Clare Webster stands in a quiet forest clearing near Davos Laret, where sunlight filters through the larch canopy in shifting patterns—each beam and shadow now precisely mapped down to the meter. At the WSL Institute for Snow and Avalanche Research (SLF), Webster and her team have produced an unprecedented portrait of light across Switzerland, capturing, for the first time, how much sunlight reaches the ground at a resolution of just 10 meters—accounting for everything from mountain ridges to the crown of every individual tree. This isn’t just a map of brightness; it’s a dynamic model of energy, ecology, and time, recalculated hour by hour across an entire year.
Light shapes life in more ways than we often realize. In Switzerland, where a third of all precipitation falls as snow, understanding when and where sunlight strikes the ground is critical. Solar radiation accelerates snowmelt, influences water availability, and determines microhabitats for plants and animals. A shaded slope may hold snow weeks longer than one in full sun, with cascading effects on flood risk, hydropower generation, and alpine ecosystems. “Especially in forests, conditions can vary greatly from one meter to the next,” Webster explains. And with forests covering 30% of the country, those tiny differences add up.
The model draws on ultra-high-resolution topographic data from swisstopo, integrating terrain, building footprints, and tree-level canopy structure. What sets it apart is its ability to simulate how deciduous trees and larches—both of which lose their needles or leaves in winter—alter light availability seasonally. This nuance allows researchers to model not just shadows, but seasonal rhythms of exposure, offering insights into forest microclimates and snowpack behavior at an unmatched scale. The dataset has already been used in detailed snow simulations across Swiss mountain forests, revealing how elevation, tree density, and aspect interact to slow or speed up melt.
Now publicly available on the EnviDat platform, the maps open doors for scientists, urban planners, and conservationists. Ecologists can pinpoint ideal habitats for shade-sensitive species; hydrologists can refine flood forecasts; foresters can assess how tree planting or removal alters ground energy balance. The dataset, published in Scientific Data in 2025, is more than a technical achievement—it’s a foundational tool for understanding environmental change in complex landscapes.
As climate patterns shift and snow seasons shorten, knowing exactly where the sun falls—and where it doesn’t—will become ever more essential. In Switzerland’s intricate mosaic of forest, field, and mountain, light is no longer invisible. It’s measured, mapped, and made meaningful.