Geoscience Reference
In-Depth Information
temperature harms people, animals and plants, including rice.
The higher the concentration of greenhouse gases, the more the
trapping of heat in the atmosphere and the reduced escape of
heat back into space. The higher heat results in a change in cli-
mate and altered weather patterns. In 2001, the 'UN-sponsored
Intergovernmental Panel on Climate Change' reported that
worldwide temperatures have increased by more than 0.6°C in
the past century and estimated that by 2100, average tempera-
tures will increase by between 1.4°C and 5.8°C (Nguyen, 2005).
8.3
Global warming and rice productivity
High temperatures or global warming would decrease the rice
production globally (Furuya and Koyama, 2005). There is a
need to plan for appropriate strategies to adapt to and miti-
gate the global warming for achieving long-term food secu-
rity. Both lowland rice cultivation and upland rice production
under slash-and-burn shifting cultivation results in the emis-
sion of methane and nitrous oxide gases and, thus, contributes
to global warming. Increased concentration of carbon dioxide
in the atmosphere along with rising temperatures are two major
factors making rice agriculture a larger source of greenhouse
gas 'methane' which may double by the end of this century.
Methane is produced from carbon and hydrogen by bacteria
in the soil. Some carbon enters the soil from the roots of rice
plants, which have taken it from the atmosphere via photosyn-
thesis. The rice plants grow faster under higher carbon dioxide
concentration. This growth, in turn, pumps up the metabolism
of methane-producing microorganisms in soil in rice field,
thus generating more methane. Rice farming is responsible for
approximately 10% of the methane released. Researchers at
Northern Arizona University gathered published research from
63 different experiments on rice paddies, mostly from Asia and
North America. The meta-analysis was used and found two
strong patterns: first, more carbon dioxide boosted emissions
of methane from rice paddies, and second, higher temperatures
caused a decline in rice yields. According to the study, in the
future the amount of methane emitted from rice paddies is
likely to increase. Together, higher carbon dioxide concentra-
tions and warmer temperatures predicted by the end of this cen-
tury will double the amount of methane emitted per kilogram
of rice produced (NAU, 2013). Since half of the worlds' human
population is highly dependent on rice, the production systems
for this crop are, thus, vital for the reduction of hunger and
