Impacts of climate-driven loss of giant kelp forests on local dive tourism.

BACKGROUND AND AIMS: Kelp forests provide myriad ecosystem services to human society, many of which are being eroded by climate-driven extreme events, before they have been measured. Here, we assess how dive tourism in giant kelp forests (Macrocystis pyrifera) has been impacted by marine heatwaves over three decades in southeast Tasmania. METHODS: Dive trip logs and business records were compiled from 1991-2021 from the Tasman Peninsula, Tasmania. Dives sites were georeferenced and matched to the dominant habitat (e.g. cave, wreck, sponge garden, kelp forest) for each dive site. The distribution and frequency of all dives conducted in giant kelp forests were analysed to determine changes in the gross margin of kelp forest dives over time. Dive patterns were compared to marine heatwave metrics and patterns in kelp forest cover from remote sensing data. KEY RESULTS: Giant kelp forest diving steadily increased in Tasmania between 1991-2010, before repeated marine heatwaves in 2010 and 2016 caused abrupt loss of kelp and eventual collapse of kelp forests diving by 2017. The sharp decline in dives in 2011 resulted in a 255% decrease to the gross margin for the local operator. Poleward retreat of giant kelp forests between 2001-2017 resulted in a ∼44 km increase in travel and 15% reduction in gross margin per trip, before their eventual loss from the region. CONCLUSION: Our results provide one of the first quantitative assessments of kelp forest dive tourism and highlights the fragility of these ecosystems to climate disruption. This study adds to the growing body of literature demonstrating social and economic impacts of climate extremes on kelp forest ecosystems and highlights the fundamental importance of healthy, functional kelp forests to support ecosystem services.