Hurricanes

Vegetation changes on the island of Saba, effects of huricanes, people and non-native species

Powerpoint presentation with findings of a 4 week vegetation fieldvisit on Saba:

  • what is vegetation (research)?
  • historic findings (1956 and 1999)
  • current findings (49 repeated plots, 28 additional plots)
  • preliminary results for different zonation belts
    • elfin forest (highest zone)
    • elephants ears scrub
    • transitional forest
    • dry tropical forest
    • grasslands, shrubland and coastal cliffs (lower zone)
  • conclusions
    • elfin forest far from 'original'
    • zonation 2,3 and 4: no big changes, some expansion of elephant ears, more forest succesion resulting in more closed vegetation and poorer in bio-diversity
    • invasive species are more abundant in the lower zone: coralita, rubber vine,'india grass' and others
Date
2020
Data type
Other resources
Theme
Research and monitoring
Geographic location
Saba
Author
Image

Density-dependent colonization and natural disturbance limit the effectiveness of invasive lionfish culling efforts

Culling can be an effective management tool for reducing populations of invasive species to levels that minimize ecological effects. However, culling is labour-intensive, costly, and may have unintended ecological consequences. In the Caribbean, culling is widely used to control invasive Indo-Pacific lionfish, Pterois volitans and P. miles, but the effectiveness of infrequent culling in terms of reducing lionfish abundance and halting native prey decline is unclear. In a 21-month-long field experiment on natural reefs, we found that culling effectiveness changed after the passage of a hurricane part-way through the experiment. Before the hurricane, infrequent culling resulted in substantial reductions in lionfish density (60–79%, on average, albeit with large uncertainty) and slight increases in native prey species richness, but was insufficient to stem the decline in native prey biomass. Culling every 3 months (i.e., quarterly) and every 6 months (i.e., biannually) had similar effects on lionfish density and native prey fishes because of high rates of lionfish colonization among reefs. After the hurricane, lionfish densities were greater on all culled reefs compared to non-culled reefs, and prey biomass declined by 92%, and species richness by 71%, on biannually culled reefs. The two culling frequencies we examined therefore seem to offer a poor trade-off between the demonstrated conservation gains that can be achieved with frequent culling and the economy of time and money realized by infrequent culling. Moreover, stochastic events such as hurricanes can drastically limit the effectiveness of culling efforts.

Date
2017
Data type
Other resources
Theme
Research and monitoring

Potential and limits of combining studies of coarse- and fine-grained sediments for the coastal event history of a Caribbean carbonate environment

The coastal deposits of Bonaire, Leeward Antilles, are among the most studied archives for extreme-wave events (EWEs) in the Caribbean. Here we present more than 400 electron spin resonance (ESR) and radiocarbon data on coarse-clast deposits from Bonaire’s eastern and western coasts. The chronological data are compared to the occurrence and age of fine-grained extremewave deposits detected in lagoons and floodplains. Both approaches are aimed at the identification of EWEs, the differentiation between extraordinary storms and tsunamis, improving reconstructions of the coastal evolution, and establishing a geochronological framework for the events. Although the combination of different methods and archives contributes to a better understanding of the interplay of coastal and archive-related processes, insufficient separation, superimposition or burying of coarse-clast deposits and restricted dating accuracy limit the use of both fine grained and coarse-clast geoarchives to unravel decadal- to centennial-scale events. At several locations, distinct landforms are attributed to different coastal flooding events interpreted to be of tsunamigenic origin. Coastal landforms on the western coast have significantly been influenced by (sub)-recent hurricanes, indicating that formation of the coarse-clast deposits on the eastern coast is likely to be related to past events of higher energy.

 

Date
2013
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire

Effects of tropical storm Bret on Curaçao reefs

Here we report on damage caused by tropical storm Bret, passing south of the island of Curacao at a distance of 110-145 km in August 1993. Damage on marine life was surveyed 2 weeks after the storm at five localities along the leeward coast of the island. Severe damage was recorded for the scleractinian corals Acropora palmata and Millepora complanata. Dendrogyra cylindrus was incidentally damaged in shallow water, <5 m.

Date
1995
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Curacao

How much time can herbivore protection buy for coral reefs under realistic regimes of hurricanes and coral bleaching?

Abstract:

Coral reefs have been more severely impacted by recent climate instability than any other ecosystem on Earth. Corals tolerate a narrow range of physical environmental stress, and increases in sea temperature of just 1 1C over several weeks can result in mass coral mortality, often exceeding 95% of individuals over hundreds of square kilometres. Even conservative climate models predict that mass coral bleaching events could occur annually by 2050. Unfortunately, managers of coral-reef resources have few options available to meet this challenge. Here, we investigate the role that fisheries conservation tools, including the designation of marine reserves, can play in altering future trajectories of Caribbean coral reefs. We use an individual-based model of the ecological dynamics to test the influence of spatially realistic regimes of disturbance on coral populations. Two major sources of disturbance, hurricanes and coral bleaching, are simulated in contrasting regions of the Caribbean: Belize, Bonaire, and the Bahamas. Simulations are extended to 2099 using the HadGEM1 climate model. We find that coral populations can maintain themselves under all levels of hurricane disturbance providing that grazing levels are high. Regional differences in hurricane frequency are found to cause strikingly different spatial patterns of reef health with greater patchiness occurring in Belize, which has less frequent disturbance, than the Bahamas. The addition of coral bleaching led to a much more homogenous reef state over the seascape. Moreover, in the presence of bleaching, all reefs exhibited a decline in health over time, though with substantial variation among regions. Although the protection of herbivores does not prevent reef degradation it does delay rates of coral loss even under the most severe thermal and hurricane regimes. Thus, we can estimate the degree to which local conservation can help buy time for reefs with values ranging between 18 years in the Bahamas and over 50 years in Bonaire, compared with heavily fished systems. Ultimately, we demonstrate that local conservation measures can benefit reef ecosystem services but that their impact will vary spatially and temporally. Recognizing where such management interventions will either help or fail is an important step towards both achieving sustainable use of coral-reef resources and maximizing resource management investments. 

Date
2011
Data type
Scientific article
Theme
Research and monitoring
Geographic location
Bonaire