Our world has undergone five mass extinctions of lifeforms in the distant past as a result of naturally occurring catastrophic events. The most recent occurred around 65 million years ago when an asteroid impact near the Yucatan peninsula of Mexico caused the extirpation of virtually all dinosaurs and many other species. That dramatic event marked the end of a geologic period known as the Cretaceous.
Today, the world has entered into a sixth great extinction of animal and plant species with a causation that is categorically different from all previous ones: mankind. Homo sapiens – perhaps a misnomer – has walked the Earth for a mere 200,000 years, a minuscule fraction of the 3 billion years over which some form of life has existed. Yet in the past 200 years or so, mankind, through a combination of voracious exploitation of the natural world and a seemingly unquenchable penchant for combustion of fossil fuels, has set a course that has already led to the extinction of nearly 700 vertebrate species. Moreover, we are on a course that will yield much greater devastation described below.
As humanity’s population has exponentially ballooned over the past two centuries from 910 million in 1800 to over 7.7 billion today, the sheer number of humans and their aggregate activities have transformed the face of the Earth as huge forests have been cleared, hundreds of large cities (including approximately 35 megacities)1 have been built, vast swaths of natural flora have been replaced by monocultures of grain crops, widespread use of pesticides has become commonplace, natural wildlife habitats have been steadily converted to man’s use, and mining of coal, metals and minerals for energy and industrial use has scarred millions of acres. Approximately 96 percent of the mass of all mammals on Earth is made up by humans (33 percent) and the livestock we raise for food (over 62 percent).2 Wild mammals – terrestrial and marine – account for only 4 percent, a percentage that is shrinking daily. The vast scope of the physical impacts to the Earth from man’s activities has led some scientists to refer to the current era as the Anthropocene.
Concomitant with this massive usurpation of Earth’s land masses for man’s use has been the loss of natural habitat for wildlife, one of the dominant causes of the extinctions mentioned above. But loss of habitat is not the sole cause of threats to natural lifeforms. Overfishing of the world’s oceans by industrial fishing fleets at higher than sustainable rates has already reduced some marine fish and shellfish species to such low numbers that their survival is seriously threatened. The perceived threat to livestock posed by large, apex predators, such as wolves, grizzly bears, tigers, and leopards, has led to severely diminished numbers of these species as they are hunted by farmers and ranchers. Then there is the marked reduction of elephants, rhinoceroses, sharks and certain other species that are poached for their tusks, horns, fins and other body parts that have substantial black market value due to inane superstitions.
More recently -- over the past 40 years or so, climate change has begun to exacerbate the stresses already being imposed on natural wildlife habitats. The most immediate impact of human-caused climate change has been global warming. The global average surface temperature has risen about 1.1°C (nearly 2°F) since 1900 and by 2100 the increase in global average temperature is projected as likely to reach 3°C to 5°C (5.4°F to 9°F) over the 1900 level if aggressive measures and not undertaken in the very near future to drastically reduce fossil fuel combustion emissions. The temperature increases over land masses are approximately twice the global average increase and even higher in the Arctic.
These temperature increases are substantial and will lead to frequent, severe heat waves in many parts of the world that will be directly dangerous to wildlife or exacerbate the habitat destruction already occurring.3 The rising global temperatures will also cause worsening extremes in weather, such as increasing rainfall in many areas while increasing drought in other areas such as the American West. Wildfires, which destroy wildlife and habitat, will increase in frequency in those areas where climate change exacerbates drought conditions. These trending impacts are likely to lead to transitions in dominant plant forms in many areas of the world or to desertification in others. Such changes may result in particular natural habitat areas no longer providing the plant species on which indigenous animal species are reliant.
However, other, indirect effects will be problematic as well. For example, the oceans are absorbing slightly over 30 percent of the carbon dioxide emitted into the atmosphere from fossil fuel combustion4 and over 90 percent of the heat generated as the anthropogenic carbon emissions remaining in the atmosphere exert their greenhouse effect.5 This is increasing the acidity and temperature of near surface ocean waters to the point that it threatens the survivability of most coral reefs. This will have a critical adverse impact on marine biodiversity since coral reefs act as giant nurseries for many species of marine aquatic life. If the current trend continues, it is projected that most coral reefs will be “dead” by 2035.
The combined impacts of climate change and man’s aggressive activities to convert vast areas of Earth to his use threatens the elimination of around 1 million animal (vertebrate, invertebrate and insect) and plant species.6 This is a staggering number, representing roughly 10% to 12% of all animal and plant species. Several recent studies have indicated similar but more complex impacts on insect species, including declines in terrestrial insect populations, while freshwater insect populations have increased.7
Two human traits are predominant in shaping the actions that have brought about the Anthropocene extinction: greed and ignorance.
Greed is as old as mankind.8 One would have hoped that over the many thousand years of our history, we would have come to be wary of the insidious effects of unrestrained greed. But no, it is with us as much as ever, it seems. In fact, greed seems to be running rampant in the present day and may be thought of, we suggest, as a defining characteristic of the Anthropocene.
How else do we explain:
• The recent fatal shooting of the last male white rhinoceros, leaving two females to live out the end of their species – so that a poacher could harvest the coveted rhino horn;
• The micro-evolutionary response of elephants toward smaller tusks since elephants with large tusks are slaughtered by poachers before they can produce offspring;
• The burning of large swaths of the Amazonian rainforest -- with the Brazilian government’s blessing -- so that large agricultural companies can profit from growing more soybeans, a cash crop sought by the Chinese;
• The growing wealth gap between wealthy business owners and middle/low income workers who have experienced stagnant wages for decades;
• The lobbying of the ultra-wealthy against universal health insurance for all Americans;
• The hubris inherent in spreading toxic herbicides and pesticides across the countryside with little, if any, thought about unintended consequences, such as the decimation of pollinators;
• The persistent, disingenuous denials by oil & gas company executives, lobbyists and “experts” of the truth of climate change, despite their clear understanding of its scientific validity?9
Greed, truly, is one of the greatest obstacles to a better life for mankind.
Then there is “ignorance.” What is meant by this term in the context of man’s widespread destruction of our natural world? It refers to the rather profound lack of understanding, at least in developed, industrialized societies, of the interdependence of mankind and the natural world. As examples, we depend on clean, drinkable freshwater, much of which is drawn from groundwater, yet we have been filling in wetlands anytime and anywhere we find them to be an obstacle to a new development project without a thought to the value of wetlands as sources of recharging of groundwater supplies. We blithely cut down rainforests without the least concern for the loss of their (i) carbon absorption benefits, (ii) transpiration of water into the atmosphere to provide rain for downwind areas, and (iii) housing of myriad lifeforms, some of which have provided ingredients for new medications of modern science. We overfish the oceans to the verge of extinction of its fisheries with no consideration of the unsustainability of such rapacious practices.
Modern urban society, where the great majority of humanity lives, has spawned a perceptional disconnect between artificial, sterile urban environments and the natural world. Moreover, our hubris leads us to think we don’t need to care about preservation of the natural world that birthed us. And, sadly, we have lost appreciation for the awe that arises in our hearts when we witness the beauty of the natural world and the wildlife that inhabits it.
We can – and we must – choose a more mature path in which we wisely appreciate that we are an integral part of nature rather than retain the tragically mistaken mindset of a “conqueror” of the natural world. Should we fail to do so, the Anthropocene will witness mankind’s inexorable march down its current path of extinguishing natural lifeforms. We will all be the poorer for it.
Typically, a megacity is defined as one with a population of 10 million inhabitants.
2 Attenborough, D., A Life on Our Planet, Grand Central Publishing, New York, NY, 2020.
3 Cahill A, Aiello-Lammens M, Fisher-Reid M, Hua X, Karenewsky C, Ryu H, Sbeglia G, Spagnolo F, Waldron J, Warsi O, and Wiens J, How does climate change cause extinction?, Proceedings of the Royal Society B, 280, 2012.1890.
4 Gruber, N., et al., The Oceanic Sink for Anthropogenic CO2 from 1994 to 2007, Science 15 Mar 2019.
5 Zanna, L., et al., Global Reconstruction of Historical Ocean Heat Storage and Transport, University of Oxford 2018., PNAS
6 Summary for policymakers of the global assessment report on biodiversity and ecosystem services, UN Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, May 6, 2019.
7 Wagner DL, Granes EM, Forister ML, Berenbaum MR, and Stopak D, Insect decline in the Anthropocene: Death by a thousand cuts, PNAS January 12, 2021 118(2) e2023989118; Van Klink R, et al., Meta-analysis reveals declines in terrestrial but increases in freshwater insect abundances, Science, 24Apr 2020, Vol. 368, Issue 6489, 417 – 420.
8 It is actually exhibited in many animal species as well. The difference, though, is that man has the native intelligence to act upon his greedy motivation much more powerfully and effectively than can the animal world.
9 Hall S, Exxon Knew about Climate Change almost 40 years ago, Scientific American, October 26, 2015.
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