Term Paper on "Global Warming and Decreased Crop Production"

Term Paper 13 pages (3634 words) Sources: 15 Style: APA

[EXCERPT] . . . .

GLOBAL WARMING & DECREASED CROP PRODUCTION

This work in writing will make a review of the literature related to global warming and expected decreases in crop production. This subject is of particular interest due to the impact that decreases in crop production will have upon the entire world.

As global warming causes the Earth's average temperatures to rise, crop production will experience a decrease.

Conceptualization

Various methods have been used in measuring the effect of climate change on agricultural crop production yield rates. Three approaches most commonly used in research are the: (1) crop yield analysis; (2) Spatial analysis; and (3) Agricultural systems analysis. (Smit, Ludlow, and Brklacich, 1988) the crop yield analysis makes estimation of the effects of alteration to environments upon the productivity levels of crops. Because of the gradual nature of the change in normal climate with greenhouse gases elevation levels being causal there could be time allowed in which changes in patterns of agriculture and practices of management to change. The study conducted within the scope of this work will be in the nature of a qualitative review of literature and specifically literature which documents research stating findings that changes in temperatures either increases or decreases agricultural crop production yield rates.

IV. Literature Review

The work of Pritchard and Amthor states that: "several notable, ongoing environmental changes have especially important implications for crop yield, production, and quality which are those as follows:

1) Increasing global atmospheric carbon dioxide (CO2) concentration;

2) Climatic changes associated with increasing atmospheric concentrations of CO2 and other greenhouse gases most importantly global warming;

3) Increasing ozone (O3) concentrations in the lower atmosphere across large crop-growing regions; and 4) Soil salinization in area of irrigated crops. (Pritchard & Amthor, nd)

The work of McKeown, Warland, McDonald and Hutchinson (nd) in the work entitled: "Global Season Crop Production Trends: a Possible Signal for Global Warming" states that: "Yield of cole crops, rutabaga and potatoes were found to decrease with warmer average temperature..." (nd) the work of Dr. Christopher Field of Carnegie Institution released on March 16, 2007 and entitled: "Crops Feel the Heat as the World Warms" states that over the past twenty years major food crop losses have totaled approximately $5 billion. In fact, from the time period beginning in 1981 and ending in 2002 "warming reduced the combined production of wheat, corn, and barley...by 40 million metric tons per year." (Field, 2007) Field states that a study released March 16, 2007 in the Environmental Research Letters journal will state findings that the decline is "due to human-causes increases in global temperatures." (Field, 2007)

According to a recent report from China it has been stated that: "Experts estimated that crop yields could increase up to 20% in East and Southeast Asia while it could decrease up to 30% in Central and South Asia by 2050s." (China View 7 Apr 2007) the work of David Pimentel entitled: "Climate Changes and Food Supply" published in the Forum for Applied Research and Public Policy (1993) states that climate change will affect food production due to:

1) rising temperatures;

2) decreasing rainfall;

3) increasing rainfall;

4) coastal flooding.

In a report entitled: "Global Climatic Change and Agricultural Production: An Assessment of Current knowledge and Critical Gaps" it is stated the effects that climate change will have on agricultural production include the following derived from various models in use for prediction of: "...changes in land productivity and the geographical shift in agricultural land use as a function of changes in climate and food demand" (Bazzak and Sombroek, 2007) Simultaneously the CO2 in the atmosphere expected to double with the following outcomes:

1) "Agro-ecological zones would shift because of temperature increase and improved water-use efficiency, with significant regional differences; (Bazzaz and Sombroek, nd)

2) Crop yields and winter grazing in mid- and high-latitude regions (i.e., mostly developed countries) would improve because of increased photosynthesis, longer growing periods and extension of frost-free growing regions, provided optimum growth conditions are maintained, e.g., by judicious fertilizer and biocide use on agricultural land; (Bazzaz and Sombroek, nd)

3) in most developing countries, crop productivity would diminish (some 10% reduction in cereals), which could raise agricultural prices on local and world markets and increase the need for cereal imports, although the global food supply/demand ratio might change only little; (Bazzaz and Sombroek, nd) and 4) There can be much risk in tropical and subtropical regions, and the greatest risk to food security would be in Sub-Saharan Africa. The magnitude of the threat will also depend on the behavior of non-agricultural sectors of the economy in the future." (Bazzaz and Sombroek, nd)

Science and Technology Review article entitled: "Climate and Agriculture: Change Begets Change" reports a Livermore study conducted for the purpose of modeling the effect of climate change on six California perennial crops: (1) wine grapes; (2) almonds; (3) table grapes; (4) oranges; (5) walnuts; and (6) avocados. David Lobell and colleagues from Livermore, the University of California at Merced, Carnegie Institution and Stanford University utilized climate models that were developed by research organizations. The following chart labeled Figure 2 shows the yield change in percent projected for the years 2020, 2050, and 2080 for wine grape, almond, table grapes, oranges, walnuts and avocados.

Yield Change Percentage for years 2020, 2050, and 2080

Source: Climate and Agriculture: Change Begets Change (2007)

Findings from the study of Lobell and colleagues state findings that: "...the overall trend was for a decrease in yield." (Science & Technology Review, 2007)

Findings in the work of Richard M. Adams, of the International Research Institute for Climate Prediction state after data analysis from USDA-NASS, in the work entitled: "Climate Variability and Climate Change: Implications for Agriculture" relates that: "...state level climate data from the National Oceanic and Atmospheric Administration (NOAA) stated to have as its basis the time series observations for thousands of weather stations. Data were analyzed through "using established production functions forms to estimate the result of both the average effect of climate on yield, and on the variance of yield. Results suggest that temperature and precipitation changes affect both the mean and variances of crop yield. On average, crop yields increase with more rainfall and decrease with higher temperatures. In terms of variability, increases in rainfall result in decreased variability of crop yield, and an increase in temperature results in increased variability of crop yield. When looking at specific crops, it was found that with increasing temperature, corn yields decrease and yield variance increases. This suggests that a warmer future climate in corn growing regions could result in reduced yields and greater year-to-year fluctuations in corn yields and total production. The yield functions were evaluated using a different source of climate change data to compute the projected yield changes. The results showed uniform decreases in corn and cotton yield variability, and mixed results of yield variability for sorghum, soybean and wheat.." (2000) report published online the Food Navigator.com website are the findings of a study conducted by Carnegie Institution researchers and Lawrence Livermore National Laboratory who reports that: "from 1981 to 2002, warming reduced the combined production of what, corn and barley..." (2007) a Pew Synthesis report on climate change states relating to agriculture and climate change that: "Crop yields are likely to be greatly affected by climate change. Changes in temperature, precipitation, and CO2 concentrations can result in large reductions in growth and water use of some crops and large increases in others. This will be dependent greatly upon the "changes in temperature, precipitation and CO2 concentrations..." As well as other factors.

Summary of National Impacts by Sector and Extent of Temperature Change

Source: Pew Climate Synthesis Online available at http://www.pewclimate.org/docUploads/Pew-Synthesis.pdf.

The region believed most likely to see growth in production of agricultural products is the Middle Eastern area of the United States although other studies state findings that crop productive will actually be decreased. (2006; paraphrased)

The work of Joel B. Smith (2006) entitled: "A Synthesis of Potential Climate Change Impacts on the U.S." states: "When choosing a model and designing an experimental approach it is necessary to consider the nature of the likely temperature impact on a given crop. If a crop is sensitive to temperature thresholds, such as a requirement for a low temperature vernalization period (e.g. winter wheat) or has a critical maximum temperature for survival (e.g. 32 oC for cotton fruit survival..." (Smith, 2006) Related by Smith is that the model must be sensitive in these areas. Smith states that: "For most crops elevated temperature causes a reduction in yield as there is less time for the capture of light, water and nutrients by the plant (Lawlor and Mitchell, 2000). It is important to try to capture the effects of temperature sequences during critical vernalization and growth periods when simulating climate change impact. Elevated temperature during early growth stages will often be beneficial, but during the time of maximum growth can be detrimental due to shortening this period." (Smith, 2006)

The following table illustrates the changes that are expected to… READ MORE

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