Species

Caribbean islands exhibit high levels of unique biodiversity resulting from a long history of species colonizations and adaptations to geographically isolated conditions. The U.S. Virgin Islands host unique assemblages of unique terrestrial species, many of which are endemic to these islands. The suites of species found on St. John and St. Thomas are similar both to each other and to neighboring Puerto Rico due to their proximity and shared geological history. St. Croix’s distance from other islands and lack of connection to the Puerto Rican Bank has given rise to endemic species unique only to St. Croix. The range of terrestrial habitats offer niches for a variety of reptiles, amphibians, bats, and resident land and waterbirds, and the islands are important stopping off sites, both as a destination and for short refueling visits, for summer and winter migratory birds. Cays offer refuges for ground-nesting birds while coastal saline wetlands and guts provide critical food resources. The rich variation and connectivity within marine habitats, including coral reefs, mangroves, and seagrasses, offer habitat niches for an enormous variety of marine organisms, including fish, corals, molluscs, echinoderms, and others--too many to include in this document. The variation between islands also means that species that are common on one island may be absent or in decline on other islands. These distributional variations make territory-wide status assessments challenging. 

Additionally, geographic isolation combined with human-mediated species transport make it difficult to unravel biogeographic patterns. Localized threats may have significant impacts on isolated populations that potentially represent a significant portion of a species distribution within the region, but without consistent survey and monitoring effort across all islands, these differences are difficult to detect. The focus of limited research and monitoring resources are distributed differently on each island, based on species distributions and personnel expertise. 

Terrestrial and marine species in the Caribbean have experienced high levels of population declines and extinctions due to habitat conversion and degradation, encroachment, and invasive species, coupled with stochastic events such as hurricanes and other disturbances. Corals and other marine organisms are increasingly affected by rising ocean acidification and sea surface temperatures, and increasingly severe hurricanes, precipitation events, and droughts create unprecedented impacts to both marine and terrestrial species.

The suite of species that have been designated as SGCNs were designated as such through review of reports, monitoring data analysis, and expert review. Additionally, in this 2025 update, we have included an analysis of the USVI SGCNs in the Regional Context.

We identified the Species of Greatest Conservation Need (SGCN) through a multi-step process combining historical records, expert review, literature surveys, and existing territorial and federal listings. We additionally listed Species of Greatest Information Need (SGIN) if the species were identified by respondents, or were previously listed as SGCN, without any additional information available to make a determination at this time. 

U.S. Virgin Islands Species of Greatest Conservation Need

Each species was scored using criteria such as known population trend, rarity, range contraction, threat exposure, and potential for management intervention. We choose criteria by which each species will be evaluated. Possible criteria based partly on reviewer feedback and standard conservation planning included: 

Threat exposure / severity 

How many threats affect the species, and how severe those threats are 

Trend / decline 

Whether the species is declining, stable, or unknown 

Rarity / distribution 

How restricted its range is (is it geographically limited within the USVI) 

Habitat vulnerability / loss risk 

How threatened its habitat(s) are (e.g. high land‐use change) 

Feasibility of conservation action 

Whether practical intervention is possible (cost, risk, social/political constraints) 

Data availability / knowledge gaps or expert elicitation 

Whether there is enough information to act confidently, or whether data deficiency increases uncertainty (for prioritizing research) 

Multiplier / leverage potential 

If acting on this species also benefits many others (e.g. umbrella, keystone) or expert elicitation is used for confidence 

Many of these data were missing for species in the U.S. Virgin Islands and one of our actions for the next ten years is to fill in these gaps. In lieu of ranking species using any sort of system for global assessments, we created an expert elicitation framework with two types of uncertainty measurements. We are then binning those into de facto ranks for conservation action prioritization. 

The highest scoring species were prioritized for immediate conservation planning based on a metric of conservation status provided in guided workshops by over a dozen experts with two indicators of confidence used to evaluate that conservation status: 

Expert Elicitation Ranking System chosen for the 2025 SWAP

1. Status level → Base Score 

1. Very High Concern = 5 

2. High Concern = 4 

3. Medium Concern = 3 

4. Low Concern = 2 

5. Blank / Not specified = 1 

2. Confidence (stars) → Multiplier 

1. ★★★★★ = 1.2 

2. ★★★★☆ = 1.1 

3. ★★★☆☆ = 1.0 

4. ★★☆☆☆ = 0.9 

5. ★☆☆☆☆ = 0.8 

6. ☆☆☆☆☆ = 0.7 

3. Confidence (categories) → Multiplier 

   1. 1. 1. High Confidence = 0.9

         2. Some Confidence = 0.5

         3. Low Confidence = 0.1

         4. No Confidence = N/A

4. Priority Score = Status Base × Confidence Multipliers

This ensures that species with higher concern and higher confidence in the data rise to the top, while lower concern and low confidence species get a smaller score. 

The tiers from the expert elicitation for the Species of Greatest Conservation Need are now as follows:

1. Low Risk - if no conservation action occurs, the species will likely not be affected

2. Medium Risk - conservation action is warranted

3. High Risk - conservation action is needed in order for the species to persist

4. High Risk (possibly Extinct) - conservation action is needed to determine if the species persists

5. Species of Greatest Information Need - it is unknown, but likely, that conservation action is needed. The species was identified as a new or existed previously as a Species of Greatest Conservation Need in 2015 and/or 2005 with no new information available.

Species Ranges and Occurrence

1. A checklist of 1,842 species observed in the citizen science platform iNaturalist: https://www.inaturalist.org/check_lists/13080-Virgin-Islands-Check-List Species can be individually viewed for location observed. 

2. DFW Wildmon Acoustic Data across 150 USVI sites focused on amphibians and birds – find site and species list: https://dashboard.wildmon.ai/project/usvi-dfw-biodiversity-monitoring