellfish Noun

    any aquatic animal that has a shell.

    shelter Noun

    structure that protects people or other organisms from weather and other dangers.

    skyrocket Verb

    to increase rapidly.

    soil Noun

    top layer of the Earth's surface where plants can grow.

    species Noun

    group of similar organisms that can reproduce with each other.

    strategy Noun

    plan or method of achieving a goal.

    stream Noun

    body of flowing water.

    Encyclopedic Entry: stream
    survive Verb

    to live.

    sustainable development Noun

    human construction, growth, and consumption that can be maintained with minimal damage to the natural environment.

    synthetic Adjective

    manufactured by people, not occurring naturally.

    teak Noun

    hardwood tree native to Asia.

    technique Noun

    method of doing something.

    technology Noun

    the science of using tools and complex machines to make human life easier or more profitable.

    timber Noun

    wood in an unfinished form, either trees or logs.

    topsoil Noun

    the most valuable, upper layer of soil, where most nutrients are found.

    tourism Noun

    the industry (including food, hotels, and entertainment) of traveling for pleasure.

    toxic Adjective

    poisonous.

    transportation Noun

    movement of people or goods from one place to another.

    tropical Adjective

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

    tropics Noun

    region generally located between the Tropic of Cancer (23 1/2 degrees north of the Equator) and the Tropic of Capricorn (23 1/2 degrees south of the Equator).

    Encyclopedic Entry: tropics
    United Nations Noun

    international organization that works for peace, security and cooperation.

    vital Adjective

    necessary or very important.

    water Noun

    chemical compound that is necessary for all forms of life.

    water shortage Noun

    reduction in the amount of fresh water available for drinking, hygiene, and industrial and agricultural use.

    water stress Noun

    situation faced by a nation or community when the amount of available water is less than 1,700 cubic meters per person.

    weatherproof Verb

    to equip a shelter or other building so it can withstand extreme heat and cold and protect the people inside.

    wetland Noun

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

    Encyclopedic Entry: wetland
    World Health Organization (WHO) Noun

    United Nations agency responsible for health.

    xeriscaping Noun

    process of landscaping that requires minimal water use.

    Encyclopedic Entry: xeriscaping
    zoo Noun

    place where animals are kept for exhibition.

    Encyclopedic Entry: zoo
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