Geoscience Reference
In-Depth Information
frameworks are needed for their implementation (Wassmann
et al., 2009a).
8.6
Water shortage and rice productivity
Rice cultivation needs plenty of water. The changes in climate
leading to a week without rain in upland rice-growing areas
and 2 weeks in shallow lowland rice-growing areas can cause
reduction in rice yields in the range of 17-40%. The intensity
and frequency of droughts are predicted to increase in rain-fed
rice-growing areas. Such changes are also expected in reduce
water-short irrigated areas for rice cultivation. It affects rain-
fed rice production in an area of 23 million hectares in South
and Southeast Asia and about 20 million hectares of rain-fed
lowland rice in Africa. The scarcity of water may also affect
rice production in Australia, China, the United States and other
countries. Drought stress is also expected to aggravate through
climate change; a map superimposing the distribution of rain-
fed rice and precipitation anomalies in Asia highlights espe-
cially vulnerable areas in East India/Bangladesh and Myanmar/
Thailand (Wassmann et al., 2009a,b).
8.7
Global warming and its impact on pests,
diseases and weeds
The IRRI experiments over the last 10 years at farmers' fields
indicated that rice diseases and pests are influenced greatly by
climate change. The incidence of diseases like brown spot and
blast increases due to shortages of water, irregular rainfall pat-
terns and related water stresses. On the other hand, the inci-
dence of sheath blight or whorl maggots or cutworms reduces
due to a change in the environmental conditions and shifts in
production practices adopted by farmers to reduce the impact
of climate change. It, thus, results in an emergence of new crop
health dynamics. Global warming will enhance rice-weed com-
petition. Rodent population outbreaks in Asia may increase due
to unseasonal and asynchronous cropping as a result of extreme
weather events. A combined simulation model (CERES-Rice
coupled with BLASTSIM) was used to study the effects of
global temperature change on rice leaf blast epidemics in sev-
eral agro-ecological zones in Asia. At least 5 years of historical
daily weather data were collected from each of 53 locations
in five Asian countries (Japan, Korea, China, Thailand and
