From last July: CityLab looks at the “darker side” of urban tree-planting initiatives. Simply planting a million trees—or, say, two billion—is not enough; those trees have to survive to maturity for their environmental benefits to be realized. “Keeping new trees alive in the city is tricky. And it’s not cheap to plant trees right. Too often, when cities set their eyes on planting an impressive number of trees, Hutyra says, they underestimate the investment—natural resources, labor and funding—needed to keep them alive long enough to see those gains.”