Geoscience Reference
In-Depth Information
specific diseases or through increased pathogenicity of organ-
isms by mutation induced by environmental stress (Gregory
et al., 2009). The severity of disease in oilseed rape could
increase within its existing range and can also spread north-
ward over the next 10-20 years (Evans et al., 2008). Changes in
climate variability may also be significant affecting the predict-
ability and amplitude of outbreaks (Gornall et al., 2010).
Of all crop pests, weeds are the most damaging, but they
will cease to be so in the event of CO
2
increases in the atmo-
sphere (Chakravarty and Mallick, 2003). This is because the
condition that will generally favour crop production over weed
growth. Out of the world's 18 most noxious weeds, 14 are C
4
plants, and out of the 20 most important food crops, 16 are
C
3
plants (Wittwer, 1990). As discussed earlier, C
3
plants will
respond more vigorously in elevated atmospheric CO
2
domi-
nating the C
4
weeds (Chakravarty and Mallick, 2003). Climate
change will shift the agricultural potential to new regions, but
may also shift with the introduction of new pest species. Barley
now growing as a highly marginal crop in Iceland may become
cultivable throughout lowland Iceland due to longer growing
seasons, but losses to pest and diseases will rise up to 15% from
today's minimal level (Bergthorsson et al., 1988).
Sea level will rise owing to thermal expansion of the exist-
ing mass of ocean water and water flowing in after melting of
land ice due to the warming climate inundating coastal land
(Titus, 1990; Gornall et al., 2010). The potential sea-level rise
due to melting and discharge of West Antarctic, East Antarctic
and Greenland ice sheets will be approximately 2 m by 2100
(Pfeffer et al., 2008; Rohling et al., 2008). The crop production
will be vulnerable, where large sea-level rise occurs in conjunc-
tion with low-lying coastal agriculture, such as in major river
deltas, which are valuable agricultural land owing to the fertil-
ity of fluvial soils. Sea-level rise threatens to inundate agricul-
tural lands and salinise groundwater in the coming decades in
the United States (Park et al., 1988) and 20% of farmland in
Bangladesh and Egypt (Broadhus et al., 1986). Although inun-
dation may not pose a major threat to US agriculture, it would
be a major threat for countries such as Bangladesh and Egypt
whose nationwide productivity mainly depends on cultivated
river deltas (Chakravarty and Mallick, 2003).
Moreover, the main culprit of climate change, the carbon
emissions, can also help agriculture by enhancing biomass
production due to the net increase in photosynthetic gain
(especially in C
3
crops such as wheat, rice and soya beans)
because of the reduction in photorespiration, increase water-use
