The only way is down: subterranean survival warning As space agencies prepare to return humans to the Moon, top engineers are racing to design a tunnel boring machine capable of digging underground colonies for the first lunar inhabitants. Solutions to the biggest threats facing our planet lie underground, according to experts who insist climate change, overpopulation and food shortages can all be tackled by going subterranean. IMAGES of the World Tunnel Congress AND SOUNDBITES of tunnel and planning experts