van der Wal, J.T.

Even though there are very many scattered seabird sighting records for the pelagic waters of the wider Caribbean Sea, only few studies bring these data together to generate a more comprehensive understanding of seabird use of the offshore areas of the region. The same is the case for the Dutch Caribbean EEZ which amounts to about 92 thousand km2 of the Caribbean Sea. As a consequence, information on seabird use of offshore waters has been identified as a key knowledge gap and research priority for both EEZ conservation and management purposes (Jongman et al. 2010, Meesters et al. 2010) and in support of a Bonaire-Curacao UNESCO World Heritage nomination that has been a Bonaire government ambition since 2003 (Debrot et al. 2017).  
 
In this project we followed up on these information needs by compiling many older but as-yet unpublished seabird records around the Dutch Caribbean islands, the eastern Caribbean as well as many poorly accessible seabird records for the waters off the coasts of Colombia and Venezuela. The most important additions of previously unavailable or new records for the eastern Caribbean were as follows: 1824 records by Poppe (1974), 627 by Halewijn (1972), 443 recent records by M. de Boer and J. Saulino (2014) all principally for the waters of the Dutch Caribbean, 547 records from Casler and Lira (1979) and Casler and Pirela (2004) for the northwestern sector of Venezuela and 249 records by Naranjo (1979) and Estela et al. (2004) for the Caribbean coast of Colombia. These were subsequently merged with several smaller and larger sources of seabird sighting records to yield a current total compilation of 150,372 sighting records with either exact or approximate position determinations. 
 
The database provides temporal and positional occurrence information for 65 nominate species and 13 larger familial or generic species groups in the Caribbean basin. As such, it provides a major new opportunity for the WUR to study and publish on various aspects of seabird distribution in the coming years. The potential topics include: 1) the community composition of the pelagic seabirds of the Caribbean in comparison with the community structure of other pelagic seabird communities, 2) how different habitat features (such as upwelling areas, proximity of nesting and/or roosting areas) are used by different species, 3) the identification of temporal trends in seabird species distribution and abundance, 4) identification of areas deserving conservation and management priority, either around seabird colonies or at the high seas. 

Introduction and aims 

With the introduction of smart phones that also take photos combined with GPS tracking applications, more tourists are able to take more geo-tagged photo’s during their travels. In combination with the options to upload these photos to online platforms, new ways of collecting data from the Internet provide new research opportunities. These digital footprints, combined with their specific meta-data regarding geo-location the data provide much information to be of use in spatial-temporal research. 

A previous study on Bonaire showed the potential of this kind of research. It showed some understanding of the spatial movement of tourists and the number of tourists that visit different parts of Bonaire. In order to use these kinds of data in e.g. potential impact studies, we aimed to give a follow up. 

In the present study the approach from Schep et al. (2016) was revisited with the following goals: 

• Update distribution maps with the latest data (2016-2020) and evaluate the reproducibility of the maps. 

• Detect whether distribution patterns and densities has changed following the recent developed trails and thus tourist spreading. 

• Study if densities at specific locations can be related to local characteristics, such as:

 Spatial characteristics such as distance roads 

 Landscape characteristics (landscapes) 

 Tourist type (cruise versus stay-over) 

Methods 

For this study, FLICKR was the only online platform to collect photographs and their metadata. Others were no longer available or unsuitable. All photographs taken between November 2002 and October 2019, within a Bonaire surrounding bounding box were collected, including their meta-info. This resulted in 13026 photos, coming from 421 photographers. 

Using a self-built Python application “PhotoCategoriser” each photo was assigned to a category (coastal, seascape, wildlife, underwater, terrestrial, other). Metadata of each photo and the assigned category allowed to analyse on origin of the photographer, to estimate the type of tourist (cruise or stay-over), their interest, and differences in spatial and temporal distribution. The specified resolution to aggregate the data was set at grid cells with a mean surface area of 0.301 km2. 

Photographer intensity is determined by condensing photographs into Photo User Days (PUD). One PUD stands for one (or more) photographs taken on a given day by specific photographer for a category in a grid cell.

Results and conclusions 

Overall results 

- The report provides various figures and maps presenting the spatial distribution of PUD as a proxy for tourist distribution. Temporal aspects in PUDs reflect the annual dynamics in tourist numbers. 

- Trends in tourist numbers are not equally reflected in the numbers of PUDs. PUDs are therefore a proxy of tourist distribution, but not a strong indicator for trends in absolute numbers and intensity. 

Reproducibility 

- The additional ~ 4000 photos on top of the estimated ~ 10.000 FLICKR photos that were analyzed by Schep did not add much extra information. Also, the applied resolution did not refine the possibilities of performing risk assessments on habitats or species due to the limited number of data in those areas. Distribution patterns and intensity trends were similar. Category distribution however differed slightly. This can be explained by the differences in used datasets, and by the boundary criteria for assigning categories. 

Detection of (changed) distribution and relation to local characteristics 

- The overall distribution of PUDs shows higher intensity along the west coast, near Kralendijk and its tourist area. In addition, some higher intensity spots are visible near Sorobon in the east, and Seru 

Largu in the middle of the island. The hotspots such as Goto and Washington Slagbaai in the north are clearly highlighted, as well as several scenic spots along the southern flats (Salt pans, Slavery houses, Lighthouse). 

- Less frequented regions mainly include landscapes on the eastern part of the island. The low numbers of PUDs in these regions did not allow additional analysis on changes in distribution of PUD between years. It was considered not to be of added value. Hence, the effectiveness of the recent established trails could not be assessed any further, and an additional preliminary risk assessment for habitats or species was left out of the study. 

- Distribution of PUDs reflect mainly the accessibility of regions: hence the roads and hotspots are clearly visible, and only limited PUDs were plotted further away. Analysis of distribution of tourists in specific habitats or nearby certain living areas of species were therefore considered not to be of added value. 

- The interests (reflected by the categories) of the photographers slightly vary over the years and within a year, both by origin and by tourist type (also reflected by the cruise season). Also, the distribution and intensity of tourist types and origins seems to slightly vary. Details are provided in the report. 

Future application and methodological issues 

- We suggest that studies that use these data sources first look into the generic distribution and intensity of photo’s PUDs collected (data coverage) before taking the effort of categorizing. Based on the general overview, following analysis steps such as categorizing and environmental risk assessment could be added. 

- Manual assignment of categories to photos is a subjective exercise. Assigning categories requires strict criteria and midterm evaluation of results. 

- Online platforms are variable in their existence and terms of use, leading to an uncertain accessibility and application of these kinds of data in future studies. 

Document referenced in BioNews 40 article "Using Digital Footprints to Manage Conservation Efforts"