"and a collapse of the global economy."
That I could see. Far ranging international trade was well established far earlier than that courtesy of the Greek, Chinese, Persian, and Roman empires.
British tin routinely ended up in Asia, Asian silks ended up in Europe, Indian spices ended up everywhere, and the trade in foodstuffs -- olive oil, fish and meat products, grain, etc. -- was monumental.
A collapse in the agricultural economy would have had devastating and far reaching effects on all types of trade.