In the Middle of a Mass Extinction

by Krista Bergesen

The phrase “mass extinction” can conjure some scary images. Maybe one person imagines a giant meteorite hitting the earth and killing all of the dinosaurs, while another person may think of the last article they read about the human impact on the environment. Either way, it doesn’t sound like a very upbeat topic.

But what is mass extinction anyway? For one, it encompasses much more than what many of us can fathom. It usually means that at least 75% of the species globally have or are dying out on the planet. The planet would never have the same species again, and it would take around 10 million years to regenerate the same species diversity that had once existed.

It may not surprise a lot of people to know that we are in the midst of the largest extinction since that of the dinosaurs. Magazines, television ads, and even movies have tried to spread the word. Some of the messages are depressing, some are inspirational. Either way, the message is clear: the extinction is happening and humans are a major cause.

In a recent study done on the mammals in North America and their extinction rate, a group of scientists concluded that with the migration of humans to the North American continent the “normal” species’ richness declined 15-42%. Going by the definition of a mass extinction said earlier, North American mammals are already one fifth to one half of the way there. And this was before the effects of industrialization.

The anthropogenic time period, or era in which humans have existed is referred to as the “Holocene Period.” When compared with fossil samples from preceding periods, it was concluded that the beginning of the dominance of humans on the North American continent is concurrent with the decline of mammalian diversity. There has been an extinction of nine subspecies and a significant loss of habitat for other North American mammals because of the predominance of humans on the landscape.  Also, the growth of human biomass has matched the decline of the biomass of other species. Thus, the diversity of mammals, as well as the diversity of other animals is being greatly threatened by human development.

Although the study done on North American mammals is by no means representative of the whole world, it does establish one important fact. It quantifies the extinction of a certain type of animal that stands for an important part of the animal population.

In 2006, an estimate was put out by the World Conservation Union stating that 844 species had gone extinct in the past 500 years, attributing the causes to “habitat change, over-exploitation, the introduction of invasive species, nutrient loading, and climate change.” Techniques used for agriculture homogenize the plant life, and often can rid animals of their habitat or food sources. And none of these problems have shown any sign of slowing.

So what can be done? It’s pretty obvious that things have not been going well for other species on the planet with the rapid growth of the human population. For one, awareness, along with conscious action will be very important. Reserves for the natural environment need to be maintained and added to, as well as a development of sustainable energy and food production practices. Sounds difficult, and maybe impossible at this point. But the point is that something needs to be done now or the planet will face a loss of many diverse and important creatures.

Sources:

Reuters. “Humans spur worst extinctions since dinosaurs.” ABC News Online.< http://www.abc.net.au/news/newsitems/200603/s1596740.htm >. 21 March 2006.

Carrasco, Mark, et al. “Quantifying the Extent of North American Mammal Extinction Relative to the Pre-Anthropogenic Baseline”. PloS one. 2009. Volume 4; Issue 12. 8331.

Barnosky, Anthony. “Megafauna biomass tradeoff as a driver of Quaternary and future extinctions.” The National Academy of Sciences of the USA. 2008. Volume 105. 11543-11548.

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Filed under Biology, Ecology, Policy

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