What Is a Relative Threat Ranking and Why Is It Useful?
Good conservation planning involves prioritization at several points in the planning process. Because human and financial resources are limited, a project team cannot address every threat to ecosystems, species and natural resources or implement an unlimited number of different conservation strategies. The team should use explicit procedures to establish its priorities, so that all team members and relevant stakeholders understand how and why the team decided to focus its actions on X instead of Y. Threat ranking enables the team to determine which threats are having the greatest impact on natural resources and biodiversity and use this information to decide which threat to address.
To evaluate threats, a project team can conduct an absolute target-by-target rating (as described in Step 1C: Identify Critical Threats) or a relative threat ranking. For relative rankings, teams consider all threats and rank them relative to one another. This method for relative threat ranking, adapted from Margoluis and Salafsky (1998), represents an example of matrix ranking, which is useful not only for ranking threats, but also for prioritizing strategies or even targets, based on specific criteria.
As shown in Table 1, there are advantages and disadvantages to relative and absolute threat rating methods. In general, relative rankings are quicker and can be easier to do if you do not have a lot of information about your targets. Another advantage of relative rankings is that they force a spread across the threats so that the threats are not ranked the same.
How to Do a Relative Threat Ranking
Relative threat ranking involves considering the threats for the overall site, not target-by target, as presented in the section addressing Step 1C. The suggested criteria also differ somewhat (see Box 1). For both absolute target-by-target and relative whole-site ratings, we suggest the use of the scope and severity criteria. For the relative whole-site ranking, however, you should not use the irreversibility criterion. This is because irreversibility is highly dependent upon a specific target’s resilience to a given threat. For example, a threat of acid rain might pose a minimal threat to a forest but completely eliminate aquatic life in streams and lakes found in that forest. If the acid rain threat were eliminated, its effect on the forests could be reversed, but it might be impossible to reverse its effect on streams and lakes – and, in particular, the aquatic species that were eliminated. Because of this issue with irreversibility in whole site ratings,we suggest you use urgency as your third criterion. Urgency refers to the importance of taking immediate action to address the threat. Generally, a threat that is occurring now will be more urgent than one that is likely to occur in the future. However, if, with minimal resources, you could take action today on a threat and avoid significant resource investment in the future, then that threat would also be considered urgent. A good example of such a threat is an invasive exotic species.
The following steps provide guidance for a relative ranking. For definitions of each criterion, see Box 1.
A. List All the Threats at Your Site – Using the table below (Table 2), create a matrix with each threat occupying a row and the columns containing the criteria, total rating, and classification for your site.
B. Rank Each Threat for SCOPE – List your rating of the threats based on the area of your site affected. Assign the largest number (equal to the total number of threats) to the threat affecting the largest area and continuing down to a rank of 1 for the threat that affects the smallest area. For example, if you have 6 threats, the threat affecting the greatest scope would receive a 6, while that affecting the least scope would receive a 1. Add up the total of the rating numbers and record that total at the bottom of the column (Note: As a check on your calculations, this total should be the same for scope, severity, and irreversibility).
C. Rank Each Threat for SEVERITY – In the next column, headed SEVERITY, assign ratings to the threats based on the impact or severity of destruction to the area or scope affected, again with the largest number (equal to the total number of threats) assigned to the threat of greatest severity and continuing down to a rank of 1 for the least severe threat. To avoid confusing scope and severity, where possible we recommend comparing the severity of threats within a uniform area (e.g., a hectare of clearcutting vs. a hectare of firewood collection). Add up the total of the rating numbers and record that total at the bottom of the column.
D. Rank Each Threat for URGENCY – In the column headed URGENCY, list the rank ordering you established for the threats, with the largest number (equal to the total number of threats) assigned to the threat for which you need to take immediate action to reduce it. Continue down to a rank of 1 for the threat that you can wait longer to address. Add up the total of the rating numbers and record that total at the bottom of the column. Before proceeding to the next step, be sure that the three criteria column totals add up to the same number, and, if not, correct the numbers.
E. Sum Up Your Ratings – Scope and severity, taken together, give you a sense of the magnitude of the threat. As such, they are the most important criteria for ratings. For this reason, we recommend double-weighting them. This will also help avoid situations where a threat that affects only a very small portion of the site but has High severity (e.g., infrastructure) receives an unduly high overall rating. To get a total threat score, for each threat, double its scope and severity scores and add them to its urgency score. Enter the total number in the table (The worksheet in Table 2 will do this automatically if you can open it in Excel).
F. Rank Each Threat for SEVERITY – In the next column, headed SEVERITY, assign ratings to the threats based on the impact or severity of destruction to the area or scope affected, again with the largest number (equal to the total number of threats) assigned to the threat of greatest severity and continuing down to a rank of 1 for the least severe threat. To avoid confusing scope and severity, where possible we recommend comparing the severity of threats within a uniform area (e.g., a hectare of clearcutting vs. a hectare of firewood collection). Add up the total of the rating numbers and record that total at the bottom of the column.
G. Classify Your Threats – Although it may be tempting to evaluate your threats based solely on the numbers, it is better to classify them into categories of Very High, High, Medium, and Low. These categories are more appropriate, given the somewhat imprecise and subjective nature of the rating process. For example, the difference between a threat with 12 points and one with 10 points is likely not significant, but the difference between one with 12 points and one with 5 is significant. You should use this classification for both the threats and the site overall. Determining a threat’s importance for the overall site will help you determine its effect on your site as a whole and whether you should devote a lot of project resources to trying to minimize it.
The following is an example of a threat rating applied at the level of the whole site and using a relative ranking method. This is based on a real-world rating done by a project team working in a tropical forest site. Three criteria (scope, severity, and urgency) are used to evaluate nine direct threats.