New maps show Heard Island glaciers are retreating faster—and offer guidance for their protection

Heard Island recently made headlines when US President Donald Trump imposed a 10% tariff on it and the nearby McDonald Islands—despite no trade occurring there and no human visits to the islands since 2016. But there is much more to these islands than being an isolated home to hundreds of thousands of penguins and seals.

The Heard and McDonald islands, managed by the Australian Government and located 4,100km southwest of Perth, are UNESCO World Heritage-listed as one of the world’s least human-impacted ecosystems. Dominated by Big Ben, an over 2,800-metre-high active volcano blanketed in snow and glaciers, Heard Island is more than 61% ice-covered. With few introduced species and minimal human impacts, it offers a rare glimpse of nature largely unchanged by people. However, climate change—the human impact that can still reach the most remote places on Earth—is encroaching.

Tracing a vanishing icy landscape

Whilst developing new maps of Heard Island’s glaciers, SAEF researchers have shown they are retreating due to a warming climate. Their results have just been published in The Cryosphere.

“Heard Island has lost a considerable amount of its icy landscape (~64 square kilometers) over this period, highlighting the impact of changing environmental conditions. To give you a better idea, this is about the size of the Republic of San Marino, in Southern Europe,” SAEF research fellow Dr Levan Tielidze from Monash University, who led the study explains.

The team, which also includes Professor Andrew Mackintosh and Dr Weilin Yang from Monash University, have revealed that the rate of ice loss doubled between 1988 and 2019. They have linked this rapid retreat to climate change, showing that a temperature rise of 0.7°C over the past 70 years is the main cause.

Despite their value, Heard Island’s glaciers are relatively understudied, largely due to the island’s remoteness, glaciated terrain, and the logistical challenges and costs of mounting expeditions.

To overcome these barriers, the researchers used topographical maps from 1947 and satellite imagery from historical and current Earth observation platforms. The resulting maps catalogue 29 glaciers, tracing their outlines in 1947, 1988 and 2019. They also document key morphological features, including area, slope, aspect and elevation—enabling the estimation of key information such as mass balance, glacier volume, surface velocity and the impact of volcanic and other surface debris.

“By comparing these maps over time, we can quantify the rate of glacier retreat or advance, which directly reflects changes in regional climate in the sub-Antarctic region,” Dr Tielidze said.

The team found that the glaciers on the eastern slopes of Heard Island are retreating much faster than in other regions of the island. Stephenson glacier showed the greatest retreat, of approximately 5.8km. This was driven by the collapse of its terminus and the formation of a large lagoon, with has further accelerated melt.

A warning from the Southern Ocean

While these maps show that some further ice loss is locked in, the fate of Heard Island’s glaciers is not. This bellwether of change in the Southern Ocean underscores a stark reality: there are different futures still available to us. Whether we secure the future of these glaciers or lose them almost entirely depends on the greenhouse gas emissions pathways we follow in the coming years.

In one future, emissions continue to rise, global temperatures climb past 2°C, and Heard Island becomes largely ice free, transforming the landscape and the biodiversity that relies on it. In another future, we accelerate the transition to renewable energy sources, such as solar and wind, drastically reducing emissions. Some glaciers survive. Ecosystems adapt rather than collapse. Nature, though altered, holds on.

As our climate future unfolds, these maps will help inform conservation strategies and management plans, as well as support the team’s ongoing research.

Earlier this year, Professor Mackintosh and colleagues were  awarded an ARC Discovery Project to study how glacier retreat threatens mountain biodiversity, which is poorly understood. Dr Tielidze also contributed to a recent study, published in Nature, which tracked how ecosystems develop as glaciers retreat.

“Glacier retreat alters freshwater inputs and landscape morphology, affecting the local ecosystems. For example, glacier retreat exposes new land surfaces, which can be colonized by plants and animals. The new inventory helps track these changes in habitat availability and ecosystem dynamics,” Dr Tielidze said.

Later this year, SAEF researchers plan to join a voyage to the islands aboard the RSV Nuyina as part of the Australian Antarctic Program.

“The team hope to be able to collect some newly emerging bedrock from areas where the team have mapped this dramatic ice retreat,” Professor Mackintosh says.

“By looking at cosmogenic isotopes in the bedrock, we will be able to assess whether this late 20th and early 21st century retreat is unprecedented across the island’s history. Furthermore, by carrying out glacier modelling experiments as part of the Discovery Project, we can investigate what has driven the retreat including the extent to which humans are responsible.”

As scientists piece together the island’s glacial past and project its glacial and ecological future, they’re helping to illuminate the broader consequences of climate change on glaciers and biodiversity across the globe. This tiny, remote island in the middle of the Southern Ocean is a reminder: that even the most remote places on Earth are not beyond human impact, or human responsibility.

Read more

Tielidze, L., Mackintosh, A.N. & Yang, W. (2025) Glacier inventories reveal an acceleration of Heard Island glacier loss over recent decades. The Cryosphere, 19, 7, 2677–2694. https://doi.org/10.5194/tc-19-2677-2025