Why architects should stop drawing trees on top of skyscrapers

Vanessa Quirk Tim De Chant argues that the practice of drawing trees on top of skyscrapers in architectural renderings should stop. First, because pretty, high-altitude foliage is the first thing that cost-conscious developers jettison when the actual building is underway; but secondly, because trees can't really survive at that altitude:

There are plenty of scientific reasons why skyscrapers don’t—and probably won’t—have trees, at least not to the heights which many architects propose. Life sucks up there. For you, for me, for trees, and just about everything else except peregrine falcons. It’s hot, cold, windy, the rain lashes at you, and the snow and sleet pelt you at high velocity. Life for city trees is hard enough on the ground. I can’t imagine what it’s like at 500 feet, where nearly every climate variable is more extreme than at street level.

Wind is perhaps the most formidable force trees face at that elevation. Ever seen trees on the top of a mountain? Their trunks bow away from the prevailing winds. That may be the most visible effect, but it’s not the most challenging. Wind also interrupts the thin layer of air between a leaf and the atmosphere, known as the boundary layer. The boundary layer is tiny by human standards—it operates on a scale small enough that normally slippery gas particles behave like viscous fluids.

Bottom line: if we're going to have skyscrapers, let's build them without the illusion that they'll harbor high-altitude forests.

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