When Carpobrotus edulis first arrived from South Africa, it was seen as a practical way to stabilize railway embankments and roadsides in California. Over a century later, this succulent, better known as the ice plant, has taken hold along coastlines from California to Spain, overrunning dunes and cliffs and spreading through grasslands. Its thick, creeping stems can grow up to 90 centimeters a year, forming dense mats that smother native vegetation and alter the field.
Originally valued for holding sandy soils in place, Carpobrotus edulis has spread well beyond the sites where it was planted. Its creeping stems root as they grow, while animals that eat its fruit can disperse the seeds. Once established, intertwined stems and shallow roots form a living carpet that blocks light and outcompetes local flora. Dense mats can bury native plants, reducing habitat for native insects and other wildlife. The plant also changes the soil beneath an infestation, making it harder for native vegetation to return after removal.
In Spain, the ice plant is a familiar sight along Mediterranean and Atlantic coasts, where it is also known as uña de gato or hierba del cuchillo. Its spread is particularly problematic in protected dune systems and on coastal cliffs. Spain’s national structure for invasive alien species is the Catálogo Español de Especies Exóticas Invasoras. The plant’s inclusion in the catalogue has prompted controls on possession and transport, as well as on sale, and targeted removal campaigns in sensitive areas. Eradication is difficult because fragments can take root and form new colonies, making careful extraction and follow-up monitoring impressive to prevent regrowth.
California faces similar challenges. Railway and highway authorities planted ice plant on coastal slopes because it tolerates drought and salt exposure. It also became a popular ornamental groundcover. The California Invasive Plant Council gives highway ice plant a High rating, and the California Department of Fish and Wildlife includes it on its “Don’t Plant Me” list. For decades, public-works crews planted it deliberately. As the Basic Coast State Parks Association puts it, “now experts spend large time and money pulling it out.” Rooting stems and seeds dispersed by animals have made established infestations difficult to contain.
The ecological consequences reach beyond competition for light. “The plant also changes soil chemistry beneath it, making a native comeback harder,” the Basic Coast State Parks Association notes. Decomposing leaves and stems can add organic matter to sandy soils, while dense growth suppresses native seedlings and shrubs. The association also warns against assuming ice plant reliably holds a slope: its roots are relatively shallow, and water-filled leaves add weight. During major storms, mats can slide downhill and carry soil with them.
Coastal dunes are shaped by wind and waves, and shifting sand creates habitat for specialized plants and animals. Ice plant mats stabilize the surface, turning open, mobile dunes into more static vegetated areas and reducing habitat for wildlife adapted to exposed sand. Restoration takes more than removing the plant: managers also work to re-establish native vegetation and the ecological processes that sustain dune habitats. The California Department of Fish and Wildlife recommends purple sage, Salvia leucophylla, as an alternative for dry coastal slopes. This drought-tolerant native shrub provides flowers for pollinators, unlike a dense ice-plant monoculture.
Manual removal takes large labor and money, so California managers are pairing fieldwork with technology. The National Center for Ecological Analysis and Synthesis at the University of California, Santa Barbara, has launched a project that uses satellite imagery and aerial surveys, with machine learning to map and track Carpobrotus edulis. Researchers are testing the approach in the Jack and Laura Dangermond Preserve, aiming to monitor more than 300 acres of infested land. The maps help direct removal teams to priority areas and track restoration over time.
Spain’s coastal managers face similar hurdles. After removal, native plants must be reintroduced to reduce the chance that ice plant will reclaim bare ground. Follow-up monitoring is also needed to detect regrowth. The experience echoes other ecological restoration efforts, including the eradication of invasive fish in the Pyrenees, which contributed to the recovery of native species and clearer waters. The story is detailed in this report on the restoration of Pyrenean lakes.
The case of Carpobrotus edulis shows how a plant introduced to address erosion can become a persistent threat to fragile coastal habitats. In California, authorities have shifted from planting ice plant to discouraging its use and removing established mats, a response to the costs of its spread. Across Spain and beyond, the challenge is to restore native vegetation and coastal processes while stopping the invader from taking hold again.
