South African Invader Swallows Moroccan Dunes, Landmark Survey Warns

Along a windswept stretch of Morocco’s Atlantic coast, an ecological takeover is unfolding in slow motion. At Haouzia Bay in El Jadida Province, a team of Moroccan researchers has completed the most detailed quantitative inventory yet of the dune vegetation of this fragile coastal system, and the results read like a warning label for the entire North African shoreline. Of the 123 vegetation plots surveyed across three distinct dune habitats, more than half were already colonized by Carpobrotus edulis, a succulent groundcover native to South Africa. In the sheltered backdune zone, the invader’s average cover reached an astonishing 93.8 percent, effectively smothering the native plant communities beneath a dense carpet of fleshy leaves. The study, published in Plant Biosystems, documents not only what remains of the dune flora but how quickly the remainder could disappear.

Coastal dunes are among the most underappreciated ecosystems on Earth. They buffer inland areas from storm surges, trap sand that would otherwise erode beaches, store carbon, and harbor specialized plants and animals found almost nowhere else. Yet along the North African Atlantic coast, they face a double squeeze: rising human pressure from tourism, construction, grazing and trampling, and increasing aridity driven by climate change. Previous work on Moroccan coasts has documented alarming coastal vulnerability, including erosion and flooding risks amplified by sea-level rise. What has been missing, the authors argue, is fine-grained ecological data on the dune vegetation itself, the kind of baseline needed to justify and direct conservation action before the habitat is gone.

The research team, led by Jihane Tellal and Said Moukrim of Mohammed V University in Rabat together with colleagues from the National School of Forest Engineers and Chouaib Doukkali University, carried out 123 phytoecological surveys distributed across three dune facies: embryonic dunes closest to the beach, the primary foredune, and the backdune. Each 16-square-meter plot was recorded using the classic Braun-Blanquet approach, the century-old method of plant sociology that scores species presence and cover, combined with modern statistical tools. In total they recorded 53 vascular plant taxa belonging to 50 genera and 26 families. That tally included one endemic taxon, one near-endemic, and one threatened species, a reminder that even a species-poor dune system can hold irreplaceable biological heritage.

The numbers themselves tell a stark story about the condition of the ecosystem. Average species richness across all stations was just 5.13 species per plot, an exceptionally low figure for coastal dunes, which in better-preserved Mediterranean sites can support far richer communities. Richness differed sharply between zones: embryonic dunes averaged only 3.78 species per plot, while the primary foredune held 6.54, a statistically significant difference confirmed by a Kruskal-Wallis test with p below 0.001. The pattern follows a well-known ecological rule of thumb, that the harshest conditions closest to the sea, with salt spray, sand burial and nutrient poverty, filter out all but the toughest specialists, while conditions relax slightly inland.

The life-form spectrum reinforced the semi-arid, sandy character of the flora. Therophytes, plants that complete their entire life cycle within a single favorable season and survive the rest as seed, dominated at 34 percent, followed by geophytes, which retreat to underground bulbs and rhizomes during drought, at 18.9 percent. This signature, first formalized by the Danish botanist Christen Raunkiaer in the 1930s, is exactly what ecologists expect from a stressed, semi-arid psammophilous, meaning sand-loving, flora. It is a botanical fingerprint of a landscape where water is scarce, disturbance is frequent, and only opportunists and buried survivors can make a living.

Diversity indices painted a subtler picture. Shannon diversity values ranged from 0.650 to 0.957 across the dune zones, and Pielou evenness, a measure of how evenly individuals are distributed among species, ranged from 0.447 to 0.571. Intriguingly, pairwise comparisons between zones showed no significant differences for either index. The researchers attribute this homogenization to one culprit: Carpobrotus edulis. Because the invasive succulent dominates so many plots across all zones, it flattens the natural ecological differences between them. The marginal overall effect of dune zone on Shannon diversity, the authors conclude, reflects the invader’s differential dominance across facies rather than a uniform disturbance signal. In other words, the invasion is not just removing species; it is erasing the ecological structure of the dune landscape itself.

Multivariate analysis confirmed that genuine floristic differentiation among the three dune zones still exists, structured along the sea-to-inland environmental gradient. A PERMANOVA test, a non-parametric method for analyzing multivariate variance, returned an R-squared of 0.179 with p below 0.001, meaning that dune zone explains a meaningful share of the variation in community composition. This zonation, from the salt-tolerant pioneers of the embryonic dune through the dune-building grasses of the foredune to the more sheltered backdune communities, is the fundamental architecture of a healthy dune system. Each band plays a role in sand capture and stabilization, and losing any one of them weakens the whole protective structure.

The invasion dynamics, however, are the study’s most urgent finding. Carpobrotus edulis, known variously as hottentot fig or ice plant, was present in 51.2 to 70.7 percent of stations depending on the dune zone, and its mean cover in the backdune hit 93.8 percent. The plant’s strategy is brutally effective: it forms dense, impenetrable mats, its thick succulent tissues shade out seedlings, its fallen leaves alter soil chemistry, and it spreads both vegetatively and by seed dispersed by fruit-eating animals. A major meta-analysis led by Montserrat Vilà found that invasive alien plants like Carpobrotus consistently reduce native species richness and alter ecosystem processes. Recent Mediterranean studies have shown that even after Carpobrotus removal, recovery of native communities can be slow and incomplete, which makes early intervention far cheaper and more effective than later restoration.

The authors frame their findings as a call for integrated management rather than a single-fix solution. Their recommendations include mechanical control of invasive species, assisted restoration of native dune-building vegetation, and strict regulation of anthropogenic pressure such as trampling, vehicle traffic and uncontrolled development. The logic is interlocking: removing Carpobrotus without replanting native dune builders simply opens bare sand for reinvasion, while replanting without controlling human pressure condemns seedlings to being trampled. The work was supported by the BiodivRestore Program through the RESPOND Project, funded by Morocco’s Ministry of Higher Education, Scientific Research and Innovation, and builds on the team’s earlier research on environmental controls of psammophilous plant distribution in the same dune system.

What happens at Haouzia Bay matters far beyond one Moroccan bay. North African coastal dunes sit at the front line of climate change, with studies warning of alarming coastal vulnerability across the region’s deltaic and sandy beaches. Dune systems like this one are also biodiversity assets within the Mediterranean Basin, one of the planet’s recognized biodiversity hotspots. The Haouzia survey provides something rare for the region: a rigorous, plot-level baseline against which future change can be measured. If the 93.8 percent backdune cover of a South African succulent is not a wake-up call, it is hard to imagine what would be. The dunes of North Africa have survived millennia of wind and salt; whether they survive the next few decades of human pressure and biological invasion will depend on whether studies like this one translate into action on the ground.

Subject of Research: Floristic diversity and invasive species dynamics in North African Atlantic coastal dune vegetation

Article Title: Floristic diversity, biological spectrum and invasion dynamics of psammophilous vegetation in North African Atlantic coastal dunes (Haouzia Bay, Morocco): implications for conservation

Article References: Floristic diversity, biological spectrum and invasion dynamics of psammophilous vegetation in North African Atlantic coastal dunes (Haouzia Bay, Morocco): implications for conservation. (n.d.). https://doi.org/10.1007/s44473-026-00296-1

Image Credits: AI Generated

DOI: 10.1007/s44473-026-00296-1

Keywords: coastal dunes, Morocco, Carpobrotus edulis, invasive species, psammophilous flora, plant ecology, biodiversity, conservation, Atlantic coast, dune zonation, therophytes, habitat restoration