Unexpected high number of endemics for the windward Dutch Caribbean Islands

On Saba, St. Eustatius, St. Maarten and the Saba Bank there are a minimum of 35 animal and plant species that exist nowhere else in the world, so-called endemic species.

Additionally, 188 species only occur on those islands and the surrounding islands. There are only two endemics recorded in the Netherlands’ mainland, which means that the biodiversity of these islands is very rich.

This study, led by Wageningen Marine Research at the request of the Ministry of Agriculture, Nature and Food Quality (LNV), has shed light on the richness of the biodiversity of the Dutch Caribbean islands. Each island has its own unique history with its own special ecosystems and habitats teeming with rare and special life.

The remarkable variety of terrestrial and marine habitats, including coral reefs, mangroves and rainforests means that the diversity of species is astonishing. In this spectacular natural world, rare and extraordinary species live that occur nowhere else in the world (.

Probably many more endemics present

The researchers’ task was to put together a preliminary checklist of existing endemic animal and plant species of the SSS islands and the Saba Bank. Existing species lists were supplemented with recent discoveries described in reports and publications. This newly created checklist of endemics surpassed all expectations and highlights the richness and rarity of the biodiversity of the SSS islands and the Saba Bank. In total, 223 endemics were identified, including 198 animal and 25 plant species.

The vast majority (162 species) of these endemics are terrestrial and belong to five species groups: beetles, snails, spiders, birds and locusts. Many of the recorded species are endemic to a somewhat larger geographical area (Lesser and Greater Antilles), however 35 species are island endemics, meaning that they are found only on one of the SSS islands or the Saba Bank. The island of St. Maarten was found to have the highest number of island endemics (12), however this will have to be re-assessed following the devastation of Hurricane Irma in 2017 and the growing trash dump that causes harmful fires.

While the checklist of endemics is impressive, it is likely far from exhaustive, as species groups that were not included (e.g. fungi) or considered understudied (e.g. beetles and small mollusks) may yield many more rare species.

Protection needed
The challenge now is to make sure these extraordinary rare species are protected from extinction. This requires knowing which of the 223 endemics listed in the study are currently under threat. Despite the heightened vulnerability of endemic species because they only occur in such a small area, the IUCN Red List of Threatened Species - largely considered as the worldwide reference on endangered species - has, to date, only assessed a small portion of the world’s endemics. Just 42 of the 223 species listed have had their status assessed.

Of these, six endemic terrestrial reptiles are currently classified as threatened or near-threatened. It is highly likely that many more endemics are endangered due to the increasing number of invasive species and increase in natural and human induced threats facing these islands. This study has helped highlight the remarkable biodiversity of the SSS islands and Saba Bank and their astounding number of endemic species.

All information about the endemics has been described in the report of Bos et al. (2018), which can be found on the Dutch Caribbean Biodiversity Database (www.dcbd.nl) and is searchable through the Dutch Caribbean Species Register (www.dutchcaribbeanspecies.org). What we need now is to make sure that not a single one of these rare species lands on the extinct species list.