If the people of the world did not recycle, eventually all the natural resources that are needed to manufacture new products would be used up. Oil and gas resources, metals extracted from iron ore, and trees cut down for paper would all cease to exist. The world would need to discover or invent new sources or methods to produce the products people use.
In addition, it the world did not recycle, greenhouse gases will continue to increase global warming and deplete the earth’s ozone layer. If things got that bad, it probably wouldn’t matter that our natural resources were gone, because we would all be dead from severe exposure to the sun due to the lack of protection from the ozone layer or we’d die from water taking over all the land surfaces.