Humans and Extinction in the Past and Present

One of the mysteries of prehistoric North America is why many large mammals suddenly became extinct around 11,000 years ago. At least some hypotheses put the blame on the arrival of humans on the continent.

For decades, the dominant theory, proposed by Paul Martin, a geoscientist at the University of Arizona in Tucson who's now retired, was a rampage of hunting by humans who'd just arrived across a land bridge from Asia. Within a few hundred years, Martin theorized, a "blitzkrieg'' of killing wiped out more than half of all the mammals that weighed more than 100 pounds.

As a result, "Americans live in a land of ghosts,'' Martin wrote in his 2005 book, "Twilight of the Mammoths."

MacPhee, however, thinks that it wasn't over-hunting but the diseases people brought with them that ravaged animal populations in North America. As a parallel example, he noted how microbes introduced by European conquerors destroyed Central and South American civilizations 500 years ago.

Other scientists, such as Russell Graham, a museum director at Pennsylvania State University in University Park, think that climate change was "the major driving force that caused the extinctions.'' It destroyed animals' native habitats and reduced their geographic range so much that they could no longer survive.

We probably cannot know for certain what was the most important factor in that wave of extinctions. The fossil record gives an incomplete picture at best, and we do not have eyewitness accounts, unlike with more recent extinctions. This is not an idle question, as our planet is currently undergoing radical changes due to anthropogenic climate change and habitat destruction. The upshot may be another mass extinction event in the near future. Already 12% of the world's birds are threatened, and 1 in 10 odonates face extinction. Knowing how past extinctions occurred could give some insight into how we might prevent the current one.

Human contribution to prehistoric extinctions becomes more believable each time I read of something like this.

Asia Pulp & Paper and Sinar Mas Group have acquired a license to clear hundreds of hectares of unprotected rainforest near Bukit Tigapuluh National Park on the Indonesian island of Sumatra, report environmental groups who say the activity threatens a population of critically endangered orangutans that have been re-introduced into the wild.

"It took scientists decades to discover how to successfully reintroduce critically endangered orangutans from captivity into the wild. It could take APP just months to destroy an important part of their new habitat," said Peter Pratje of the Frankfurt Zoological Society. "These lowland forests are excellent habitat for orangutans, which is why we got government permission to release them here beginning in 2002. The apes are thriving now, breeding and establishing new family groups."

Asia Pulp & Paper and Sinar Mas intend to log the concession for timber and plant it for industrial timber and oil palm plantations. The companies say they plan to follow all legal procedures according to Reuters, but environmental groups are nonetheless concerned about the fate of orangutans and other endangered species, including Sumatran tigers and elephants. Bukit Tigapuluh is home to perhaps a quarter of the world's remaining wild Sumatran tigers.

When Walmart declines to buy your products because of environmental concerns, it is a pretty good indicator that your practices are out of line. In this case, APP is threatening the survival of two large mammal species, and presumably hundreds of endemic birds, herps, and invertebrates. And this is just one company in one tract of land.