DOI: 10.6075/j0000314
title: Island-Ocean Connection Challenge Monitoring Data

description: We developed a suite of standardized approaches to quantify the impact of island restorations on terrestrial and near-shore communities across geographies. Please note not all methods were used in every project. Please review the individual project's metadata for more detailed descriptions of the methods used. A summary of the methodologies follows:

Benthic surveys - Large-area imaging. We use photographic survey techniques to describe the benthic composition from each site. Further, we employ novel approaches of underwater large-area imaging technology to document the spatial structure and competitive dynamics of benthic taxa. This approach can generate multiple digital products, including images collected in the field, composite 3D models, 2D orthorectified images of the 3D models, and annotations of the 2D orthorectified images. These maps, or large-area images, are of sufficient scale to capture thousands of coral colonies, including details of taxonomy, size, and position of all individual colonies. By re-visiting exact locations and replicating the large-area images, we have the unprecedented opportunity to track the dynamics of individual corals and patches of algae. With advanced image analysis we can track how a reef community changes, addressing questions of coral growth, death, and competition.

Benthic surveys - Photoquadrats. Digital photographs are collected to provide raw data on the species composition, relative abundance of sessile benthic taxa, and physiological health of corals, algae, and other benthic taxa. Images are collected with a digital underwater camera using a frame to produce a consistent image area of 0.6m x 0.9m (0.54 m^2).

Benthic surveys - In-situ surveys. We use underwater visual census approaches to enumerate the density, species composition, and relative abundance of sessile benthic taxa.

Fish surveys. We use underwater visual census approaches to enumerate the density, size structure, and species composition of the fish assemblage at each site. The surveys enable us to quantify critical elements of the size structure, trophic structure, and species diversity.

Macroinvertebrate surveys. We use underwater visual census approaches to enumerate the density, size structure, and species composition of the macroinvertebrate assemblage at each site.

Vegetation surveys - High resolution, large-area imagery. We use aerial photographic survey techniques to describe the vegetation composition for each site. Further, we employ structure-from-motion photogrammetry approaches to document vegetation spatial structure. This approach can generate multiple digital products, including images collected in the field, composite 2D orthomosaics, composite 2D and 3D digital surface models, composite 2D and 3D digital terrain models, and composite 2D and 3D canopy height models. These maps, or large-area images, are of sufficient scale to document changes in vegetation percent cover and canopy height, which can be used as ground-truthed data to complement satellite earth observation data and other products to infer biomass and vegetation condition. Images are collected using a drone or other aircraft over the entire island when feasible, otherwise over subsections of the island focusing on terrestrial survey sites. Flights target a ground sampling distance of &lt;10cm and side and forward and overlap of &gt;60%.

Vegetation surveys—plots. We use vegetation plots to document seedling recruitment, percent cover, biomass, and vegetation condition at sites across the island. In addition, this dataset provides ground-truthed data to complement satellite earth observation data.

Vegetation surveys – photomonitoring. We create a visual catalogue of the island at permanent survey points by taking four photos in the four cardinal directions.

Connector species surveys – seabird point counts. We use 5-minute-long surveys of all seabirds on and over land or over water that coincide with marine survey sites to evaluate the diversity and relative abundance of species at each site. Point counts are conducted from a boat at survey locations 50-150m from shore or, in some cases, conducted from the coastline, due to ocean conditions or preferred visibility. We record location of birds (“on or over” the island or over water), behavior (sitting/standing on island or flying) and number of nests observed.

Connector species surveys – acoustic surveys. To document and measure ambient acoustic activity of the nocturnal and diurnal seabird community and quantify diversity and relative abundance, we deploy acoustic recording units at coastal terrestrial sites.

Connector species surveys – land crab transects. We use night-time land crab transects to enumerate the diversity and relative abundance of islands’ land crab community.

Connector species surveys – land crab camera traps. Images are collected using weatherproof “camera traps” set to an hourly, night-time timelapse setting. Images are reviewed to determine abundance and diversity of land crabs within photos.

Connector species surveys – marine iguana large-area imagery. To calculate a population estimate for a subset of marine iguana leks in the Galápagos islands, we utilized a drone equipped with a camera flown from the coastline to approximately 20m inland. An orthomosaic of each lek is constructed, and a count of iguanas observed is completed.

Nutrient availability sampling. Terrestrial vegetation, soil, and near-shore marine macroalgae samples are collected and processed for stable isotope analysis. The results from the stable isotope analysis tell us about the source of nutrients and their availability in the environment.

Environmental context - Remotely sensed data. A suite of remotely sensed meteorological, oceanographic, and topographic data (annual precipitation, elevation, slope, aspect, annual land surface temperature, vegetation type, soil hydrology, chlorophyll-a, wave energy, and sea surface temperature) are collected for each island to provide environmental context.

Environmental context - In-situ data. In-situ water temperature loggers are deployed at four sites (at 10m depth) around each island to provide higher resolution spatiotemporal oceanographic context data.

Environmental DNA - marine data. In unique or sensitive marine environments, like marine lakes, novel approaches have been employed. Aquatic eDNA sampling methods can be used to determine presence/absence of vertebrate species, such as fish. For aquatic sampling, water is pushed through a filter until it clogs, a preservative is then applied to the filter, and the filter is mailed to the lab for sequencing.

Environmental DNA - terrestrial data. Methods were piloted in the terrestrial environment at case study sites Ulong, Late, and Floreana. Our terrestrial eDNA results have the potential to indicate presence/absence of species. Samples were collected from standing fresh water (e.g., lagoon, pond), ephemeral streams following rain events, standing marine water in high tide pools, and soil or sand soaked in bottled drinking or distilled water. Collected or soaked water is pushed through a filter until it clogs, a preservative is then applied to the filter, and the filter is mailed to the lab for sequencing.
description: The Island-Ocean Connection Challenge (IOCC) is a global effort that aims to better understand the linkages between islands and the ocean by using standardized monitoring methods to measure the impact of island restorations on the terrestrial environment and the near-shore marine environment. The restorations are largely achieved through the eradication of invasive alien species (IAS). We use a Before-After Control-Impact (BACI) experimental design to estimate the true effect of the restoration. For each project location we collect a suite of data Before (“pre-restoration”) and After (“post-restoration”) eradication at both a Control (“control”) island and an Impact (“restoration”) island. In this collection we provide the monitoring data collected as part of the IOCC for the following projects: the Ulong Project, the Floreana Project, and the Late Project. 

In 2021, research began on a long-term project with the Koror State Government’s Department of Conservation and Law Enforcement (DCLE) to not only remove invasive species but also promote biosecurity for the Rock Island Southern Lagoon World Heritage Site. Koror is the most populous Palauan state, and their collaborative spirit and guidance is integral to success. Once invasive species are removed, biosecurity is a critical aspect to ensure an island is protected from reinvasion. This project will serve as a template for similar interventions on other Palauan islands in the future. Once biosecurity measures become a routine and integrated part of Ulong, the natural heritage can be preserved for generations to come. For this project, the Impact (“restoration”) island is Ulong and the Control ("control") island is Ngeruktabel, both located in the Rock Islands of Koror State in Palau. 

On Ulong and Ngeruktabel, multiple rat species pose significant threats to native wildlife. To address this, Island Conservation carried out a targeted rat eradication on Ulong Island from 22 March to 15 April 2023, focusing on the removal of Rattus tanezumi and Rattus tiomanicus. Meanwhile, Ngeruktabel Island served as a control site with no eradication carried out and continues to host several invasive vertebrates such as rats (Rattus tanezumi, Rattus exulans, and unconfirmed reports of Rattus norvegicus) as well as feral cats (Felis catus). Although the eradication initially showed a decrease in rodent populations, rodents were detected again on Ulong in April 2024, about one year after the operation, highlighting the ongoing challenge of preventing reinvasion and protecting island biodiversity. For more information on the Ulong Project please visit IOCC Projects - Ulong Island, Republic of Palau: https://www.jointheiocc.org/iocc-projects.

Floreana Island is located on the southern end of the Galápagos Archipelago off the west coast of continental Ecuador. IOCC partners are working with Floreana community members and stakeholders to remove destructive rats (Rattus rattus), mice (Mus musculus), and feral cats (Felis catus) from the island. But the long-term project includes far more than making Floreana safe from invasives. In the coming years, team members will reintroduce at least 12 species that have been locally extirpated from Floreana, such as the Floreana Giant Tortoise (Chelonoidis niger niger), the Floreana Racer (Pseudalsophis biserialis biserialis), the Vermillion Flycatcher (Pyrocephalus rubinus), the Galápagos Rail (Laterallus spilonotus), the Galápagos Hawk (Buteo galapagoensis), the Lava Gull (Leucophaeus fuliginosus), the Floreana Mockingbird (Mimus trifasciatus) and five species of Darwin’s Finches. The restoration of Floreana Island’s ecosystem will benefit not only native wildlife, but also the health, agricultural production, and tourism endeavors of the local community. For this project, the Impact (“restoration”) island Floreana and the Control ("control") island is Espanola, both located in the southern Galápagos Archipelago. 

On Floreana, rats (Rattus rattus), mice (Mus musculus), and cats (Felis catus) pose threats to threats to the native flora and fauna. However, Espanola has remained free of invasive vertebrates. Rodent eradication efforts spanned 3 Oct to 26 Nov 2023 and, unfortunately, rodents were detected in Sept 2024 post-implementation. Cat eradication efforts with baiting spanned 27 Nov - 22 Dec 2023 and is planned to continue as spot treatments until complete. For more information on the Floreana Project please visit IOCC Projects - Floreana Island, Galápagos, Ecuador: https://www.jointheiocc.org/iocc-projects.

Late, located in the Southwest Pacific, is a tropical volcanic island belonging to the Vava’u island group in the Kingdom of Tonga. Working with local representatives, IOCC partners conducted extensive baseline research on Late prior to implementing an eradication of the rodents causing widespread damage. Scientists are monitoring the benefits of the intervention, which are expected to include recovered seabird and terrestrial plant and animal communities, as well as the improved health of the surrounding reefs and marine life. With invasive species removed, Late offers a unique and essential opportunity to safeguard the species that have persevered there, such as the Tongan Whistler (Pachycephala jacquinoti) and the Friendly Ground Dove (Pampusana stairi), but also to translocate native species to the islands to aid in their recovery. For example, establishing the Tongan Megapode (Megapodius pritchardii) on Late will increase the species range and further secure it from extinction. For this project, the Impact (“restoration”) island Late and the Control ("control") island is Tofua (for terrestrial monitoring) and Fonualei (for marine monitoring). 

On both Late and Tofua, rats (Rattus exulans) are present. However, Fonualei is rat free and is currently the only place in Tonga where the reintroduced population of the Tongan Megapode (Megapodius pritchardii) is still thriving today. Rodent eradication implementation spanned 8 to 27 July 2023. Rats were detected on Late in May 2024 post-implementation. For more information on the Late Project please visit IOCC Projects - Late Island, Kingdom of Tonga: https://www.jointheiocc.org/iocc-projects.

In this collection we provide the monitoring data collected as part of the IOCC: Ulong Project (in progress), Floreana Project (in progress), and Late Project (data forthcoming).

For more information on the entire IOCC project beyond the locations where we are monitoring impacts, please visit www.jointheiocc.org.