Changes in terrestrial carbon storage in the United States. 2: The role of fire and fire management

Abstract

Areas burned annually in the United States between 1700 and 1990 were derived from published estimates of pre‐European burning rates and from wildfire statistics of the US Forest Service. Changes in live and dead vegetation following fire and fire exclusion were determined for 18 types of biomes and added to a book‐keeping model to calculate the long‐term effect of fire and fire management on carbon storage. Over the 290‐year period, burning declined by an estimated 98%, first, because wildlands were converted to agricultural lands, essentially eliminating fire from 236 × 106 ha and, secondly, because wildfires were excluded and suppressed in the remaining forests and non‐forests. Adding fire and fire management to an analysis of land‐use change (companion paper) reduced the emissions of carbon over the period 1700–1990 by 25% (8 PgC). Less carbon was released because fire reduced the average biomass of forests cleared and burned, and because fire exclusion led to an increase in carbon storage in forests. The wildfire statistics of the USDA were insufficient for addressing two kinds of change: fire exclusion before 1926 and changes in the burning of non‐forest ecosystems. We estimate here that as much as 4 and 12 PgC, respectively, may have accumulated in vegetation as a result of these changes, but the estimates are uncertain and likely to be upper limits. The maximum rate of carbon accumulation attributable to all changes in land use, including fire management, was 300–400 TgC/year and occurred around 1980. Less than half of this uptake was in forests. Uptake by forests was constrained by the fact that most forests were already accumulating carbon in response to earlier harvests. Fire exclusion added little to this uptake.

Revised estimates of the annual net flux of carbon to the atmosphere from changes in land use and land management 1850–2000

“…Re-analyses of the US (Houghton et al, , 2000aHoughton and Hackler, 2000) and, more crudely, Canada (this work) yielded estimates of flux different from the earlier estimate for North America (Houghton, 1999). In the re-analysis of the US we estimated fluxes for three processes not previously included: woody encroachment, 'thickening' of western pine forests from early fire suppression and gains in soil carbon as a result of changes in agricultural management.…”

Managing Forests for Climate Change Mitigation

“…In one of the most comprehensive synthesis efforts undertaken so far, the Fourth Assessment of the Intergovernmental Panel on Climate Change estimated that an economic potential of 0.12 Pg C year Net carbon sequestration can also be achieved by increased forest carbon density, through both stand-scale management and landscape-scale strategies such as longer harvesting cycles or reduced disturbances. Fire suppression and harvest exclusion in U.S. forests during the 20th century, although not implemented for the purpose of carbon sequestration, led to a 15% (8.1 Pg C) increase in forest biomass between 1927 and 1990 (13). The overall biophysical potential of management activities to increase carbon density can be substantial and comparable to that of reforestation (10).…”

Reviews on Impact Assessments of Land-Use Change on Key Ecosystem Services

“…Firstly, many researchers adopted empirical data to simulate carbon emission and sequestration. Houghton et al (1983Houghton et al ( , 2000Houghton et al ( , 2003 calculated the carbon emission resulting from LUC and the potential for sequestering carbon of different land covers mainly based on the parameters set for each vegetation type in each regime (Houghton et al , 2000(Houghton et al , 2003, and the model was called the "bookkeeping" terrestrial carbon model. Further, Houghton et al (2001) documented a numeric data package that consists of annual estimates of the net flux of carbon between terrestrial ecosystems and the atmosphere resulting from deliberate LUC, especially forest clearing for agriculture and the harvest of wood for wood products or energy from 1850 through 1990 (Houghton et al 2001).…”