The study, published in the journal Ecology and Evolution, reports the results of a survey tracking coral feeding scars and surviving coral tissue after predation by individual crown-of-thorns starfish. The fieldwork was carried out at the University of Sydney’s One Tree Island Research Station on the southern Great Barrier Reef, in protected areas where healthy populations of fish and other predators keep the starfish at naturally low densities. In these balanced conditions, the researchers found something surprising: living coral tissue remained after almost 75 percent of the starfish feeding events they examined.

Dr Shawna Foo, a University of Sydney Horizon Fellow in the School of Life and Environmental Sciences who led the research, explained that the starfish at One Tree Reef behave very differently from the destructive swarms that have plagued other parts of the Great Barrier Reef. Rather than demolishing an entire coral colony in a single assault, starfish at low density appear to consume a relatively consistent amount of coral during each meal before moving on to another colony. This grazing pattern frequently leaves live coral tissue remnants behind, giving the corals a chance to recover.

That distinction matters enormously for how scientists and reef managers understand the species. Crown-of-thorns starfish are native to the Great Barrier Reef, where they have long been part of the ecological fabric. Since the 1960s, however, the reef has experienced four major outbreaks, erupting at intervals of approximately 15 years, each capable of causing mass coral destruction. The new findings do not diminish the significance of these devastating events, which coral populations struggle to recover from. Instead, they highlight an overlooked upside of low-density starfish populations functioning within a healthy marine ecosystem.

The mechanism behind the starfish’s constructive role lies in the competitive hierarchy of corals themselves. On many reefs, fast-growing species in the family Acroporidae, which includes the familiar branching and table corals of the genus Acropora, can rapidly colonize available space and shade out slower competitors. The study found that remnants of these fast-growing Acroporidae corals did not regenerate over the feeding scars left by starfish. Regeneration occurred mostly among much slower-growing Montipora and massive Porites corals, which gradually reclaimed the damaged areas. By preferentially trimming back the dominant, fast-growing species, low-density starfish populations open space for slower-growing corals to persist.

In effect, the starfish act as reluctant gardeners, pruning the most aggressive competitors and preventing any single coral species from monopolizing the reef. This increases the structural and taxonomic diversity of the coral community, a quality widely associated with healthier, more resilient reef ecosystems. Foo noted that by feeding on fast-growing corals such as Acropora, low-density populations create space for slower-growing species, helping to increase overall coral diversity across the reef.

The results align closely with a foundational concept in ecology known as the intermediate disturbance hypothesis. Professor Maria Byrne, a co-author of the study, said the findings are consistent with this important framework in ecology and conservation. The hypothesis proposes that occasional, moderate disturbance within an ecosystem can actually help maintain biodiversity, because it prevents dominant species from excluding others while stopping short of the catastrophic damage that eliminates species altogether. Crown-of-thorns starfish feeding at low densities appear to fit this pattern precisely, applying a measured pressure that keeps coral competition in balance without pushing the system toward collapse.

Understanding when starfish shift from ecological regulators to reef destroyers is a central question for conservation. The balance appears to hinge on predation. Diminishing populations of crown-of-thorns predators, including the giant triton snail and multiple species of coral reef fishes, heighten the vulnerability of the Great Barrier Reef and marine environments worldwide to outbreaks. Where those predators thrive, as in the protected zones surveyed at One Tree Reef, starfish numbers remain low and their feeding becomes a modest, even beneficial, component of reef dynamics. Where predator populations have collapsed, starfish can multiply into swarms that consume coral faster than it can regrow.

The research also carries practical implications for how managers respond to outbreaks. Current control efforts rely heavily on culling programs in which divers inject starfish to remove them from affected reefs. Foo emphasized that the new findings can help determine when and why culling should occur, and what the ecological endpoint of a cull should be. Once an outbreak has been suppressed, she argued, the goal should not necessarily be to eliminate crown-of-thorns starfish entirely. Instead, culling needs to be complemented by strong marine management that protects the starfish’s natural predators and keeps populations in check, allowing the species to resume its natural role rather than tipping back toward destructive abundance.

The study, an observational survey of coral feeding scars conducted on the Great Barrier Reef, reframes one of the ocean’s most feared invertebrates as a species whose impact depends entirely on context. In a functioning ecosystem with its predators intact, the crown-of-thorns starfish is a native coral predator performing a role that has shaped reef communities for millennia. Only when that balance is disrupted does it become the reef-wrecker of popular imagination. For a Great Barrier Reef facing warming waters, bleaching and repeated outbreaks, the message from One Tree Island is a nuanced one: the enemy of corals can, in the right numbers, be part of their salvation, and conservation strategies that restore ecological balance may prove more powerful than eradication alone.

Subject of Research: The ecological role of crown-of-thorns starfish predation in maintaining coral reef biodiversity

Article Title: Crown-of-thorns starfish can help reefs thrive

Article References: Crown-of-thorns starfish can help reefs thrive. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: crown-of-thorns starfish, coral reefs, Great Barrier Reef, biodiversity, intermediate disturbance hypothesis, marine ecology, coral predation, One Tree Island, reef management, culling, Acropora, University of Sydney

The research, led by Athanasia Ntouzou of the National and Kapodistrian University of Athens with colleagues including Jakovos Demetriou, Eleftheria Kyriazidi, Anastasia Misseyanni and Christos Georgiadis, is published in The Science of Nature. Between June 2022 and May 2023, the team deployed pitfall traps across the forest, capturing ground-dwelling arthropods in natural sites and in areas with clearly detectable human activity. After sorting and curating thousands of specimens, the researchers identified every ant to species level and subjected the resulting dataset to a battery of statistical tests designed to probe how, and whether, urban disturbance reshapes insect communities.

The team’s starting hypothesis was deliberately pessimistic. Drawing on ecological filtering theory, they predicted that anthropogenic habitat modification would act as a sieve, eliminating specialized soil-dwelling and leaf-litter species sensitive to drying microclimates and vegetation loss, and replacing them with hardy, disturbance-tolerant generalists. They laid out three sequential predictions: species richness and Shannon diversity should decline significantly with disturbance; community composition should shift measurably from specialist-dominated to generalist-dominated assemblages; and differences between communities should be driven by species turnover rather than simple species loss. In each case, the ants declined to cooperate with the hypothesis.

In total, the researchers identified 24 ant species across the study area, with 19 recorded in undisturbed sites and 21 in disturbed ones. Notably, not a single non-native species turned up in the traps, although one endemic Greek species, Camponotus laconicus, was detected. Non-metric multidimensional scaling of community composition showed substantial overlap between disturbed and undisturbed plots, with stress values of 0.169 and 0.122 for presence/absence and abundance data respectively, figures considered acceptable for interpretation. A permutational multivariate analysis of variance found no statistically significant partitioning between the two habitat types, whether the analysis used presence/absence data (p = 0.684) or abundance data (p = 0.073), although with abundance data disturbance explained roughly 19 percent of compositional variation, leaving the result tantalizingly close to the conventional significance threshold.

The finer statistical machinery was equally unambiguous. Indicator value analysis failed to identify any species reliably associated with either habitat type, meaning no ant in this forest qualifies as a simple disturbance fingerprint. Beta diversity partitioning, which separates the effects of species replacement from those of nested species loss, showed no significant differences between disturbed and undisturbed sites in turnover, nestedness, or overall dissimilarity, with p-values ranging from 0.728 to 0.779. Species richness and both Shannon and Simpson diversity indices were statistically indistinguishable between habitat types, and linear mixed-effects models confirmed the pattern across seasons: month of sampling exerted an overwhelming influence on ant activity, while disturbance itself had no significant effect, and the interaction between the two was similarly non-significant.

What did matter was the calendar. Species richness and abundance peaked in July, followed by April, October, and January, a seasonal rhythm typical of Mediterranean-type ecosystems where the hot, dry summer months coincide with maximum colony activity and worker foraging. Interestingly, disturbed habitats hosted more species and individuals in spring and summer, a pattern the researchers attribute to anthropogenic subsidies such as irrigation and littering, which boost soil moisture and resource availability precisely when the natural landscape is at its most parched. In October, as early autumn rains released ants from the constraints of summer drought, the balance tipped the other way, with undisturbed sites hosting the richer assemblages. Either way, the overall statistical verdict was clear: these are differences of timing and texture, not of fundamental community structure.

These findings align closely with the intermediate disturbance hypothesis, first proposed by Joseph Connell in 1978, which holds that biodiversity peaks at moderate levels of disturbance. In peri-urban settings, human activities such as planting, irrigation, and fertilization alter resource flows and generate microhabitats that can temporarily favor native species, potentially raising local diversity rather than eroding it. The absence of non-native ants in the traps strengthens the interpretation that this forest has not yet crossed the threshold where disturbance opens the door to invasive species. The researchers caution, however, that this resilience has a shadow side: disturbance of any intensity is known to facilitate biological invasions, and Attica’s defenses are thin. Only four of Greece’s 16 known alien ant species have been documented in the region, and the invasive Argentine ant, Linepithema humile, is already expanding through metropolitan Athens. Its eventual spread into peri-urban refugia could fundamentally rewrite the diversity patterns documented here, as it has in Portugal, Spain, Italy, and elsewhere around the Mediterranean.

The study is not without caveats, which the authors confront directly. Sampling relied on twelve traps selected from an initial network of 22, constrained by the labor-intensive task of sorting and identifying specimens, though the researchers argue the selected traps captured representative niches on both sides of the disturbance divide. Site proximity in a fragmented landscape raises concerns about spatial autocorrelation, but the team documented physical barriers such as paved corridors and drainage structures separating plots, and their multivariate results point to local disturbance severity rather than geography as the driver of any community differences. The authors also note that ants, with their specialized functional traits, cannot serve as a direct proxy for all arthropods, though their fine-grained sensitivity to soil and microhabitat alteration makes them excellent bioindicators of localized anthropogenic pressure. Expanding pitfall networks across broader regional and biome gradients, they argue, will be essential to test the generality of these results.

The broader message is one of cautious optimism for conservation planning in an urbanizing world. Attica’s urban footprint has exploded in recent decades, rising from roughly 17.7 percent land coverage in 1945 to 68.5 percent by 1995, with continued low-density sprawl since. Against that backdrop, the demonstration that a peri-urban forest can sustain intact, diverse, entirely native ant assemblages under moderate disturbance positions such green spaces as genuine biodiversity reservoirs rather than degraded remnants. The authors recommend management strategies that maintain microhabitat heterogeneity while curbing direct pressures like pollution and littering and forestalling the introduction of non-native species. Preserved and thoughtfully managed, these transitional landscapes may serve as ecological connective tissue across the urban grid, sheltering arthropod communities that intensifying urbanization would otherwise erase. The ants of Mount Hymettus, quietly going about their business beneath the pines, suggest that nature’s margins are not always its weakest points.

Subject of Research: Resilience of Mediterranean peri-urban ant communities to moderate urban disturbance

Article Title: Resilience of ant communities (Hymenoptera: formicidae) to moderate urban disturbance in a mediterranean peri-urban landscape

Article References: Resilience of ant communities (Hymenoptera: formicidae) to moderate urban disturbance in a mediterranean peri-urban landscape. (n.d.). https://doi.org/10.1007/s00114-026-02152-w

Image Credits: AI Generated

DOI: 10.1007/s00114-026-02152-w

Keywords: ants, Formicidae, urban ecology, peri-urban forest, intermediate disturbance hypothesis, biodiversity, Mediterranean ecosystems, Greece, invasive species, community ecology, pitfall trapping, bioindicators