MIXED (#156)

The Mixed Grassland ecoregion is the southernmost and driest of ’s ecoregions. A northern extension of the shortgrass that stretches south to Mexico, this ecoregion is characterized by the vast open of the , with prairie potholes and several large shallow . It provides habitat for over 35 species at risk and is an important region for waterfowl nesting. The semi-arid climate limits crop production. Approximately 42% of this ecoregion remains in natural cover and almost 11% is within conserved/ protected areas, including 4% in community pastures.

LOCATION Arching from southcentral to southcentral along the U.S. border, this ecoregion forms the northern part of the semi-arid shortgrass prairie in the Great Plains of . This ecoregion extends southward along the Missouri River into northeastern , northwest and central , and central (in the U.S., this ecoregion is called the Northwestern Mixed Grasslands). CLIMATE/GEOLOGY The Mixed Grassland ecoregion generally has long, dry and cold winters, with a short, warm and a relatively wet spring and summer. The mean annual temperature is approximately 3.5⁰C. Mean summer tempera- ture is 16⁰C and mean winter temperature is approximately -10⁰C. The mean annual precipitation ranges from 240 to 350 millimetres, with higher rain and snowfall in the eastern portion. Overall, this ecoregion is semi-arid, and compared to other regions of the Prairies, it has rela- tively low amounts of snow cover. Western sections of the ecoregion experience a higher frequency of warming Chinook winds in the winter. The Mixed Grassland is a gently rolling landscape with flat expanses in some areas. There is a wide diversity of other landscapes, including scattered alkaline lakes, salt flats, inland dunes and badlands. Prairie potholes are less common than in the Moist Mixed Grassland and ecoregions, with the exception of the Missouri Coteau. VEGETATION The Mixed Grassland is characterized by short and mid-sized grasses and sedges intermixed with prairie wildflowers and low . The native grass- lands are dominated by needle-and-thread (Hesperostipa comata), western wheatgrass (Pascopyrum smithii) and prairie junegrass (Koeleria macrantha), with blue grama (Bouteloua gracilis) and blunt sedge (Carex obtusata) in the driest areas or under heavy grazing. A variety of shrubs and herbs also occur, including hoary sagebrush ( cana), prickly rose (wild rose) (Rosa acicularis) and brittle prickly-pear (Opuntia fragilis). Trees are rare. Thickets of scrubby trembling aspen (Populus tremuloides), eastern cottonwood (Pop- ulus deltoides), American silverberry (wolf-willow) (Elaeagnus commutata), snowberry (Symphoricarpos albus), serviceberry (Saskatoon berry) (Amelanchier alnifolia) and choke cherry (Prunus virginiana) are found in low areas, river slopes and . Fire, grazing by and drought were once key natural disturbances to this grassland ecosystem and played important roles in the abundance and

1 Ranking categories for biodiversity threat and conserved/protected area are relative to other ecoregions in the southern Canada study area (5=highest, 4=higher, 3=high, 2=low, 1=lower, 0=lowest). The lowest score for conserved/protected area is 1. For biodiversity and threat, the highest category based on measures and criteria approach is used. Photo by Calvin Fehr Kyle Marquardt MIXED GRASSLAND (#156)

FRESH WATER AND COASTS The ecoregion is dominated by the Nelson River drainage (Hudson Bay basin). Major rivers include Upper and Lower South Saskatchewan, Qu’Appelle and Red Deer. The southern portion of the ecoregion includes the headwaters of the Missouri River, which is in the Mississippi River drainage (Gulf of Mexico basin) (Figure 1). Some parts of the Mixed Grassland ecoregion are dotted with concentrations of semi- permanent and seasonal wetlands, often referred to as prairie potholes or sloughs. There are also several permanent and seasonal lakes that are generally shallow and alkaline, such as Old Wives south of . Other major lakes include Pakowki Lake and Many Island Lake. Lake Diefenbaker was created by damming the and Qu’Appelle River (completed in 1967), and Lake Newell is a reservoir on the (constructed in 1914). Wetlands and water cover approximately 4.3% of the ecoregion, although this is likely an under-estimate as smaller potholes would not be included in this figure. Mike Dembeck AT-RISK VEGETATION COMMUNITIES Rare vegetation communities have not been well-documented from this ecoregion. Asso- ciations that are of potential global conservation concern include:

• longleaf wormwood - prairie sandreed (Artemisia longifolia - Calamovilfa longifolia) sparse vegetation

WILDLIFE Photo by Karol Dabbs The mosaic of grasslands and wetlands provides habitat for a diversity of species, includ- ing a large number of species that are not found in other ecoregions. The Mixed Grassland ecoregion has a very high richness of mammals and breeding birds compared to other ecoregions in southern Canada. Common wildlife species include pronghorn (Antilocapra americana), (Odocoileus hemionus), white-tailed deer (Odocoileus virgin- ianus), (Canis latrans), Richardson’s ground squirrel (Urocitellus richardsonii), western meadowlark (Sturnella neglecta) and yellow-headed blackbird (Xanthocephalus xanthocephalus). AT-RISK AND ANIMALS There are over 35 national species at risk in the Mixed Grassland ecoregion. Sites with higher numbers of national species at risk include the intact prairies in and around . In addition, there are approximately 20 species of global conser- vation concern, with the highest number associated with the Great Sandhills region of Saskatchewan (Figure 2). Species at risk include:

• black-tailed prairie dog (Cynomys ludovicianus) • slender mouse-ear-cress (Virgate Halimolobos) (Halimolobos virgate, )* • Ord’s kangaroo rat (Dipodomys ordii) • gold-edged gem moth (Schinia avemensis)* • sage thrasher (Oreoscoptes montanus) • swift fox (Vulpes velox)* • greater short-horned lizard (Phrynosoma hernandesi) *nationally and globally at risk (NatureServe)

Photo by Branimir Gjetvaj MIXED GRASSLAND (#156)

LAND USE Agriculture dominates this prairie landscape (Figure 3). Lands are cultivated on the plains, and there is extensive irrigation in the western portion of the ecoregion. Many of the native prairie grasslands are used for ranching. Oil and gas extraction is common in the western portion of this ecoregion. The rate of land conversion (2000-2010) in this ecoregion is one of the highest in southern Canada. This is primarily native managed grasslands being converted to cropland (Table 1). The area of these grasslands decreased by 30%, while the area of crop increased by about the same percentage. More recent data shows that more than 236,000 hectares (more than 583,000 acres) of previously plowed land was returned to perennial cover. It is not known if this is a trend in land cover, or if it represents crop rotation practices. Major communities include Medicine Hat, Leader, Swift Current, Assiniboia, Maple Creek, Shaunavon and Kindersley. The total population Photo by NCC (2016) is 204,767, with a growth rate of 7.8% since 1996. CONSERVATION CONCERNS The most significant threat to this ecoregion is habitat loss, including the on-going conversion of wetlands and native grasslands. Compared to the rest of southern Canada, this ecoregion has experienced a high recent rate of conversion of natural habitats to agri- culture, and it ranks higher for the threat of lack of water (based on water demand verses water supply). High-ranking threats identified from the Nature Conservancy of Canada’s (NCC’s) Natural Area Conservation Plans (NACPs) in this ecoregion include invasive terrestrial species and droughts resulting from climate change. These threats may not be relevant to all areas of the ecoregion. Populations of grassland birds and shorebirds that breed in this ecoregion have been rapidly declining. CURRENT CONSERVATION STATUS With 42% natural cover, the Mixed Grassland ecoregion has some of the largest blocks of intact prairie habitat remaining in Canada. The largest intact blocks of habitat occur along the U.S. border, in the Great Sandhills region, and the area north of Medicine Hat in and around the Canadian Forces Base Suffield National Wildlife Area. This ecoregion is fragmented; however, there are several major corridors along the river valleys. A major north-south corridor extends from the U.S. border around and through the Cypress Uplands ecoregion into the intact grasslands of east-central Alberta (Figure 4). Approximately 11% of the ecoregion is conserved (Figure 5). This includes a large area (3.9%) of federal and provincial pasturelands. The amount of conserved area ranks second in the Prairies ecozone (after Cypress Uplands). This ecoregion also has a higher percent- age of landform features conserved than most other ecoregions in the Prairies ecozone. Key Biodiversity Areas (KBAs) in this ecoregion focus on important areas for migratory and breeding waterfowl and shorebirds. KBAs include Bigstick Lake Plain, Chaplin Lake, Chappice Lake, East Lake Diefenbaker, Luck Lake, Old Wives Lake, Pakowki Lake, Reed Lake, South Saskatchewan River and Willowbunch Lake. NCC has three active NACPs that cover 31.6% of the ecoregion: Milk River Basin, Missouri Coteau and Pakowki Lake. Key NCC proper- ties include Old Man on His Back Prairie and Heritage Conservation Area, Buffalo Valley, Mortlach and Wideview.

Ducks Unlimited Canada is very active in this ecoregion and has, for example, conserved properties at Quill Lakes and Bearhills Lake, and with many private landowners.

2 NACPs that cover >5% of the ecoregion as of December 31, 2017.

Kyle Marquardt MIXED GRASSLAND (#156)

POTENTIAL CONSERVATION STRATEGIES Of all the prairie ecoregions in Canada, the Mixed Grassland offers the best opportunity to protect large areas of intact and connected prairie habitats. The importance of this opportunity extends beyond Canada. Parts of this ecoregion have been identified by the International Union for Conservation of Nature as one of only four global areas with the greatest potential for native temperate grassland conservation on a large scale. The Mixed Grassland in Canada and the U.S. was also identified as one of the “Global 200” priority ecoregions for global conservation, with a conservation status of critically endangered (northern prairie). Long-term protection can be accomplished through a combination of increasing the number of conserved lands and improving partnerships and incentives that support ranchers. Potential conservation strategies for this ecoregion include: 1. Maintain the cover of native grasslands and wetlands to at least 40% (currently 42%) over the next 10 years. LARGEST 2. Increase the amount of conserved lands to 17% (national Target 1 goal), including longer term and more secure status for community pastures. This is CONSERVED probably the only prairie ecoregion in Canada where this goal can be met in the next 10 years. AREAS 3. Develop and implement a connectivity plan. There is still an opportunity (TOP 10, BY SIZE) to maintain and restore linkages between protected areas and large blocks of natural habitat. In particular, there is a large-scale circular linkage in the 1. Grasslands National Park of Canada ecoregion that includes the Missouri Couteau, along the South Saskatchewan (73,000 hectares/180,387 acres) River then south to the Milk River watershed. 2. Canadian Forces Base 4. Focus species at risk recovery on prairie species that require large areas of Suffield National Wildlife Area intact prairie grasslands, including swift fox and plains bison. Recovering and (45,836 hectares/113,263 acres) down-listing these species will benefit many other species of conservation concern, including grassland birds. Explore how to link the recovery of these 3. Val Marie Community Pasture species to creating jobs and expanding economic opportunities in (40,656 hectares/100,463 acres) local communities. 4. Great Sand Hills Representative 5. Develop long-term partnerships and incentives to maintain ranching on Area Ecological Reserve native grasslands, and expand on practices that improve grassland diversity (37,343 hectares/92,277 acres) and health, including grazing rotation, fire and invasive species management. 5. Old Wives Lake 6. Develop and implement strategies to link grassland and wetland conservation Migratory Bird Sanctuary to water security. This ecoregion is likely to experience greater water stress in (32,391 hectares/80,040 acres) the future, and conservation can help meet the water demands of urban areas and agriculture. 6. Matador Community Pasture (31,470 hectares/77,764 acres) 7. Explore opportunities to improve baseline biodiversity information, including more consistency in the tracking and mapping of species of conservation 7. Battle Creek Community Pasture concern and the identification of at-risk vegetation communities. (28,787 hectares/71,134 acres) 8. Govenlock Community Pasture (28,148 hectares/69,155 acres) 9. Arena Community Pasture (25,211 hectares/62,298 acres) 10. Nashlyn Community Pasture (24,894 hectares/61,514 acres)

To learn more about this ecoregion and NCC’s conservation assessment for southern Canada, visit natureconservancy.ca/casc. Photo by Mark Taylor MIXED GRASSLAND (#156)

KEY REFERENCES

Allen, L. 2014. Alberta Conservation Information Management System Ecological Community Tracking List. Alberta Tourism, Parks and Recreation, , Alberta. Ecological Stratification Working Group. 1995. A National Ecological Framework for Canada. Agriculture and Agri-Food Canada, Research Branch, Centre for Land and Biological Resources Research and Environment Canada, State of the Environment Directorate, Ecozone Analysis Branch, Ottawa/Hull. Report and national map at 1:7500 000 scale. Hammer, U.T. 1986. Saline Lake Resources of the . Canadian Water Resources Journal 11(1): 43-57. Ricketts, T., E. Dinerstein, D. Olson, C. Loucks, W. Eichbaum, K. Kavanagh, . . . W. Walters. 1999. Ecoregions of North America: A Conservation Assessment. Washington DC: Island Press. Riley, J.L., S.E. Green and K.E. Brodribb. 2007. A Conservation Blueprint for Canada’s Prairies and Parklands. Nature Conservancy of Canada, Toronto, Ontario. 226 pp. plus DVD-ROM Shorthouse, J.D. 2010. Ecoregions of Canada’s Prairie Grasslands. In Arthropods of Canadian Grasslands (Volume 1): Ecology and Interactions in Grassland Habitats. Edited by J.D. Shorthouse and K.D. Floate. Biological Survey of Canada. pp. 53-81. World Wildlife Fund. 2018. The Ploughprint Report 2018. https://c402277.ssl.cf1.rackcdn.com/publications/ 1171/files/original/Plow printReport_2018_FINAL_082318LowRes.pdf?1535470091.

Suggested citation: Nature Conservancy of Canada. 2019. Ecoregional summary – Mixed Grassland. Nature Conservancy of Canada, Toronto. Last updated: data (August 2017); text (December 2019) MIXED GRASSLAND (#156)

Figure 1: Context of the Ecoregion. This map shows towns, roads, elevation, rivers, lakes and watersheds. MIXED GRASSLAND (#156)

Figure 2: Species of Conservation Concern (COSEWIC and global). These maps show the number of different Committee on the Status of Endangered Wildlife in Canada (COSEWIC)-assessed and globally rare species. The information is current to 2015. Some areas of the ecoregion may be data deficient, and higher numbers of species of conservation concern may occur. There are differences in which COSEWIC-assessed species are tracked in Alberta and Saskatchewan, which result in a disparity between the provinces. MIXED GRASSLAND (#156)

Figure 3: Land Use & Human Footprint. These maps show the dominant land uses and the human influence on the land- scape. Although agriculture dominates this ecoregion, there are large areas that still contain native grasslands. Human foot- print is highest in urban areas, around major roads and on lands that have been converted to croplands. The human footprint map does not show some stresses that may occur, such as invasive species. MIXED GRASSLAND (#156)

Figure 4: Connectivity. These maps show connectivity between protected/conserved areas, community pastures and large blocks of intact habitat. The bottom map depicts those regions (green) that have a higher probability of being connected within the ecoregion. MIXED GRASSLAND (#156)

Figure 5: Protected/Conserved Areas. This map shows protected/conserved areas in the ecoregion, including publicly protected areas (such as national and provincial parks), properties conserved by NCC and other non-governmental organizations (private) and community pastures.

The map also shows biodiversity designations, such as Key Biodiversity Areas (primarily Important Bird Areas). These designations only highlight important areas and are not protected or do not have legal status unless they are also within a protected/conserved area. The map also shows the boundaries of NCC Natural Area Conservation Plans. MIXED GRASSLAND (#156)

Table 1: Change in Land Use, 2000-2010