sd.png - 636 grassland that caused wetlands near Saskatoon...

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Unformatted text preview: 636 grassland that caused wetlands near Saskatoon, Saskatchewan to dry up, due mostly to increased infiltration of snowmelt, which was then subjected to greater evapotranspiration by the grass cover. In a modeling study of vernal pools in the Central California Valley, Pyke and Marty (2005) found that even with increased periods of inundation due to expected climate change, removal of grazing reduced the maximum annual duration of pending, which resulted in hydrological conditions that were less supportive of aquatic invertebrates and amphibians. During the past 200 years there has been a build- up of CO; and other greenhouse gases in the atmosphere due to human industry, deforestation, and farming (Ojima et al. 2002, IPCC 2007a). A broad range of climate models are used to make climate projections, not predictions, based on atmospheric emissions scenarios (Ojima et al. 2002. IPCC 2007a, Parry et al. 2007). The lntergovem- mental Panel on Climate Change or IPCC (2007a) projected, for a range of atmospheric emission scenarios, that by the year 2100 the globally averaged surface temperature of the Earth will have risen l.8—4.0"C. General Circulation Model (GCM) projections for the U.S. Great Plains indicate that during the 213' century, the mean annual tempera- ture will increase dramatically, with decreasing precipitation in the west and increasing precipitation in the east (Ojima et al. 1999. National Assessment Synthesis Team 2001, Ojima et al. 2002). The Northern and Central Great Plains warmed by nearly l.l°C during the 20” century (National Assessment Synthesis Team 2001, Ojima et al. 2002). An analysis of the 20"I century climate for the Prairie Pothole Region (PPR, Figure l) of North America, an 850 000 km2 matrix of grassland and agriculture, showed that the minimum daily average temperature has warmed by an average of 1°C (Millctt et al. 2009). Through regression analysis, Millett et al. (2009) also showed that the east-west precipitation gradient of the PPR steepened during the 20‘h century, becoming wetter in the east and drier in the west, with an average increase in annual precipitation of 49 mm or 9%. One potential consequence of climate change could be an intensi- fied hydrologic cycle with increased frequency of both droughts and deluges (Ojima et al. 2002, Johnson et al. 2004). There has been an increased interest in studying the effects of climate change on U.S. agricultural land use and crop production (e.g., Adams et al. 1990, Easterling et al. 1992a, 1992b. Rosenberg 1993, 2005, Rosenzweig et al. 2000, Reilly et al. 2003). These studies utilized GCMs coupled with hydrologic, economic, and crop production models, WETLANDS, Volume 29, No. 2, 2009 Figure l. Extent of Prairie Pothole Region in North America. Adapted by combining ecoregion boundaries from sources: Schut (2005) and the U. S. EPA (2006). Triangle indicates the Orchid Meadows research site near Clear Lake. SD, USA. such as USDA‘s Erosion Productivity Impact Calculator (EPIC) model (Williams 1995), to demonstrate a range of possible impacts on agricul- ture due to climate change. These studies reported that the potential economic viability of specific crops in specific regions, given an increase in global mean temperature (GMT), was highly dependent on available moisture and the adaptive capacity of the region. For a GMT increase of 25°C with a CO; concentration at 365 parts per million, Thomson et al. (2005) demonstrated through modeling that the margins of current dryland corn, soybean, and wheat production regions in the U.S. are more likely to either gain or lose potential for crop production than the central areas of these regions, the gain or loss being highly dependent on the precipitation variability produced by the GCMs. Responses to a warmer climate in the Northern Plains of the U.S. would include increased crop irrigation demand, expansion of fall-seeded small grain crops, and adoption of new crop varieties adapted to longer growing seasons or drier condi- tions (Adams et al. l990, Easterling et al. 1992a, Easterling 1996). Agronomic and economic strate- gies for the adaptation of North American agricul- ture to climate change are numerous; large adaptive capacity available at minimal costs provides little motivation to divert resources to combat climate change (Easterling 1996). ...
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