Fire emerged as one of the study’s central themes. Researchers mapped vegetation fires across five seasons, from July 2019 through 2024, revealing dramatic year-to-year swings. The largest burned areas occurred in the 2021–2022 season, when a single March peak consumed 35,425 hectares of reed-dominated landscape, while the most recent season recorded the smallest burned extent. Monthly analysis showed that fires cluster sharply in March, when winter-dried reed beds act as vast stands of standing fuel. Because reeds dominate the delta’s aquatic-to-terrestrial transition zones, fire there is not a marginal disturbance but a landscape-scale force that reshapes habitat availability for birds, mammals, and plants alike. The team selected 90 observation points based on composite fire maps from the last three seasons to track how repeated burning affects bird communities, and field surveys in April 2024 across 31 points recorded 279 birds from 36 species in and around burned zones.

The comparison between burning and harvesting as management tools produced some of the most actionable results. Working across reed beds subjected to 2024 interventions, three-year-old unmanaged stands, and ten-year-old unmanaged stands, the researchers recorded 66 plant species, of which only 22 appeared in every treatment type. Indicator species analysis revealed clear signatures: water-plantain was associated with burned reeds, sedges and bindweed with harvested reeds, and bittersweet, water hemlock, and reed canary-grass with the oldest beds. The effects shifted with the seasons—species richness peaked in three-year reeds in June, while Shannon diversity was highest in freshly harvested and ten-year-old stands by September. Burning reduced light values in the understory by shading out coexisting plants, whereas harvesting increased them, opening the canopy to companions. Stem density was highest in harvested plots, but stems there were shorter and thinner. The authors conclude that no single treatment is optimal: the biodiversity payoff comes from managing reed beds as mosaics of different ages and treatments, alternating fire and harvest to maximize habitat heterogeneity, with the benefits of any single harvest lasting only a few years.

Beyond fire and reeds, the study inventoried the delta’s harvestable natural wealth with striking precision. Three legally harvestable edible mushroom species—field mushroom, wood mushroom, and meadow mushroom—occupy roughly 9,200 hectares of suitable habitat, yielding an estimated 75 tons annually. Eighty-seven medicinal herb species contribute about 22 tons of harvestable dried biomass. Beekeeping potential was assessed through 64 key nectar plants, with standardized honey yields ranging from 5 kilograms per hectare in wetland pastures to 50 kilograms per hectare in natural wetland meadows, and eight optimized beekeeping routes were proposed. Natural pastures covering about 27,500 hectares support 195 grazing-tolerant plant species at moderate quality, while the delta’s roughly 170,000 hectares of reed beds, managed through 19 concession areas, hold an annual harvestable potential of about 88,000 tons. These figures feed a database intended to guide the reserve administration in issuing permits that balance local livelihoods against ecosystem stability.

The biodiversity surveys delivered a mixed picture. Invertebrate monitoring across dozens of sites, from the delta’s western edge to the Black Sea coast at Vadu and Histria, found a strikingly species-poor fauna: the only invertebrate of Community interest reliably observed all year was the large copper butterfly, Lycaena dispar, recorded at Zebil and Saon. The researchers attribute this scarcity to extreme weather—a cold spring followed by sudden, prolonged summer heat—and caution that the picture is incomplete because surveys focused on peripheral areas. Fourteen years of monitoring have revealed persistent knowledge gaps in the distribution of protected invertebrates, complicating both the implementation of the reserve’s management plan and the Natura 2000 standard data sheets, which themselves require periodic revision.

Fish surveys told a richer story. Sampling in the Danube River, its branches, the Somova–Parcheș lake complex, and interfluvial lakes captured 61 species, including 14 of Community interest, plus the Ukrainian brook lamprey, Eudontomyzon mariae, and the cryptic gudgeon Romanogobio kessleri antipai, both absent from the official standard form. Official 2023 catch data showed freshwater species dominating at 91.5 percent of total fishery resources, led overwhelmingly by gibel carp at 40.4 percent, followed by Asian carps, breams, and common carp. Migratory fish accounted for 8.3 percent, almost entirely Pontic shad. More troubling were the trends among predators: pike, after a continuous decline from 5.7 percent of catches in 2019 to 2 percent in 2022, showed a slight recovery to 2.9 percent, but zander continued to fall, representing just 1.6 percent of catches—under 41 tons. Climate change compounds the pressure, with rising temperatures, reduced precipitation, and falling water levels desiccating delta ponds.

Herpetofauna and bird surveys filled in other pieces of the puzzle. Four of the five reptile and amphibian species of Community interest were detected in 2024, with the European pond turtle the most frequently encountered at 11 points and the steppe viper, Vipera ursinii moldavica, reduced to a single observation inside a fish farm; the Dobrogean crested newt went undetected. Among birds, the reserve’s 26 colonial waterbird species formed 102 colonies holding an estimated 61,834 to 63,915 pairs—one of the highest population levels of the past five years. Medium to high water levels favored black terns, black-headed gulls, and common terns, but in Lake Sinoie, insufficient drainage flooded colonies on Ceaplace and Prundul cu Păsări Islands, shrinking nesting habitat. Predation took its own toll: brown rats caused high chick mortality in the Musura colony of Caspian gulls, and falling water levels at Sărături Murighiol let predators reach nests. The great cormorant, an exclusively piscivorous species, declined over the past two years—most likely, the authors suggest, because persistently high water limited its access to food, making it a living bioindicator of fish resources.

Mammal monitoring across the ROSCI0065 and ROSCI0066 Natura 2000 sites recorded seven of nine species of Community interest. The Eurasian otter reigned as the most frequently encountered, present at 57 of 130 surveyed locations with 175 individuals. The European mink appeared at eight locations with nine individuals—and, notably, was observed in summer for the first time, having previously been recorded only in autumn, winter, and spring. The beaver expanded to three areas, up from one in previous years. The Dobrogean hamster, a Balkan endemic restricted to Romania and Bulgaria, clung to its known stronghold at Cape Iancina, while the European ground squirrel numbered 957 individuals concentrated in northwestern steppe habitats. At sea, 46 harbor porpoises and 46 bottlenose dolphins were recorded along the coast, but three dead porpoises found on Sulina Beach pointed to a grim pattern: interviews with reserve staff indicate that two to three porpoises drown daily in fishing nets, most often during the mackerel season. The steppe polecat and marbled polecat were not observed at all.

Invasive aquatic plants added another warning sign. Two species—Vallisneria spiralis and Elodea nuttallii—were identified across the delta’s lakes through phytocoenological surveys of 93 plots and cluster analysis of vegetation data. Vallisneria spread through eight lakes, thriving especially in Furtuna, Uzlina, and Parcheș, while Elodea appeared in four lakes, with significant coverage in Lake Uzlina ranging from 0.5 to 62.5 percent. The analysis classified lake vegetation into 12 community types, from stonewort meadows to waterlily-dominated stands, providing a baseline for tracking how these invaders reshape native submerged communities under warming conditions.

The human dimension rounded out the assessment. In Jurilovca commune, a case-study community whose population has fallen 15.2 percent since 2011, questionnaires administered to 125 residents revealed a cautiously contented but anxious population: 52 percent saw their living conditions as unchanged and expected stagnation, fewer than half considered their incomes sufficient for a decent standard of living, and 67.2 percent identified job creation for young people as the single most important need. Yet tourism is booming. The Jurilovca area recorded 4,721 tourists and 10,435 overnight stays in 2024, with visitors averaging three days—drawn by the Gura Portiței beach, a new tourist port, and the cultural traditions of the Lipovan community, earning Jurilovca fourth place among Romania’s top destinations from FIJET. The Murighiol area, easier to reach, attracted 31,765 tourists for 78,500 overnight stays, its accommodation capacity more than doubling since 2019, and was certified as Tulcea County’s first official tourist resort. Together, the two areas illustrate the delta’s emerging model: tailored ecotourism that balances visitor experience with conservation and local prosperity—provided the fires, the falling water, the invasive plants, and the porpoises in the nets are managed with the same rigor that this year’s research has now established.

Subject of Research: Integrated 2024 assessment of biodiversity, reed habitat management, resource use, invasive species, and socio-economic trends in the Danube Delta Biosphere Reserve

Article Title: Status of biodiversity, reed habitats, sustainable exploitation of natural resources, invasive species, and socio-economic implications in Danube Delta Biosphere Reserve in 2024

Article References: Lupu, G., Covaliov, S., Doroftei, M., Mierlă, M., Simionov, M., Năstase, A., Cenișencu, I., Fomici, I., Chirilă, S.-D., Naum, A., Doroșencu, A., Bolboacă, L., Marinov, M., Alexe, V., Sicrieru, F., & Ene, L. (2025). Status of biodiversity, reed habitats, sustainable exploitation of natural resources, invasive species, and socio-economic implications in Danube Delta Biosphere Reserve in 2024. Scientific Annals of the Danube Delta Institute, 30, 141-162. https://doi.org/10.3897/saddi.30.163613

Image Credits: AI Generated

DOI: 10.3897/saddi.30.163613

Keywords: Danube Delta, biosphere reserve, reed beds, wildfire ecology, biodiversity monitoring, invasive species, colonial waterbirds, fisheries, Natura 2000, ecotourism, sustainable resource use, Black Sea porpoise