The Human Footprint Index expresses as a percentage the relative human Influence in every biome on the land’s surface. HFP value ranges from 1 to 100. For instance similar areas. Human footprint is based on the premise that the impact of human influence varies by biogeography. A score of 1 in moist tropical forests in Africa indicates that that grid cell is part of the 1% least influenced or “wildest” area in its biome, the same as a score of 1 in North American broadleaf forest (although the absolute amount of influence in those two places may be quite different).