Venice’s landmarks teem with tourists — so many, in fact, that the city has had to implement restrictions, like banning guides from using loudspeakers. But just outside the famous canals and resplendent architecture sits an ecosystem that teems with less obnoxious forms of life: the Venetian lagoon. For millennia, its marshes have hosted a bevy of flora and fauna, and for centuries protected the city from invasion by its enemies.

Now, protecting this habitat, and others like it, can help protect people and the planet. Traipsing through the wetland and sampling plants, researchers identified a carbon-capturing powerhouse, known as sea lavender, of the genus Limonium. By restoring these biomes, conservationists would not only boost local biodiversity, but also ensure its ability to trap that planet-warming gas. “Salt marshes are not only sites of carbon sequestration,” said Tegan Blount, a geoscientist at Italy’s University of Padova, lead author of a new paper describing the research. “Their conservation also protects many other ecosystem services, which are vitally important from a local to global scale.”

Above ground, sea lavender is a stunner. True to its name — though technically it isn’t lavender — it produces lovely purple flowers that attract pollinators, thus supporting biodiversity. Unlike terrestrial lavender, though, Limonium tolerates salty, water-logged conditions, allowing it to thrive in the wetlands of the Venice lagoon. “During summer, the salt marsh meadows are tinted purple by an undulating mass of sea lavender flowers, rife with bees and other insects,” Blount said.

While Limonium is great to look at and all, these researchers were more interested in what’s below ground. Instead of a network of fine filaments, sea lavender’s mature rhizome system grows like a hand reaching up from the soil, with foliage sprouting from the fingertips at the surface. (That’s them in the photo.)

This impacts the Venetian marshes in several ways. With its sturdy root system and foliage, sea lavender anchors the waterlogged soil, generates organic material, and traps sediment, which reduces erosion and habitat loss in the face of pressures like sea-level rise. It also can create a more stable and amenable environment for other salt-tolerant species, further boosting biodiversity. “So it can also be a stepping stone,” Blount said.

Even after it dies, this marvelous plant’s root system can persist for long periods, continuing to engineer the mud. The study found that compared to other marshy species in the area, like those in the genera Sarcocornia and Juncus, Limonium creates much more biomass below the ground than above it, and markedly enhances the organic carbon content of the sediment. In fact, sea lavender can retain 12 times as much biomass underground than you see growing topside. 

By protecting these ecosystems, sea lavender can prosper alongside other species, so conservationists wouldn’t need to constantly tend to them, Blount said. Species of Limoniumgrow all over the world, too, from the coasts of North America to Africa to Asia. Restoring those habitats, then, would benefit biodiversity while enhancing carbon sequestration and storage. Additionally, healthy wetlands help absorb the force of hurricane storm surges, mitigating the inundation of coastal cities.

Properly restored, coastal ecosystems can be self-sustaining. Infrastructure like sea walls, on the other hand, is expensive to construct and maintain, especially as ocean levels rise. Given enough space to creep inland, wetlands can adapt. “These systems can keep up pace with sea level rise, as long as they can migrate backwards,” said Emily Landis, global climate adaptation and resilience director at the Nature Conservancy, who wasn’t involved in the study. “That means they can still provide that essential adaptation, flood reduction benefit.”

They bring economic benefits too, when conservationists work with Indigenous communities to determine how they use these ecosystems. Subsistence fishing, for instance, can be done in a measured way that ensures piscine populations don’t crash, which would be terrible both for the ecosystem and the humans that rely on it. “They know how to take care of their coastline,” Landis said. “They know what is sustainable.”

In the Venetian lagoon, fishers have long used valli da pesca, essentially ponds that function as artificial ecosystems. This provides shelter for baby fish to grow big enough to harvest. Taking animals out of these habitats may sound counterproductive, but in a way it incentivizes protecting these areas. “So conservation is not just a matter of preserving the environment, but also to have something back,” said Alice Stocco, an ecologist at the Ca’ Foscari University of Venice, who studies the valli da pesca but wasn’t involved in the new paper.

The value of sea lavender, then, isn’t just how much carbon it captures in the Venetian lagoon, but the habitats — and therefore economic and ecological benefits — it provides. “An ecosystem — nature in general — has its own value, which is intrinsic and sometimes cannot be measured,” Stocco said. “Healthy ecosystems allow for healthy people.”