Breathe ...not so easy

Gar Smith

Now that the United States Environmental Protection Agency (EPA) has defined carbon dioxide as a pollutant under Section 202(a) of the Clean Air Act, we should probably mutter "Beg pardon" whenever we respire. On average, an adult human gulps down 250ml of oxygen per minute and puffs out 200ml of carbon dioxide. With 6.6 billion human lungs at work, that adds up to 2.16 trillion tons of CO2 a year.

Humankind's carbon "breathprint" accounts for as much as 9% of global CO2 - roughly equivalent to driving 500 million cars. With the United Nations estimating the world's population will swell another 37% by 2050, all those extra lungs would add another 824 billion tons/year to the human breathprint by mid-century.

Since air-breathing animals first appeared on Earth 600 million years ago, CO2 and O2 levels have fluctuated (in the case of oxygen, from 16 to 35%). Before the Industrial Revolution, the human breathprint wasn't such a concern since every human sigh and shout was part of Nature's Carbon Cycle. The CO2 we expelled was absorbed by plants; the plants were eaten by animals; the plants and animals were eaten by humans. But when we started burning fossil fuels, we began introducing a huge new load of carbon to the equation - carbon that had been sequestered since the days of the dinos.

As the authors of Out of Thin Air: Dinosaurs, Birds and Earth's Ancient Atmosphere observe, four of Earth's "Big Five" extinctions occurred during high-CO2/low-O2 periods and even minor drops in oxygen levels have been linked with "wholesale species disappearances". Many of Earth's species are already experiencing massive die-offs while others - from tigers to polar bears - are facing extinction. As the seas absorb excess CO2, ocean acoustics are going haywire. The racket of ship propellers and military sonar is becoming louder, suggesting a future in which deafened dolphins will be dying in progressively carbonated seas.

It's not just our cars and factories that spew CO2. Our appetite for meat is also breathtaking. The Food and Agriculture Organisation notes that "meat and dairy animals now account for about 20% of all terrestrial animal biomass". Livestock occupy 30% of the world's land surface and generate 18% of the world's greenhouse gases (more than the transport sector). Even worse, cow burps generate vast stores of methane (with 23 times the global warming potential of CO2) and nitrous oxide (296 times more heat-trapping than CO2). Meanwhile, we've further disrupted the Carbon Cycle by replacing CO2-storing prairies and forests with sprawling, methane-belching cattle farms.

Because methane remains in the atmosphere for only a few years, the quickest way to address global warming is to reduce methane emissions, not CO2. That's why Dr Rajendra Pachauri, the world's leading climate scientist, has issued a global plea to stop eating meat. (It's a simple choice: Would you rather have a steak today or a stake in a sustainable future tomorrow?)

- Third World Network Features