Table 7.

Comparison of the estimates of agricultural GHG mitigation potential (Mt CO₂-eq. yr⁻¹) by 2030 with previous global and regional estimates, for combinations of practices, gases considered and different marginal costs assumed.

study	region—practice	gas considered	price of CO2	previous mitigation potential estimate (Mt CO2-eq. yr−1)	equivalent mitigation potential estimate from this study (Mt CO2-eq. yr−1)
IPCC (1996; TAR)a	globe—soil sequestration	CO2 only	biophysical potential	1400–2900	1370–3880
Lal (2003, 2004a)a	globe—soil sequestration	CO2 only	biophysical potential	3300±1100	1370–3880
IPCC (2000; SR-LULUCF)b	globe—soil sequestration	CO2 only	biophysical potential	1470	1370–1470
Manne & Richels (2004)c	globe—soil sequestration	CO2 only	US$ 27 t CO2-eq.−1	1700	1370–1470
IPCC (2001; TAR)d	globe—all measures	CO2, CH4 and N2O	US$ 27 t CO2-eq.−1	1300–2750	1540–1640
Caldeira et al. (2004)e	globe—all measures	CO2, CH4 and N2O	biophysical potential	4510	4300–5950
Lal & Bruce (1999)f	globe—croplands only	CO2 only	biophysical potential	1580–2090	1980–2140
Conant et al. (2001)g	globe—permanent pastures only	CO2 only	biophysical potential	6860	1360–1560
Squires et al. (1995)h	globe—desertification control only	CO2 only	biophysical potential	3670	approximately 650
Lal (2001)h	globe—desertification control only	CO2 only	biophysical potential	730–1470	approximately 650
US-EPA (2006)i	globe—soil N2O only	N2O only	US$ 100 t CO2-eq.−1	200	120
US-EPA (2006)i	globe—rice CH4 only	CH4 only	US$ 100 t CO2-eq.−1	230	230
US-EPA (2006)i	globe—livestock CH4 only	CH4 only	US$ 100 t CO2-eq.−1	200–300	210
US-EPA (2006)i	US—livestock CH4 only	CH4 only	US$ 20 t CO2-eq.−1	40	32
US-EPA (2006)i	China—livestock CH4 only	CH4 only	US$ 50 t CO2-eq.−1	45	42
US-EPA (2006)i	India—livestock CH4 only	CH4 only	US$ 10 t CO2-eq.−1	17	12
US-EPA (2006)i	Brazil—livestock CH4 only	CH4 only	US$ 30 t CO2-eq.−1	23	46 (for all South America)
Smith et al. (2000)j	Europe (excluding Russia)	CO2 only	limited by suitability	205	120, 160, 240
Lal et al. (2003)k	US—croplands only	CO2 only	biophysical potential	165–360	140
Lal et al. (2003)k	US—grasslands only	CO2 only	biophysical potential	48–257	60
Lal et al. (2003)k	US—land conversion only	CO2 only	biophysical potential	77–282	—
Lal et al. (2003)k	US—land restoration only	CO2 only	biophysical potential	92–220	30
Sperow et al. (2003)k	US—croplands only	CO2 only	biophysical potential	220–257	140
Boehm et al. (2004)l	Canada—all agriculture	CO2 only	biophysical potential	16.5–29.9	—
Boehm et al. (2004)l	Canada—all agriculture	CO2, CH4 and N2O	biophysical potential	4–15.6	—
Lal (2004c)m	China	CO2 only	biophysical potential	436–829	425
Lal (2004d)l	Central Asia	CO2 only	biophysical potential	approx. 60±30	—
Lal (2004e)n	India	CO2 only	biophysical potential	approx. 160±18	330 (for all South Asia)
Lal (2005)o	Brazil	CO2 only	biophysical potential	400	570 (for all South America)

^aEconomic potentials estimated here at up to 20 US$ t CO₂-eq.⁻¹ of approximately 1300–1400 Mt CO₂-eq. yr⁻¹ rising to 2200–2400 and 3600–3900 Mt CO₂-eq. yr⁻¹ at up to 50 and up to 100 US$ t CO₂-eq.⁻¹, respectively.

^bIPCC LULUCF (2000) estimate is based on C stock change in croplands, grazing lands, agroforestry, rice paddies and urban lands. Compared to estimates here at 0–20 US$ t CO₂-eq.⁻¹.

^cManne & Richels (2004) estimates for 2010 assuming a marginal cost of US$ 100 t C ⁻¹ (equivalent to US$ 27 t CO₂-eq.⁻¹); figures from this study are from closest comparable price range of 0–20 US$ t CO₂-eq.⁻¹.

^dIPCC TAR (2001) estimates for 2020 assuming a marginal cost of US$ 100 t C ^–1 (equivalent to US$ 27 t CO₂-eq.⁻¹); figures from this study are from closest comparable price range of 0–20 US$ t CO₂-eq.⁻¹.

^eCaldeira et al. (2004) estimates are for all gases for practices: enteric fermentation, rice cultivation, biomass burning, animal waste treatment and agricultural soils over a 0–20 year time horizon; estimates here are between the estimates at 0–100 US$ t CO₂-eq.⁻¹ and total biophysical potential (up to 6000 Mt CO₂-eq. yr⁻¹).

^fEstimate for croplands only; comparable figure is for the biophysical potential of cropland management, plus restoration of degraded croplands.

^gThe Conant et al. (2001) estimate for permanent pasture only is much larger than many estimates for all agricultural mitigation measures combined; as such, it may be unrealistically high.

^hComparable estimates for this study are for restoration of degraded lands.

ⁱAll US-EPA (2006) estimates are for 2020. Global estimates are for prices of 100 US$ t CO₂-eq.⁻¹. US-EPA (2006) estimate for Brazil should be equivalent to approximately 60% the estimate from this study for South America. Rice figures are taken directly from US-EPA (2006).

^jComparable figures for this study are quoted for prices of up to 20, up to 50, up to 100 US$ t CO₂-eq.⁻¹, respectively. Other studies from individual countries are not included as there is no comparable area in the present study.

^kFrom this study, biophysical potentials used for all North America (US plus Canada) from cropland management, grassland management and restoration of degraded lands.

^lNo comparable area in the present study.

^mEstimate in this study for East Asia.

ⁿEstimate in this study for South Asia; covers a larger area than just India.

^oLal (2005) estimates that 180 Mt CO₂ yr⁻¹ could be sequestered in the soils of Brazil, plus a further 220 Mt CO₂ yr⁻¹ mitigated by erosion prevention; estimate from this study from South America; covers a larger area than just Brazil.