Ecological restoration in the deep sea: Desiderata

TLDR

Deep‑sea industrialization is accelerating, prompting governance frameworks and scientific advances, yet ecological restoration remains largely absent from stewardship discussions. The paper aims to identify what is needed to minimize or repair deep‑sea damage and to explore how past harm can be rectified. It develops a restoration discourse and guidance by presenting two deep‑sea case studies—stony corals on the Darwin Mounds and hydrothermal vents in Manus Basin—contrasted with saltmarsh restoration, and evaluates socio‑economic, ecological, and technological decision parameters. Estimated costs for deep‑sea restoration scenarios are two to three orders of magnitude higher per hectare than those for shallow‑water marine restoration.

Abstract

An era of expanding deep-ocean industrialization is before us, with policy makers establishing governance frameworks for sustainable management of deep-sea resources while scientists learn more about the ecological structure and functioning of the largest biome on the planet. Missing from discussion of the stewardship of the deep ocean is ecological restoration. If existing activities in the deep sea continue or are expanded and new deep-ocean industries are developed, there is need to consider what is required to minimize or repair resulting damages to the deep-sea environment. In addition, thought should be given as to how any past damage can be rectified. This paper develops the discourse on deep-sea restoration and offers guidance on planning and implementing ecological restoration projects for deep-sea ecosystems that are already, or are at threat of becoming, degraded, damaged or destroyed. Two deep-sea restoration case studies or scenarios are described (deep-sea stony corals on the Darwin Mounds off the west coast of Scotland, deep-sea hydrothermal vents in Manus Basin, Papua New Guinea) and are contrasted with on-going saltmarsh restoration in San Francisco Bay. For these case studies, a set of socio-economic, ecological, and technological decision parameters that might favor (or not) their restoration are examined. Costs for hypothetical restoration scenarios in the deep sea are estimated and first indications suggest they may be two to three orders of magnitude greater per hectare than costs for restoration efforts in shallow-water marine systems.