Tue, Aug 18, 2015 - Page 9 News List

How humans cause mass extinctions

Rapidly expanding human activity is disrupting the climate and poisoning our environment — with deadly consequences

By Paul Ehrlich and Anne Ehrlich

Illustration:Yusha

There is no doubt that Earth is undergoing the sixth mass extinction in its history — the first since the cataclysm that wiped out the dinosaurs about 65 million years ago.

According to one study, species are going extinct between 10 and several thousand times faster than they did during stable periods in the planet’s history, and populations within species are vanishing hundreds or thousands of times faster than that. By one estimate, Earth has lost half of its wildlife during the past 40 years. There is also no doubt about the cause: We are it.

We are in the process of killing off our only known companions in the universe, many of them beautiful and all of them intricate and interesting. This is a tragedy, even for those who might not care about the loss of wildlife. The species that are so rapidly disappearing provide human beings with indispensable ecosystem services: regulating the climate, maintaining soil fertility, pollinating crops and defending them from pests, filtering fresh water and supplying food.

The cause of this great acceleration in the loss of the planet’s biodiversity is clear: Rapidly expanding human activity, driven by worsening overpopulation and increasing per capita consumption. We are destroying habitats to make way for farms, pastures, roads, and cities. Our pollution is disrupting the climate and poisoning the land, water and air. We are transporting invasive organisms around the globe and overharvesting commercially or nutritionally valuable plants and animals.

The more people there are, the more of Earth’s productive resources must be mobilized to support them. More people means more wild land must be put under the plow or converted to urban infrastructure to support sprawling cities such as Manila, Chengdu, New Delhi and San Jose. More people means greater demand for fossil fuels, which means more greenhouse gases flowing into the atmosphere, perhaps the single greatest extinction threat of all. Meanwhile, more of Canada needs to be destroyed to extract low-grade petroleum from oil sands and more of the US needs to be fracked.

More people also means the production of more computers and more mobile phones, along with more mining operations for the rare earths needed to make them. It means more pesticides, detergents, antibiotics, glues, lubricants, preservatives and plastics, many of which contain compounds that mimic mammalian hormones. Indeed, it means more microscopic plastic particles in the biosphere — particles that might be toxic or accumulate toxins on their surfaces. As a result, all living things — us included — have been plunged into a sickening poisonous stew, with organisms that are unable to adapt pushed further toward extinction.

With each new person, the problem gets worse. Since human beings are intelligent, they tend to use the most accessible resources first. They settle most productive land, drink the nearest, cleanest water, and tap the easiest-to-reach energy sources.

So as new people arrive, food is produced on less fertile, more fragile land. Water is transported further or purified. Energy is produced from more marginal sources. In short, each new person joining the global population disproportionately adds more stress to the planet and its systems, causing more environmental damage and driving more species to extinction than members of earlier generations.

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