A practical guide to the application of the IUCN Red List of Ecosystems criteria

Abstract

The newly developed IUCN Red List of Ecosystems is part of a growing toolbox for assessing risks to biodiversity, which addresses ecosystems and their functioning. The Red List of Ecosystems standard allows systematic assessment of all freshwater, marine, terrestrial and subterranean ecosystem types in terms of their global risk of collapse. In addition, the Red List of Ecosystems categories and criteria provide a technical base for assessments of ecosystem status at the regional, national, or subnational level. While the Red List of Ecosystems criteria were designed to be widely applicable by scientists and practitioners, guidelines are needed to ensure they are implemented in a standardized manner to reduce epistemic uncertainties and allow robust comparisons among ecosystems and over time. We review the intended application of the Red List of Ecosystems assessment process, summarize 'best-practice' methods for ecosystem assessments and outline approaches to ensure operational rigour of assessments. The Red List of Ecosystems will inform priority setting for ecosystem types worldwide, and strengthen capacity to report on progress towards the Aichi Targets of the Convention on Biological Diversity. When integrated with other IUCN knowledge products, such as the World Database of Protected Areas/Protected Planet, Key Biodiversity Areas and the IUCN Red List of Threatened Species, the Red List of Ecosystems will contribute to providing the most complete global measure of the status of biodiversity yet achieved.

Keywords: IUCN Red List of Ecosystems; ecosystem conservation; ecosystem risk assessment; ecosystem types; risk of collapse; threatened ecosystems.

Figure 1.

Mechanisms of ecosystem collapse, and symptoms of the risk of collapse. From Keith et al. [4].

Figure 2.

Structure of the IUCN Red List of Ecosystems categories (thresholds are summarized in the electronic supplementary material, appendix S1). (Online version in colour.)

Figure 3.

Steps followed for the application of the IUCN Red List of Ecosystems Categories and Criteria. For risk status symbols, follow figure 2. AOO, area of occupancy, EOO, extent of occurrence. (Online version in colour.)

Figure 4.

Proportional versus absolute rate of decline [24]. The figure shows an ecosystem type whose initial area in 1974 was 1000 km². It declined at a rate of 2% per year during the following few years, but the outcome over a longer period (50 years) was substantially different depending on whether the decline was considered proportional or absolute. If decline is proportional, the decline is a fraction of the previous year's remaining area (0.02 × last year's area), whereas in an absolute rate of decline, the area subtracted each year is a constant fraction of the area of the ecosystem at the beginning of the decline (0.02 × 1000 = 20 km² per year). If the ecosystem type is assessed in 2014, under a proportional decline scenario this ecosystem type would be considered Endangered under criterion A2b (50–80% decline over any 50 year period including the present and future, electronic supplementary material, appendix S1), whereas under an absolute decline scenario, it is projected to disappear by 2024, and is thus considered Critically Endangered under criterion A2b (>80% decline). If the ecological evidence on patterns and mechanisms of decline suggests that both of these models are plausible, then the status of the ecosystem type is EN-CR, reflecting the uncertainty in projecting rates of distribution decline.

Figure 5.

All trajectories for distribution size in this figure have the same endpoints over a 40-year time frame: 300 km² in 1970 and 100 km² in 2010. A simple interpolation between the two extremes assumes linear decline (a). Addition of intermediate distribution size estimates could reveal that the decline is not linear (b). Different ecosystem types could also exhibit contrasting trajectories with identical endpoints: future projections of distribution considering these trajectories would clearly differ (c).

Figure 6.

Distribution of Tepui shrublands, southern Venezuela. The ecosystem is mapped using remote sensing and field data (a) to determine present extent (8548 km²). The extent of occurrence (b) is calculated as the area within a minimum convex hull around the ecosystem (266 218 km²), and the area of occupancy (c) determined by determining the number of 10 × 10 km grid cells that contain more than 1 ha of the ecosystem (276 grid cells). Based on data from reference [4]. (Online version in colour.)