Table 1.

Estimated land-use areas in 1990 and average net fluxes of carbon to the land for the 1980s

	Area, 104 km2	B	S	Total
Forest	248	0.10 (0.11–0.15)	0.13 (0.03–0.15)*	0.23 (0.14–0.30)
Nonforest and pasture	336	0.11 (NA)	0.02 (NA)	0.13 (0.12–0.13)*
Cropland	183	0.00 (NA)	−0.03 (0.00–0.04)	−0.03 (0.00–0.04)†
Total	767	0.21	0.12	0.33 (0.26–0.47)‡

Positive values indicate carbon sinks on land. B is for live biomass. S is other organic matter in litter, necromass, and soils. Numbers in parentheses are lower and upper bounds from ref. 1. NA, not available. 

^*Upper-bound in ref. 1 based, in part, on the use of the ED model. 

^† The estimates using ED do not include the effects of modern agricultural techniques, such as conservation tillage, that help sequester soil carbon as do the estimates in ref. 1. 

^‡ Estimates of carbon sinks that ED does not simulate must be added to these estimates to obtain a comprehensive estimate (see text).