The Northern short grasslands is the largest grassland ecoregion in North America, covering almost 640,000 km2. This ecoregion covers parts of southeastern Alberta and southwestern Saskatchewan, much of the area east of the Rocky Mountains, central and eastern Montana, western North and South Dakota, and northeastern Wyoming. Four major features distinguish this unit from other grasslands: the harsh winter climate, with much of the precipitation falling as snow; short growing season; periodic, severe, droughts; and vegetation. Two environmental gradients determine species composition in mixed and shortgrass prairies: increasing temperatures from north to south and increasing rainfall from west to east. With increasing latitude, the shortgrass prairies take on an aspect more similar to mixed-grass such as in this ecoregion, where many cool-season species predominate (Sims 1988). Mean annual temperature in this part of the ecoregion ranges from 3.5°C , but rises as high as 5°C in the west. Mean summer temperature is 16°C and mean winter temperature is -10°C. In late summer, moisture deficits occur, due to low precipitation and high evapotranspiration. In general, this ecoregion has an arid grassland ecoclimate.
In pre-settlement times, drought, fire, and grazing were probably the major disturbance factors, with fire playing less of a role than in other grassland ecoregions. Today, virtually all of this ecoregion is either converted to wheat farms or rangelands. However, the potential for large-scale restoration is perhaps greater in this ecoregion than in almost any other in North America. Attempts to reestablish populations of native black-footed ferrets (Mustela nigripes) and bison (Bison bison) are well underway.
Description
Biological Distinctiveness
The dominant grass communities include grama (Bouteloua spp.)-needlegrass (Stipa spp.) and wheatgrass (Agropyron spp.), and wheatgrass-needlegrass (Kuchler 1964). Further north into Canada the natural vegetation of this area is characterized by spear grass (Poa annua), blue grama grass, wheatgrass and, to a lesser extent, June grass (Koelaria spp.), and dryland sedge (Carex spp.). A variety of shrubs and herbs also occurs, but sagebrush (Artemesia tridentata) is most abundant, and on drier sites yellow cactus and prickly pear (Opuntia spp.) can be found. On shaded slopes of valleys and river terraces, scrubby aspen (Populus spp.), willow (Salix spp.), cottonwood (Populus sp.), and box-elder (Acer negundo) occur. Saline areas support alkali grass (Puccinellia spp.), wild barley (Hordeum spp.), greasewood (Sarcobatus wermiculatus), red samphire (Salicornia rubra) and sea blite (Suaeda depressa).
Prior to 1850, the Northern short grasslands contained some of the last extensive habitat for bison in the U.S. and Canada. Bison populations likely had a major impact on the structure and composition of this ecoregion. Their numbers are increasing again as herds are growing on Native American lands and private ranches. Black-footed ferrets were also once common here, and reintroductions should eventually capitalize on abundant prairie dog (Cynomys spp.) populations. Recovery efforts are underway for swift fox (Vulpes velox) in the northern part of the ecoregion.
The Northern short grasslands are surprisingly rich in mammals for an ecoregion so far north. Much of the bird fauna is composed of species typically associated with the prairie potholes: ferruginous hawk (Buteo regalis) and Swainson's hawk (Buteo swainsoni), golden eagle (Aquila chrysaetos), sharp-tailed grouse (Tympahuchus phasianellus) and sage grouse (Centrocercus urophasianus), mountain plover (Charadrius montanus) and clay-colored sparrow (Spizella pallida). Black-tailed and white-tailed deer (Odocoileus hemionus and O. virginianus), bobcat (Lynx rufus) and cougar (Felis concolor) are typical large mammals. Short-horned lizard (Phrynosoma douglassi) and western rattlesnake (Crotalus viridis) occur here as well.
The Northern short grasslands contain the largest breeding population of endangered piping plovers (Charadrius melodus) around alkaline lakes in all of North America, and important breeding populations for rails (Rallus spp.) and more threatened species of sparrows. Conservation efforts are increasing around threatened birds such as the burrowing owl (Athene cunicularia) and ferruginous hawk.
Conservation Status
Habitat Loss and Degradation
More than 85 percent of the ecoregion is now grazed by livestock or converted to dryland farming. In the Canadian portion, it is estimated that only about 2 percent of the ecoregion remains as natural, intact habitat. Considerable potential exists for habitat recovery in some areas to the extent of only partially modified grazing lands. However, oil and gas development and the creation of road networks are very significant factors on the Canadian side of the border and tame grazing and hay crops are increasingly replacing more native grasslands.
Essentially no unaltered habitat remains in this ecoregion. However, there is extraordinary potential for rapid recovery as much of it is degraded rather than converted. A few exotic species have invaded, but most of the dominant plant species still persist on rangelands. Plant species characteristic of the vegetation of this ecoregion evolved to withstand intense grazing by bison. Thus, it is not surprising to see that many previously dominant plants still persist and are likely to become reestablished where restoration efforts are carefully managed.
Remaining Blocks of Intact Habitat
None of the following blocks are considered intact, but many are only partly altered and quite large. These include:
•western North Dakota
•Roosevelt National Park, within the Little Missouri National Grassland - western North Dakota
•Missouri Coteau - south-central North Dakota
•Little Missouri National Grassland
•Badlands National Park/Buffalo Gap National Grassland - southwestern South Dakota
•Thunder Basin National Grasslands - eastern Wyoming
•Lower Yellowstone River - eastern Montana (The largest section of intact Missouri River, undammed and with a population of endangered paddlefish)
•Charles M. Russell National Wildlife Refuge - northwestern Montana
•Suffield National Wildlife Area - southeastern Alberta - 420 km2
•Butala Ranch - southwestern Saskatchewan - more than 100 km2
•Matador Grasslands - southwestern Saskatchewan
•Grasslands National Park and surrounding area - southern Saskatchewan
•Great Sand Hills - southwestern Saskatchewan
•South Saskatchewan River riparian zones - southwestern Saskatchewan.
•Sage Creek area, southeastern Alberta
Degree of Fragmentation
Among the rangelands that are "relatively intact," fragmentation is low because they occur in close proximity. Habitat fragmentation is relatively higher in some areas on the Canadian side of the border. A combination of oil and gas pipelines and road network densities contribute to the greater dissection of the landscape.
Degree of Protection
What little remains of fully intact habitat is under protection in the
•Charles M. Russell National Wildlife Refuge - east-central Montana
•Badlands National Park - western South Dakota
•Grasslands National Park - southern Saskatchewan
and in smaller patches in
•Bittercreek Mountain Wilderness Study Area
•Sage Creek (Badlands) - western South Dakota
•Saskatchewan Landing Provincial Park - southwestern Saskatchewan - 57.97 km2
•Prairie Coulees - South, Ecological Reserve - southeastern Alberta -14.29 km2
•Kennedy Coulee Ecological Reserve - southeastern Alberta - 10.68 km2
•Matador Grasslands Provincial Park - southwestern Saskatchewan - 7.78 km2
Types and Severity of Threats
The major threat is conversion of altered habitat (rangland) to wheat production. Major degradation threats are exotic species such as leafy spurge (Euphorbia sp.) and yellow sweet clover. There is increased industrial activity (particularly oil and gas), road expansion (with associated access issues) and widespread application of pesticide and herbicide in agricultural production.
Suite of Priority Activities to Enhance Biodiversity Conservation
•Restoration of the following important sites for the Northern short grasslands include:
•Matador Grassland- home to a former International Biome Program research site
•USDA Agricultural Research Center
•Sydney, Montana
•Bozeman, Montana Rangelands Insect Research
•Old Wives Lake - important for migratory birds
•Community pastures in Saskatchewan and Manitoba
•Little Missouri Badlands
•Lower Yellowstone River
•Charles M. Russell NWR - possibility of adding 640 km2 to area.
•improving contact with ranchers to encourage model grazing programs
•increasing efforts to restore the ecological integrity of this ecoregion through carefully managed programs including bison and black-footed ferret reintroductions and prairie dog recovery
•encouraging the development of ecotourism as an alternative to ranching in ecologically valuable areas and in areas that have been depopulated over the past few decades
•increasing protection standards for Suffield National Wildlife Area, Alberta
•giving stronger conservation attention to PFRA pasture lands in Saskatchewan. Increasing protection standards for the most significant PFRA pasture lands and Wildlife Habitat Protection Act lands.
•completing Grasslands National Park in Saskatchewan.
•The province of Saskatchewan should lend greater support to private initiatives to protect the Great Sand Hills.
Conservation Partners
Alberta Wilderness Association
Canadian Nature Federation
Canadian Parks and Wilderness Society
Ducks Unlimited Canada
Endangered Spaces Campaign - Saskatchewan
Federation of Alberta Naturalists
Great Sand Hills Planning District Commission
Natural Resources Conservation Service
The Nature Conservancy,Alberta
Nature Saskatchewan
Prairie Conservation Forum Calgary/Banff Chapter
Prairie Farm Rehabilitation Administration
Saskatchewan Wildlife Federation
Society of Grassland Naturalists
World Wildlife Fund Canada
Several Native American tribes active in restoration of bison range
Relationship to other classification schemes
The boundaries of the Northern short grasslands are taken from an amalgamation of Omernik (1995) ecoregions 41 (Northern Montana Glaciated Plains), 42 (Northwestern Glaciated Plains), 43 (Northwestern Great Plains), and 45 (Northeastern Great Plains) in the US. It corresponds to Küchler (1985) units 57 (Grama-needlegrass-wheatgrass) and 59 (wheatgrass-needlegrass). The boundary overlaps with Bailey (1994) sections 331D (Northwestern Glaciated Plains), 331E (Northern Glaciated Plains section), and 331F (Northwestern Great Plains section).
The Northern Short Grassland ecoregion corresponds to the Mixed Grassland terrestrial ecoregion (TEC 159) (Ecological Stratification Working Group 1995). Aspen Grove Boreal forest (17) and Grassland characterize this region of south Alberta and Saskatchewan (Rowe 1972).
Prepared by: S. Primm, J. Shay, S. Chaplin, K. Carney, E. Dinerstein P. Sims, A. G. Appleby, R. Usher, K. Kavanagh, M. Sims,G. Mann
