Thinking about the Biodiversity Loss in This Changing World (original) (raw)
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The Sixth Species Extinction Event by Humans
The number of species becoming extinct has drawn a significant deal of attention from scientists and non-scientists alike. This research reviews recent literature citing evidence for the impact humans have had on our planet and how our biological systems are affected in both known species of flora and fauna as well as unknown species of flora and fauna, the latter lacking documentation as well as sightings by humans. Theoretical research is derived from previous research investigating the impacts of humankind's use of the land as well as population increases. Though there are many different definitions of what a mass extinction is and gradations of extinction intensity, a conservative approach is used to assess the seriousness of the current ongoing extinction crisis, setting the highest level of recognition for mass extinction, in extreme diversity loss associated with the Big Five extinction events (Barnosky, 2011). Understanding the relationship between extinction and functional diversity over time will be critical for making conservation work (Boyer & Jetz, 2014). If another mass extinction is allowed to progress, it would mean the end of biodiversity as we know it and would also mean that greater pressure would be placed on both humans and flora and fauna to survive in a world completely changed by the Anthropocene. Over the course of 8,000-10,000 years, humans grew in population and changed the landscape
Proceedings of the National Academy of Sciences, 2017
Significance The strong focus on species extinctions, a critical aspect of the contemporary pulse of biological extinction, leads to a common misimpression that Earth’s biota is not immediately threatened, just slowly entering an episode of major biodiversity loss. This view overlooks the current trends of population declines and extinctions. Using a sample of 27,600 terrestrial vertebrate species, and a more detailed analysis of 177 mammal species, we show the extremely high degree of population decay in vertebrates, even in common “species of low concern.” Dwindling population sizes and range shrinkages amount to a massive anthropogenic erosion of biodiversity and of the ecosystem services essential to civilization. This “biological annihilation” underlines the seriousness for humanity of Earth’s ongoing sixth mass extinction event.
Vertebrate biodiversity losses point t sixth mass extinction
The human race faces many global to local challenges in the near future. Among these are massive biodiversity losses. The 2012 IUCN/SSC Red List reported evaluations of *56 % of all vertebrates. This included 97 % of amphibians, mammals, birds, cartilaginous fishes, and hagfishes. It also contained evaluations of *50 % of lampreys, *38 % of reptiles, and *29 % of bony fishes. A cursory examination of extinction magnitudes does not immediately reveal the severity of current biodiversity losses because the extinctions we see today have happened in such a short time compared to earlier events in the fossil record. So, we still must ask how current losses of species compare to losses in mass extinctions from the geological past. The most recent and best understood mass extinction is the Cretaceous terminal extinction which ends at the Cretaceous– Paleogene (K–Pg) border, 65 MYA. This event had massive losses of biodiversity (*17 % of families, [50 % of genera, and [70 % of species) and exterminated the dinosaurs. Extinction estimates for non-dinosaurian vertebrates at the K–Pg boundary range from 36 to 43 %. However, there remains much uncertainty regarding the completeness, preservation rates, and extinction magnitudes of the different classes of vertebrates. Fuzzy arithmetic was used to compare recent vertebrate extinction reported in the 2012 IUCN/SSC Red List with biodiversity losses at the end of K–Pg. Comparisons followed 16 different approaches to data compilation and 288 separate calculations. I tabulated the number of extant and extinct species (extinct ? extinct in the wild), extant island endemics, data deficient species, and so-called impaired species [species with IUCN/SSC Red List designations from vulnerable (VU) to critically endangered (CR)]. Species that went extinct since 1500 and since 1980 were tabulated. Vertebrate extinction moved forward 24–85 times faster since 1500 than during the Cretaceous mass extinction. The magnitude of extinction has exploded since 1980, with losses about 71–297 times larger than during the K–Pg event. If species identified by the IUCN/SSC as critically endangered through vulnerable, and those that are data deficient are assumed extinct by geological standards, then vertebrate extinction approaches 8900–18,500 times the magnitude during that mass extinction. These extreme values and the great speed with which vertebrate biodiversity is being decimated are comparable to the devastation of previous extinction events. If recent levels of extinction were to continue, the magnitude is sufficient to drive these groups extinct in less than a century.
Global biodiversity loss: Exaggerated versus realistic estimates
For the past 50 years, the public has been made to feel guilty about the tragedy of human-caused biodiversity loss due to the extinction of hundreds or thousands of species every year. Numerous articles and books from the scientific and popular press and publicity on the internet have contributed to a propaganda wave about our grievous loss and the beginning of a sixth mass extinction. However, within the past few years, questions have arisen about the validity of the data which led to the doom scenario. Here I show that, for the past 500 years, terrestrial animals (insects and vertebrates) have been losing less than two species per year due to human causes. The majority of the extinctions have occurred on oceanic islands with little effect on continental ecology. In the marine environment, losses have also been very low. At the same time, speciation has continued to occur and biodiversity gain by this means may have equaled or even surpassed the losses. While species loss is not, so far, a global conservation problem, ongoing population declines within thousands of species that are at risk on land and in the sea constitute an extinction debt that will be paid unless those species can be rescued.