Causes of Climate Change - Climate Resilient Agriculture for Ensuring Food Security - page 22

Fig. 2.4 Global CO 2 emissions, 1751−2003 [Carbon Dioxide Information Analysis Center (CDIAC), August 2010]

2.3.3 Methane (CH 4 )

agriculture, we are transferring carbon from liv-
ing biomass into the atmosphere (dry wood is
about 50 % carbon).
Logging and clearing land for agriculture or
livestock release huge amounts of carbon dioxide
and other harmful greenhouse gases into the
atmosphere. It also diminishes those regions'
ability to absorb carbon pollution.
The result is that humans are adding ever-
increasing amounts of extra carbon dioxide into the
atmosphere. Because of this, atmospheric carbon
dioxide concentrations are higher today than they
have been over the last half-million years or
longer.
CO 2 emissions from manufacture of fertilizers
and pesticides add to the overall carbon footprint
of agriculture. For example, industrial fertilizer
production is estimated to emit 6.7 kg CO 2 e per
kg N manufactured.
Atmospheric CO 2 levels have dramatically
increased in recent years. If we “zoom” in on just
the past 250 years, we see the increasing trend
(Fig. 2.4 ).
Carbon dioxide is an inorganic form of carbon
cycled through photosynthesis and respiration
(Fig. 2.5 ). The cycle of photosynthesis and respi-
ration is crucial to sustaining life so it is the other
processes which release carbon dioxide which
need to be addressed.

Methane is another important greenhouse gas in
the atmosphere. Wetlands, organic matter decay,
cattle and refuse landfi lls, termites, and natural
gas and oil extraction are the main sources of
methane, whereas escape into the stratosphere
and adsorption by soil are the main sinks. The pri-
mary sources of methane emission in agriculture
include rice cultivation, biomass burning, animal
digestive processes, and manure storage and han-
dling. About ¼ of all methane emissions are said
to come from domesticated animals such as dairy
cows, goats, pigs, buffaloes, camels, horses, and
sheep. These animals produce methane during the
cud-chewing process. Methane is also released
from rice or paddy fi elds that are fl ooded during
the sowing and maturing periods. When soil is
covered with water, it becomes anaerobic or lack-
ing in oxygen. Under such conditions, methane-
producing bacteria and other organisms
decompose organic matter in the soil to form
methane. Nearly 90 % of the paddy-growing area
in the world is found in Asia, as rice is the staple
food there. China and India, between them, have
80-90 % of the world's rice-growing areas.
Estimated CH 4 emissions from agricultural
production activities have been steadily increas-
ing since 1990. The increase in emissions from