Ranking Methodology

Ecology Contents

About CDC Ecology Ranking Methology Element Occurrence Ranking Element Occurrence Ranks Element Occurrence Ranking Factors Element Occurrence Specifications Spatial Patterns

This section of the website describes in detail the methods used by the CDC Ecology group to rank ecological community elements and element occurrences. We use the same methodology that is used for plants and animals, with modifications to take into account the ecology of plant communities. This methodology is used in every province in Canada, in every state of the U.S.A., and in many countries of Central and South America.

Ecological communities

We define a ecological community as a type of vegetation with a relatively uniform plant species composition and physical structure. Ecological communities also tend to have characteristic environmental features such as bedrock geology, soil type, topographic position, climate, and energy, nutrient and water cycles.

Element Conservation Status Ranking

• Determines the conservation status rank of a ecological community.
• Ranks are based on all readily available information and expertise, and are peer-reviewed.
• Ranks are based on factors and methods found in NatureServe Conservation Status Assessments: Factors for Assessing Extinction Risk and NatureServe Conservation Status Assessments: Methodology for Assigning Ranks.
• This rank is not applicable to individual occurrences; occurrences are ranked separately (see Element Occurrence Ranking next).

Element Occurrence Ranking

• Occurrences are ranked as excellent, good, fair, or poor. See Basic EO Ranks.
• Occurrence ranks are based on three factors: size, condition, and landscape context. See EO Rank Factors.
• Occurrence ranks are calculated by prioritizing and weighting ranking factors based on the type of ecological community (matrix, large patch, small patch, or linear). See EO Ranking.
• EO ranks can be determined by comparison with Element Occurrence Specifications (see next).

Element Occurrence Specifications

• EO Specifications describe the minimum requirements for an element occurrence and the characteristics of excellent, good, fair, or poor occurrences of a particular ecological community. See Element Occurrence Specifications.
• EO Specifications can be written for individual ecological communities or guilds of similar ecological communities.
• EO Specifications allow any ecologist to rank element occurrences if adequate field data are collected.

Ecological community conservation

• Conservation priority for individual sites should be determined by a combination of element conservation status rank and element occurrence rank.
• Conservation plans should focus on the best quality occurrences of rare ecological communities.
• Restoration will be required for ecological communities that have few or no excellent or good quality occurrences left.