Türkiye’s First National Census Counts 271 Established Non-Native Species

Türkiye has taken its first comprehensive national inventory of established non-native species, and the results reveal a country quietly transformed by biological invasions. A research team has documented 271 non-native species with self-sustaining populations in the wild, drawn from 160 families spanning 25 classes and 11 phyla. The findings, published in the journal NeoBiota, mark a turning point for a nation whose position at the crossroads of Europe, Asia, and the Middle East makes it both a major recipient and a potential source of invasive species moving across borders.

The new assessment deliberately departs from earlier approaches. Türkiye’s only previous national list, published in 2020, tallied 872 non-native species, but it included every species ever recorded in the country regardless of whether those populations had actually taken hold. The distinction matters enormously for management. A species that has been introduced but has not formed a self-sustaining population poses uncertain and often negligible risk, whereas an established species is far more likely to spread and exert ecological or economic impacts. By filtering out native, cryptogenic, and non-established records, the researchers reduced the national total to roughly a quarter of the earlier figure, producing a dataset that reflects genuine biological reality rather than a catalogue of historical sightings.

The taxonomic composition of the list is strikingly lopsided. Marine species dominate with 198 of the 271 established non-natives, followed by 42 terrestrial species, 27 freshwater species, three species occupying both terrestrial and freshwater habitats, and one freshwater-marine species. Among phyla, Chordata leads with 111 species, followed by Mollusca with 67 and Arthropoda with 52. The most species-rich class is Actinopterygii, the ray-finned fishes, with 100 species, ahead of Gastropoda with 48 and Malacostraca with 26. At the family level, ants of the Formicidae top the ranking with 14 established species, followed by the small parasitic snails of Pyramidellidae with nine, penaeid shrimp with eight, pufferfishes of Tetraodontidae with seven, and cardinalfishes of Apogonidae with five.

This marine dominance is not accidental. Türkiye’s extensive coastline along the Black, Aegean, and Mediterranean Seas provides a vast array of habitats, and these waters are under intense pressure from maritime traffic, aquaculture, and fisheries, all well-documented pathways for species introductions. The prominence of fish, snails, and crustaceans in the list mirrors the constant movement of ships, ballast water discharge, and farmed organisms through Turkish waters. By contrast, the comparatively low numbers of terrestrial and freshwater species likely reflect a combination of genuine ecological constraints and significant gaps in research and reporting. Türkiye has a long history of plant introductions for agriculture and horticulture, but the relatively small number of vascular plants in the dataset probably signals under-surveying rather than true absence.

The geographic pattern of establishment follows the pulse of human activity. Drawing on more than 10,000 occurrence records from the Global Biodiversity Information Facility, the researchers found that established non-native species concentrate in the western part of the country and decline eastwards. The provinces of Kayseri and Muğla each host 37 established non-native species, with Antalya close behind at 34. Urban and coastal areas, with their dense populations, robust trade networks, and well-developed infrastructure, offer multiple routes for species introductions, including maritime transport, the ornamental plant and pet trades, and ballast water discharge. Remote inland and mountainous regions show far fewer invasions, consistent with global patterns linking invasion intensity to human footprint.

Notably, a handful of birds dominate the occurrence data. The rose-ringed parakeet alone accounts for 5,080 records, or 49.3 percent of the total, with the Alexandrine parakeet contributing 2,166 records and the common myna another 879. Together these three species represent nearly 79 percent of all GBIF records for established non-native species in Türkiye, a reminder that detection effort is heavily skewed toward conspicuous, well-studied organisms in accessible locations. The apparent scarcity of non-natives in remote regions may therefore partly reflect a lack of surveying rather than a genuine absence of invasion.

Tracing the geographic origins of 256 established species, the study found that the Indo-Malayan realm is the dominant source, contributing 116 species or 45.3 percent of the total. Australasia follows with 52 species, then the Palearctic with 39, the Afrotropical realm with 17, the Nearctic with 16, and the Neotropical with six. This pattern underscores Türkiye’s role as a hub in global invasion networks, receiving organisms from across the tropical and subtropical world, largely through trade and transport corridors that connect it to Asia, Africa, and beyond.

Perhaps the most sobering finding concerns what remains unknown. Only 47 of the 271 established species, or 17 percent, have documented ecological or economic impacts within Türkiye, although the proportion rises to 41 percent when impacts reported anywhere in the world are considered. Among species with known impacts, ecological and environmental effects are the most frequently cited, followed by economic and socio-cultural harms. Competition is the most commonly reported impact mechanism, ahead of predation and rapid growth, with habitat alteration and disease transmission also recorded. The reporting gap is uneven across environments: freshwater species show a documented impact ratio of 38 percent, nearly double the 19 percent for marine species, while among phyla, Tracheophyta lead at 28 percent and Chordata trail at 14 percent. This bias toward well-known invaders means many threats may be growing silently, undetected until they become costly or irreversible.

Risk screening adds a further layer of urgency. Using the Aquatic Species Invasiveness Screening Kit, a decision-support tool comprising 55 questions covering basic and climate-change risk assessments, the researchers compiled results for 62 established species, roughly 23 percent of the national total. Under current climate conditions, 4.8 percent of screened species posed a very high risk of invasiveness, 40.3 percent a high risk, and 53.2 percent a medium risk. Under predicted climate change conditions, the picture darkens dramatically: the share of very high-risk species jumps to 21 percent, meaning that more than 60 percent of screened species fall into the high or very high risk categories as warming shifts the Turkish climate. Warming waters may allow tropical invaders arriving through the Suez Canal and shipping lanes to establish and spread more readily, turning today’s medium-risk species into tomorrow’s crises.

The study’s authors argue that this inventory provides a critical foundation for strengthening biosecurity policy, guiding targeted monitoring, and coordinating management responses at local, national, and international scales. They call for systematic impact assessments targeting under-studied groups and habitats, expanded screening of terrestrial animals and plants using recently developed tools, and a prioritization framework that weighs both risk scores and impact potential to allocate limited conservation resources where they matter most. Given that established populations in one region can serve as stepping stones for secondary spread within the country, through activities such as recreational angling and aquaculture, prevention at points of entry must be paired with vigilance against internal translocations. For a country whose rich biodiversity underpins agriculture, fisheries, and tourism, the message of this first national census is clear: the window for proactive management is open now, but it will not remain so indefinitely.

Subject of Research: National assessment of established non-native species in Türkiye

Article Title: The first national assessment of established non-native species in Türkiye

Article References: Tarkan, A. S., Yapıcı, S., Kurtul, I., Błońska, D., Vilizzi, L., Baş Sermenli, H., Farooq, S., Aldemir, C., Uçma Uysal, T., Giannetto, D., Bilge, G., Çiftçioğlu, M., Najafi-Majd, E., Aktay-Sözüer, L., Kaya, C., Bayçelebi, E., Aydın, İ., Haubrock, P. J., Briski, E., & Soto, I. (2026). The first national assessment of established non-native species in Türkiye. NeoBiota, 105, 297-317. https://doi.org/10.3897/neobiota.105.176362

Image Credits: AI Generated

DOI: 10.3897/neobiota.105.176362

Keywords: invasive species, non-native species, Türkiye, biodiversity, biosecurity, marine invasions, freshwater ecosystems, climate change, risk assessment, biological invasions, species monitoring, NeoBiota