Arctic marine forest distribution models showcase potentially severe habitat losses for cryophilic species under climate change

Abstract

The Arctic is among the fastest-warming areas of the globe. Understanding the impact of climate change on foundational Arctic marine species is needed to provide insight on ecological resilience at high latitudes. Marine forests, the underwater seascapes formed by seaweeds, are predicted to expand their ranges further north in the Arctic in a warmer climate. Here, we investigated whether northern habitat gains will compensate for losses at the southern range edge by modelling marine forest distributions according to three distribution categories: cryophilic (species restricted to the Arctic environment), cryotolerant (species with broad environmental preferences inclusive but not limited to the Arctic environment), and cryophobic (species restricted to temperate conditions) marine forests. Using stacked MaxEnt models, we predicted the current extent of suitable habitat for contemporary and future marine forests under Representative Concentration Pathway Scenarios of increasing emissions (2.6, 4.5, 6.0, and 8.5). Our analyses indicate that cryophilic marine forests are already ubiquitous in the north, and thus cannot expand their range under climate change, resulting in an overall loss of habitat due to severe southern range contractions. The extent of marine forests within the Arctic basin, however, is predicted to remain largely stable under climate change with notable exceptions in some areas, particularly in the Canadian Archipelago. Succession may occur where cryophilic and cryotolerant species are extirpated at their southern range edge, resulting in ecosystem shifts towards Librarians. WOA Institution: The University of Melbourne. Blended DEAL: CAUL 2022.temperate regimes at mid to high latitudes, though many aspects of these shifts, such as total biomass and depth range, remain to be field validated. Our results provide the first global synthesis of predicted changes to pan-Arctic coastal marine forest ecosystems under climate change and suggest ecosystem transitions are unavoidable now for some areas.

Climate‐driven shifts in kelp forest composition reduce carbon sequestration potential

“…This scenario is imaginable since L. hyperborea and L. digitata and their arctic congener Laminaria solidungula, the CSP of which is unknown, could expand their ranges poleward, potentially mitigating or overcompensating the loss of trailing edge populations. If, however, there is little to no novel arctic habitat for boreal and arctic kelps to expand into (Bringloe et al, 2022), then their global range will contract and their potential contribution to carbon sequestration diminish, mirroring the local processes we predict. This scenario is arguably more likely due to decreased salinity and increased turbidity through glacial and permafrost melt in combination with coastal erosion, and photoperiod-mediated disruption of growth and reproductive cycles in taxa adapted to lower latitudes (Bringloe et al, 2022;Martins et al, 2022).…”

“…If, however, there is little to no novel arctic habitat for boreal and arctic kelps to expand into (Bringloe et al, 2022), then their global range will contract and their potential contribution to carbon sequestration diminish, mirroring the local processes we predict. This scenario is arguably more likely due to decreased salinity and increased turbidity through glacial and permafrost melt in combination with coastal erosion, and photoperiod-mediated disruption of growth and reproductive cycles in taxa adapted to lower latitudes (Bringloe et al, 2022;Martins et al, 2022). We nevertheless emphasise that our predictions of declining CSP beyond the local scale represent a thought experiment, intended to stimulate further study and debate rather than provide firm predictions, being based as they are on finite empirical data.…”

Drivers of change in Arctic fjord socio-ecological systems: Examples from the European Arctic

“…Modelling efforts to predict the impact of potential warming and acidification scenarios by 2100 on demersal fish showed that habitat loss would be small (0 to 11%), with no appreciable difference between losses for Arctic and Arctic-boreal species (Renaud et al, 2019). The extent of marine forests (macrophytobenthos) within the Arctic basin is also predicted to remain stable (Bringloe et al, 2022), if not increase due to the changing climate (Krause-Jensen et al, 2020). The depth structure of these forests however is likely to shift to shallower waters (Bartsch et al, 2016).…”

Whole genome population structure of North Atlantic kelp confirms high‐latitude glacial refugia

“…Any patterns regarding functions specifically gained or lost in these populations are purely speculative at the moment; besides needing a more comprehensive formal analysis, the function of many genes will remain biased towards housekeeping genes or otherwise unknown for the time being. Nonetheless, functional differentiation of populations will be an exciting avenue to explore for future work, and potentially highly relevant for predicting climate change responses (Bringloe et al, 2022 ) and informing global kelp/marine forest restoration strategies (Coleman et al, 2020 ).…”

“…Global analyses highlight wide variability in kelp ecosystem trends, with local‐scale variation exceeding a small global average decline in abundances (Krumhansl et al, 2016 ). Polar regions may experience expansion of some kelp species as sea‐ice retreat opens new habitat (Bringloe et al, 2022 ; Krause‐Jensen et al, 2020 ), while in other regions, warming threatens to extirpate cold‐adapted flora in favour of warm‐adapted turf‐forming species, with accompanying changes to ecosystem function (Filbee‐Dexter & Wernberg, 2019 ; Filbee‐Dexter et al, 2020 ; Pessarrodona et al, 2021 ; Vergés et al, 2016 ). Safeguarding kelp and the accompanying services they provide will require genomic insights to unravel details about past evolution, the historical environmental processes that underpin current biogeographical patterns, dispersal and exchange of genomic information among populations, and ultimately the capacity for genetic adaptation of populations in a changing climate.…”