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As land under tropical agriculture occupies a wide range of soil
types and climates, the capacity for carbon sequestration can
differ considerably. In hot and dry areas where soil has been de-
graded, implementation can restore carbon and prevent further
losses. In humid climates the potential for carbon sequestra-
tion can reach one tonne per ha. According to some estimates,
degraded soils represent half of the world’s carbon sequestra-
tion potential (Lal 2004a).
One management practice with a high potential for carbon
sequestration in tropical areas is agroforestry. In agroforest-
ry systems, food production is combined with tree planting.
Because of the trees, agroforestry systems store more carbon
as plant biomass and have a higher potential for soil carbon
sequestration than conventional agricultural systems (Nair
et al.
2009). Biodiversity benefits may also be realised. Aver-
age carbon storage by agroforestry practices is estimated at
around 10 tonnes per ha in semi-arid regions, 20 tonnes per
ha in sub-humid and 50 tonnes per ha in humid regions, with
sequestration rates of smallholder agroforestry systems in
the tropics being around 1.5–3.5 tonnes of carbon per ha per
year (Montagnini and Nair 2004). In addition, agroforestry
systems can reduce the pressure on natural forests thereby
having indirectly a positive effect on carbon storage in the lat-
ter (Montagnini and Nair 2004).
However, as with conventional agricultural systems, sustain-
able management practices also need to be adopted in agrofor-
estry systems to ensure carbon sequestration and sustainable
water use.
In some systems, interference interactions between crop species
and trees planted as part of agroforestry measures may have a
negative impact on crop yields (Garcia-Barrios 2003). In these
circumstances, compromise solutions may be best, aiming to
store reasonable rather than maximum amounts of carbon while
still ensuring profitability from crops (Verchot
et al.
2005).