Publication Abstract

Giant kelp is a ‘foundation species’: providing food, habitat and shelter to diverse marine organisms. But it is also sensitive to climate change, and recent heatwaves have caused major losses of kelp forests around the globe. Here we ask: what is the potential impact of future climate change on giant kelp habitat, both globally and at local sites where kelp forests currently provide critical habitat? For Southern California (USA) and Baja California (Mexico), Tristan da Cunha and Gough Island (South Atlantic), and eastern Tasmania (Australia), we address this question under both a ‘Low Emissions’ and ‘High Emissions’ future climate change scenario (respectively, SSP1-2.6 and SSP5-8.5). Our results indicate that globally by late-century, major shifts are to be expected in the areas with suitable giant kelp habitat, particularly under the High Emissions Scenario. For the local sites we find that while current conditions are within the species’ temperature tolerance ranges, this is not the case by late-century under the High Emissions Scenario: sea temperatures off Southern and Baja California, Tasmania, and 3 of the 4 islands of the Tristan Group are then projected to exceed these. Off Baja California, giant kelp forests are projected to be imperilled even under the Low Emissions Scenario. Conditions around Gough Island (the southernmost island of the Tristan Group) are, under all scenarios, projected to remain within the species’ tolerance ranges. This study underlines the importance of the Tristan Archipelago as a potential refugium for giant kelp into the future, as climate change makes many other parts of the globe less and less suitable for giant kelp. It also suggests that climate change may result in widespread losses of present-day giant kelp forests, particularly at the equatorward parts of the distribution range – which is critical given the many associated species dependent on giant kelp.

Georg H. Engelhard^*, James B. Bell^* and Elena Couce*