16.1 Trends in the Species at Risk Index (SARI)

Last Updated: 
November 12, 2015

This indicator tracks trends in future biodiversity loss in the NWT using the Species at Risk Index.

The Species at Risk Index (SARI) predicts the rate of future biodiversity loss based on the number and status of species at risk in an area. This allows us to track the likelihood of overall risk of species endangerment over the next 100 years. When the risk of overall species extinction worsens, the index goes up. When the species are less likely to become extinct, the index goes down.

The SARI calculation is based on the Red List Index1, which measures global progress towards stopping biodiversity loss2. SARI uses data from as far back as 1900, local knowledge and formal species status assessments, enabling us to track the risk of extinction for the past 100 years.

The information used to calculate the current index is derived from species lists for the NWT3 and status assessments developed for Canada4,5. These assessments use quantitative criteria and project the risk of species extinction over the next 100 years or so. The index also provides a projection of extinction risk for the future and can be compared with projections from other regions of the world.

NWT Focus

As in all northern regions, the NWT is home to fewer species than more temperate and tropical regions but each species is well adapted to the harsh and variable northern environment. Short food webs and life at the limit of survival make northern ecosystems fragile. The effects of the loss of just one keystone species can have an irreversible impact on whole northern ecosystems. SARI provides an overall look at how species in the NWT are doing. Both past problems and the current extinction risk of NWT species can be tracked using SARI.

Current view: status and trend

The current SARI is about one percent for all species in the NWT. This means that, based on current threats, less than one per cent of all tracked species in the NWT are at risk of becoming extinct.

The following graph shows the probability of species endangerment for each of the major groups of species in the NWT over the past 100 years. Changes in the SAR index for mammals illustrate how SARI works. In the 1960s, the status of muskox improved as a result of protection measures. This is reflected in the decrease SARI measure at (a). In the 1970-80s, the status of grizzly bear, polar bear, wolverine and caribou worsened, due largely to increasing human access and use of wildlife habitat, including increasing use of snowmobiles. This resulted in an upward trend in the SARI (b). In 2000, the status of bowhead whale improved after 60 years of hunting restrictions. This resulted in a decrease in the SARI seen at (c).

Species at Risk Index
SARI calculated by ENR, based on status assessments following COSEWIC. Assessments back-casted prior to 1970 are based on literature and local knowledge of past species numbers and trends. Detailed information available from ENR. Circle notes for mammal SARI: a: status of muskox improved in the 1960s; b: status of grizzly bear, polar bear, wolverine caribou worsen due mostly to increasing habitat use and access, including increasing use of snowmobiles; c: status of bowhead whale noted as improved after almost no hunting for the past 60 years. Number of species tracked is in parentheses.

The risk of species endangerment for freshwater fishes, migratory birds, mammals, and amphibians has changed the most during the past 100 years. The NWT is home to only five species of amphibians and one reptile, all of which are at the extreme northern edge of their range. The assessment of two species as Special Concern has been enough to bring the overall risk of endangerment for this group up above any other group. Similarly, nine out of the 55 species of terrestrial and marine mammals in the NWT that are tracked are at some risk of extinction – and have been for 100 years or more – making the overall risk of endangerment for this group higher than others.

Looking forward

The risk of biodiversity loss for the NWT is extremely low and is expected to remain low in the near future. But recent species status assessments indicate it may be slowly increasing. For example, arctic-nesting shorebirds and birds that are aerial insect feeders have rapidly declined in numbers during the past 20-30 years. red knots, common nighthawks and olive-sided flycatchers are now at some risk of extinction. This will be reflected in the future index. The exact reasons for these declines are not known, but lessons from the past, such as the peregrine falcon, demonstrate northern species can respond positively when threats are stopped or reduced.

New challenges, including increasing habitat change, facing species in the NWT may affect the probability of species survival. In some cases, we may have little control over the changes, such as climate change and land use decisions made in southern regions that may threaten the survival of NWT species.

Looking around

The Red List Index has been calculated for migratory birds in large-scale regions of the world. SARI for NWT birds can be compared to the Red List Index for birds in other regions. In 2004, the species survival probability for birds in the NWT was better than for birds in all other regions of the world. A similar index has not yet been calculated for other jurisdictions in Canada.

Find out more

  • For more information on the COSEWIC list
  • For more information on the Red List
  • For more information on the Convention of Biological Diversity and the 2010 Target
  • The Status of forest-associated species at risk is also a core indicator in the Forest Criteria and Indicators developed by the CCFM.

Other focal points

Technical Notes

  • Species At Risk Index (SARI)3 = (M-Tt)/M expressed as a percentage, where M (maximum threat score possible for any one tracked species) = W*N and T (current threat score for any one tracked species) = summation of all status weight for all tracked species at time t. W is highest possible status weight (=4) and N is number of species tracked. Scores are Extinct =4, Endangered =3, Threatened =2, Special Concern =1, Not at Risk =0. Status categories follow COSEWIC definition.
  • The SARI is based on the Revised Red List Index3 and transformed 1-x. The range is from best = 0%, i.e., no species are at risk of becoming extinct, to worst =100%, i.e., all species are in danger of becoming extinct. Tracked species exclude species assessed as “Data Deficient” by COSEWIC4 or ranked as “Undetermined” in the NWT5. Percent of species that are tracked over the total number of native species in the NWT per group: 77% mammals; 100% amphibians-reptile; 81% birds; 56% freshwater fishes, 90% vascular plants5.

NWT Species at Risk Index – Scores 2010

Scores based on COSEWICa status

Northern Arctic, Southern Arctic, and Northern Mountain Ecozones
Peary Caribou and Dolphin-Union Herd 3e
Grizzly 1
Wolverine 1
Northern Mountain Caribou 1
Eskimo Curlew 3
Ivory Gull 3
Olive-sided Flycatcher 2
Red Knot 2b
Peregrine Falcon (tundra-type) 0.5c
Taiga Plains and Taiga Shield Ecozonesd
Wood Bison 2
Boreal Caribou 2
Whooping Crane 3
Canada Warbler 2
Common Nighthawk 2
Olive-sided Flycatcher 2
Rusty Blackbird 1
Peregrine Falcon (forest type) 0.5b
Short-eared Owl 1
Yellow Rail 1
Horned Grebe 1
Freshwater Fishes
Shortjaw Cisco 2
Northern Leopard Frog 1
Western Toad 1
Marine (Ice) Ecozones
Bowhead Whale 3
Polar Bear 1

a - COSEWIC assesses the status of species using quantitative criteria similar to criteria used for the Red List (IUCN). Scores: Extinct = 4, Endangered = 3, Threatened = 2, Special Concern = 1, Not at Risk (not listed) = 0.
b - Averaged for two subspecies of Red Knot: rufa – 3; islandica – 1
c - Averaged for one species in two ecosystems: Peregrine Falcon – 1.
d - Status of all species in the Taiga Plains and Taiga Shield Ecozones are tracked as forest-associated species and reported to the CCFM Criteria and Indicators program.
e - Peary caribou is assessed as "endangered" and Dolphin-Union herd is assessed as "Special Concern"; the score is for both groups and given the highest score, not averaged.


Found an error or have a question? Contact the team at NWTSOER@gov.nt.ca.


Ref 1 - Butchart et al. 2009. Improvements to the Red List Index. PLoS ONE 2:e140 doi:10.1371/journal.pone.0000140

Ref 2 - Butchart et al. 2005. Using Red List Indices to measure progress towards the 2010 Target and beyone. Phil. Trans. R. Soc. B. 360:255-268

Ref 3 - Working Group on General Status of NWT Species, 2011. NWT Species Infobase 2011-2015. Available at NWT Species at Risk, Yellowknife, GNWT.

Ref 4 - COSEWIC. 2008. COSEWIC Webpage.

Ref 5 - Working Group on General Status of NWT Species .2011. NWT Species 2011-2015 General Status Ranks of Wild Species in the Northwest Territories , GNWT, Yellowknife. 171p.