The effects of warming on loggerhead turtle nesting counts
Data files
Jan 09, 2025 version files 788.97 KB
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nestingbeaches_GCB.dbf
139.46 KB
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nestingbeaches_GCB.prj
145 B
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nestingbeaches_GCB.qix
7.08 KB
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nestingbeaches_GCB.qmd
1.09 KB
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nestingbeaches_GCB.shp
639.70 KB
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README.md
1.50 KB
Abstract
Global trends in marine turtle nesting numbers vary by region, influenced by environmental or anthropogenic factors. Our study investigates the potential role of past temperature fluctuations on these trends, particularly whether warmer beaches are linked to increased nesting due to higher female production (since sea turtles have temperature-dependent sex determination). We selected the loggerhead turtle (Caretta caretta) due to its wide distribution, strong philopatry, and vulnerability to environmental changes. We compiled nest counts per year on 35 globally significant rookeries, analysing trends at regional and individual beach levels. We compiled air (CHELSA) and land surface (MODIS) temperature datasets spanning the last four decades (1979-2023) for each location. To analyse temporal trends in nest counts and temperatures, we used generalised additive models and Mann-Kendall trend tests. Additionally, we correlated nest counts with lagged air temperature variables. We found significant warming at 33 nesting locations, 23 of which also showed significant increases in nest counts. Our results suggest that rising temperatures may be boosting nest numbers in regions of the Caribbean, Atlantic Ocean, and Mediterranean (sites in Cayman, Mexico, Brazil, Cyprus, and Turkey). Furthermore, while some regions temporarily benefit, continued warming could precipitate long-term population declines. This regional variability helps predict species responses to climate change, with the general global increase in nest counts already indicating short-term warming effects. Nesting count trends might reflect a combination of natural ecological phenomena, conservation efforts, and warming effects. Long-term studies are needed to assess global trends in the sex ratio of hatchlings and the extent to which feminisation is driving nest numbers.
README: The effects of warming on loggerhead turtle nesting counts
https://doi.org/10.5061/dryad.b8gtht7n5
Description of the data and file structure
This dataset contains digitised polygons representing loggerhead turtle nesting beaches across the globe. The data were obtained by delineating polygons using Google satellite imagery within QGIS 3.32.2 (QGIS Development Team, 2020). Spatial-temporal fluctuations of nest counts across nesting grounds were analyzed using the Mann-Kendall trend analysis (Kendall, 1990) with the ‘MannKendall’ function in the R package ‘Kendall’. The dataset does not include locations of nests, and the polygons represent generalised beach boundaries* *and no precise nesting locations or coordinates have been included.
File structure
Shapefile: nestingbeaches_GCB.shp
- Code: Individual polygon code representing one beach.
- Beach Name: Name of the beach, when available.
- Country: Country where each beach is located..
- State: State/ island/ region of the country where each beach is located.
- RMU: Regional management unit.
- MannKendal: Mann-Kendall slope of loggerhead turtle nesting trends.
Code/Software
This dataset was processed and analysed using the following software:
- QGIS: Version 3.32.2 (QGIS Development Team, 2020)
- *R: * Version 4.3.0 (R Core Team, 2023).
- *R Packages: '*Kendall', used for Mann-Kendall trend analysis.