He calls it "a record of environmental history in progress", and once it is completed later this year, his photographs taken from the air above more than 70 countries will form a unique end-of-the-century inventory of our relationship with the planet.
He has a sharp eye for the patterns we impose on the Earth's surface, from ancient landmarks and gentle patchworks of fields to the brutal imprint of road systems or open cast mines. Often, he takes pictures at the "magic hour", that brief time of day around dawn or dusk, beloved of cinematographers, when the near horizontal light of the sun throws objects on the ground into stark relief.
His vertical take on things can be like that of the cartographer, distant, bird's-eye views of river deltas or desert trails or, like this photograph from the Ivory Coast of a man resting on giant cauliflower-like bales of cotton, more personal.
This image is pleasing to the eye, but it also tells a story. Two hundred and five years ago, Eli Whitney, a farm labourer from New England, invented the cotton gin. It replaced the once laborious job of separating the cotton from its seed with a simple mechanical process, making cotton the cheapest fabric in history and condemning this man's ancestors to lives of slavery.