Humans Caused 322 Animal Extinctions in Past 500 Years

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Our species caused 322 animal extinctions over the past 500 years, with two-thirds of those occurring in the last two centuries, according to a paper published in a special issue of the journal Science this week.

Many animals are threatened with human-caused extinction now, with researchers expressing particular concern over amphibian and invertebrate (creatures without a backbone) losses. Numbers of the latter group have nearly halved as our population doubled in size over the past 35 years.

Ecologists, zoologists and other scientists believe that, without urgent steps to stem the losses, we are facing global scale tipping points from which we may never look back or recover.

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"Indeed, if current rates (of human population growth) were to continue unchecked, population size would be, by 2100, about 27 billion persons -- clearly an unthinkable and unsustainable option," co-author Rodolfo Dirzo, professor of environmental sciences at Stanford University, told Discovery News.

Dirzo and his colleagues call for "decreasing the per capita human footprint," by developing and implementing carbon-neutral technologies, producing food and goods more efficiently, consuming less and wasting less.

They also say it is essential that we ensure lower human population growth projections are the "ones that prevail."

Haldre Rogers and Josh Tewksbury, authors of another paper in the same issue, believe that, "animals do matter to people, but on balance, they matter less than food, jobs, energy, money, and development."

They continued, "As long as we continue to view animals in ecosystems as irrelevant to these basic demands, animals will lose."

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Keeping animals alive and ecosystems healthy translate to big bucks on a global scale. Tewksbury, director of the Luc Hoffmann Institute of the World Wide Fund for Nature, pointed out that Southeast Asia's Mekong River Basin, through its fisheries, supports 60 million people. Rogers, a researcher in Rice University's Department of Ecology & Evolutionary Biology, added that 73 percent of visitors to Namibia are nature-based tourists, with their money accounting for 14.2 percent of that nation's economic growth.

"Whale watching in Latin America alone generates over 275 million dollars a year," Tewksbury said. "Multiple studies have demonstrated how turtles are worth more alive than dead."

In the United States, he added, shark-watching results in $314 million per year, directly supporting 10,000 jobs.

He and the other researchers point out that human health, pollination, pest control, water quality, food availability and other critical factors are also dependent on ecosystem stability.