In Gabon, where Mike Fay's epic walk across central Africa ended four years ago, a brand-new park is up and running. Fay and photographer Michael Nichols return to the continent's great unspoiled coastline

There's no question that the Earth is getting hotter—and fast. The real questions are: How much of the warming is our fault, and are we willing to slow the meltdown by curbing our insatiable appetite for fossil fuels?