Intruding tree roots often crack concrete sidewalks, and the city of Santa Monica, Calif., Street Maintenance Division has studied the results of that damage over the last 20 years. The division has projected the cost benefits of using Terrewalks sidewalk pavers next to ficus trees, which have the most intrusive and damaging root systems in the city's community forest.

By replacing concrete walks with Terrewalks adjacent to some 3,500 ficus trees, the city is forecasting an 80 percent reduction in future sidewalk maintenance through the 20-year maintenance cycle of those ficus trees.

Terrewalks are made of 30 percent recycled passenger tires and 70 percent recycled plastic.

The health and well-being of the city's trees will be enhanced, city officials say, because sidewalk repairs that impact tree roots will be less frequent with the replacement pavers. In addition, fewer sidewalk repairs will mean less plastic, concrete, asphalt and tires will be flowing into landfills.