Dead Men walking

Do you ever walk around with the vague feeling that you're going to die soon? That could be because -- according a recent study -- the Earth might be due for a catastrophic mass extinction.

Population ecologists -- scientists who study the relationship between species and the environment -- from the Universities of York and Leeds in Great Britain took a closer look at the fossil record recently. They found that, historically speaking, we're living in a climate that traditionally has seen the extinction of large numbers of species.

The fossil record is the history of our planet. It's composed of information gathered from fossils, rock layers, ice samples and other geological phenomena. When put together, this information forms a picture of life and climate on Earth over the past 550 million years.

The population ecologists compared 520 million years of Earth's climate change with species extinction throughout the same period. What they found is somewhat alarming. During times of cool weather -- called icehouse periods -- biodiversity thrives. Biodiversity is the presence of a large number of different species. If an ecosystem (or planet) is diverse, then the conditions are right to support evolution, reproduction and genetic divergence. In other words, if our planet was a business, then biodiversity means business is good.

But during warm greenhouse periods, biodiversity suffers. This lack of biodiversity appears to be due to mass extinction -- the loss of large numbers of different species. According to the British population ecologists' study, as the global climate has heated up in the past, large numbers of species have died out.

So why might this be a big deal for us? Some of the worst mass extinctions found in the fossil record took place during climates very similar to the one in which we currently live. The York and Leeds researchers suggest that, based on predicted increases in temperatures over this century, Earth could see another mass extinction event as soon as a few generations from now. That means our younger readers' grandchildren could be around when this mass extinction occurs.

But science can't say for certain that it will. There's no evidence that periods of global warming have been directly responsible for mass extinctions. But researchers are able to show direct correlations between global warming and mass extinctions in the past. Higher temperatures loom conspicuously during these periods of extinction.

The worst mass extinction found in the fossil record took place 251 million years ago, during the Permian Period at the end of the Paleozoic Era. At that time, 95 percent of all of the species on Earth met their demise [source: University of York]. No one can say exactly why this mass extinction took place. Some scientists believe that a series of comets hit the planet and caused the oceans to become acidic (also creating acid rain inland). Others believe that poisonous gas from erupting volcanoes caused the same acidic cataclysm. Either way, it's clear that during this same period the global temperature also rose.

Regardless, why should we humans care if the planet may soon see another mass extinction like the one at the end of the Permian Period? After all, we've beaten acid rain before. And even if it gets hot outside, we have air conditioners. We (and our pets) should be okay, even if a mass extinction occurs -- right? Probably not. Find out on the next page why losing 95 percent of all species is really, really bad for the surviving 5 percent.

The Importance of Biodiversity
We humans have come a long way in gaining our independence from the whims of Mother Nature. We've learned how to build shelters and clothe ourselves. Through agriculture and irrigation, we can control our own food supply. We've built schools, hospitals, computers, automobiles, airplanes and space shuttles. So what's the big deal if a bunch of plants, animals and simple organisms die out?

Here's the problem with the loss of biodiversity: The Earth functions like an incredibly complex machine, and there don't appear to be any unnecessary parts. Each species -- from the lowliest microbe to humans -- plays a part in keeping the planet running smoothly. In this sense, each part is related. If a lot of those parts suddenly vanish, then the machine that is Earth can't function properly.

For example, the crops that we grow though our clever use of agriculture are enabled by the nitrogen present in the soil. This nitrogen nourishes and strengthens our crops. But where does it come from? Worms, bacteria and other life found within the soil love to decompose vegetation. When they eat, these organisms produce nitrogen as waste, which crops really love. This is also how nutrient-rich compost is made. If these bacteria species were killed off, then our crops would not grow properly.

This holds true for ocean ecosystems too. The ocean -- along with land-based plant vegetation -- plays a major role in absorbing carbon dioxide -- a gas that humans can't breathe. The ocean doesn't absorb this CO2 on its own. It relies on organisms like phytoplankton -- microscopic aquatic plant life -- to absorb the CO2. Loss of phytoplankton means we lose adequate levels of breathable air.

Even some of our own modern advances in technology depend on nature. Modern medicine owes much to the properties found naturally in plants and bacteria. Medications like painkillers, penicillin and inoculations are based on natural organisms. The structure of these living things has been analyzed and synthesized to produce some medications, but others -- like antibiotics -- still use the actual organisms. In total, this accounts for one-quarter of all the prescription drugs we use [source: David Suzuki Foundation]. What's more, if the Earth suddenly lost its hearty biodiversity, drugs that have yet to be discovered would also be lost.

Even if we humans could find a way to overcome a catastrophic loss of biodiversity, our existence on Earth would certainly be changed. There's a very important economic aspect to biodiversity as well. In 1997, Cornell University scientists tallied the dollar value of all the services provided for humanity by life on Earth. Everything from ecotourism and pollination to soil formation and pharmaceuticals was taken into account. The total for services provided to humanity by Mother Nature came to $2.9 trillion per year (another study concluded the total was $33 trillion) [source: Science Daily].

These services would still be required, with or without a diverse global ecosystem. As the resources that provided these services (like nitrogen produced by worms) dwindled, humans would have to replace them in order to survive. Stores of things like nitrogen for soil and medicine for the sick would quickly and significantly increase in value. Competition for these dwindling resources would develop, with wealthier and better armed countries inevitably winning. Life, indeed, would change for humanity as a result of a loss of biodiversity. It would quickly get worse

HowStuffWorks