Effects of Climate Change in the U.S. Great Plains on Winter Wheat Yields.

There is a clear consensus, particularly among the scientific community, that greenhouse gases are warming the earth. Since about 1985, the global average land and ocean temperature has increased more than 1⁰C and the average land temperature has increased almost 2⁰C. Because plants are intensely affected by temperature, rising land temperatures will result in some areas becoming more productive while others less productive. This paper looks at temperature changes from 1895 to 2015 for North Central Texas, Oklahoma, Kansas, Nebraska, South Dakota, and North Dakota, and how the yields (kg/ha) of winter wheat (Triticum Aestivum) were affected. Average annual temperature for North Central Texas is about 18⁰C and decreases approximately 3⁰C for each state moving to North Dakota that has an average temperature of about 5⁰C. Average temperatures for 1986-2015 compared to 1895-1985 were 0.3⁰C, 0.3⁰C, 0.6⁰C, 0.7⁰C, 0.9⁰C, and 1.0⁰C for North Central Texas, Oklahoma, Kansas, Nebraska, South Dakota, and North Dakota, respectively. Average annual precipitation was slightly higher for the 1986-2015 period than for 1895-1985 for every area. Survey data from USDA National Agricultural Statistics Service show winter wheat yields for North Central Texas and Oklahoma have not increased since the 1980s and are trending downward. For Kansas and Nebraska, farmer yields have remained somewhat constant, but winter wheat yields in South Dakota and North Dakota increased more than 50%. We hypothesize that even though the average temperature rise in the southern areas have been less than in the northern regions, it has been sufficient to significantly advance the heading so that yield components are being developed under less favorable conditions ahead of early spring precipitation. Higher temperatures also increase the vapor pressure deficits that increase water requirement.