2  Science

2.1 Conceptual Framework

The term (\(V\)) is a function of (\(E\)), (\(S\)) and (\(A\)) (Equation 2.1).

\[ V = f(E, S, A) \tag{2.1}\]

The more exposed and sensitive an area is—and the less able it is to recover—the more vulnerable it is to impacts from offshore human activities. The MST currently focuses on the sensitivity component, quantifying the intrinsic biological sensitivity of marine ecosystems based on the species present and their conservation status. Exposure and adaptive capacity components are planned for future phases (see Chapter 8).

2.2 Cell Vulnerability

For a given cell \(c\), the vulnerability score for a species group \(g\) is the sum across all \(S_g\) species of the product of species presence probability \(p_{sc}\) and extinction risk weight \(w_s\) (Equation 2.2):

\[ v_c = \sum_{s=1}^{S_g} p_{sc} \cdot w_s \tag{2.2}\]

where:

• \(v_c\) = vulnerability score of cell \(c\) for species group \(g\)
• \(p_{sc}\) = probability of species \(s\) presence in cell \(c\) (0–1 scale, from merged species distribution models)
• \(w_s\) = extinction risk weight for species \(s\) (0–1 scale, derived from ESA/MMPA/MBTA/IUCN status; see Chapter 5)
• \(S_g\) = total number of species in taxonomic group \(g\) (e.g., bird, fish, mammal, coral, invertebrate, reptile/turtle)

In other words, if a cell has many species that are both likely to be present and at high risk of extinction, it gets a higher sensitivity score. This helps identify places where rare or threatened species are concentrated.

2.3 Sensitivity Components

The MST assesses sensitivity through three components:

1. Species — by taxonomic category (bird, coral, fish, invertebrate, mammal, reptile/turtle): extinction risk weighted species distribution models across 9,819 valid species (see Chapter 3, Chapter 5)
2. Habitats — benthic habitats such as coral reefs, seamounts, and hydrothermal vents (planned for future phases)
3. Primary Productivity — satellite-derived net primary productivity from the Vertically Generalized Production Model (VGPM), measured as metric tons C km^-2 yr^-1 (see Chapter 3)

2.4 Ecoregional Rescaling

Raw cell scores vary naturally across regions due to differences in species richness and oceanographic conditions. To enable meaningful cross-region comparison, scores are rescaled to a [0–100%] range within each BOEM ecoregion (Equation 2.3):

\[ v'_c = \frac{v_c - v_{min}}{v_{max} - v_{min}} \times 100 \tag{2.3}\]

where \(v_{min}\) and \(v_{max}\) are the minimum and maximum cell scores within the ecoregion. This accounts for the natural gradient from species-rich tropical waters to less diverse polar regions, ensuring that a “high sensitivity” score has consistent meaning across all program areas.

Ecoregional rescaling makes it easy to compare areas within the same region, and Program Area aggregation gives an overall sensitivity score for each area, considering both the sensitivity of each part and how big each part is.

See subsequent chapters for detailed descriptions of: data sources (Chapter 3), taxonomic integration (Chapter 4), extinction risk scoring (Chapter 5), model merging (Chapter 6), and scoring methodology (Chapter 7).