PLYMOUTH, United Kingdom — Does the global space industry pose a bigger threat to mankind than plastic pollution? Researchers say derelict objects left in orbit and other disintegrating space junk may cause a catastrophic collision above our atmosphere. Scientists are calling for a legally-binding treaty to ensure Earth doesn’t suffer irreparable harm by future space expansion. “The issue of plastic pollution, and many of the other challenges facing our ocean, is now attracting global attention. “We were well aware of the issue of plastic pollution a decade ago, and had we acted then the quantity of plastic in our oceans might be half of what it is today.