NatureMetrics worked with Kelp Blue and the Kelp Forest Foundation to evaluate the biodiversity impacts of an offshore giant kelp farming pilot off the coast of Namibia. Over two years of monthly eDNA sampling, the project built a detailed biodiversity baseline and tracked changes as the pilot farm developed. The data is helping Kelp Blue scale responsibly and supporting the development of a universal kelp ecosystem health metric.

Large-scale offshore kelp farming holds exciting promise for boosting biodiversity, creating sustainable jobs and products, and sequestering carbon. Before scaling up, though, Kelp Blue needed to demonstrate these benefits and investigate any negative impacts. Key unknowns included:

• How wild and farmed kelp would interact
• The risk of unintentionally introducing alien species

Robust, long-term biodiversity monitoring was essential to answer these questions as the pilot farm developed.

NatureMetrics trained the Kelp Blue team and supplied eDNA kits. Kelp Blue staff and Namibian postgraduate students then collected water and sediment samples every month for two years, in and around the pilot farm and at control sites. The samples were analysed across taxonomic groups, from vertebrates to microorganisms. The result is a robust biodiversity baseline for monitoring how communities change as the farm matures.

The surveys detected 25 fish species, including:

• The ocean sunfish (Mola mola), listed as Vulnerable on the IUCN Red List
• The endemic Cape elephantfish, a species of chimaera

Other vertebrates detected included:

• Seabirds: Endangered African penguins and cormorants
• Marine mammals: Humpback whales, Heaviside’s dolphins and Cape fur seals

The invertebrates were just as diverse, from rock lobsters, urchins and sea stars to jellyfish and mussels. Ecological analysis is already revealing seasonal and spatial patterns in biodiversity.

• Scaling responsibly: The robust baseline helps Kelp Blue scale cultivation responsibly.
• A global health metric: The data will support the development of a universal kelp ecosystem health metric to inform kelp conservation worldwide.
• New investment: Quantified biodiversity gains can unlock pioneering biodiversity credit finance, driving investment in seaweed ecosystems and sustainable blue economies.
• Local capacity: Training local teams in eDNA sampling has strengthened Namibia’s long-term capacity for science-based marine monitoring.
• A fuller picture: The eDNA data is being combined with many other datasets to build a multidimensional picture of how the ecosystem changes as cultivated kelp matures.