Arens' theory argues that impacts are weaker in effect than is generally thought. But a growing consensus of researchers believes that doesn't go far enough. They believe eruptions, not cosmic impacts, are the real killers. "I'm not so sure craters really have anything to do with it," Gregory Retallack of the University of Oregon said, adding: "I don't like the 'press' term very much. If you look closely at the isotope record, you can see that flood basalts [large-scale eruptions] are a series of pulses, paving the golden path toward annihilation." "I'm not saying it's impossible to have an extinction with just a 'press' or a 'pulse' event," Arens admitted. The study states only that it's more likely when the two combine. Humanity is creating exactly that scenario today, she said. Over the last 6,000 years, subsistence farming began changing the climate and clearing wilderness slowly enough to constitute 'press'-type stresses on the environment. But people began burning fossil fuels in earnest during the Industrial Revolution, and carbon concentrations have skyrocketed while growing population numbers have led to widespread habitat loss around the globe. Arens argued this constitutes a 'pulse' event, and the sixth great mass extinction may already be underway. Related Links: Go to Discovery Earth for slide shows, quizzes, interviews and more. |
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