Abstract Introduction Global degradation of natural ecosystems demands urgent action to stem losses and, where possible, identify opportunities for scalable restoration. Giant kelp forests, formed by Macrocystis pyrifera , have declined by ~95% along eastern Tasmania in recent decades, with limited propagule supply constraining recovery. Direct interventions to restore giant kelp have been attempted here since the 1990s, although attempts have been constrained by methodological and logistical limitations, underscoring the challenges of scaling restoration in subtidal marine environments. Objectives This study details the methodological development of a rapid and forest‐scale in situ approach to reseed threatened giant kelp forests that have declined. Methods Here we provide an overview of the “holdfast‐graft” method, as a forest‐scale technique to reseed reefs with mass‐produced hatchery‐reared giant kelp sporophytes seeded to twine. Taking inspiration from true grafting of terrestrial vascular plants, we apply an analogous approach of effectively binding the equivalent of a “scion” (i.e., hatchery‐reared giant kelp sporophytes) to a “root‐stock” (i.e., holdfast stubs of other common seaweed species). By comparing rates of kelp sporophyte attachment between twine seeded to holdfast stubs and directly to boulders, as well as seeded gravel, we evaluate the effectiveness of this method. Results We reveal a 40‐fold higher rate of kelp sporophyte attachment to the reef when twine was wrapped around holdfast stubs compared to twine wrapped over boulders or deployments of hatchery seeded‐gravel methods. Refinement of the “holdfast‐graft” method led to targeted wrapping of short 60‐cm seeded twine lengths directly to individual holdfast stubs, enabling rapid and forest‐scalable deployment by divers. Conclusions The “holdfast‐graft” method represents an efficient and scalable method for out‐planting giant kelp.
Ling et al. (Tue,) studied this question.