The cooling power of trees in urban areas has long been known. Now, scientists have learned that urban trees can also provide warmth by shielding homes and offices from the chill of cool winds.

A new study, published in the journal Advances in Water Resources, could help urban planners to design urban landscapes to enhance peoples’ comfort and prevent energy loss, while also improving weather forecasts by helping meteorologists predict the impact of storms on structures and pedestrians.

Marco Giometto, who wrote the paper as a civil engineering postdoctoral fellow at the University of British Columbia (UBC), said, “Wind pressure is responsible for as much as a third of a building’s energy consumption. We were surprised to find such a dramatic decrease in wind speed. Trees act as a filter, protecting us from what’s above, that is, high wind speeds, turbulence and particulate matter.”

The scientists used remote-sensing laser technology to design a highly-detailed computer model of a Vancouver neighbourhood down to every tree, plant, and building. A computer simulation then played out how different scenarios — no trees, trees in full leaf, and bare trees — affected air flow and heat patterns on the streets and homes, and compared them against ten years of measured wind data from a nearly 100-foot tall research tower operated by the university in the same Vancouver neighbourhood.

The researchers found that removing all the trees could increase wind speed by a factor of two, “which would make a noticeable difference to someone walking down the street,” Giometto said. Secondly, the scientists found that removing all the trees around buildings increased the buildings’ energy consumption by as much as 10% in the winter and 15% in the summer.

“The beneficial effects of trees in reducing wind speed was actually well known by farmers before this study,” he said. “Now we have a tool to quantify it and help the design of future windbreaks to maximize their effects.”