Retreating glaciers are forcing Switzerland to redraw its maps

Swisstopo’s latest aerial survey is capturing a Swiss landscape that has shifted since the last time the cameras passed overhead. Thousands of photographs are arriving at the federal mapping office in Wabern, near Bern, after flights over the Alps in Valais and Vaud. The images will update the country’s three-dimensional Topographic Landscape Model and the national map used by authorities, hikers and planners.

The timing matters. Glamos reports that average glacier ice thickness fell by 2.5 to 4 metres between 2025 and 2026. The summer heatwave left a visible mark in the new imagery, while low winter snowfall had already reduced the ice available to withstand the warm season. In some locations, only remnants remain, creating so-called dead ice.

The changes also reach beyond the white surface shown on familiar maps. Glacier forelands are rearranging as ice retreats, exposing rock, sediment and moraine. Tobias Providoli, who leads the 35-person swisstopo team, says the scale of change is difficult to watch. His staff must turn that moving terrain into precise, usable geographic data.

Switzerland’s mapping system revisits every part of the country within three years, giving glacier retreat a regular place in the national record. Swisstopo flies over roughly one third of Switzerland each year, then uses the imagery to revise its digital models and printed maps. The institution has documented the country since 1838 and has operated its own aerial photography service since 1926.

The survey schedule follows the landscape. Aircraft typically photograph the Swiss Plateau in spring, when sparse vegetation makes the ground easier to read. In the Alps, flights take place in August and September, when seasonal snow has cleared from most terrain. Clear skies and good visibility remain essential, so weather can determine when the cameras get their opportunity.

Two aircraft now carry out the work. Their high-resolution cameras record several kinds of imagery at once, including standard colour and infrared photographs. That combination gives specialists more than a visual archive. It helps them identify terrain boundaries, surface changes and vegetation patterns as they build a detailed model of the country.

The result is a recurring measurement system for a landscape that used to appear relatively fixed on paper.

The clearest evidence of retreat often appears when new photographs are placed beside older ones. At Morteratsch Glacier near Pontresina in Graubünden, swisstopo images show the glacier tongue moving back by dozens of metres between 2022 and 2025. The comparison makes the change visible at a glance, yet the digital model records more than the position of the front edge.

Providoli says the computer images reveal lost glacier volume as well as retreat. That distinction matters because a glacier can lose substantial thickness before its tongue moves a comparable distance. Glamos estimates that the average ice thickness decline reached 2.5 to 4 metres in a single year, from 2025 to 2026.

The 2026 heatwave is now embedded in the aerial record. In places where the ice has thinned dramatically, dead ice can remain beneath or beside the active glacier. Meanwhile, newly exposed ground begins to change as water, rockfall and sediment reshape the foreland.

Swisstopo’s work therefore documents a transition from an ice-dominated landscape to a more unstable and varied terrain. The map must follow each stage, from intact ice to exposed moraine and bare rock.

A retreating glacier changes the ground that maps are expected to describe. Traditional two-dimensional maps can show a glacier’s outline, but they struggle to convey how much ice has disappeared or how quickly the surrounding foreland is being rebuilt by natural processes. Swisstopo’s three-dimensional model gives surveyors a more complete view of that terrain.

The practical consequences reach across Switzerland. Digital national maps must reflect altered glacier boundaries. Paper hiking maps also depend on the same aerial data, even though their printed contours and symbols may remain in circulation for years. Trails, access routes and points of reference can become harder to interpret when a familiar ice field gives way to loose sediment, exposed rock or meltwater channels.

Providoli describes the foreland as highly dynamic. Rocks shift, moraine areas expand and loose material accumulates as the ice withdraws. Those changes complicate the job of deciding where one geographic feature ends and another begins.

The mapping office is not redrawing the country in one sweeping revision. It is updating the national picture through repeated surveys, regional processing and comparisons with historical imagery. Each cycle adds another precise record of how Alpine ground is changing.

The next Swiss map will record a country whose Alpine landmarks are becoming less stable and less permanent. The survey programme gives officials a way to track that change across decades, linking the latest photographs to the archive that began in the nineteenth century. It also gives researchers a consistent basis for comparing glaciers and their surrounding terrain from one cycle to the next.

For residents and visitors, the most visible effects will appear in places where ice once provided a clear geographic reference. A glacier tongue can retreat beyond the position shown on a familiar map, while its foreland develops new channels, deposits and rock surfaces. The process varies from valley to valley, so national mapping depends on detailed local observation.

The 2026 survey will enter that long record after a year in which Glamos measured another sharp loss of ice thickness. Swisstopo’s aircraft will continue returning to different regions, while its specialists convert photographs into updated digital and paper representations.

Maps cannot halt the physical changes they document. They can provide a reliable account of where the terrain stands at a given moment, helping Switzerland manage its Alpine geography as the ice retreats and the ground adjusts.