Climate change and shifts in the food web are continuing to threaten the survival and reproduction of penguins in Antarctica, a Chinese expert has warned.

"The loss of sea ice has imposed breeding pressure on emperor penguins, which rely on stable sea ice for chick rearing," said Liang Qi, an associate professor at the School of Geospatial Engineering and Science at Sun Yat-sen University.

"Meanwhile, as ocean temperatures rise, Antarctic krill — their key prey — have shifted their distribution toward higher latitudes. This has lengthened the foraging distance of penguins to some extent, increasing their energy expenditure during the breeding season," Liang said.

Liang recently carried out research and multiple unmanned aerial vehicle, or UAV, survey flights in the penguin breeding area on Adelie Island in Antarctica as part of a Chinese Antarctic expedition.

The expedition team returned to Shanghai aboard the polar icebreaker Xuelong, or Snow Dragon, in April following a 160-day voyage to Antarctica. It was part of the country's 42nd Antarctic expedition to the world's southernmost region and achieved fruitful scientific research outcomes.

"Previously, we mainly monitored penguin populations using remote-sensing satellite data. Now remote sensing methods face several limitations in penguin identification, fine characterization of habitats and population inversion due to poor algorithm generalization and a lack of ground observation validation samples," Liang said.

In addition to measuring individual penguins' body size, Liang also accurately identified and mapped penguin nests. "In the past, we mainly relied on satellite monitoring, but satellites operate at a long distance and are easily affected by weather conditions. The application of drones has provided solutions to these problems," he said.

The number of penguin nests, or breeding pairs, is a key indicator for assessing the current population size in penguin habitats and predicting future population dynamics. It is also one of the core parameters recorded in on-site Antarctic penguin surveys.

Under normal circumstances, expedition team members must endure harsh Antarctic conditions and make repeated trips to penguin breeding colonies to obtain data through manual counting.

By using drone photography, however, Liang achieved accurate identification and counting of penguin nests in the colonies.

During the expedition, Liang completed more than 60 drone flights and obtained various observational data on penguin habitats, including visible light, multispectral, thermal infrared and Light Detection and Ranging, or LiDAR, data.

In addition, he conducted ground-based Simultaneous Localization and Mapping, or SLAM, scanning to measure penguin morphology. Penguins are widely distributed across the Fildes Peninsula, Liang said.

To implement the integrated space-air-ground observation system, Liang sometimes had to hike 10 kilometers through the field to reach penguin habitats for spectral measurements and manual population counts, with a total round trip spanning 20 km.

"The survey conducts penguin habitat observations simultaneously on satellite, unmanned aerial vehicle and ground-based platforms, enabling more refined satellite remote-sensing observations of Antarctic penguin populations," he said.

"This survey will provide important support for the subsequent establishment of a large-scale spatial and long-term time-series monitoring network for Antarctic penguin population dynamics," he added.

Liang said he can currently only reveal some preliminary data because final data analysis is still underway and requires more time.

According to Liang, Antarctica has four of the most common penguin species — emperor penguins, Adelie penguins, chinstrap penguins and gentoo penguins — with a total population of roughly tens of millions.

Liang said protecting penguins requires an urgent, two-pronged approach of monitoring and emission reduction.

A large-scale, high-frequency monitoring network should be established using multisource satellites and unmanned aerial vehicles to gain a deeper understanding of changes in penguin population distribution and habitat conditions, he said.

Meanwhile, slowing the rate of ocean warming and maintaining the physical stability of the Antarctic sea ice and fast-ice system would buy valuable time for the restoration of penguin breeding habitats, he added.

Hu Xiaotong contributed to this story.