This project, led by Michael Burnett (University of California, Santa Barbara), aims to better understand how the main tree species on Tetiaroa use groundwater resources. The study focuses in particular on coconut trees (Cocos nucifera), pu’atea (Pisonia grandis), tāhinu (Heliotropium foertherianum), fara (Pandanus tectorius), and naupata (Scaevola taccada). It examines the relationships between vegetation, freshwater depth, and salinity in order to improve our understanding of how atoll ecosystems function.
Summary of field activities
Since the launch of the project, sensors measuring tree water use have been installed across several motus to monitor how different species rely on available water resources.
A field mission conducted in July 2025 made it possible to retrieve the sensors, download the collected data, and carry out approximately 80 geophysical surveys to measure the depth of freshwater and saltwater lenses. These observations were complemented by vegetation surveys.
Impacts and preliminary results
Preliminary analyses suggest that coconut trees use an average of 92 liters of water per day, while pu’atea typically use between 20 and 50 liters per day, although additional data are still needed.
Perspectives
Data analysis is ongoing and will help refine our understanding of the water needs of different species across the atoll. This work will contribute to anticipating how island ecosystems may respond to climate variability.