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    if all individuals in the last remaining population of a particular frog species were all highly related, which type of diversity would be of greatest concern when planning to prevent the species from going extinct?


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    Top 10 U.S. Endangered Species Threatened by Human Population

    On July 12, 2011, the Center for Biological Diversity struck a historic legal settlement with the U.S. Fish and Wildlife Service, requiring the agency to make initial or final decisions on whether to add hundreds of imperiled plants and animals to the endangered species by 2018.

    Top 10 U.S. Endangered Species Threatened by Human Population

    As the human population grows and the rich countries continue to consume resources at voracious rates, we are crowding out, poisoning and eating all other species into extinction. With the world population hitting 7 billion, the Center is marking this milestone by releasing a list of species in the United States facing extinction caused by the growing human population. The 10 species represent a range of geography, as well as species diversity — but all are critically threatened by the effects of human population. Some, like the Florida panther and Mississippi gopher frog, are rapidly losing habitat as the human population expands. Others are seeing their habitat dangerously altered — like the small flowering sandplain gerardia in New England — or, like the bluefin tuna, are buckling under the weight of massive overfishing. Still others, like the polar bear, are facing extinction because of fossil fuels driving catastrophic global warming.

    Here are a few highlights:

    As Florida's panther numbers plummeted, the state's human population nearly doubled over the past 30 years. Recent development patterns pose extreme threats to panthers. As the Florida coasts approach full buildout and have become unaffordable to most people, development has moved inland to the same places panthers retreated to as safe havens decades ago.

    Of greatest concern is the western Atlantic bluefin tuna that spawns in the Gulf of Mexico and has declined by more than 80 percent since 1970 due to overharvesting. Prized as a sushi fish around the world, it has become more valuable as it has become rare. One fish in 2011 sold for $396,000. The large, warm-blooded bluefin tuna is a common, upscale sushi menu item and has been severely overfished. The Atlantic bluefin, like so many other ocean species, is threatened by humans' ravenous appetites: Demand far exceeds sustainable fishing levels.

    Ninety-five percent of the U.S. breeding population of loggerheads nests in Florida, whose human population has doubled in the past 30 years. Thanks to careful management, the species' population increased 24 percent from 1989 to 1998, but under intense pressure from development and recreational beach use, it declined dramatically thereafter, raising concerns it should be uplisted to endangered status. The population has increased in recent years, but is still highly vulnerable to nesting habitat destruction and disruption. Just 42,000 nesting attempts were made on Florida beaches in 2011.

    In New England and the Atlantic coast, brush fires once thinned out dense pine forests and created a constantly moving mosaic of grasslands and prairies. The fires have been suppressed to protect human structures, causing open habitats to be permanently replaced by forest and brush. This nearly caused the extinction of the sandplain gerardia, a coastal plant in the snapdragon family.

    Lange's metalmark lives only in the Antioch Dunes at the southern end of San Francisco Bay. This unique ecosystem harbored many unique species, and many species have gone extinct as its dunes were hauled away in massive increments. After the 1906 fires, the city of San Francisco was rebuilt using brick-building material removed from the dunes.

    Lange's metalmark is one of the most endangered species in the United States. It declined from some 250,000 in historic times to just 154 in 1986. It improved a bit, but then declined to just 45 butterflies in 2006. Today the species is still on the knife edge of extinction, with about 150 individuals remaining.

    The U.S. Fish and Wildlife Service proposed to designate 7,015 acres as protected critical habitat for the Mississippi gopher frog in Mississippi and Louisiana in 2011.

    Reduced to approximately 100 individuals in the wild, the Mississippi gopher frog exists in just three small ponds just outside the proposed town of Tradition, Mississippi. Planned development would have a devastating effect on this rare frog.

    The Southern Nevada Water Authority has proposed a massive project to pump billions of gallons of groundwater a year from eastern Nevada and western Utah through a 300-mile pipeline to supply rapidly growing urban areas like Las Vegas. The project will have a disastrous effect on dozens of imperiled species, including the White River spinedace, which was protected as an endangered species in 1985. One population of this rare fish was extirpated in 1991 because of irrigation diversion, and fewer than 50 fish remained in a single population in northeast Nevada.

    The rapid growth of the global human population — which has doubled since 1970 — has fed a massive push for more and more polluting fossil fuels and dramatically altered the planet's atmosphere. A 2009 study on the relationship between population growth and global warming found that the carbon legacy of just one person can produce 20 times more greenhouse gases than one person saves by carbon-reducing steps such as driving high-mileage, using energy-efficient applicants and light bulbs. Few animals are bearing more of the brunt of the global climate crisis than the polar bear.

    The gulf sturgeon, an anadromous fish, was placed on the threatened species list in 1991. Its most imperiled populations occur in the Apalachicola River, fed by rivers from Lake Lanier. Gulf sturgeon lay eggs on the waterlines along the banks of rivers, and maintaining the right level of water is critical to their breeding success.

    The kit fox was listed as endangered in 1967. Today there are fewer than 7,000 scattered among fragmented populations. The four counties with known San Joaquin kit foxes have grown by 60 percent — by another 1.5 million people — since 1983.

    Besides habitat loss, the San Joaquin kit fox is threatened by pesticides and rodenticides associated with intensive agricultural use, industrial activities and residential areas in the Central Valley. Kit foxes' small-mammal prey base has been significantly reduced by rodenticides, which not only kill life-sustaining prey but can also kill kit foxes when they build up in the foxes' bodies. Kit foxes have adapted to get their water from the prey they eat making them even more dependent on their food source. They also often burrow in other animals' dens, leaving them vulnerable to other human activities such as fumigants used to kill coyotes.

    Top 10 U.S. Endangered Species Threatened by Human Population

    Source : www.biologicaldiversity.org

    Threats to Biodiversity

    Lakes and islands are particularly vulnerable to extinction threats from introduced species. In Lake Victoria, as mentioned earlier, the intentional introduction of the Nile perch was largely responsible for the extinction of about 200 species of cichlids. The accidental introduction of the brown tree snake via aircraft from the Solomon Islands to Guam in 1950 has led to the extinction of three species of birds and three to five species of reptiles endemic to the island. Several other species are still threatened. The brown tree snake is adept at exploiting human transportation as a means to migrate; one was even found on an aircraft arriving in Corpus Christi, Texas. Constant vigilance on the part of airport, military, and commercial aircraft personnel is required to prevent the snake from moving from Guam to other islands in the Pacific, especially Hawaii. Islands do not make up a large area of land on the globe, but they do contain a disproportionate number of endemic species because of their isolation from mainland ancestors.

    It now appears that the global decline in amphibian species recognized in the 1990s is, in some part, caused by the fungus Batrachochytrium dendrobatidis, which causes the disease chytridiomycosis. There is evidence that the fungus, native to Africa, may have been spread throughout the world by transport of a commonly-used laboratory and pet species: the African clawed toad (Xenopus laevis). It may well be that biologists themselves are responsible for spreading this disease worldwide. The North American bullfrog, Rana catesbeiana, which has also been widely introduced as a food animal, but which easily escapes captivity, survives most infections of Batrachochytriumdendrobatidis and can act as a reservoir for the disease.

    Climate Change and Biodiversity

    The global warming trend is recognized as a major biodiversity threat, especially when combined with other threats such as habitat loss.

    Learning Objectives

    Evaluate climate change and its impact on biodiversity

    Key Takeaways

    Key Points

    Key Terms

    Climate Change

    Climate change, specifically, the anthropogenic (caused by humans) warming trend presently underway, is recognized as a major extinction threat, particularly when combined with other threats such as habitat loss. Scientists disagree about the probable magnitude of the effects, with extinction rate estimates ranging from 15 percent to 40 percent of species by 2050. Scientists do agree, however, that climate change will alter regional climates, including rainfall and snowfall patterns, making habitats less hospitable to the species living in them.

    Impact of Climate Change on Biodiversity


    Grizzly-polar bear hybrid: Since 2008, grizzly bears (Ursus arctos horribilis) have been spotted farther north than their historic range, a possible consequence of climate change. As a result, grizzly bear habitat now overlaps polar bear (Ursus maritimus) habitat. The two kinds of bears, which are capable of mating and producing viable offspring, are considered separate species as historically they lived in different habitats and never met. However, in 2006 a hunter shot a wild grizzly-polar bear hybrid known as a grolar bear, the first wild hybrid ever found.

    The warming trend will shift colder climates toward the north and south poles, forcing species to move with their adapted climate norms while facing habitat gaps along the way. The shifting ranges will impose new competitive regimes on species as they find themselves in contact with other species not present in their historic range. One such unexpected species contact is between polar bears and grizzly bears. Previously, these two species had separate ranges. Now, with their ranges are overlapping, there are documented cases of these two species mating and producing viable offspring. Changing climates also throw off species’ delicate timing adaptations to seasonal food resources and breeding times. Many contemporary mismatches to shifts in resource availability and timing have recently been documented.

    Range shifts are already being observed. For example, some European bird species’ ranges have moved 91 km northward. The same study suggests that the optimal shift based on warming trends was double that distance, suggesting that the populations are not moving quickly enough. Range shifts have also been observed in plants, butterflies, other insects, freshwater fishes, reptiles, and mammals.

    Climate gradients will also move up mountains, eventually crowding species higher in altitude and eliminating the habitat for those species adapted to the highest elevations. Some climates will completely disappear. The rate of warming appears to be accelerated in the arctic, which is recognized as a serious threat to polar bear populations that require sea ice to hunt seals during the winter months; seals are the only source of protein available to polar bears. A trend to decreasing sea ice coverage has occurred since observations began in the mid-twentieth century. The rate of decline observed in recent years is far greater than previously predicted by climate models.

    Finally, global warming will raise ocean levels due to glacial melt and the greater volume of warmer water. Shorelines will be inundated, reducing island size, which will have an effect on many species; a number of islands will disappear entirely. Additionally, the gradual melting and subsequent refreezing of the poles, glaciers, and higher elevation mountains, a cycle that has provided freshwater to environments for centuries, will also be jeopardized. This could result in an overabundance of salt water and a shortage of fresh water.

    Threats to Biodiversity

    Source : courses.lumenlearning.com

    endangered species

    Endangered species, any species that is at risk of extinction because of a sudden rapid decrease in its population or a loss of its critical habitat. Previously, any species of plant or animal that was threatened with extinction could be called an endangered species.

    IUCN Red List of Threatened Species

    One of the most well-known objective assessment systems for declining species is the approach unveiled by the International Union for Conservation of Nature (IUCN) in 1994. It contains explicit criteria and categories to classify the conservation status of individual species on the basis of their probability of extinction. This classification is based on thorough, science-based species assessments and is published as the IUCN Red List of Threatened Species, more commonly known as the IUCN Red List. It is important to note that the IUCN cites very specific criteria for each of these categories, and the descriptions given below have been condensed to highlight two or three of the category’s most salient points. In addition, three of the categories (CR, EN, and VU) are contained within the broader notion of “threatened.” The list recognizes several categories of species status:

    IUCN categories

    cardboard palm

    The IUCN system uses five quantitative criteria to assess the extinction risk of a given species. In general, these criteria consider:

    All else being equal, a species experiencing a 90 percent decline over 10 years (or three generations), for example, would be classified as critically endangered. Likewise, another species undergoing a 50 percent decline over the same period would be classified as endangered, and one experiencing a 30 percent reduction over the same time frame would be considered vulnerable. It is important to understand, however, that a species cannot be classified by using one criterion alone; it is essential for the scientist doing the assessment to consider all five criteria to determine the status. Each year, thousands of scientists around the world assess or reassess species according to these criteria, and the IUCN Red List is subsequently updated with these new data once the assessments have been checked for accuracy to help provide a continual spotlight on the status of the world’s species.

    Svalbard Global Seed Vault

    The IUCN Red List brings into focus the ongoing decline of Earth’s biodiversity and the influence humans have on life on the planet. It provides a globally accepted standard with which to measure the conservation status of species over time. By 2019 more than 96,500 species had been assessed by using the IUCN Red List categories and criteria. Today the list itself is an online database available to the public. Scientists can analyze the percentage of species in a given category and the way these percentages change over time. They can also analyze the threats and conservation measures that underpin the observed trends.

    Other conservation agreements

    The United States Endangered Species Act

    In the United States, the U.S. Fish and Wildlife Service (USFWS) of the Department of the Interior and the National Oceanic and Atmospheric Administration (NOAA) of the Department of Commerce are responsible for the conservation and management of fish and wildlife, including endangered species, and their habitats. The Endangered Species Act (ESA) of 1973 obligates federal and state governments to protect all life threatened with extinction, and this process is aided by the creation and continued maintenance of an endangered species list, which contains 1,662 domestic and 686 foreign species of endangered or threatened animals and plants as of 2019. According to the USFWS, the species definition extends to subspecies or any distinct population segment capable of interbreeding. Consequently, threatened subsets of species may also be singled out for protection. Furthermore, the ESA includes provisions for threatened species—that is, any species expected to become endangered within a substantial portion of its geographic home range. It also promotes the protection of critical habitats (that is, areas designated as essential to the survival of a given species).

    rusty patched bumblebee

    The ESA is credited with the protection and recovery of several prominent species within the borders of the United States, such as the bald eagle (Haliaeetus leucocephalus), the American alligator (Alligator mississippiensis), and the gray wolf (Canis lupus).

    bald eagle


    To prevent the overexploitation of species as they are traded across national boundaries, the Convention on International Trade in Endangered Species of Wild Flora and Fauna (CITES) was created by international agreement in 1973 and put into effect in 1975. The agreement sorts over 5,800 animal and 30,000 plant species into three categories (denoted by its three appendixes). Appendix I lists the species in danger of extinction. It also prohibits outright the commercial trade of these species; however, some can be traded in extraordinary situations for scientific or educational reasons. In contrast, Appendix II lists particular plants and animals that are less threatened but still require stringent controls. Appendix III lists species that are protected in at least one country that has petitioned other countries for help in controlling international trade in that species. As of 2017, CITES had been signed by 183 countries.

    Species assessment and management

    Together, the thousands of scientists and conservation organizations that contribute to the IUCN Red List and other systems of assessment provide the world’s largest knowledge base on the global status of species. The aim of these systems is to provide the general public, conservationists, nongovernmental organizations, the media, decision makers, and policy makers with comprehensive and scientifically rigorous information on the conservation status of the world’s species and the threats that drive the observed patterns of population decline. Scientists in conservation and protected area management agencies use data on species status in the development of conservation planning and prioritization, the identification of important sites and species for dedicated conservation action and recovery planning, and educational programs. Although the IUCN Red List and other similar species-assessment tools do not prescribe the action to be taken, the data within the list are often used to inform legislation and policy and to determine conservation priorities at regional, national, and international levels. In contrast, the listing criteria of other categorization systems (such as the United States Endangered Species Act, CITES, and CMS) are prescriptive; they often require that landowners and various governmental agencies take specific mandatory steps to protect species falling within particular categories of threat.

    It is likely that many undescribed or unassessed species of plants, animals, and other organisms have become or are in the process of becoming extinct. To maintain healthy populations of both known and unknown species, assessments and reassessments are valuable tools. Such monitoring work must continue so that the most current knowledge can be applied to effective environmental monitoring and management efforts. For many threatened species, large well-protected conservation areas (biological reserves) often play major roles in curbing population declines. Such reserves are often cited by conservation biologists and other authorities as the best way to protect individual species as well as the ecosystems they inhabit. In addition, large biological reserves may harbour several undescribed and unassessed species. Despite the creation of several large reserves around the world, poaching and illegal trafficking plague many areas. Consequently, even species in those areas require continued monitored and periodic assessment.

    endangered species

    Source : www.britannica.com

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