The Sixth Species Extinction Event by Humans

Extinctions in better known groups of vertebrates are at rates comparable to many mass extinctions in the geological past. There is evidence to suggest that contemporary extinctions have not been as high as predicted for a number of reasons. Some of the reasons that contemporary extinctions have not been as high as predicted include effective conservation efforts, species surviving in managed landscapes, and "extinction debt", a term that loosely means "future extinction of species due to events in the past". Extinction debt occurs due to time delays between the impacts on a species, such as the destruction of habitat, and the species' actual extinction or disappearance. Conservation is effective in delaying extinction because the policies it initiates can protect key environments and restore habitats and populations to their former status. There are also some species that are so versatile that they can survive in a world where climate has changed as well (Costello, 2013). The marine species are a great example of this phenomenon because of their ability to thrive in a variety of climates in different oceans and seas.

Yet while marine species may be able to adapt to distribution to climate change more easily than terrestrial species are able to, there are a number of problems that affect them as well. Induced acidification of oceans due to climate change, stratification, and deoxygenation are the sort of changes that have contributed to mass extinctions of marine species over the course of millions of years. It is for this reason that global environmental changes present greater risk of mass extinction because of anthropogenic influences on the natural world than recent human-mediated extinctions. One other reason for this concern is local threats, including habitat loss, hunting, and harvesting, are now contributing to the possibility of an anthropogenic mass extinction along with climate change (Costello, 2013).

Human populations have had a direct impact on Earth's biodiversity. Coupled with their unique use of land, this species of ape has changed more than three-quarters of the terrestrial biosphere into what have been called "anthropogenic biomes" or anthromes. This has occurred by replacing native ecosystems with agricultural croplands and settlements and by managing and disturbing remnant and recovering ecosystems that are located within these used lands. This form of direct anthropogenic transformation has caused unprecedented global changes in the Earth's biodiversity as native species struggle to survive and many are also ultimately driven to extinction locally and globally. Domestic and exotic species are rapidly becoming established as well (Ellis, 2012).

Coral reefs are also another example of an exotic species that is on the brink. Due to the ocean acidification from human emissions, many suffer bleaching, which ultimately kills off the coral and eventually the species of fish and other animals that depend on such organisms for survival. Coral reef fisheries also depend on these unique creatures in order to maintain a livelihood for tens of millions of people. Sadly, with devastating habitat degradation and unsustainable fishing there is severe depletion of stocks of reef fish occurring. Understanding how the social and economic factors of humans play a role in interacting with fishing and habitat degradation with respect to fish stocks is of vital concern if sustainability of the coral reefs is to be ensured as well (Brewer, 2013).

Discussion

From the sources analyzed, there appears to be a few general ideas that emerge about a possible sixth mass extinction by humans. Ninety-nine percent (99%) of all life that has ever existed on this planet has become extinct (Pievani, 2014). For a large portion of their history, humans have been dependent on the environment for plants, animals, and water supply (Foley, 2013). Human population density, which drives land use intensification, might be the best indicator of anthropogenic ecological change than land use or habitat loss (Ellis, 2012). Local population pressure and external markets, for instance, have had additive negative effects on vulnerable reef fish (Brewer, 2013).

Preservation will only be possible if humans work hard enough, though it is harder than parachuting species into cross-cutting assemblages of social interest and material praxis (McKee, 2014). In other words, preservation is possible if the human race pushes for it, while at the same time we cannot just expect to take animal and plant species from certain areas and just leave them in an area we design specifically for them. There is a number of impacts this study has, not just for biologists, but for every living person on Earth who is affected by biodiversity loss. More research should be done on specific species of flora and fauna that are not as documented as well as other animals.

Conclusion

As the human race progresses into the future, crucial decisions must be made regarding the fate of the Earth's biodiversity. Technology will have to cooperate with all of Earth's floral and faunal species. Every single economy will have to be remade to allow species to recover and thrive. There should be investigation into the status of unknown species as there is a lack of documentation and sightings for these species. There should also be consideration in maintaining and protecting Earth's ecosystems while living in harmony with the environment.

Acknowledgements

This research paper is made possible from many people who have supported me in my academic studies. I would like to thank my mother for always having faith in my abilities and my father for always giving me guidance when I needed it. I would also like to thank my older brother for his role as a peer reviewer and as a teacher who helped me improve my writing abilities. And finally, I would like to thank my younger brother for his peer reviewing and honest critique of the literature in this paper.

Author

Victor Nazarevich is a student in the Bachelor of Science (Physical Sciences, Earth and Planetary Sciences) degree program at MacEwan University.

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Figure 1. Effect of Fragmentation of Species Number. Adapted from "Species-area relationships and extinctions caused by habitat loss and fragmentation," by Ilkka Hanski, Joel Rybicki & Brian Enquist, 2013, Ecology Letters, 16 (Supplements 1), p. 29. Copyright 2013 by the National Academy of Sciences of the United States of America. Adapted with permission.

Figure 2. Effect of habitat fragmentation on the number of tropical bird species. Adapted from "Species-area relationships and extinctions caused by habitat loss and fragmentation," by Ilkka Hanski, Joel Rybicki & Brian Enquist, 2013, Ecology Letters, 16 (Supplements 1), p. 29. Copyright 2013 by the National Academy of Sciences of the United States of America. Adapted with permission.

Figure 3. Relationship between extinction rates and the time interval over which the rates were calculated, for mammals. Adapted from "Has the Earth's sixth mass extinction already arrived?" by Anthony D. Barnosky, Nicholas Matzke, Susumu Tomiya, Guinevere O. U. Wogan, Brian Swartz, Tiago B. Quental, Charles Marshall, Jenny L. McGuire, Emily L. Lindsey, Kaitlin C. Maguire, Ben Mersey & Elizabeth A. Ferrer, 2011, Nature, 471, p. 51-57. Copyright 2011 by Nature Publishing Group, a division of Macmillan Publishers Limited. Adapted with permission.

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