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CH 4 and N 2 O emissions have increased by nearly 17% from
1990 to 2005, an average annual emission increase of about 60
MtCO 2 -eq. year −1 (Anonymous, 2006a,b). Three sources—bio-
mass burning (N 2 O and CH 4 ), enteric fermentation (CH 4 ) and
soil N 2 O emissions—together explained 88% of the increase.
Livestock (cattle and sheep) account for about one-third of
global anthropogenic emission of CH 4 (Murray et  al., 1976;
Kennedy and Milligan, 1978; Crutzen, 1995; Anonymous,
2006a). Agricultural lands generate very large CO 2 fluxes
both to and from the atmosphere (Anonymous, 2001a) but the
net flux is small (Smith et  al., 2007a), which amounts to 40
MtCO 2 -eq. in 2000, less than 1% of global anthropogenic CO 2
emissions (Anonymous, 2006b). GHG emissions from defor-
estation mainly in tropical countries contributed an additional
5.9 Pg CO 2 -eq. per year (with an uncertainty range of ±2.9 Pg
CO 2 -eq.), thus equalling or exceeding emissions from all other
agricultural sources combined.
Agricultural N 2 O emissions will increase 35-60% till 2030
due to increasing use of nitrogenous fertiliser and animal
manure production (Mosier and Kroeze, 2000; Anonymous,
2003, 2006a). If the demands for food increase and the diet
shifts as projected, then annual emissions of GHGs from
agriculture may escalate further (Smith et  al., 2007a). If CH 4
emissions increase proportionately with increasing livestock,
then it is projected that CH 4 emission will increase by 60% till
2030 (Anonymous, 2003) while both enteric fermentation and
manure management will increase CH 4 emission by 21% from
2005 to 2020 (Anonymous, 2006a). Further, although global
rice production areas will increase to 4.5% by 2030, substantial
CH 4 emission is not expected, which may be due to less rice
grown in continuous flooding under future water-scarce condi-
tions or due to rice cultivars emitting less CH 4 (Wang et  al.,
1997). But a sustained increase in the area of irrigated rice
between 2005 and 2020, a 16% increase in CH 4 emission is pro-
jected (Anonymous, 2006a). The baseline 2020 emissions for
non-CO 2 GHGs is 7250 MtCO 2 -eq. Non-CO 2 GHG emissions
in agriculture are projected to increase by about 13% from 2000
to 2010 and by 13% from 2010 to 2020 (Anonymous, 2006b).
Unfortunately, for non-CO 2 GHG emission estimates, there
is no baseline for 2030. Assuming a similar rate of increase
from 2000 to 2020, the 2030 global agricultural non-CO 2 GHG
emissions were projected to increase 13% during 2000-2010
and 2010-2020, while 10-15% increase were projected for
2020-2030, that is, from 8000 to 8400 with a mean of 8300
MtCO 2 -eq. by 2030 (Anonymous, 2006a). Moreover, the future
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