The Mysteries of Methane

If we’ve told you once, we’ve told you a thousand times that we here at Plenty are not mopey by nature. Sure, we occasionally indulge in a little stewing over the colossal bummer of climate change—and yes, we did coin the phrase “eco-anxiety” (see our August/September 2006 issue). But when it comes right down to it, we’re into silver linings.

Which is why our little optimist ears perked up today when we heard about a new study  that while carbon dioxide concentrations  in the atmosphere may be climbing, methane levels are slowly leveling off. According to an article in the Portland Oregonian, scientists at Portland State University and Oregon Health & Science University found that yearly rises in methane concentrations have tapered off over the last quarter century, from 25 parts per billion in 1980 to roughly 5 parts per billion in 2004.

This is surprising, given the dramatic increase in other greenhouse gases, and no one is quite sure what’s behind the dip. One factor, says the Oregonian, might be changing rice-growing practices in China:

In the past 30 years, China has reduced rice-growing areas and replaced methane-generating organic fertilizers -- animal and human excrement -- with nitrogen-based fertilizers, they said. In addition, the growers are using less water, which also reduces methane emissions.

Thing is, nitrogen-based fertilizers can leak into waterways and cause algal blooms, which, in turn, can create dead zones. And some scientists doubt that the fertilizer change in China had much to do with it at all:

An international research team reported in September in the journal Nature that the slowdown in atmospheric levels of methane during the past decade was caused by a temporary decline in industrial emissions during the early 1990s, along with an ongoing drought that shrank tropical wetlands.

The study by 18 scientists said that methane emissions by fossil-fuel use from industrial sources have been rising since 1999, but the increase has been masked by a dip in wetland emissions caused by drier conditions. If the drying trend is reversed, they say, methane levels could increase again.

In conclusion, it might be a little early to start planning your methane-decrease celebration. In the meantime, take a look at Enviroweb’s tips for reducing methane emissions. If you don’t have time to take a look, well, suffice it to say, recycle. Recycle, recycle, and then recycle some more.