Grasslands

Status and Trends
rate of loss slowed; extent impaired and health compromised in many areas
Impaired, getting worse at a slow to moderate rate
data not comprehensive, but trends are clear
High confidence in finding

KEY FINDING 2. Native grasslands have been reduced to a fraction of their original extent. Although at a slower pace, declines continue in some areas. The health of many existing grasslands has also been compromised by a variety of stressors.

This key finding is divided into two sections:

Grasslands are open ecosystems dominated by herbaceous (non-woody) vegetation. Typical temperate grasslands, like those in Canada, occur where there is low moisture, cold winters, and deep, fertile soils. Maintained historically by drought, fire, and grazing, temperate grasslands are the Earths most altered, and one of the most threatened ecosystems, with the highest risk of biome-wide biodiversity loss.1, 2 Although other ecosystem types, such as oak savannahs, alvars, and dunes support grasslands, this finding focuses on prairie and steppe. Grasslands are important as habitat for many species, including many species at risk. They also provide soil and water conservation, nutrient recycling, pollination, habitat for livestock grazing, genetic material for crops, recreation, climate regulation, and storage for about 34% of the terrestrial global carbon stock.1, 3

Historical loss of grasslands
Estimated percent loss up to early 1990s
Map and charts: historical loss of grasslands in Canada. Click for graphic description (new window).

Sources: B.C. map adapted  from Grassland Conservation Council of British Columbia, 2009;17 prairie map adapted from Ostlie and Haferman, 1999 cited in White et al., 2000;3  Manitoba map adapted from Joyce and Morgan, 1989;9 Ontario map adapted from  Natural Heritage Information Centre cited in Ontario Tallgrass Prairie and Savanna Association 18

Sources on graphic: Riley et al., 2007;4 Joyce and Morgan, 1989;9 Ontario Ministry of Natural Resources, 2009;10 Grasslands Conservation Council of British Columbia, 2004;11 British Columbia Ministry of Environment, 2007;12 Watts, 1969;14 Samson and Knopf, 1994;15 Bakowsky, 199316

Changes in extent

Losses of grasslands exceed those of other major biomes in North America.2 Although most grassland loss in Canada occurred prior to the 1930s,4 largely the result of conversion for cropland,2  it continues today with small remnants often suffering the most.5, 6

  • Mixed and fescue prairie covers over 110,000 km2 (25%) of the Prairie provinces. It is estimated, based on remote sensing, that 70% of original vegetation, including grasslands, was converted to other uses by the 1990s.4 Conversion of native grasslands continues,6, 7 but at a slower rate. Overall loss from 1971 to 1986 was estimated at 3%.7 Losses vary among regions, for example a 10% loss was found from 1985 to 2001 in some areas.6
  • Tallgrass prairie, North America’s most threatened prairie,8 now covers approximately 100 km2 of its former 6,000 km2 in Manitoba9 and 820 km2 in Ontario.10 The small patches that remain are still threatened by conversion, with 23% of remnant patches in Manitoba converted between 1987 and 2006. Only a few of the larger patches secured for conservation increased in size, due to active restoration.5 
  • Bunchgrass/sagebrush in B.C. suffered losses of 15 to 19% prior to 1990.11, 12 Between 1990 and 2005, an additional 1% of the original grasslands were lost.12 Losses in some areas were higher, for example declines in South Okanagan grassland communities from 1800 to 2005 ranged from 33 to 75%.13 Only small remnants of former expansive grasslands in northern B.C. remain.12

Photo: mixed grass prairie, Grasslands National Park, Saskatchewan © Parks Canada, M. Finkelstein, 2005
Mixed grass prairie, Grasslands National Park, Saskatchewan

Globe

Global Trends

Temperate grasslands, covering 8% of the Earth,31 lost 70% of their native cover by 1950, with an additional 15% lost since.32 In North America, over 97% of tallgrass prairie,8, 33, 34 71% of mixed prairie, and 48% of shortgrass prairie had been lost by 2003.8

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Grassland health

In addition to direct loss, the remaining grasslands in Canada are under stress. Natural disturbance regimes that historically maintained grasslands have been altered; in particular, the suppression of fire and replacement of free-ranging bison with confined cattle have modified the structure and composition of native grasslands. Also, many of the richest soils have been cultivated,2, 19 leaving remaining grasslands on less productive soils. Other threats to grassland health include invasive non-native species, overgrazing, forest encroachment, continued fragmentation from development, and intensification of agriculture. Overall results from two studies investigating rangeland health in Alberta and Saskatchewan in 2008 showed that 49% were healthy, 8% unhealthy, and 43% healthy with problems.20, 21 In the Okanagan Valley, between 19 and 69% of rangelands were in poor condition in the 1990s.13 In Manitoba, 14% of remnant tallgrass prairie patches were so severely degraded by non-native species between 1987 and 2006 that patches could no longer be recognized as tallgrass prairie. Patch quality declined significantly over the time period and few are likely self-sustaining.5

Canadian grassland birds

Breeding Bird Survey Abundance Index, 1967 to 2006
Graph: abundance of Canadian grassland birds. Click for graphic description (new window).
Source: adapted from Breeding Bird Survey22 by Downes et al., 201023

 

Grassland birds are showing steep and widespread declines throughout North America.24, 25 In Canada, there has been an overall loss of 44% of the populations of grassland species since the 1970s, with individual species showing significant declines of up to 87%.23

Photo: grasshopper sparrow © iStock.com/WilliamShermanGrasshopper sparrow, declined by 78% since the 1970s23

Grazing and grassland health

Degree of alteration
of Saskatchewan grasslands due to grazing
Percent, 2007
Graph: degree of alteration of Saskatchewan grasslands due to grazing. Click for graphic description (new window).
Source: Thorpe, 200927

Large areas of intact grasslands are used as rangelands for livestock grazing. The relationship between grazing and grassland health is complex. Most grasslandsevolved with grazing by herbivores. Maintaining a range of grazing intensities is important for biodiversity as habitats with different grazing intensities support different species. Although improvements in land management practices have been made in some areas, for example community pastures and other stewardship initiatives in the Prairies,4, 21, 26 livestock grazing can affect grassland health. Using data on species composition to indicate change, Thorpe27 found almost 50% of plots in the Aspen Parkland and Mixed Grassland regions of Saskatchewan had, by 2007, been moderately or severely altered by livestock grazing. In B.C., about 90% of grasslands are now grazed by domestic livestock,11 resulting in grasslands that are in early stages of succession, with many invasive species.13, 28-30

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