your cell phone may seem far removed from the african serengeti, that vast repository of wildlife that is one of the natural wonders of the world. but there's a connection that has environmentalists alarmed and it's all about a road. nbc's chief foreign correspondent richard engel gives us a rare look at a wild and pristine world, now threatened. >> reporter: the serengeti national park in northern tanzania is an eden of biodiversity. with two-ton hippos, giraffes, zebras and lions, the proud kings. but environmentalists say the serengeti is at risk of total collapse. the government plans to build a road for commercial trucks, straight through the serengeti. we set off in a 4 x 4 jeep on trails used by park rangers that could soon become a two-lane 33-mile highway. our first impression, zebra,