Seamounts and knolls together cover approximately 20.5% of the global seafloor — rising to roughly 23% within the high seas (ABNJ), where these features are proportionally more common than within national waters. This is a combined estimate: seamounts (≥ 1,000 m relief) plus knolls (~500–1,000 m relief), drawn from published global seamount feature inventories.
This briefing outlines the methodology used to establish these figures.
Download the full science brief for policymakers, “Seamounts and Knolls cover 21% of the global seafloor”, here.
More information on the UN Bottom Fisheries Review and a complete Advocacy Pack for policymakers is available here.