Northern short grasslands
The Northern short grasslands is the largest grassland ecoregion in North America, covering nearly 640,000 square kilometers. This ecoregion extends over portions of southeastern Alberta and southwestern Saskatchewan in Canada, as well as considerable land area east of the Rocky Mountains, including central and eastern Montana, western North and South Dakota, and northeastern Wyoming in the USA. This grassland ecoregion is bisected by the Yellowstone River.
Four major features differentiate this ecoregion from other grasslands: the harsh winter climate, with considerable precipitation occurring as snow; short growing season; periodic, severe, droughts; and vegetation palette. Two key 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 assume an aspect similar to mixed grassland communities such as in this ecoregion, where many cool-season grass species predominate. 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.
Prior to human settlement, drought, fire, and grazing by large native herbivores were major disturbance factors, with fire playing a lesser role than in most other grassland ecoregions. Today, virtually all of this ecoregion has been converted to either wheat farms or rangelands. However, the potential for large-scale restoration is perhaps greater in this ecoregion than in almost any other part of North America. Attempts to re-establish populations of native Black-footed Ferrets (Mustela nigripes) and American Bison (Bison bison) are in progress.
The grass communities in this ecoregion include the following dominant taxa: Grama (Bouteloua spp.)-Needlegrass (Stipa spp.); Wheatgrass (Agropyron spp.); and Wheatgrass-Needlegrass. Further north into Canada the native grass vegetation of this area is characterized by Annual Meadow Grass (Poa annua), Blue Grama (Chondrosum gracile), wheatgrass and, to a lesser extent, June Grass (Koelaria spp.), and dryland sedge (Carex spp.). A variety of shrubs and herbs also occurs, but Big Sagebrush (Artemesia tridentata) is most abundant, and on more arid sites, Prickly Pear (Opuntia spp.) and other cacti 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 vermiculatus), Western Glasswort (Salicornia rubra) and American Sea Blite (Suaeda calceoliformis).
Prior to 1850, the Northern short grasslands contained some of the last relictual habitat for American Bison in the USA and Canada. Bison populations are thought to have had a major impact on the vegetative structure and composition of this ecoregion. Today populations of these large grazers are increasing again as herds are growing on public 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.
This terrestrial ecoregion here is populated by 337 species of vertebrates. Other notable mammals found in the short grasslands are the Gray Wolf (Canis lupus); Black-tailed Prairie Dog (Cynomys ludovicianus); the Desert Cottontail (Sylvilagus audubonii); the Red Fox (Vulpes vulpes); Richardson's Ground Squirrel (Urocitellus richardsonii). One notable bird that breeds in the lower Yellowstone River Basin (as its most northern range) is the Interior Least Tern (Sternula antillarum athalassos), a USA federally listed threatened species.
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 (Tympanuchus phasianellus) and Greater 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 Mountain Lion (Felis concolor) are typical large mammals. Short-horned Lizard (Phrynosoma douglassi) and Western Rattlesnake (Crotalus viridis) occur within the ecoregion as well.
The Northern short grasslands host the largest breeding population of the Endangered Piping Plover (Charadrius melodus) in all of North America, which occur near alkaline lakes; the ecoregion also hosts important breeding populations for rails (Rallus spp.) and other taxa of threatened sparrow taxa. Conservation efforts are increasing directed at threatened birds such as the Burrowing Owl (Athene cunicularia) and Ferruginous Hawk (Buteo regalis).
Amphibians occurring in this ecoregion are: the Wood Frog (Lithobates sylvaticus); the Striped Chorus Frog (Pseudacris triseriata); the Dakota Toad (Anaxyrus hemiophrys); Great Plains Toad (Anaxyrus cognatus); the Plains Spadefoot Toad (Spea bombifrons); and the Eastern Tiger Salamander (Ambystoma tigrinum), which is the largest and most widely distributed terrestrial salamander in North America.
Reptiles found in the short grasslands reach include the: Red-lipped Plateau Lizard (Sceloporus undulatus), Eastern Hog-nosed Snake (Heterodon platirhinos); False Map Turtle (Graptemys pseudogeographica); Sagebrush Lizard (Sceloporus graciosus ); the non-venomous Milk Snake (Lampropeltis triangulum). The Spiny Softshell Turtle (Apalone spinifera) is an aquatic taxon present in the lower Yellowstone Basin as well as the Missouri River Basin.
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 two 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, overgrazing by sheep and cattle and the creation of road networks are significant factors on the Canadian side of the border, as tame grazing and hay crops are increasingly replacing more native grasslands.
Essentially very little 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 alien species of vegetationhave 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 American 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.
The adverse outcome of overgrazing is often associated with large expanses of USA federal lands, where grazing leases are typically offerred at below market rates. To gain an understanding of the magnitude of the concessions below market, one needs to consider that the Federal government set the base lease rate of $1.23 per AUM (animal unit month) in the year 1966; one AUM is the amount of forage needed to support one cow plus calf (or five sheep) for a month. The present Federal lease fee in 2013 is $1.35 per AUM, indicating the Federal grazing base fee has nowhere nearly kept pace with inflation, and effectively taxpayers are subsidizing the fecal coliform pollution of Yellowstone River and many other western USA watercourses.
Remaining blocks of intact habitat
None of the following blocks are considered fully intact, but many are only partially altered and quite extensive. 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
- 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 overgrazed lands 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 ongoing conversion of altered habitat (rangeland) to wheat production. Major degradation threats are alien plant species such as leafy spurges (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.
- 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 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 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). Aspen Grove Boreal forest (17) and Grassland characterize this region of south Alberta and Saskatchewan.
- J.M.Hoekstra, Molnar, J. L.; Jennings, M.; Revenga, C.; Spalding, M. D.; Boucher, T. M.; Robertson, J. C.; Heibel, T. J. et al. (2010). Molnar, J. L., ed. The Atlas of Global Conservation: Changes, Challenges, and Opportunities to Make a Difference. University of California Press. ISBN 978-0-520-26256-0
- Kirk A. Miller, Melanie L. Clark and Peter Wright. 2004. Water quality assessment of the Yellowstone River Basin, Montana and Wyoming: Quality of fixed sites, 1999-2001. National Water Quality Assessment Program. U.S.Geological Survey. Report 2004-5113
- U.S.Department of Interior. 2013. Fact Sheet on the BLM’s Management of Livestock Grazing: Grazing on Public Lands. Bureau of Land Management. USDI, Washington DC
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