Matthijs van den Burg

Sint Eustatius was hit by two major hurricanes, Irma and Maria, during the high-intensity season of 2017. Two new studies aid our understanding of how local populations deal with these destructive events. 

Caribbean flora and fauna have always dealt with the destructive forces of hurricanes. However, as climate change is leading to an increase in their frequency and strength and many species have decreased in abundance due to anthropogenic causes, a better understanding of how hurricanes effect local populations is essential. 

The Caribbean hurricane season of 2017 was the most intense recorded to date. Both Irma and Maria, category-5 hurricanes, closely passed Sint Eustatius and caused major destruction on the island; reported on in this Nature Today article. Although immediately after the storms it became clear that trees were heavily affected and mostly defoliated, understanding how and which species were affected requires time for data collection and comparison. Since 2017, several studies have provided pieces of information in order to understand how local populations coped, or not, with the 2017 hurricane season. 

Since 2017, researchers have found that >90% of all trees were defoliated by more than ¾, and that especially trees at higher elevations (such as on the Quill volcano) were affected more severely. Another study that focused on the endangered Bridled Quail-dove (Geotrygon mystacea), demonstrated that the population declined by 77% in 2019 compared to pre-hurricane levels. A follow-up study in 2021 (not yet published) recorded a further decline to just 125 individuals, and the Bridled Quail-dove will likely be re-assessed by the IUCN. 

Focusing on reptile species, two novel studies further aid our understanding of the ecosystem-wide impact that the 2017-hurricane season had on Statian biodiversity: 

Red-bellied racer. Photo credit: Henkjan Kievit

The first study demonstrates that the Red-bellied Racer (Alsophis rufiventris), indicated as Vulnerable by the IUCN, a harmless snake species now found only on St. Eustatius and Saba, was dramatically affected by the hurricanes. Compared to pre-hurricane density estimates (9.2 racers per hectare), post-hurricane estimates decreased by almost 50%. Encounter rates of individual racers have dropped from 16.0 snakes/hour in 2011 to less than 0.5 snakes/hour (post-hurricane). Given the current small size of the remaining population and the fact that the species’ current range is just 11% of its original extent, local extirpation is a real risk. 

Lesser Antillean Iguana. Photo credit. Philippa King

The second study, focusing on the Critically Endangered (Iguana delicatissima), shows that its population decreased by at least 20% during 2017. Comparing sighting and survey data from 2017–2018, the authors found a decrease in both the abundance and population size of the iguana species. Importantly, no recovery was observed in 2019, suggesting this small population needs multiple consecutive years without major hurricanes to recover. Interestingly, similar to Statia’s forests, iguanas at higher elevations were found to have been affected more severely.  

Small islands such as Sint Eustatius are home to declining populations of rare and endangered species. In many cases, these isolated populations are unable to migrate between islands and thus populations can only locally increase in size. These new studies highlight the need to improve habitat quality and lower anthropogenic threats to optimize the natural recovery of both species. Ideally, at least for Iguana delicatissima, population increase could be aided by a local head-starting project where baby iguanas are nourished and released once they are larger and more likely to survive.  

Recently published articles: 

Find me if you can: Pre- and Post-hurricane Densities of the Red-bellied Racer (Alsophis rufiventris) on St. Eustatius, and a review of the genus in the Caribbean. Read Report

Hurricane-induced population decrease in a Critically Endangered long-lived reptile Read Report

Article published in BioNews 46

Although the La Soufrière volcano on St. Vincent saw its latest explosive eruption over a week ago, and the threat level has decreased to Orange, caution is still necessary. Uncertainty for the St. Vincent population therefore remains, as thousands of people had to evacuate their villages and stay elsewhere on the island. Further uncertainty and hardship are caused by the eruptions’ effect on local food and water supplies. Gratefully, in a region where catastrophic weather events are not uncommon, regional organizations and nations quickly mobilized relief efforts to aid Vincentians.

In a letter to the journal Science, biologists from 12 Caribbean organizations, including STENAPA on St. Eustatius, highlight the need to prioritize both humanitarian aid and biosecurity when responding to natural disasters. The authors note how bypassing biosecurity could cause additional long-term harm to both the local ecosystems and the human population. Erik Boman, Director of STENAPA, pointed out that this threat is especially grave on islands. The letter also “urge governments and aiding parties responding to catastrophes to recognize and mitigate potential risks”.

Several of the authors have been involved in invasive species control on Dominica, where during the humanitarian aid campaign that followed the passing of Hurricane Maria in 2017, several non-native species were introduced. The local NGO WildDominique is currently working hard to remove both amphibian and reptile species that established populations there. The green iguana is also a biosecurity issue for local iguana, Iguana delicatissima on St. Eustatius. Although thousands of dollars have already been invested in these eradication efforts, a complete assessment of all species that arrived with the aid supplies still awaits. In the aftermath of natural disasters, when the natural environment is heavily affected and recovering, arriving non-native species will have the opportunity to spread out further and would form a major threat to the isolated and native flora and fauna on the island.

The letter further addresses the need for wide and multi-organizational collaborations to prepare for future large-scale humanitarian aid campaigns, of which each will be unique.

Link to Letter at Science: https://science.sciencemag.org/content/372/6542/581

Article published in BioNews 43