Tourists visiting the Notre-Dame de Paris cathedral in Paris might be seeking a religious or aesthetic experience. But they often leave feeling woozy for other reasons. In the increasingly hot Paris summers, visitors queueing outside are doubly baked by the sun and heat radiating from the light stone paving underfoot. A devastating 2019 fire provided an opportunity to rethink the cathedral grounds. How could a new plaza mitigate the “heat island” effect?
Belgian architect Bas Smets, professor in practice of landscape architecture, turned to nature. In his winning commission for the Notre-Dame grounds, he envisioned the cathedral site as a series of microclimates—hyperspecific spaces linked to natural features. That western plaza, for example, could be conceived as a forest clearing. A ring of trees will provide shade, a gentle breeze from the Seine will circulate air, and a novel system that periodically pumps a five-millimeter layer of water onto the stone to induce evaporative cooling.
Smets, profiled in the July-August 2024 Harvard Magazine, brings this project and two others to life in his new exhibition, “Changing Climates,” on display through December 20 at the Graduate School of Design (GSD). The title reflects the exhibit’s dual purpose. It warns, showcasing the changing climate and the resulting, varied challenges. But it also provides hope, showing how architects can change local climates to help keep a warming world inhabitable.
Consistent with his approach to design, Smets began planning the exhibition by envisioning the gallery itself as a natural landscape. He interpreted Gund Hall’s columns as trees framing three models of his urban landscape projects, each responding to a different challenge: heat islands in Paris; biodiversity in Arles, France; and sea level rise in Antwerp, Belgium. The models, impressive in their own right, are enhanced by projected light displays that highlight each climatic intervention.
Alongside the models, visitors can view a rotating photographic display of various Smets projects. Rather than simply snapping a photograph of each project as it appeared on opening day, photographer Michiel De Cleene, returned each season, capturing Smets’s works as they mature, becoming part of the natural urban landscape.
The exhibition showcases what GSD chair of landscape architecture Gary Hilderbrand called “the reciprocity between the teaching and the practice.” One wall displays the final projects from the first two iterations of Smets’s GSD studio, “Biospheric Urbanism.” In the course, a dozen students collaborate with a city that wants to prepare for a warmer world with more volatile weather. For New York, students suggested planting “green roofs” on buildings and creating mini-parks atop sidewalk scaffolding. In Paris, students proposed turning some traffic lanes into water-retaining bioswales and creating underground socialization spaces in parking garages. “I really encouraged them to hack into the system and find ways of greening the city without cost,” Smets said in a lecture about the exhibition.
On the far end of the exhibit is what Smets called “probably the biggest IPCC chart ever printed.” The 70-foot wall displays the Intergovernmental Panel on Climate Change’s history of global temperature change since 1850—with ominous projections to 2100. The early years are represented by hues of blue (less than a 0.5-degree Celsius increase since 1850), but the chart grows progressively redder (a 2.8-degree Celsius rise by 2100). “When you see the graph in a book, you say, ‘Yeah, it’s getting redder,’” said Smets. “When you walk those 70 feet, you feel the heat.”
Though the future appears daunting, Smets hopes that his microclimatic approach will help cities adapt to the changing world. His highest-profile microclimate project will open in just a few weeks. On December 8, Notre-Dame de Paris will welcome visitors for the first time in five years. Before entering, tourists will walk through the first 20 meters of Smets’s redesigned plaza. Though a single project cannot cool the world, he hopes the new plaza will show how landscape architects can help harness nature to keep people safe and comfortable on this ever-warming planet.
