DOI: 10.5061/dryad.b8gtht7n5
title: The effects of warming on loggerhead turtle nesting counts

description: 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.
description: # The effects of warming on loggerhead turtle nesting counts
 [https://doi.org/10.5061/dryad.b8gtht7n5](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.