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The significance of mass extinction events environmental sciences essay

Personal use only; commercial use is strictly prohibited for details see Privacy Policy and Legal Notice. Until the turn of the 18th century, deeply held and widely shared beliefs about the order of nature led to a firm rejection of the possibility that species could entirely vanish. During the 19th century, however, resistance to the idea of extinction gave way to widespread acceptance following the discovery of the fossil remains of numerous previously unknown forms and direct experience with contemporary human-driven decline and the destruction of several species.

In an effort to stem continued loss, at the turn of the 19th century, naturalists, conservationists, and sportsmen developed arguments for preventing extinction, created wildlife conservation organizations, lobbied for early protective laws and treaties, pushed the significance of mass extinction events environmental sciences essay the first government-sponsored parks and refuges, and experimented with captive breeding.

In the first half of the 20th century, scientists began systematically gathering more data about the problem through global inventories of endangered species and the first life-history and ecological studies of those species.

Powerful new laws, like the U. Endangered Species Act of 1973, have been enacted and numerous international agreements negotiated in an attempt to address the issue. Despite considerable effort, scientists remain fearful that the current rate of species loss is similar to that experienced during the five great mass extinction events identified in the fossil record, leading to declarations that the world is facing a biodiversity crisis.

Responding to this crisis, often referred to as the sixth extinction, scientists have launched a new interdisciplinary, mission-oriented discipline, conservation biology, that seeks not just to understand but also to reverse biota loss.

Scientists and conservationists have also developed controversial new approaches to the growing problem of extinction: Even with the development of new knowledge and new tools that seek to reverse large-scale species decline, a new and particularly imposing danger, climate change, looms on the horizon, threatening to undermine those efforts. During that century, naturalists discovered a growing number of past extinctions in the fossil record and documented the decline and loss of numerous contemporary species, first on islands and then on continents.

An initial indifference to the prospect of human-caused extinction gave way to a growing concern by the end of the century, concern that resulted in the development of arguments for species preservation, the founding of early wildlife protection organizations, the passage of pioneering conservation laws, successful negotiation of the first international wildlife treaties, and preliminary experiments with refuges and captive breeding programs.

Rethinking extinction

During the 20th century and continuing to the present, scientists have sought to get a better handle on the scope, scale, and causes of contemporary extinction by pursuing a series of global inventories of lost and vanishing species and by carrying out ecological and life-history studies of those that remained.

The rise of the modern environmental movement in the post-World-War-II period heightened political and financial support for the study and protection of threatened wildlife and led to the passage of the U. Endangered Species Act of 1973, a bold, sweeping, and controversial law that sought both to prevent extinction and the significance of mass extinction events environmental sciences essay restore depleted plant and animal populations to sustainable levels. Despite this and numerous other national and international conservation initiatives, by the end of the 20th century, scientists warned that the world was facing a biodiversity crisis, an accelerating rate of species loss that was on par with or even exceeded the five mass extinction events that paleontologists first identified during this period.

Concerned scientists not only sought to publicize the biodiversity crisis and lobby for protective laws and treaties, they also established a new mission-oriented, interdisciplinary field—conservation biology—that focused explicitly on responding to and countering the problem of extinction. Recently they have also proposed controversial new approaches to the crisis beyond the regulations, laws, conventions, captive breeding programs, and protective refuges that have predominated thus far.

Advocates of rewilding propose that the structure and healthy functioning of ecosystems might be restored and biodiversity loss reduced by establishing large-scale core reserves, creating connections between those reserves to facilitate species migration, and the significance of mass extinction events environmental sciences essay or reintroducing the apex predators that play a key role in shaping ecosystems. At the same time, proponents of de-extinction believe that recent developments in genomics and reproductive technologies offer the hope of resurrecting lost species using the DNA found in fossils and other museum specimens.

Discovering Extinction The Order of Nature Until the end of the 18th and the beginning of the 19th centuries, the prevailing view in the West was that extinction was impossible. The Swedish taxonomist Carolus Linnaeus fleshed out that expression in an influential essay that helped lay the foundations for the science of ecology following its publication in 1791. The great chain of being, or scala naturae, provided a second, related basis for rejecting the possibility of extinction Lovejoy, 1966.

According to this widely embraced notion, the diversity of the natural world could be imagined as a long chain encompassing every possible kind of organism in a single continuous series. For those under the sway of the great chain of being, the loss of even a single species was unacceptable because it represented a threat to the entire edifice.

The Problem of Fossils Fossils, gathered in the cabinets of curiosity that proliferated across Europe during the Renaissance, provided physical evidence that might have overturned the widespread belief that extinction violated notions about the order of nature. But rather than relinquishing the assumption about a divinely ordered nature where extinction was unthinkable, naturalists clung to the hope that the organic remains of creatures that differed from those of any known living animal might still be found in deep oceans or other unexplored regions of the globe.

This is precisely the strategy that Thomas Jefferson, an avid fossil collector and founder of North American paleontology, pursued at the end of the 18th century.

The French naturalist Georges Cuvier finally broke the grip that the deeply held belief in an ordered nature presented to the acceptance of extinction. In groundbreaking papers published in 1796 and 1806, Cuvier pointed out the improbability that any unknown creature as large as an elephant might still be discovered roaming the earth. Using principles of comparative anatomy that he had developed, he also differentiated between the two living species of elephant and the fossil elephants that had been unearthed thus far, including the mastodon, which he named and described for the first time.

How humans are driving the sixth mass extinction

Cuvier later characterized a raft of other lost species, asserting they had been destroyed in the series of geological catastrophes that had periodically swept the globe Rudwick, 2014pp. In the 1820s, the Scottish zoologist and physician James Fleming argued that human predation was responsible not only for recently documented declines in wildlife populations but also the prehistoric loss of large mammals whose fossil remains were being unearthed throughout Great Britain Rehbock, 1985.

The destructive potential of humans soon received confirmation with the published accounts of the loss of three island birds in the mid-18th century: This swan-sized, flightless bird once inhabited Mauritius, an Indian Ocean island roughly 500 miles east of Madagascar. Within less than a century after the arrival of the Portuguese in the early 16th century, the species fell victim to overhunting and predation from the animals that Europeans had introduced to the island.

The destruction proved so complete that by the end of the 18th century, naturalists began to doubt whether the dodo had ever actually existed. A few years earlier the British paleontologist and comparative anatomist Richard Owen began reconstructing the story of another lost island bird, the moa, based on a specimen that had come from a trader on the east coast of North Island, New Zealand.

Owen published the first account of the species in 1838, and over the next 40 years would go on to name and describe nearly two dozen different moa species. The great auk Pinguinus impennis provided a more recent example of the destruction of an island bird through human agency Fuller, 1999.

The species had once inhabited the boreal and low-Arctic waters of the North Atlantic, where it the significance of mass extinction events environmental sciences essay hunted for its meat, eggs, feathers, and oil and widely used as fishing bait. As the great auk became rare, egg and skin collectors also decimated the species.

  1. The ensuing case, TVA v. But for now, most geologists do not accept the impact model for the crisis at the end of the Permian.
  2. We are re-enriching some ecosystems we once depleted and slowing the depletion of others. After facing limited opposition, the new field of conservation biology prospered.
  3. But what happens if the release of methane is so huge and fast that normal feedback processes are overwhelmed? First and foremost, the end of the Permian was indeed characterised by huge volcanic eruptions.

As these human-caused island extinctions were coming to light, the British naturalist Charles Darwin was slowly developing the theory of evolution by natural selection.

Following Lyell, Darwin believed that the level of biological diversity had remained roughly constant throughout the history of life, with the rate of extinction and the rate of species replacement staying about equal.

  1. The range of dates in that statement reflects profound uncertainty about the current rate of extinction.
  2. Wolves, cave lions, and wolverines occupied the landscape as predators. Seeking an eye-catching name for the gathering, Walter G.
  3. They show a massive shift towards the light isotope, carbon-12, exactly at the time of the big extinction.
  4. The carbon isotopes suggest what might have caused the temperature increase.

He thus recast the old notion of the economy of nature as a dynamic equilibrium. Documenting Continental Extinctions With the exception of Alfred Newton, the naturalists who wrote about extinction up to this point seemed largely indifferent about its occurrence. The well-publicized demise or near-demise of several species in the second half of the 19th century shattered that apathy and led to the first systematic efforts to save declining wildlife.

In North America, the nearly simultaneous decline of the passenger pigeon Ectopistes migratorius and the American bison Bison bisontwo once-superabundant species, prompted widespread concern about the issue of wildlife extinction. Many eyewitness reports detail sightings of passenger pigeon flocks that blackened the skies for hours, and the total population of the species at the time of European contact may have reached as high as four billion birds Schorger, 1955.

Similarly, 20—30 million bison, the largest land mammal on the continent, once resided on the Plains Isenberg, 2000. While numerous factors diminished both species, commercial hunting on a massive scale, facilitated by the expansion of telegraph and railroad networks that linked rural areas to the significance of mass extinction events environmental sciences essay markets, was the primary cause of their dramatic population reductions. The final large nestings of the passenger pigeon took place in western Wisconsin and northern Pennsylvania in 1882, and the last confirmed sighting of the bird in the wild was in 1902 Greenberg, 2014.

Martha, a captive bird in the Cincinnati Zoo who drew her last breath in 1914, was likely the final living passenger pigeon. The American bison nearly met a similar fate, reaching a population in the wild of less than a thousand before being rescued from the jaws of extinction. Driven by nationalistic pride and nostalgic longing for a rapidly fading past, the American taxidermist turned conservationist and zoo director William T.

Hornaday played a leading role in establishing two new institutions, the National Zoological Garden in Washington, DC 1889 and the New York Zoological Garden 1899that he hoped would provide a safe haven for numerous endangered native animals.

He also helped found and led a new organization, the American Bison Society, that sought to preserve its namesake.

After several failed attempts, Hornaday managed to begin building a bison breeding herd in the South Bronx, and in 1907 he shipped 15 of the animals back west, to the newly established Wichita National Game Reserve in Oklahoma Territory, the first of several reintroduction projects involving the species Barrow, 2009pp.

In Europe, the extinction of the aurochs Bos primigeniusthe ancestor of domestic cattle, in 1627 seems not to have garnered much attention or concern Vuure, 2005. The species once ranged throughout western, central, and south-eastern Europe, where it helped shape broadleaf forests and forested steppe ecosystems. Deforestation and overhunting dramatically reduced its range and overall population, and by the end of the 19th century, there were only two populations remaining in the wild: The extinction of the quagga Equus quagga quagga provided another example of the destructive potential of humans.

Impressive herds of this equid species, whose front half resembled a zebra while its back half looked more like a horse, once ranged across the great plains of southern Africa. By 1860 only a small remnant population survived near the Vaal River, and the last wild quaggas were captured around 1870.

Early Responses to the Extinction Threat As the story of the bison reveals, romantic nostalgia and ardent nationalism were two key arguments in early campaigns to rescue endangered species.

Assertions about the economic value of organisms—as sources of food, drugs, leather, fiber, oils, and other commodities—also loomed large in many the significance of mass extinction events environmental sciences essay conservation initiatives.

The longstanding belief that every organism plays a vital role in maintaining the stability of the world—an idea initially suggested by the notion of economy of nature and later reinforced with the emergence of the science of ecology—provided a fourth justification for species preservation. The evolutionary argument that, as the product of eons of time, species were living monuments every bit as worthy of protection as ancient cultural monuments, was also occasionally voiced.

At the same time, naturalists maintained that plants, animals, and biotic communities should be preserved to allow for the possibility of the continued scientific study of them.

Ethical arguments, either that organisms had a fundamental right to continued existence or that protecting declining plant and animal populations was an important obligation to future human generations, also began to emerge during the first half of the 20th century. Finally, many of those supporting conservation efforts felt a strong sense of emotional attachment to threatened species and landscapes that they sought to protect. Moved by these considerations and a growing sense that wildlife populations were under threat, naturalists, sportsmen, and concerned citizens began mobilizing by the end of the 19th century.

In England, the earliest evidence of interest in protecting declining non-game species came when a committee within the British Association for the Advancement of Science joined forces with the Yorkshire Association for the Protection of Sea Birds in 1868 to lobby for the Sea Birds Preservation Act of 1869 Cowles, 2013.

More than two decades later the Plumage League and the Fur and Feather League merged to create the Society for the Protection of Birds, an organization that received a royal charter in 1904 Allen, 1994pp.

Numerous other wildlife conservation organizations sprouted up in Europe and the United States during this period. The first local and state Audubon Societies were founded in the mid-1880s, while the National Association of Audubon Societies, the predecessor to the National Audubon Society, was launched in 1905 Barrow, 1998 ; Doughty, 1975.

Following prodding from the Dutch naturalist Peter van Tienhoven, in 1928 the International Union of Biological Sciences established a conservation organization that would soon be known as the International Office for the Protection of Nature Boardman, 1981.


Conservationists also secured groundbreaking legislation and treaties aimed at protecting threatened wildlife. That agreement was superseded by the Convention Relative to the Preservation of Fauna and Flora in the Natural State the London Convention of 1933which established a two-class classification schema for threatened wildlife in Africa: In 1916, the U.

Documenting Extinction Inventories of Extinction The widespread decline of wildlife also prompted efforts to get a more precise handle on the scope and scale of the significance of mass extinction events environmental sciences essay problem. Museum-based naturalists compiled the earliest catalogs of endangered and extinct species Barrow, 2009. The wealthy British banker and naturalist Walter Rothschild, who amassed a massive natural history museum at his family estate at Tring Park, published the first extensive inventory of birds believed to be lost in 1907.

His lavishly illustrated volume, Extinct Birds, included 166 species, most of which were known from fossils. In the 1920s, curators at the Museum of Comparative Zoology MCZ at Harvard began a card catalog of rare and vanishing bird species as part of their campaign to fill out their collection with representatives from every known avian genus. Based on this catalog, John C. Not until 1954 did the American Committee publish James C. The new organization, which included representatives from national governments and NGOs, sought to use the power of science to shield the natural world from the onslaught of civilization, but from the beginning rescuing endangered species was among its highest priorities.

At its first conference in 1949, delegates approved a resolution highlighting 13 birds and 14 mammals of particular concern, and, at the prodding of Harold J. In 1961 the British ornithologist Max Nicholson helped establish the World Wildlife Fund to provide financial support for the IUCN and other conservation organizations, and two years later, the British wildlife artist, aviculturalist, and IUCN board member Peter Scott created the first Red Data Books, to systematically document the status of endangered species Barrow, 2009.

In the late 1920s, the Harvard-trained ornithologist Alfred O. Among those who benefited from this new funding source was the Cornell doctoral student James T. Tanner, who spent several seasons studying the elusive ivory-billed woodpecker Campephilus principalis at a site in northeast Louisiana that was being actively logged.

Audubon also sponsored the research of Carl Koford, who spent more than 400 days in the remote mountain regions of central and southern California observing the rare California condor Gymnogyps californianusthe largest soaring land bird in North America, before publishing his report in 1953.

Legislating Endangered Species Protection in the Environmental Age Technological developments in the post-World War II era had the paradoxical effect of exacerbating the threats to wildlife across the globe and, through advances in and popularization of the science of ecology, rendering those threats more visible to a broader public Worster, 1994.

Particularly notable in its impact was the bomb, an unprecedented destructive force that released dangerous radioactive fallout that was soon being detected in biotic communities, food supplies, and human bodies across the globe Winkler, 1993.

In an influential bestselling book, Silent Spring 1962Rachel Carson used growing concern about fallout from routine atmospheric testing of nuclear weapons to strengthen her case about the dangers posed by the new synthetic pesticides that began to be widely used in agricultural production and public health campaigns in the second half the significance of mass extinction events environmental sciences essay the 20th century.

A series of highly publicized environmental disasters—oil spills, smog events, fish kills, algal blooms, and others—not only further raised public consciousness about contemporary environmental threats but also led to calls for stronger laws and regulations to protect human and land health McCormick, 1989.