Global Warming & Decreased Crop Term Paper

Excerpt from Term Paper :

Changes (Global, National, Region, Local, and Farm)


Smith (2006)

In the work entitled: "Climate Change and Agriculture" a brochure prepared for the UK Ministry of Agriculture, Fisheries and Food written by Muriel, Downing, and Hulme, et al. In Section 4: Impact of Climate Change on Crops report findings that:

1) Elevated temperature increased their rate of grain growth but shortened the duration of grain filling;

2) Higher temperatures may have decreased the availability of assimilates so decreasing grain size, grain yield and mass per grain; and 3) Higher temperatures reduced average mass per grain, in one experiment, by 25% in normal CO2 and 14% in elevated conditions." (Muriel, Downing, and Hulme, et al. nd)

The following chart demonstrates the effect that CO2, temperature, and CO2 combined with a higher temperature had on crop yields in this study.

Change in yield (%)

Source: (Muriel, Downing, and Hulme, 2006)

There are stated to be few crops that will experience benefit from higher temperatures with production rates increasing however, some will and one of these is stated to be carrots.

Regional differences are also noted as in a separate report entitled: "Will African Agriculture Survive Climate Change?" public in the World Bank Economic Review August 23, 2006, it is stated that a study was conducted using:"data from a survey of more than 9,000 farmers across 11 African countries, a cross-sectional approach estimates how farm net revenues are affected by climate change compared with current mean temperature." (World Bank Economic Review 23 Aug, 2006) it is important to note the two following facts:

Revenues fall with warming for dryland crops (temperature elasticity of -1.9); and livestock; and Revenues rise for irrigated crops (elasticity of 0.5) which are located in relatively cool part of Africa that are buffered by irrigation from the effects of warming." (Kurukulasuriya, P. et al., 2006)

Finally, the third finding stated is that: "warming has a little net aggregate effect as the gains for irrigated crops offset the losses for dryland crops and livestock." (2006) Simultaneously warming will bring about reduction in dryland farming income on an immediate basis. Africa is stated to be conducive to adaptations to climate change through irrigation of crops.

A report entitled: "Projected Climate Change Impacts on Agricultural Management in Indiana" states that studies relating to climate change on agricultural production generally suggest a probable increase in crop productivity due to longer growing seasons and CO2 fertilization, with the potential for negative production impacts in warmer latitudes. (Bowling and Laufik, nd) a recent study conducted by researchers at the Carnegie Institution and Lawrence Livermore National Laboratory according to a March 16, 2007 report entitled: "Study: Warming Causing Decline in Global Crop Production" states findings that crop production has fallen since 1981 due to temperature changes. Specific changes in crop production are shown in the following chart labeled

Changes in Crop Production Since 1982 Due to Higher Temperatures

Source: (Study: Warming Causing Decline in Global Crop Production, 2007)

The work of Bolin, Jager and Doos (1986) reporting studies of "the crop yield effects of climate change generally show that with no change in precipitation, a warming of 2 deg.C might reduce average yields of maize and wheat in the mid-attitudes of North America and Western Europe by 10+/-7% assuming no change in cultivars, technology of management. (Crosson, 1989)

The work of Andresen and Cheng (2006) states that field crops will benefit from longer-frost free growing season results in higher crop productivity potentials but there was also be greater pest, weed, and disease pressures and organisms that are new problems in some regions will also be a threat to crop productivity. An overall increase in potential productivity for most crops, with reductions in water stress playing a major role" is stated as well. (Andresen and Cheng, 2006)

The work of Williams, et al. (1999) states that: "Climate models indicate there will be an increase in both average annual temperature and rainfall in the Midwestern U.S. By the year 2050 which will result in warmer, wetter conditions. Perhaps the most important factor will be less predictable weather patterns that will emerge, increasing the frequency of extreme weather events..." (Williams, et al., 1999) Droughts, floods, late season frosts and heavy precipitation are also noted as results of the variability in weather patterns. Findings stated in the work of Williams et al. (1999) include the increase of "average daily maximum temperatures of about 3.5
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degrees C. And assumes a doubling of CO2. The authors state their findings "coincide with those of Adams (1989) "who reported a 12 to 19% decrease in corn yields for the Corn Belt area and North Plains using the GDFL climate simulation." (Williams et al., 1999)

The work of Indur M. Goklany is an excerpt from the work of Okonski "Adapt or Die: The Science, Politics and Economics of Climate Change" (2003) and states that: "For many climate-sensitive sectors and indicators matters have actually improved...Global agricultural productivity has never been greater. An acre of cropland sustains about twice as many people today as it did in 1990, and it sustains them better." (2003) Goklany states that it has been noted by the Finnish branch of the WWF that: "Thanks to the warming trend, the growing season has grown...At the same time the spring migration of birds, including finches, larks, wagtails, and swifts has begun an average of ten days earlier than before." (2003) Noted additionally in the work of Goklany is that: "...on time scales of a few decades, the current observed rate of warming...suggest that anthropogenic warming is likely to lie in the range of 0.1 to 0.2 degrees C. per decade over the next few decades." (2003) the following chart illustrates the net habitat loss to cropland vs. increase in agricultural productivity from 1997 and projected until 2050 in the work of Goklany.

Net habitat loss to cropland vs. increase in agricultural productivity

Source: Goklany (2003)

The work of Peng et al. (2004) examines the impact of higher temperatures at night, which have occurred due to global warming on the production of rice and evaluated the data through examination of trends in temperature and how this affected the rice yield. Findings states that production of rice was reduced by 10% for every 1% Celsius increase in temperature minimums however, findings state that there was an insignificant effect on crop yield due to maximums in temperatures. Therefore findings were that nighttime temperature increases associated with global warming causes decreases in production of rice crops. The work of Reily (2002) in an examination of the effect that global warming has upon production of various crops states findings that increases in temperatures are likely to increase weeds and pests which will only serve to compound the negative effect upon the production of agriculture crops.

VI. Summary & Conclusion

One important factor to crop production, and specifically fruit crop production is that failures are likely to occur due to the early growth of these crops in warmer weather resulting in the loss of crops due to cold snaps. This has been noted in the research in the foregoing literature. As well, there are agriculture crops that will initially be more productive however, the literature in the foregoing review has illustrated the likelihood that in the longer run, crops certain crops will be less productive due to higher temperatures. There are some crops in some regions of the world that are expected to reach greater productivity in higher temperature climates. Also noted with the increase in temperatures is the increase in pests that threaten agriculture products. There are many variables both known and unknown related to climate change temperature driven changes and impacts. Temperature extremes have shown to dramatically reduce the agricultural productivity potential. The growing season has been shown in this study to have an impact on agriculture productivity and this study has noted that certain crop production in longer growing seasons may be more productive barring however, regions that experience cold snaps after the warmer season has already promoted spring crop growth beginning and then being damaged by the colder temperatures.

Technology will play an important part of productivity of crops and the countries, which are wealthier, will be better prepared for technological supports due to their ability to afford the use of these supports. Some regions of the world will naturally become more conducive to agricultural production while others will become more adverse to production of agriculture. It has been noted in this work that variable temperatures and other climate change factors will require flexibility in crop substitution and crop mix. As noted in the work of Goklany agricultural production should become more efficient due to technology as while cropland decreases the productivity of cropland will increase.

Temperature increases will be both positive and negative depending upon the region of the world that the agricultural crop production is taking place as well as other impacts, which are not identified in the course of this study…

Sources Used in Documents:


Chipanshi, a., Chanda, R., & Totolo, O. (Dec 2003). Vulnerability assessment of the maize and sorghum crops to climate change in Botswana. Climatic Change, 61(3).

Dhakwa, G. & Campbell, L. (Dec 1998). Potential effects of differential day-night warming in global climate change on crop production. Climatic Change, 40(3).

Isik, M. & Devadoss, S. (20 April 2006). An analysis of the impact of climate change on crop yields and yield variability. Applied Economics, 38(7).

Peng, S., Huang, J., Sheehy, J., Laza, R., Visperas, R., Zhong, X., Centeneo, G., Khush, G., & Cassman, K. (6 July 2004). Rice yields decline with higher night temperature from global warming. Proceedings of the National Academy of Sciences of the United States of America, 101(27).

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