Grading Amphibians

To emphasize the dire situation of amphibians in the U.S., the Amphibian Report Card aims to use a familiar system to convey how well a species is doing: report card grades. However, because the Amphibian Report Card aims to simplify and communicate complex conservation issues, the grade ranges for our report card are different. Amphibians are graded on their population status, habitat status, and threat vulnerability. These three grades are averaged to provide an overall grade. All four grades will use the following scale:

  • A = 81 - 100%
  • B = 61 - 80%
  • C = 41 - 60%
  • D = 21 - 40%
  • F = 0 - 20%

These report cards are living documents that change based on the latest amphibian expert opinion received through the Amphibian Report Card website. We rely on experts to keep the information up-to-date. If you're a species expert, share your expertise here.

Expert Disagreement

When comparing expert assessment of each species, disagreement is likely to arise. In the event that happens, the mode (i.e. most common answer) will be used to calculate grades as this is common practice in other expert scoring systems. In the event that there is no clear mode, the most conservative response will be used, following the precautionary principle. In the event that there is a high degree of disagreement or uncertainty among experts, that uncertainty will be noted with an asterisk on the species’ final report card.

Population Grade

The Population Grade will be assessed by the species’ endangered status and its recent population trends in the U.S. To assess the species’ endangered status, we classified populations into their IUCN/ESA status, each of which corresponds with a percentage. Those are:

  • Extinct or Extinct in the wild (IUCN): 0
  • Critically endangered (IUCN)/Endangered (ESA): 1
  • Endangered (IUCN)/Threatened (ESA): 2
  • Vulnerable (IUCN)/Candidate species (ESA): 3
  • Near threatened (IUCN) : 4
  • Least concern (IUCN): 5

In the event that the IUCN and ESA statuses are not in agreement, the most conservative assessment will be used (for instance, if a species is considered “Vulnerable” by the IUCN but is “Endangered” under the ESA, it will be considered “endangered” for the purposes of grade calculation)

Population trends refer to declines in the total U.S. population for a species. Recent population trends for the species corresponds with the following percentages:

  • Population size is strongly increasing: 5
  • Population size is slightly increasing: 4
  • No change: 3
  • Population size is slightly decreasing: 2
  • Population size is strongly decreasing: 1
  • Unknown: N/A

The Population Grade is the sum of the species’ endangered status and population trend divided by the highest possible score, 10:

Population Grade= (Status + Trend)/10

Habitat Grade:

The Habitat Grade will be assessed using the percent of currently occupied historic range and the assessment of how fragmented the habitat is. The approximate the percentage of a species’ historic (pre-Columbian) range that it currently occupies corresponds to the following percentages:

  • Species occupies approximately 81-100% of it historic range: 5
  • Species occupies approximately 61-80% of it historic range: 4
  • Species occupies approximately 41-60% of it historic range: 3
  • Species occupies approximately 21-40% of it historic range: 2
  • Species occupies approximately 1-20% of it historic range: 1
  • Species occupies none of it historic range (i.e. extinct in the wild): 0
  • Percent of occupied range is unknown

If a reviewer answers that population is severely fragmented, then the Habitat Grade is reduced by one point.

Habitat Grade= (Range - Fragmentation)/5

Threat Vulnerability Grade:

Each of the six main threats will be assessed and classified into one of five categories: Major threat, secondary threat, minor threat, emerging threat, and not a threat. By looking at the severity of each threat, a cumulative Threat Vulnerability Grade will be calculated using the following criteria:

  • Species has no major threats and no more than 2 secondary threats: 5
  • Species has 1 major threat and/or 3 of the six threats are secondary threats: 4
  • Species has at least 2 major threats and/or four of the six threats are either major or secondary: 3
  • Five of the six threats are either major or secondary: 2
  • Six of the six threats are either major or secondary: 1

Calculating the Overall Grade

The Overall Grade for each species in the Amphibian Report Card should be standardized across all species and allow for easy comparison. To do that, the Overall Grade is found by averaging the Population, Habitat, and Threat Vulnerability Grades:

Overall Grade = (Population Grade+ Habitat Grade+ Threat Grade)/3

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