Enhancing kelp productivity in restoration and assisted adaptation interventions under ocean warming.

Proactive climate interventions, such as restoration and assisted adaptation, are increasingly being used to secure the persistence of populations under climate change. Such strategies are being proposed globally for declining kelp forests, yet there remains a lack of consideration for potential impacts to other key traits that underpin their immense values. Here we assess the outcome of restoration and assisted adaptation strategies on kelp productivity - a key component of kelp forest blue carbon, habitat provision and ecosystem service values. We combine empirical field data, climate projections and knowledge of underlying genomics to compare kelp productivity across restoration and assisted adaptation scenarios that are, and are not, informed by productivity-temperature relationships within source populations. Using Western Australian kelp (Ecklonia radiata) forests, we show that the productivity of restored kelp using traditional strategies for selecting source material may decline by 16-22% under mid-century ocean warming. However, drawing on knowledge of productivity-temperature relationships to strategically select individuals could enhance the productivity of restored kelp by up to 9% even under mid-century ocean warming, while simultaneously boosting thermal resilience. Optimising trait interactions when undertaking climate interventions will be key to sustaining values associated with restored kelp forests in a warming ocean.