CHAPTER 3— District Resources and Description Bridgette Flanders-Wanner / USFWS / Bridgette Flanders-Wanner Grasslands in the Millerdale Waterfowl Production Area. The three wetland management districts manage smaller temporary and seasonal wetlands that draw thousands of noncontiguous tracts of Federal land breeding duck pairs to South Dakota and other parts totaling 1,136,965 acres: 100,094 acres of WPAs and of the Prairie Pothole Region. 1,036,871 acres of conservation easements. This chap­ ter describes the physical environment and biological CLIMATE CHANGE resources of these district lands, as well as fire and In January 2001, the Department of the Interior is­ grazing history, cultural resources, visitor services, sued Order 3226, requiring its Federal agencies with socioeconomic environment, and district operations. land management responsibilities to consider potential climate change effects as part of long-range planning endeavors. The U.S. Department of Energy’s report, “Carbon Sequestration Research and Development,” 3.1 Physical Environment concluded that ecosystem protection is important to carbon sequestration and may reduce or prevent loss The districts are located in central and eastern South of carbon currently stored in the terrestrial biosphere. Dakota from west of the Missouri River to the Minnesota The report defines carbon sequestration as “the capture state line, and from the North Dakota border roughly and secure storage of carbon that would otherwise be two-thirds of the way south to the state line of Nebraska. emitted to or remain in the atmosphere.” The increase The prairies of South Dakota have become an eco­ of carbon dioxide (CO2) in the earth’s atmosphere has logical treasure of biological importance for water­ been linked to the gradual rise in surface temperature fowl and other migratory birds. The prairie potholes commonly referred to as “global warming.” of the Dakotas support a wide diversity of wildlife, In the context of comprehensive conservation plan­ but they are most famous for their role in waterfowl ning for the districts, the strategies that manage and production. Although the Prairie Pothole Region oc­ increase grassland vegetation contribute to the se­ cupies only 10 percent of North America’s waterfowl questration of carbon, constituting a primary climate- breeding range, it produces approximately 50 percent related effect. Large, naturally occurring communities of the continent’s waterfowl population. Complexes of of plants and animals that occupy major landscapes wetlands scattered throughout the three districts at­ (for example, grasslands, forests, wetlands, tundra, tract breeding duck pairs. While semipermanent and and desert) are effective both in preventing carbon permanent wetlands provide brood-rearing habitat emission and in acting as biological “scrubbers” of and migratory stopover habitat, respectively, it is the atmospheric CO2. 28 Comprehensive Conservation Plan, South Dakota Wetland Management Districts One Service activity in particular—prescribed temperatures average 3.4°F in Mobridge and 2.9°F in burning—releases CO2 directly to the atmosphere Sioux Falls, while July maximum temperatures aver­ from the biomass consumed during combustion; yet age 85.4°F in Mobridge and 85.6°F in Sioux Falls. A it results in no net loss of carbon sequestration capac­ bigger difference is evident comparing southwest to ity because new vegetation quickly germinates and northeast. January minimum temperatures average sprouts to replace the consumed biomass. This veg­ 7.7°F in Pierre versus –0.5°F in Clear Lake, while etation sequesters an approximately equal amount July maximum temperatures average 89.2°F in Pierre of carbon as was lost through the prescribed burning compared to 81.6°F in Clear Lake. The record low (Dai et al. 2006). temperature in the three-district area was –48°F at Interestingly, the U.S. Environmental Protection Miller on January 12, 1912, while the record high was Agency’s (EPA’s) 1998 publication, “Climate Change 120°F at Gann Valley on July 5, 1936. in South Dakota” (EPA 236-F-98-007x) directly ad­ Normal annual precipitation (1971–2000) averaged dressed Service interests in the State: 24.69 inches in Sioux Falls in the southeast, decreas­ “Based on model projections, national wildlife refuges ing to 16.94 inches in Mobridge. Sioux Falls receives in South Dakota appear to be among the most vulner­ an average of 41 inches of snow per year. able in the United States to changes in climate. The region’s national wildlife refuges and prairie pothole PHYSIOGRAPHY, GEOGRAPHY, AND SOILS systems appear to be especially sensitive to changes Physiography in precipitation and temperature. Sixty percent of the Because districts cover such a large geographic area, annual variation in the number of these wetlands can the physical environment and biological resources are be explained by year-to-year changes in temperature described here in the context of level III and level IV and precipitation. Smaller wetlands may be particu­ physiographic regions (Bryce et al. 1996). Four physio­ larly vulnerable to climate change. Projections show graphic regions (ecoregions) occur in the three-district that warmer annual temperatures affect wetlands by area: Northwestern Glaciated Plains, Northwestern reducing open water and increasing vegetation cover, Great Plains, Northern Glaciated Plains, and Western independent of precipitation. Rising temperatures, if Cornbelt Plains (figure 8). continued for several years, may decrease breeding Level III ecoregions are distinguished by patterns bird density and diversity in this critically important of biotic and abiotic phenomena: vegetation, climate, waterfowl habitat. Major additional threats to eco­ soils, land use, wildlife use, and hydrology. Local bi­ systems include habitat loss and species extinction, otic and abiotic factors are used to further subdivide increased fire frequency, and increased vulnerability the level III ecoregions into level IV ecoregions—the to invasive plant and insect species.” finest level in the hierarchy (Bryce et al. 1996). The The three wetland management districts, through descriptions below of the ecoregions that constitute the Small Wetlands Acquisition Program in South the three-district area are adapted from “Ecoregions Dakota, contribute to the protection and sustenance of North Dakota and South Dakota” (USGS 2006). of migratory and resident wildlife populations by re­ storing and conserving native grassland and wetland Northwestern Glaciated Plains—Ecoregion 42 (Level III) habitats throughout northeastern South Dakota. This Portions of the Huron and Sand Lake WMDs are in preservation of grassland vegetation helps to sequester this ecoregion. The Northwestern Glaciated Plains carbon and reduce the levels of greenhouse gases in ecoregion marks the westernmost extent of continen­ the atmosphere. Such endeavors, together with other tal glaciation. The youthful morainal (ridges of rock Service conservation efforts in South Dakota (such as debris at the margins of glaciers) landscape has sig­ the Dakota Grassland Land Protection Plan), as well nificant surface irregularity and high concentrations as the creation of land conservation cooperatives by of wetlands. The rise in elevation along the eastern the Department, inevitably lead to the trapping of boundary defines the beginning of the Great Plains. carbon that would otherwise combine with other at­ Land use is transitional between the intensive dry- mospheric gases thought to be causing a greenhouse land farming in the level IV Drift Plains ecoregion to effect and consequently leading to possible acceler­ the east and the predominance of cattle ranching and ated climatic changes. farming in the Northwestern Great Plains ecoregion to the west. CLIMATE South Dakota’s interior continental climate exhibits Missouri Coteau—Ecoregion 42a (Level IV) an extreme range of temperatures between summer Like closely spaced ocean swells, the rolling mounds and winter, common high winds, and cyclic wet/dry of the Missouri Coteau enclose countless wetland de­ periods. Normal temperatures (1971–2000) vary sur­ pressions, or potholes. During its slow retreat, the prisingly little between the northwest and southeast Wisconsinan glacier stalled at the Missouri escarp­ corners of the three-district area. January minimum ment for thousands of years, melting slowly beneath a 29 CHAPTER 3—District Resources and Description Figure 8. Draft Level III and IV Ecoregions of South Dakota. 30 Comprehensive Conservation Plan, South Dakota Wetland Management Districts mantle of sediment to create the characteristic pothole Missouri Plateau—Ecoregion 43a (Level IV) topography of the coteau. The wetlands of the Missouri The Missouri Plateau typifies the “wide open spaces” Coteau and the neighboring Prairie Pothole Region of the American West. The topography was largely contain the majority of the WPAs in North America. unaffected by glaciations, retaining its original soils Land use on the coteau is a mixture of tilled agricul­ and complex stream drainage pattern. The historic ture in flatter areas and grazing on steeper slopes. shortgrass prairie is now a mosaic of wheat, alfalfa, and grazing land. Missouri Coteau Slope—Ecoregion 42c (Level IV) The Missouri Coteau Slope ecoregion declines in el­ River Breaks—Ecoregion 43c (Level IV) evation from the Missouri Coteau ecoregion to the The River Breaks form broken terraces and uplands Missouri River. Unlike the Missouri Coteau ecoregion,