Green Tip and Trade

Show some TLC for the trees on your urban street

Matt Berger Nov 30, 2010

We’ve all heard about how forests absorb CO2 from the atmosphere. But their city-slicker tree cousins help reduce production of CO2 in the first place. That’s because strategically placed trees in urban environments can reduce the need for electricity on a couple of fronts.

After Chicago’s deadly heat wave of 1995, Mayor Richard M. Daley increased the number of urban street trees in his city. His reason: Shaded asphalt and homes are cooler than those fully exposed to the summer sun. That means less air conditioning to combat the “urban heat island effect.” (Look at the ring of cooler temperatures around your city when the local news does the weather.)

Trees absorb storm water that would ordinarily go into sewer systems. Once in those pipes, it’s often treated to the same degree as water going down your toilet — even though it’s relatively clean. Pumping and filtration are a large part of what’s called “base load” on electrical grids — power we use no matter what. Numerous studies have demonstrated that stopping rainwater where it falls is the most cost-effective way to handle the challenge — and the most beautiful!

Paradoxically, despite cost-saving benefits of this type of horticultural infrastructure, these assets are often left to “volunteers” when it comes to maintenance. Professional care for street trees increases the likelihood that they will survive and grow to canopy faster, so we can start enjoying the benefits.

Until the day when cities place true value on street trees, help them out by not letting your dog pee on them (fire hydrants do just as well), not locking your bike on them, and giving them water if it hasn’t rained in a while. To hear more about treetop canopies and their importance to our ecosystem, listen to our profile of pioneering researcher Nalini Nadkarni at

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