Basic:
Agriculture
In today's global food market, only three varieties of cereal grains-maize, wheat, and rice-account for about 90% of the world's grain production1
and nearly half of all food calories consumed each year.2 These staple grains feed billions of people daily.
Yet to grow productively, they rely on specific environmental conditions. By limiting food-crop biodiversity to just
three varieties of grain, the world's food supply is at risk as temperatures warm and extreme weather events, such as
heat waves, intense storms, and droughts, threaten to wipe out entire harvests.
Agriculture is highly sensitive to weather events (daily atmospheric conditions, including temperature and precipitation).
Even small environmental changes can have serious consequences for crop productivity, especially in areas where plants
are already near their temperature thresholds. Yet, while the effects of climate change will almost certainly touch
all regions of the world, not everyone will share equally in its hardships.
In seasonally dry, low-latitude areas where most of the world's poor live, small temperature increases can devastate
annual crop and pasture yields.3 Research suggests that, India, for example, could experience a 40% decline
in agricultural productivity by 2080 as record heat waves scorch the landscape.4 A recent study of South
Africa predicts that annual crop revenues could drop as much as 90% by 2100, with small scale farmers most severely
affected.5 Developing nations are the most limited in their ability to adapt to rapid changes in climate as
well as extreme weather events such as droughts, intense storms, and heat waves.
In parts of North America, however, farmers are hailing climate change as "good news" for crop
productivity.6 The Intergovernmental Panel on Climate Change (IPCC) reports that temperature increases and
higher levels of atmospheric CO2 will likely increase crop and pasture yields to a moderate degree, at least
in the short-term. Weather changes could extend the growing season, and cropland will likely expand northward as the
climate warms. Yet, as the CO2 threshold of plants is exceeded and temperatures continue to rise, productivity
may begin to slow.7
Despite these mixed assessments of crop impacts, rising temperature could create serious general problems for the
world's agricultural sector. One ominous threat of climate change lies in extreme weather events. Drought conditions
often lead to wildfires, and intense storms can cause devastating floods. Rising sea levels in coastal areas will make
the soil and groundwater more alkaline, further stressing crops that are already struggling.8
Further, as winters and springs become warmer, insects are able to live longer and expand their ranges.9
Pest infestations create stresses on trees and crops, causing direct damage, increasing the susceptibility of plants
to disease, and creating conditions that allow invasive species to thrive and indigenous "weeds" to expand.
Some studies show that many types of weeds can adapt readily to climate shifts.10 This ability could enhance
their ability to out-compete crops for resources like minerals and moisture, diminishing yields.
Along with temperature change, crops are most affected by changes in precipitation. Changing global weather patterns
could make some areas wetter, while throwing other areas into drought conditions.11 Farmers could be forced
to abandon traditional crops to cultivate heat and drought tolerant varieties. In other areas, farmers are forced to
cultivate species able to withstand flood conditions. Scientists are currently working to develop flood resistant
rice for Asian producers coping with higher temperatures and flooding conditions.12 Moreover, winter
snowpack changes, glacial melt, shifts in stream runoff patterns, and groundwater depletion will have serious consequences
for farmers who rely on irrigation.13
Overall, crops depend on "weather" rather than "climate." Scientists agree that climate change
can cause extreme daily variations, which could have profound consequences for the world's food supply. The impacts
of climate change on food production will depend not only on environmental conditions but on farmers' ability and
willingness to utilize new technologies and cultivate different crops to meet the world's changing food demands.14
Small subsistence farmers with the poorest ability to adapt are most vulnerable to the growing impacts of climate change.
