Refining and expanding global climate change scenarios in the sea: Poleward creep complexities, range termini, and setbacks and surges

Abstract

Aim: Invasion dynamics are sensitive to global-scale changes. New marine invasions have been recorded in dramatically increasing numbers along the world's coasts, due, in part, to the global warming of the oceans and the ability of many successful invasive marine species to tolerate a broader thermal range than native species. As a response to ocean warming, a poleward movement of numerous species has been observed in many biogeographic regions. Our aim was to explore several poorly recognized and thus rarely studied aspects of ocean climate change scenarios in order to advance our understanding of finer-grained aspects of poleward movements. Location: Global.Methods: Three scenarios are investigated in our framework: (1) the existence of networks of complex intraregional origins, routes and destinations of poleward-moving species, (2) the existence of impenetrable termini where no further expansion is possible, linked to potential outflow corridors, and (3) the interplay of a warming ocean with aperiodic cold episodes.Results: Poleward advances consist of distinct regional networks of origins, routes and destinations, largely undefined in most areas, linked in turn to the potential existence of endpoints where no further expansion may be possible without escape routes and/ or human-mediated assistance. The interaction of aperiodic cooling periods may result in temporary setbacks or rate reductions in range expansions. Main conclusions:The recognition of potentially complex origin-route-destination networks may significantly advance our predictive capacity of both future invasions and range expansions and potential impacts. Thus, specific focus on high-profile donor region species pools linked to established vector routes may yield far more robust management scenarios than currently in place. While it is probable that the frequency of climate-mediated surges (inevitable warming) and setbacks (cooling periods) of species invasions will increase over time, the net outcome is likely to be positive, resulting in an inexorable poleward expansion of thousands of species.

Predicting global ascidian invasions

“…Most marine invasions have resulted of conditions for species transport and establishment, and we know that those conditions are changing fast in response to both climate change (IPCC, ) and increasing global commerce. The increase in water temperature already favours the spread of tropical species towards the poles (e.g., see Canning‐Clode & Carlton, ), and the increase in ship numbers and in new routes will increase propagule pressure and probability of establishment. Thus, a necessary approach for the future is to update the models every 10 years at least.…”

Expansion of an introduced sea anemone population, and its associations with native species in a tropical marine lake (Jellyfish Lake, Palau)

“…This type of rapid expansion and dominance has become the archetypal 'invasion', as in algal invasions of Caulerpa racemosa in Cyprus and Undaria pinnatifida in New Zealand (Schaffelke andHewitt 2007, Galil 2007). However, by 2012, the introduced sea anemone reached its lowest abundance since establishment, which may be part of boom-bust or 'surges and setbacks' cycles in which population explosions are followed by decline (Simberloff andGibbons 2004, Canning-Clode andCarlton 2017). Though some significant negative correlations between the abundance of the introduced sea anemone and certain native species were identified, the trajectory for the impact of E. pallida on the native community is still unfurling through the interplay of a range of biotic and abiotic factors.…”

An artificial habitat facilitates a climate-mediated range expansion into a suboptimal novel ecosystem

“…Thus, we retrieved 1988–2018 temperature data from the University of Georgia Marine Institute on Sapelo Island, Georgia, located only 10 km from the Sapelo Island site. To determine if the winter of 2017–2018 truly represented an extreme cold event, we adapted the definition of an extreme event from Canning-Clode and Carlton [22] as a period of five consecutive days with the minimum temperature below the 10 th percentile of daily minimum temperatures drawn from a baseline of the past 30 winters (December-March). We also used the dataset to determine if there were any particularly extreme events where the minimum temperature remained below the 5 th percentile for five consecutive days.…”

“…The geographic range of poleward-expanding species is often limited by winter temperatures [1,4]. While a species may expand northward during warmer months, winter die-backs are common at the range-edge, leading to a characteristic pattern of surges and setbacks [3,21,22]. For such species, habitats that provide thermal refuge may be critical to their ability to continue to expand poleward and have even been shown to nearly eliminate latitudinal gradients in thermal stress [23].…”