Written by Larissa Marques Pires Teixeira
Edited by Caeley Hickson Long
Feature image from Ved Chirayath/NASA Ames Lab for Advanced Sensing
Have you ever imagined monitoring the health of a coral reef without even getting into the water? As oceans continue to warm and coral bleaching events become more frequent, scientists need faster and more efficient tools to track changes in reef ecosystems. But how can we monitor ecosystems that are often located in remote and difficult-to-access areas?
The answer may be in the sky rather than underwater. Drones, which are becoming increasingly affordable and easy to operate, are emerging as valuable allies in marine conservation. A recent study conducted in Papua New Guinea showed that these aircraft can accurately assess coral cover, identify areas affected by bleaching, and even characterize different coral growth forms. The findings suggest that this technology could transform how we monitor reefs in an era of rapid environmental change (Himes & Rueger 2026).
How coral reefs are monitored
There are several ways to monitor coral reefs, varying in cost, accuracy, spatial scale, and level of detail. These methods can generally be grouped into three main categories: in situ monitoring, remote sensing, and citizen science (Obura et al. 2019).
In situ monitoring is the most traditional and detailed approach, conducted directly underwater by divers. Typically, a transect tape is laid across the reef, and researchers record the number and diversity of species encountered along the transect, either through direct observations or underwater photography.
Remote sensing relies on technologies that collect information from a distance, often using unmanned aerial vehicles (UAVs), more commonly known as drones (Hedley et al. 2016). Since some reef systems, such as the Great Barrier Reef, are so extensive that they can even be seen from space, satellites can also be used to monitor reefs at regional or global scales (Strong et al. 2011).
Citizen science involves collaboration between scientists and the general public in the production of scientific knowledge. In reef environments, recreational divers, local communities, and volunteers are often trained to collect data that are later analyzed by researchers (Forrester et al., 2015).
Which method is most effective?
Each reef monitoring method has its own advantages and limitations. For example, in situ monitoring offers high accuracy and allows researchers to identify species directly. However, it is time-consuming and typically covers relatively small areas. Imagine how long it would take a team of divers to monitor the more than 2,300 kilometers of the Great Barrier Reef, the largest coral reef system on the planet.
Citizen science provides a low-cost alternative that can cover large geographic areas while also engaging society in conservation efforts. In Brazil, for instance, researchers partnered with dive operators to document an invasive coral species. The initiative resulted in 39 new records from locations where the species had not previously been reported, and the data submitted by volunteers achieved 100% reliability (Machado et al. 2021).
Remote sensing, meanwhile, has proven to be just as effective as traditional monitoring methods. In the study conducted by Himes and Rueger (2026), estimates of live coral cover obtained from drone imagery were nearly identical to those collected by divers and photographic transects. This demonstrates that aerial images can accurately represent the structure of shallow reefs. Drones also successfully identified areas affected by coral bleaching. Estimates of bleached coral cover closely matched those obtained through underwater surveys, indicating that this technology can be used to monitor large-scale thermal stress events. When researchers evaluated coral growth forms, drones were able not only to quantify coral cover but also to distinguish among different growth forms, including branching, massive, and encrusting corals. This information is particularly valuable because the structural composition of reefs directly influences associated biodiversity and the ecosystem’s ability to recover from environmental disturbances.
UAVs as a Tool for Coral Reef Monitoring
Traditional reef monitoring requires trained personnel, diving equipment, boats, and extended periods of fieldwork. These factors limit how frequently surveys can be conducted and significantly increase monitoring costs. This is where drones offer a major advantage. They combine low operational costs with easy transportation, rapid data collection, the ability to cover large areas, frequent repeat surveys, and image storage for future analyses. These characteristics make drone technology especially valuable for developing countries and remote regions, where some of the world’s most biodiverse coral reefs are found. As climate change intensifies, coral bleaching events are becoming more frequent and severe. In this context, tools capable of rapidly detecting changes in reef health will become increasingly important.
The results from Papua New Guinea demonstrate that drones can complement—and potentially expand—traditional monitoring programs by providing reliable information on coral cover, bleaching, and community structure. Although some limitations remain, particularly when assessing deeper reef areas, drones represent a promising solution for increasing both the spatial and temporal scale of coral reef research.
At a time when the conservation of these ecosystems is more urgent than ever, accessible and efficient technologies such as drones can play a crucial role in understanding ongoing changes and guiding management and conservation efforts around the world.
References
Forrester, G., Baily, P., Conetta, D., Forrester, L., Kintzing, E., & Jarecki, L. (2015). Comparing monitoring data collected by volunteers and professionals shows that citizen scientists can detect long-term change on coral reefs. Journal for Nature Conservation, 24, 1–9. https://doi.org/10.1016/j.jnc.2015.01.002
Hedley, J. D., Roelfsema, C. M., Chollett, I., Harborne, A. R., Heron, S. F., Weeks, S., Skirving, W. J., Strong, A. E., Eakin, C. M., Christensen, T. R. L., Ticzon, V., Bejarano, S., & Mumby, P. J. (2016). Remote Sensing of Coral Reefs for Monitoring and Management: A Review. Remote Sensing, 8(2), 118. https://doi.org/10.3390/rs8020118
Himes, L., & Rueger, T. (2026). Drone imaging can accurately assess coral cover, bleaching, and growth form for shallow coral reefs. Coral Reefs. https://doi.org/10.1007/s00338-026-02864-5
Machado, A. A., Bertoncini, A. A., Santos, L. N., Creed, J. C., & Masi, B. P. (2021). Participatory monitoring of marine biological invaders: A novel program to include citizen scientists. Journal of Coastal Conservation, 25(1), 25. https://doi.org/10.1007/s11852-021-00814-7
Obura, D. O., Aeby, G., Amornthammarong, N., Appeltans, W., Bax, N., Bishop, J., Brainard, R. E., Chan, S., Fletcher, P., Gordon, T. A. C., Gramer, L., Gudka, M., Halas, J., Hendee, J., Hodgson, G., Huang, D., Jankulak, M., Jones, A., Kimura, T., … Wongbusarakum, S. (2019). Coral Reef Monitoring, Reef Assessment Technologies, and Ecosystem-Based Management. Frontiers in Marine Science, 6. https://doi.org/10.3389/fmars.2019.00580
Strong, A. E., Liu, G., Skirving, W., & Eakin, C. M. (2011). NOAA’s Coral Reef Watch program from satellite observations. Annals of GIS, 17(2), 83–92. https://doi.org/10.1080/19475683.2011.576266
