Table 2. Comparison of different assessments of the world’s intact forest area (within the forest zone).

Type of intact area Minimum size, km2 Main data source Proportion intact, %
Wilderness areas (McCloskey and Spalding 1989) 4000 Jet Navigation Charts 21.1
Frontier forests (Bryant et al. 1997) Inconsistent, but >500 Expert information 21.8
Areas with minimal (0–10) human influence index derived from Human Footprint data set (Sanderson et al. 2002) 500 Coarse-scale global maps and low spatial resolution remote-sensing data analysis results 38.0
Intact Forest Landscapes (this study) 500 High spatial resolution satellite images 23.5