ANSWER 1

In short: yes, but they arrive and spread by different means, and the invasive species with most to gain from warming are probably ones Tasmania does not have (yet).

Range extenders and invasive species are both responding to ocean warming. However, they reach Tasmania by different routes, and that decides what can be done about them. It also points to where the risk sits going forward: warm-affinity species, arriving by ship from mainland ports or by current from the north, with warm summers and marine heatwaves as the moments they gain a foothold.

Range extenders are native Australian species, mostly from New South Wales and Victoria, tracking warming water south. Waters around southern Australia are warming at two to four times the global average, and the East Australian Current pushed roughly 350 km further south over the second half of last century (Ridgway 2007). The long-spined sea urchin is the clearest Tasmanian example. Its larvae are carried south on the current, and they fail to develop below about 12 °C, so warmer winters on the east coast have let it establish and breed here (Ling et al. 2008, 2009). It is one of 198 Australian marine species with a documented distribution shift, 87% of them poleward (Gervais et al. 2021).

By contrast, invasive species are introduced from outside their native range, mostly by ship. The Northern Pacific seastar was first collected in southeast Tasmania in 1986, probably as larvae in ballast water. The European shore crab was first recorded in Port Phillip Bay in 1900, again probably by shipping.

What warming changes is whether an invasive species establishes and spreads after arrival. In New England, warmer winters let invasive sea squirts start recruiting earlier and recruit more strongly the following summer, while the natives gained no such head start (Stachowicz et al. 2002). Across marine systems, introduced species spread faster than native species shifting range with climate. However, where impacts have been measured (still rarely for range shifters), the two groups have effects of similar size and direction, mostly negative (Sorte et al. 2010).

For the invasive species Tasmania already has, warming is not obviously assisting their spread because they are primarily cold-water species from the North Pacific and North Atlantic. Modelling for the seastar predicts its Australian range will contract as waters warm, with conditions improving further south (Byrne et al. 2016). For the shore crab, suitable habitat in Australia is projected to shrink overall, with Tasmania and Victoria among the areas that stay suitable (Adamu & Hussaini 2025).

The Japanese kelp Undaria is an exception, and it shows how warming and disturbance interact. It establishes at high density where native canopy has been cleared. After a dieback of native crayweed on the east coast in 2001, Undaria reached high densities in the affected areas but stayed rare or absent where the canopy was intact (Valentine & Johnson 2004). It also persists on urchin barrens, where sediment and slow recovery of native canopy matter as much as grazing (Valentine & Johnson 2005). It follows that warming helps existing invasive species indirectly: a heatwave, disease or grazing that strips native canopy opens space for them. The 2015/16 Tasman Sea heatwave brought disease in farmed shellfish, deaths of wild molluscs and out-of-range sightings (Oliver et al. 2017), and events like it are becoming more likely.

Two things follow for management. First, biosecurity (vessel hygiene, port surveillance, early detection) works on invasive species. It does nothing for native range extenders, so the two lists deserve separate treatment even where the responses overlap. The FAO’s 2024 review of fisheries responses to invasive species uses Tasmania’s urchin as an ‘invasive species’ case study (Azzurro et al. 2024). That is fair for the responses it covers, since harvest, market development and spatial control apply to both groups. However, the label blurs the distinction that matters here: no port measure would have kept a native Australian species out of Tasmania.

Second, sightings from fishers and divers, beachcombers and other potential citizen scientists (i.e. through Redmap https://www.redmap.org.au/), remain one of the better early-warning tools for both groups. Across 2013–2022 those platforms recorded 73 species beyond their known range limits, 76 range extensions in all and 17 of them in Tasmania, and 91% had not been reported in the scientific literature from any other data (Wolfe et al. 2025). For warm-water newcomers, a citizen scientist’s photo is often the first record.

References
Adamu, H.O. & Hussaini, R.O. (2025). Maxent modelling reveals suitable habitat remains unchanged for Carcinus maenas in Australia. Australasian Journal of Environmental Management, 32, 193–204. https://doi.org/10.1080/14486563.2024.2409747

Azzurro, E., Bahri, T., Valbo-Jørgensen, J., Ma, X., Strafella, P. & Vasconcellos, M. (eds) (2024). Fisheries responses to invasive species in a changing climate: Lessons learned from case studies. FAO Fisheries and Aquaculture Technical Paper No. 704. Rome: FAO. https://doi.org/10.4060/cd1400en

Byrne, M., Gall, M., Wolfe, K. & Agüera, A. (2016). From pole to pole: the potential for the Arctic seastar Asterias amurensis to invade a warming Southern Ocean. Global Change Biology, 22, 3874–3887. https://doi.org/10.1111/gcb.13304

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Ling, S.D., Johnson, C.R., Frusher, S. & King, C.K. (2008). Reproductive potential of a marine ecosystem engineer at the edge of a newly expanded range. Global Change Biology, 14, 907–915. https://doi.org/10.1111/j.1365-2486.2008.01543.x

Ling, S.D., Johnson, C.R., Ridgway, K., Hobday, A.J. & Haddon, M. (2009). Climate-driven range extension of a sea urchin: inferring future trends by analysis of recent population dynamics. Global Change Biology, 15, 719–731. https://doi.org/10.1111/j.1365-2486.2008.01734.x

Oliver, E.C.J., Benthuysen, J.A., Bindoff, N.L., Hobday, A.J., Holbrook, N.J., Mundy, C.N. & Perkins-Kirkpatrick, S.E. (2017). The unprecedented 2015/16 Tasman Sea marine heatwave. Nature Communications, 8, 16101. https://doi.org/10.1038/ncomms16101

Ridgway, K.R. (2007). Long-term trend and decadal variability of the southward penetration of the East Australian Current. Geophysical Research Letters, 34, L13613. https://doi.org/10.1029/2007GL030393

Sorte, C.J.B., Williams, S.L. & Carlton, J.T. (2010). Marine range shifts and species introductions: comparative spread rates and community impacts. Global Ecology and Biogeography, 19, 303–316. https://doi.org/10.1111/j.1466-8238.2009.00519.x

Stachowicz, J.J., Terwin, J.R., Whitlatch, R.B. & Osman, R.W. (2002). Linking climate change and biological invasions: ocean warming facilitates nonindigenous species invasions. Proceedings of the National Academy of Sciences of the United States of America, 99, 15497–15500. https://doi.org/10.1073/pnas.242437499

Valentine, J.P. & Johnson, C.R. (2004). Establishment of the introduced kelp Undaria pinnatifida following dieback of the native macroalga Phyllospora comosa in Tasmania, Australia. Marine and Freshwater Research, 55, 223–230. https://doi.org/10.1071/MF03048

Valentine, J.P. & Johnson, C.R. (2005). Persistence of the exotic kelp Undaria pinnatifida does not depend on sea urchin grazing. Marine Ecology Progress Series, 285, 43–55. https://doi.org/10.3354/meps285043

Wolfe, B.W., Champion, C., Gaston, T., Brown, J., Coleman, M.A., Davis, T.R., Frijlink, S., Hatley, T., Heather, F.J., Jackson, G., Keane, J.P., Kjeldsen, S., McGrouther, M., Moltschaniwskyj, N., Moore, G., Pearn, R., Rodda, K.R., Strugnell, J., Stuart-Smith, J., Turnbull, J.W., Watson, S.-A. & Pecl, G.T. (2025). Continental-scale assessment of climate-driven marine species range extensions using a decade of citizen science data. Diversity and Distributions, 31, e70022. https://doi.org/10.1111/ddi.70022