For example, we find that over two-thirds (68%; 194.0 PgC) of unrealized potential carbon storage is found in the global tropics (SI Appendix, Table S2).
Nevertheless, nonwoody systems do offer modest opportunities for additional carbon storage in both temperate (4.8 PgC) and tropical (14.0 PgC) zones, with soil carbon necessarily accounting for nearly 90% (16.6 PgC) of the available opportunity (SI Appendix, Table S3).
By comparing current to potential carbon storage, while excluding areas critical to food production and human habitation, we find 287 petagrams (PgC) of unrealized potential storage opportunity, of which 78% (224 PgC) is in biomass and 22% (63 PgC) is in soil.
Our unconstrained estimate of unrealized potential carbon storage (354.4 PgC; 87 to 898 PgC) is also well within their range (272 to 702 PgC), falling just below the minimum of their inner quartiles (375 to 525 PgC) (Table 1).