Portlanders have begun planting trees to counteract the city’s notoriously high temperatures. Over several decades, a remarkable pattern became apparent.

Each tree planted in a community was linked to significant decreases in
non-accidental and cardiovascular mortality among humans, according to a
recent study led by the US Department of Agriculture (USDA) Forest Service.
More than 1,000 times the annual cost of maintaining a forest is outweighed
by the yearly economic advantages of planting trees.