Endangered species

BACKGROUND

Overview: Endangered species are organisms that have become so reduced in population size that they are at risk of becoming extinct. Endangered species have experienced a decline in population by at least 50% in the last 10 years, are confined to a fragmented area of less than 5,000 square kilometers of habitat, or have fewer than 2,500 mature organisms.

According to the U.S. Fish and Wildlife Service, there were more than 1,000 endangered plant and animal species in the United States in August 2009.

Threatened species are those at risk of becoming endangered. A vulnerable species, such as the great white shark, has a population that has declined by 30% or more during the last 10 years, is confined to a fragmented area of 20,000 square kilometers of habitat, or has fewer than 10,000 mature organisms.

The International Union for the Conservation of Nature (IUCN) assigns "critically endangered" status to species that have declined in population by at least 80% during the last 10 years, are confined to a small habitat, or have fewer than 250 individuals. An example of a critically endangered species is the Javan rhino.

Genetic variability and biodiversity: It is difficult for endangered species to find mates to breed with. As a result, animals may inbreed, or breed with their close relatives. This limits the genetic diversity of their offspring, increasing the chances of genetic disorders and congenital defects. For instance, offspring from closely related parents may not be able to develop normally, may be infertile, or may become sick and die.

Each species varies in the minimum number of organisms that is necessary to maintain genetic variability. Some species can even, for a time, reproduce asexually. For example, peanuts can self-pollinate, but if too many generations self-pollinate, the offspring become less vigorous.

Biodiversity refers to the variation in life forms on earth. Biodiversity is important for the survival of each species. Since all life forms on earth are connected, the more biodiverse each species is, the healthier all life forms are on the planet. The food chain is one example of the importance of biodiversity for many different species. For example, one food chain begins with plankton, a small oceanic plant, which is eaten by zooplankton, which is then eaten by fish; fish are then an important part of many humans' diets. Without any of the plants or animals on the food chain, humans might not have fish to eat.

Biodiversity is also important to humans, because much of modern medicine is derived from plants and animals. For example, quinidine is a drug used to treat some heart problems, and it is derived from the Cinchona tree.

Risk factors: Plants and animals can become extinct or endangered for a number of reasons, some natural and some man-made. Sometimes a species, or a portion of a species, evolves into a new species.

Natural selection and naturally occurring environmental variables may drive this process. Natural selection results in the survival of only the organisms best suited for their environments. For instance, weaker ones may not be able to find a mate or may not survive long enough to reproduce. Additionally, gradual changes in temperature, movement of tectonic plates, large forest fires, and natural disasters may also cause natural extinction.

Human actions may also play a role. For example, global warming, largely influenced by humans, is changing the habitats in which plants and animals have evolved to thrive. Human activities have dramatically increased greenhouse gases in the earth's atmosphere, thereby contributing to global warming.

Other human actions that may contribute to the endangerment of animals include the introduction of non-native invasive species, such as cats and dogs; the overexploitation of natural resources, such as logging a forest too heavily; artificial light pollution; pesticides; and overdevelopment. Light pollution may disorient migrating animals and disturb organisms' feeding behavior, pesticides may contaminate the soil and water that sustain plants, and overdevelopment may destroy habitats.

Research: There are specific animals and places on which environmentalists, biologists, and ecologists focus. Hot spots are areas that are extremely biodiverse and thus require special conservation attention. These areas are home to plants and animals that can be found nowhere else on earth. The destruction of hot spots such as Madagascar and the Amazon rainforest would likely lead to the extinction of these animals.

Specific animals, such as honeybees and amphibians, have received special attention from environmentalists, biologists, and ecologists, because they are considered bio-indicators. This means that the health of the species correlates with the overall health of the ecosystem in which they live. Both amphibian and bee populations have declined dramatically across the world during the past five decades. The reasons are unclear, but they are explored below.

Efforts to help endangered species repopulate are as diverse as the endangered species themselves. Controlling climate change is one goal of government and nongovernment organizations. Using zoos to safely house endangered animals, breeding programs, and land conservation are just some of the ways humans are working to counteract the damage done to plants and animals on earth.

TECHNIQUE

General: Endangered species are organisms that have become so reduced in population size that they are at risk of becoming extinct. Threatened species are those that are at high risk for becoming endangered. Protected species are protected by local, state, and federal laws, usually because they are endangered or threatened. This might mean hunting bans on certain animals or prohibitions on taking the animals or plants from their natural environments.

Biodiversity refs to the number and variation of organisms in a given area. California's Floristic Province is considered an especially biodiverse area. The floristic province extends roughly along California's coast and juts into Oregon and Nevada, spanning about 113,438 miles. The ecosystems in this area include salt marshes, costal sand dunes, and various types of forests (e.g., juniper-pine woodland, and riparian, cypress, sequoia, and redwood forests).

The floristic province is home to several threatened organisms, including amphibians, mammals, plants, and birds. Of these threatened species, eight amphibian, five mammal, four plant, and two bird species are considered endemic, because they are only found in this geographic location.

California's grasslands provide fertile soil for agriculture, its coastline is being developed with new homes, its forests provide valuable lumber, and its water from wetlands is used for drinking water and irrigation. The many uses of this region's natural resources places some shellfish, birds, fish, plant, and mammal populations at risk for extinction.

Another biodiverse area is the Tropical Andes, which has the highest number of endangered amphibians (115 species) in the world. Polynesia has the highest number of endangered birds (22 species) and the highest number of birds that have become extinct during the last 500 years (40 species) in the world. The Caribbean Islands have the second highest human population density of any biodiverse hotspot (155 people per square kilometer), as well as the highest number of mammals to have become extinct during the last 500 years (19 species).

Estimating populations: Scientists have different ways to estimate how large a species' population is, based on the size of the organism and how densely it is dispersed over space. One way is to count the number of organisms in a given area, then generalize to the rest of the ecosystem. For example, to measure the number of frogs in an ecosystem, scientists may designate random plots of land within the ecosystem to sample. A plot of land may be, for example, 10 square meters, large enough to give a statistically powerful estimate, but small enough for scientists to search thoroughly. Scientists may be able to generalize the number of frogs collected from the sample areas to the rest of the ecosystem.

Another method of monitoring the population size of a species is by counting every organism. Some larger animals are so severely endangered that it is possible to monitor each individual.

There are many mechanisms that may directly or indirectly reduce populations of organisms. Although extinction may occur naturally, many documented extinctions result from direct or indirect human involvement. The main contributors include invasive species, pollution, disease, habitat destruction (which may be caused by urban sprawl or natural disasters), the overexploitation of natural resources, splitting habitats, and climate change.

Invasive species: An invasive species refers to a non-native species that dominates an ecosystem. It may be introduced to the foreign/non-native environment naturally or as a result of human action.

The zebra mussel is an example of an invasive species. This type of mussel is native to southeastern Russia. It was introduced to North America when the St. Lawrence Seaway was opened in 1959. This mussel had no natural predators to control its population. As a result, it reproduced rapidly, and eventually there were so many zebra mussels that they affected power plants, boats, and water treatment plants by blocking pipelines and moving parts. The mussels also smothered and killed other aquatic species, such as crayfish and turtles. The mussel excrement was ideal food for blue-green algae, a type of bacterium. Too much algae changed the water and thus altered the habitat on which many other life forms depended. Estimates of zebra mussel control costs range from $1 billion to $1.5 billion from 1989 to 2004, according to research reviewed by the Water Science and Technology Board, a part of the National Resource Council.

Endemic species are especially vulnerable to invasive species. This is because endemic species are often uniquely adapted to only the specific habitat they live in. Therefore, any changes, such as an invasive species, may significantly threaten an endemic species.

Pollution: All types of pollution may have negative effects on ecosystems and animals.

Air pollution: Some air pollutants, including ozone and nitrate radicals, may bond with scent molecules of flowers. This impedes bees from locating flowers to pollinate and thus their reproduction.

Other air pollutants, such as dioxins and furans, may bioaccumulate in food and eventually harm humans. Both pollutants can disrupt human and animal hormone and reproductive systems; dioxins may cause cancer.

Water pollutants: Water pollution may harm many life forms. For example, the oil tanker Exxon Valdez hit Bligh Reef in Alaska, spilling 10.8 million gallons of oil into Prince William Sound and contaminating 1,235 miles of shoreline. Wildlife in this area was severely affected. Within a few days, about 2,000 otters, 302 seals, and 250,000 seabirds died. Decades after the spill, some scientists report that oil is still in the environment and negatively affecting it. Scientists note that changes to the color of water may have affected bacteria and plankton. Changes to these organisms may have impaired the functioning of the ecosystem and its food chains.

Pesticides: Air or water may carry pesticides from farms and residential yards and factory emissions to far-off places. Some research suggests that pesticides caught in snow may give ecosystems a sudden, high dose of toxins when the snow melts. This high dose of toxins may kill organisms living nearby, such as amphibians.

Persistent organic pollutants: Persistent organic pollutants (POPs) are substances found in the environment that do not break down. Instead, they may bioaccumulate in the food chain. Bioaccumulation refers to a process by which toxins build up in organisms higher on the food chain. An example of bioaccumulation is when insects eat plants sprayed with pesticides. Each insect is then contaminated. A bird or bat might eat hundreds of insects per day, absorbing contaminants in each one. Pesticides and POPs may accumulate in humans, causing ill-health effects, such as disruption of hormones and fetus development.

Ambient light pollution: Artificial lights left on at night, such as streetlights and building lights, may interfere with many different animals and plants. For example, once sea turtles hatch on the beach, they head toward the brightest light. Normally, this would be the light of the horizon, which would direct them toward the ocean. However, if the natural light is diminished or if artificial lights are present, the turtles may not find the sea.

Artificial lights may also interfere with some night-blooming flowers. These plants may not bloom, as they misinterpret night for day. The Leach's storm-petrel, a small seabird, feeds on bioluminescent plankton (i.e., plankton that emits light). This bird may fly into lighthouses or other man-made light sources. Some nocturnal amphibian species limit their activities during bright nights.

Scientists can look at nighttime photographs of light distribution around the globe. Urban areas, oil platforms, and commercial fishing activities may produce dense areas of man-made light. The light may be affecting the surrounding ecosystems.

Disease: Genetic and infectious diseases may also contribute to declines in a species' population. For instance, colony collapse disorder (CCD) has killed bees around the world. Some research from 2007 through 2008 suggests that about 35.8% of bee colonies disappeared in the United States, 60% of which displayed signs of CCD. Scientists are not sure what is causing the drastically high rates of death. The condition is characterized by bees disappearing without a trace; no dead bodies are found. Beekeepers might also note that the bees will not accept food and that older worker bees are not present in the colony. Scientists have found that various parasites and viruses are killing the bees, suggesting their immune systems may not be functioning properly.

This dramatic decline in bee populations has many implications for ecosystem balance and honey production.

Habitat destruction: One serious threat to plants and animals is the destruction of their habitats, which may occur naturally or as a result of human actions.

Natural disasters, such as earthquakes, hurricanes, tornadoes, and volcanoes, may destroy habitats. For example, the Asian tsunami of 2004 heavily affected coral reefs off the coast of Thailand, which are known to be extremely biodiverse. Thirteen percent of the reefs were heavily damaged, according to Thailand's Department of Marine and Coastal Resources (DMCR). The same report found that small organisms were severely affected; these organisms may have been important for the food chain.

Humans may destroy habitats when clearing land for residential and commercial development. For instance, roads may cut into migration patterns for land animals. Some amphibians migrate from water to land but may become blocked by a road or a home.

Overexploitation: Overexploiting natural resources, such harvesting too much lumber from a forest, may also destroy a species' habitat and contribute to declining species populations. For example, some species of bees live in fallen, hollowed logs. If these logs are removed, the bees have no habitat and may not survive. Many countries and industries limit the amount natural resources that can be exploited. For example, in the United States, the lobster industry is regulated to help promote a sustainable population.

Climate change: Climate change also contributes to declines in populations worldwide; however, it is difficult to measure and to counteract. The U.S. Environmental Protection Agency (EPA) reports that the average surface temperature for the world has increased by 1.0-1.7 degrees Fahrenheit since 1850. Climate change's effect on plants and animals is difficult to prove or quantify. One example of an effect of climate change is the spread of a chytrid fungus that infects the skin of amphibians (such as frogs, salamanders, toads, and newts). Certain temperatures create ideal environments for this fungus, called Batrachochytrium dendrobatidis, to grow.

THEORY/EVIDENCE

General: Mass extinctions have naturally occurred in the earth's past, particularly during the Ordovician, Devonian, Permian, Triassic, and Cretaceous ages. Some scientists believe the earth is in the midst of another great mass extinction, called the Holocene extinction event. This event is thought to have three general phases.

The first wave of extinctions during the Holocene extinction event coincided with the spread of modern humans 40,000 years ago up until 200 years ago. Whether humans caused the event or whether climate change triggered the event is unclear. This wave saw the loss of some species of elephant, moa (flightless birds), and lemur, as well as mammoths.

The spread of Europeans from 1500 until 1970 coincides with a second wave of extinctions. This phase saw the loss of the dodo bird, as well as some species of tortoise and fish.

The third phase of extinctions is occurring now and coincides with rapid growth in human population and globalization. Examples of species that recently became extinct include a mollusk called Achatinella elegans, a type of bird called the Cyprus dipper, the African Atlas bear, the Rocky Mountain locust, and a Chilean plant called Santalum fernandezianum. Experts are alarmed at the loss or near-loss of many amphibian species; 122 amphibian species have become extinct in the last 25 years, and many more are endangered.

The Holocene extinction event is distinct from earlier extinction events, because it has occurred in a comparatively short time. Earlier mass extinctions happened over the course of millions of years; the current extinction event has occurred over the course of only 40,000 years. This time frame is up to several hundred times faster than historical extinction periods, and it coincides with human evolutionary development, population growth, and industrial and technological development. This suggests that the modern mass extinction may be influenced by human actions.

Human population: According to the U.S. Census Bureau, at the start of the second wave of extinctions (AD 1500), the human population was about 425-540 million. In 2009, there were about 6.8 billion people in the world. Human population is expected to grow to nine billion people by 2040. Developing countries have more than nine times the amount of live births than developed countries. Many biodiverse areas are in developing countries or in areas with high population densities. For example, Japan and Sri Lanka both have populations of more than 250 people per square kilometer, whereas the world average population density is 42 people per square kilometer.

Expanding human populations in areas rich in biodiversity could have significant impacts on the environment.

Exploiting natural resources: The health of the environment depends less on how many people there are and more on how people use the environment. Even sparse human habitation may have negative effects on the environment. For example, a biodiverse area in Brazil known as the Cerrado has only 13 people per square kilometer, but its conservation status is vulnerable, due in part to human agricultural activity. Sustainable use of resources is important for human health and may become more important as the human population grows.

Genetic erosion: Endangered species are more vulnerable than non-endangered species to variations in their environments. Even slight changes can potentially kill organisms, and if the species is endangered, the loss may be sufficient enough to cause extinction.

Genetic erosion occurs when there are not enough members of a species to breed. As a result, organisms may inbreed with close relatives. This inhibits genetic diversity in their offspring and increases the risk congenital defects. The scope of the problem is large. The World Wildlife Fund (WWF) reports that 25-35% of plant genetic diversity was lost due to genetic erosion between 1988 and 2000, mostly in the tropics of South America, South Africa, and Southeast Asia.

One example of a case of genetic erosion in the United States is the Florida panther (also known as the Florida cougar or Puma concolor), an endangered species living in the Everglades. According to the U.S. Fish and Wildlife Service, overhunting and habitat destruction led to dwindling numbers of this endemic panther. Researchers could determine the cause of death for 60 panthers that were killed between 1978 and 1999; automobiles killed 25 of these cats. By 1995, there were only 20-30 in the wild. This geographically isolated species needs about 250 members to be genetically stable. As a result of these low numbers, it began to inbreed. Conservationists introduced eight female cougars from a genetically similar Texas population, which so far, seems to have increased the population and minimized inbreeding.

Bioindicators: The health of plants and animals correlates with the health of the ecosystem, but some species, such as seagulls and raccoons, adapt well to changes in their ecosystems. These species can flourish in urban and suburban areas. Some organisms are particularly sensitive to the health of their ecosystem. These organisms, called bioindicators, flourish in a healthy ecosystem but decline rapidly in an unhealthy ecosystem.

Bees and amphibians are both bioindicators. Amphibians live in both aquatic and terrestrial environments. Their porous skin causes them to absorb any toxins in both aquatic and terrestrial environments. Bees live in much of the world, and because they play such an important role in plant reproduction, they are very important members of many ecosystems. Unhealthy bees foreshadow unhealthy plants; unhealthy plants could mean less food for humans to eat.

Bees and colony collapse disorder (CCD): Colony collapse disorder (CCD) is responsible for the deaths of a significant number of bees across the world since 2006. From 2007 through 2008, research published in the Public Library of Science reports that 35.8% of bee colonies disappeared in the United States, 60% of which displayed signs of CCD. Scientists have found that various parasites and viruses are killing the bees.

The reason CCD is fatal for some bees is unclear. A genetic study by the University of Illinois and the U.S. Department of Agriculture found that bees with CCD may have more fragmented ribonucleic acid (RNA) than bees without CCD. Viruses may attack the fragmented RNA, leading the RNA to create proteins that hurt the bee. The scientists report they do not understand why this increased fragmentation of the RNA occurs. Other scientists have speculated, but not proven, that links exist between CCD and environmental variables such as pesticides, electromagnetic radiation, antibiotics used for domesticated bees, and malnutrition.

Amphibians and chytridiomycosis: Batrachochytrium dendrobatidis, a type of chytrid fungus, is infecting amphibians worldwide, even amphibians that live in environments far from human influence. It causes the fatal disease chytridiomycosis. Its origin and spread is not well understood. Some evidence suggests it originated in South Africa, where it had infected a low and consistent number of amphibians for many years before it spread through commercial trade of one species of frog. During the past 25 years, 122 species of amphibians have become extinct. Biologists are closely monitoring the impact of chytridiomycosis on amphibian populations.

The causes of chytridiomycosis are not clear. Researchers have linked records of sea-surface and air temperatures to sightings of a fungus-infected species of frog. Warming climates support the growth of the fungus. Other factors, such as deforestation, may also contribute to declining amphibian populations.

HEALTH IMPACT/SAFETY

General: It is difficult to determine and quantify the effect endangered species may have on human and animal health. The two main ways a lack of biodiversity may directly affect humans is by affecting the food chain and by destroying natural resources humans use to make medicines.

Food chain interruption: Declining populations of bees provide an example of how endangered species may affect the food chain and, ultimately, humans. According to the U.S. Department of Agriculture (USDA), well over 100 crops require pollination to reproduce, making up one-third of human diets. Pollination refers to a process whereby some species of bees, moths, bats, and birds transfer pollen grains, which contain male plant reproductive materials, to female plants. Without bees, many of these crops cannot reproduce.

Disease: Interruption of the food chain may affect more than just humans' access to food. It may also lead to overpopulation of pests that can endanger human health. For example, Lyme disease is spread by ticks; with the overpopulation of deer, tick populations increase, spreading the disease to humans more often. Some amphibians may help reduce the incidence of malaria by eating vectors (carriers of disease) such as mosquitoes. These animals may also reduce the amount of pests that attack agriculture.

Bioaccumulation: Bioaccumulation refers to a process by which toxins build up in organisms that are higher on the food chain. For example, pesticides on plants may be absorbed by insects. If a bird eats several of these contaminated insects, it absorbs even more of the pesticide. For every step on the food chain, more contaminants are collected.

Air pollutants, such as dioxin, furans, and co-planar PCBs, are known to bioaccumulate in humans. These toxins may impair the immune system, as well as disrupt hormones and fetal development. Polychlorinated dibenzo-para-dioxins (i.e., dioxins), polychlorinated dibenzofurans (i.e., furans), and polychlorinated biphenyls (i.e., coplanar PCBs) are all released during industrial processes, such as the incineration of bleached paper and polyvinyl chloride (PVC), a thermoplastic polymer. When chlorine-containing materials are incinerated, or burned at temperatures lower than 800 degrees Celsius, dioxins, furans, and co-planar PCBs may be emitted into the air. Once in the air, these materials may contaminate water and land. Organisms in the land and water may then become contaminated as well. When humans eat the contaminated plants, animals that ate the plants, or fish, they may also retain some of these toxins. After eating many of these toxic organisms, dioxins, furans, and co-planar PCBs may be present in dangerously high amounts in human tissues.

Furan and dioxin levels can become particularly high in breast milk and may impair the development of exposed babies' nervous systems. Animal studies suggest that exposure to dioxins and furans at nuisance levels (10 micrograms per cubic meter) for only two weeks may cause skin lesions. Dioxins have also been linked to cancer. Any exposure to di(2-ethylhexyl) phthalate (DEHP), a chemical used in some plastics, can damage the liver, kidneys, and lungs. It may also disrupt hormones and harm the developing fetus. Exactly how many people and animals are affected by dioxins, furans, co-planar PCBs, and other pollutants, and how serious these effects are, is difficult to determine.

Curbing the health effects of dioxin and furan lies in preventing or reducing their release into the environment. According to the World Health Organization (WHO), stricter emission regulations mandated in Europe 10 years ago are responsible for substantial decreases in dioxin and furan concentrations in food. Similar regulations have been made in the United States.

Pharmaceutical development: Many medicines originated in the environment. Therefore, it is beneficial for people to ensure that species do not become endangered. For example, captopril (Capoten©) is a medication for high blood pressure that is derived from a venomous rainforest viper. Many herbal products have been shown to have positive medicinal effects. For example, atropine is a toxic alkaloid extracted from the plant belladonna that is used to dilate the eye, to stop muscular spasms, and to increase heart rate. Another example is valerian, an herb whose root serves as a sedative and antianxiety treatment.

FUTURE RESEARCH OR APPLICATIONS

General: There are many different ways to counteract the effects of endangered species and the factors that endanger them. From individuals to large-scale, international research and conservation efforts, people are working to protect biodiversity, endangered animals, and the food chain.

Conservation and wildlife sanctuaries: Conservation is perhaps the oldest form of habitat management. As president, Franklin Delano Roosevelt designated about 230 million acres of U.S. soil as parks, monuments, game preserves, forests, and bird reservations. He was propagating a rich tradition of conservation and preservation in the United States. The California Floristic Province, which spans the coast of California and spills into Oregon and Nevada, is considered a biodiversity hot spot. There are four main national parks within the floristic province: Yosemite, Sequoia, Redwood, and Channel Islands. Nearly 40% of this 113,438-square-mile hot spot region is conserved land, meaning commercial and residential development on this land is prohibited. Land is not the only target of conservation efforts: some areas of ocean, particularly biodiverse coral reef areas, are protected from fishing, boating, and tourist activities.

Zoos and breeding programs: Land conservation is not the only type of conservation; some people are placing endangered species in zoos. This protects the species and allows them to breed; periodically, offspring may be released into the wild. Amphibian Ark is an organization that is doing this with endangered amphibians. Breeding and release efforts may or may not be successful. The California condor is an example of a breeding program that has had only limited success. Bred condors released into the Grand Canyon and other areas of the Pacific West can survive and reproduce, but they often depend on humans for healthcare and food. The Amphibian Ark has yet to determine whether its conservation and breeding program will save species of amphibians.

Research and education: Scientists, government officials, and interested community members aim to learn more about which animals are endangered, why, and what can be done to stabilize their populations. There are many people and organizations involved. One example is the Global Amphibian Assessment, a research partnership of the International Union for Conservation of Nature, Natural Resources (ICUN)-World Conservation Union, Conservation International, and NatureServe. Hundreds of amphibian experts in 60 countries contribute information about the health of amphibian populations. The global scale of both amphibian and honeybee deaths requires international coordination between people and organizations in order to collect more data.

The U.S. Department of Agriculture (USDA) is actively studying the reasons why colony collapse disorder (CCD) is killing bees across the world. Informed by research partnerships with academic institutions such as Pennsylvania State University, the USDA plans to investigate the role of pesticides in CCD. Specifically, it may turn its attention to the pesticide coumaphos. This pesticide is intended to control mites that prey on bees, but it may be increasing the severity of CCD in some colonies.

Conservation International, a nonprofit organization, sends scientists to explore hot spot regions throughout the world as part of its Rapid Assessment Program (RAP). Scientists collect data and communicate about recent events in those areas so that conservation efforts are better informed.

Education: Increasing awareness also helps protect species from endangerment. For instance, tigers used to be traded for their bones, which were used to create a traditional Chinese medicine for arthritis and rheumatism. After they became endangered, many countries prohibited their trade. However, there is still a black market for tiger bones in China. Conservation International and the International Tiger Coalition have partnered to work with traditional medicine practitioners in order to help stop illegal tiger trading.

Laws and regulations: More local, state, and federal governments are passing legislation to protect the environments of endangered species. International organizations are meeting to agree upon environmental guidelines that countries should follow. For example, in the United States, the National Marine Fisheries Service limits the amount of tuna fishermen can legally catch. The National Oceanic and Atmospheric Administration (NOAA) has proposed an international consensus on limits for fishing species that migrate between countries' jurisdictions. This agency specifically focused on regulations for tunas, sharks, swordfish, and billfish, some species of which are threatened or endangered.

Enforcement: One way regulations such as these are enforced are through permits. Hunters and fishers must purchase permits from the state or the federal government. For example, a permit in Florida allows people to kill two alligators per hunting season. Furthermore, the permit allows hunting only at specific times during the season, so that alligator deaths are evenly distributed throughout the hunting season. Often, hunters need permits for the weapons they use. The Bureau of Park Police enforces these laws by patrolling land, swamp, and water areas.

Law violations: People violate laws regarding protected species and conserved land. The Amazon rainforest, for example, is routinely subjected to illegal deforestation. Profit from the sale of trees or the clearance of the land for cattle farming promises short-term economic gains to the local population. Local governments are often not strong or committed enough to control illegal destruction of the Amazon. Some U.S.-based nonprofit organizations are advocating the creation of sustainable economic activities for local Amazon human populations, so that destroying the rainforest is not their only recourse.

Individual effort: Although there are more internationally coordinated efforts to prevent the extinction of animals, each individual can also help. Reducing harmful emissions, whether from driving or from consumer products, reduces toxins in the food chain. Using many different, native plants for home landscaping, rather than only grass, encourages biodiversity. This, and not using pesticides, may encourage bee health. Preventing more species from spreading beyond their natural habitats is important for reducing the harmful effects invasive species can have on ecosystems. Colorado state parks ask visitors to comply with rules that prevent the spread of zebra mussels, an invasive species from Russia that first invaded the St. Lawrence Seaway. This invasive mussel is overpopulated in the United States, because it has no natural enemies.

Financial support: Many conservation efforts require financial support. For example, the Amphibian Ark estimates it needs $50-60 million to save the 500 most endangered amphibian species. Local, state, and federal governments support many conservation and research efforts, but individual contributions also are essential.

AUTHOR INFORMATION

This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

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