This week's cartoon describes pervious concrete -- one type of material that's helping to ease the impact of the built environment on natural ecosystems and watersheds. As Erica Barnett wrote in a 2008 post, pervious (or porous) concrete performs as well as traditional asphalt, even under city traffic. But it also allows most stormwater to pass right through it into the ground, instead of channeling that same water into local waterways as polluted runoff. You can read about more green infrastructure innovations, including permapave, rain gardens and green alleys, in our archives.

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Editor's note: This post is part of a series featuring Worldchanging ally Andy Lubershane's original graphics. While many of the issues covered in the comics have been discussed on Worldchanging in the past, we hope that you'll be able to use this new medium in a different way … whether it's in your classroom, on your office wall, or to help explain ideas to friends and family.

Andy Lubershane researches, writes and cartoons about sustainability from his home in Boston. Check out more of his illustrations here