Space, as Douglas Adams so aptly put it, is big. Compared with the confines of our own planet, the solar system’s expanse is absurdly huge. The idea that we could deplete its vast reserves seems almost laughable.

Amazon CEO Jeff Bezos touched on such sentiments on May 9, during a speech unveiling Blue Moon, his spaceflight company’s lunar lander. “If we move out into the solar system, for all practical purposes, we have unlimited resources,” the billionaire said.

Yet a recent study suggests that at current growth rates, humanity could practically exhaust the most accessible riches in our stellar neighborhood within less than five centuries. To prevent an interplanetary economic crisis, the study’s co-authors suggest that our civilization must somehow build sustainable practices into our expansion out to space, potentially setting aside more than seven eighths of our stellar system’s off-world “real estate” as protected wilderness. The findings appear in the journal Acta Astronautica.