Not long ago, a new variety of orchid was discovered at the Newmarket racecourse in Suffolk, England. The track’s managers were horrified at first. When an endangered plant is found on your land in England, eco-regulators seize control; and this flower was, apparently, the only one of its kind in the world.

But the Jockey Club came up with an ingenious defense. If the orchid truly was unique, it argued, and if it flourished only on ground that had been churned up by horses’ hooves for the better part of 400 years, then surely the correct course was to maintain that unusual habitat.