Written by Sylvia Prehmus, ESLLC 2015-2016
In the history of the planet there have been five great mass extinctions, where between 25 to 90% of existing species were wiped out: the Ordovician-Silurian, the Devonian, the Permian, the Triassic, and the Cretaceous extinctions.
The exact causes of these extinctions are not fully known but scientists theorize that volcanic ash or large meteor impacts may have caused the latter three. Now, however, it is believed that a sixth great mass extinction is occurring or is in the near future and this one falls squarely on the shoulders of humans. By the year 2100, human activities that pollute the air and water, land clearing, and overfishing may have driven more than half of the world’s marine species to extinction to say nothing of the terrestrial species that depend on healthy oceans for their existence.
No doubt climate change is a contributor, but the problem is larger than a single species that cannot adapt to altered environments. The collapse on one species helps bring down others. In the words of geologist Peter Ward,
“You could almost analogize [mass extinctions] to a house of cards. Each species helps prop up another in a sense, because the creature that you eat is the card that is sitting under you that gives you your energy. Now let’s pretend that we start kicking out card, after card, after card, and that’s want a mass extinction does, isn’t it. It starts knocking out a species here, knocks out a species there, but pretty soon, lots of species are gone.”
Soon enough the whole house of cards comes crashing down. Humans have accelerated this process a hundred fold by bring in invasive species as well as destroying habitats through our own destructive behaviors. In Guam the brown tree snake originally from New Guinea, has traveled from its native island to others by curling up in the wheel housing of plane landing gear. Once arrived the snake would climb trees and feed on the eggs and young of the native birds which, having evolved in an environment without such predators had no defense. As a result nine of Guam’s eleven native bird species have been driven to extinction. Hawaii now faces a similar problem as the snakes move from Guam to the archipelago.
These events go to show how delicate the balance of species can be. If the remaining species, and by extension human civilization, are to be saved, the time to act has already passed. Damage control must be implemented immediately in large scale movements if we do not want to loss the rest of the diverse and magnificent species that populate our only planet.
Evolution Episode 3 – Extinction. YouTube. NOVA PBS, n.d. Web. 07 Mar. 2016
“Five Worst Mass Extinctions, The.” Endangered Species International. N.p., 2011. Web. 07 Mar. 2016.
“Mass Extinction, Mass Die-Off Information, Prehistoric Facts — National Geographic.” National Geographic. N.p., n.d. Web. 07 Mar. 2016.
Novacek, Michael. “Diversity in Clades.” Understanding Evolution. California Academy of Sciences, n.d. Web. 07 Mar. 2016.
Tung, Allison. “Silent Spring: Stop the Brown Tree Snake’s Invasion of Hawaii.” ForceChange. N.p., n.d. Web. 07 Mar. 2016.