Potential negative effects of ocean afforestation on offshore ecosystems

Philip W. Boyd, Lennart T. Bach, Catriona L. Hurd, Ellie Paine, John A. Raven, Veronica Tamsitt

Research output: Contribution to journalReview articlepeer-review

27 Citations (Scopus)


Our scientific understanding of climate change makes clear the necessity for both emission reduction and carbon dioxide removal (CDR). The ocean with its large surface area, great depths and long coastlines is central to developing CDR approaches commensurate with the scale needed to limit warming to below 2 °C. Many proposed marine CDR approaches rely on spatial upscaling along with enhancement and/or acceleration of the rates of naturally occurring processes. One such approach is ‘ocean afforestation’, which involves offshore transport and concurrent growth of nearshore macroalgae (seaweed), followed by their export into the deep ocean. The purposeful occupation for months of open ocean waters by macroalgae, which do not naturally occur there, will probably affect offshore ecosystems through a range of biological threats, including altered ocean chemistry and changed microbial physiology and ecology. Here, we present model simulations of ocean afforestation and link these to lessons from other examples of offshore dispersal, including rafting plastic debris, and discuss the ramifications for offshore ecosystems. We explore what additional metrics are required to assess the ecological implications of this proposed CDR. In our opinion, these ecological metrics must have equal weight to CDR capacity in the development of initial trials, pilot studies and potential licensing.

Original languageEnglish
Pages (from-to)675–683
Number of pages9
JournalNature Ecology and Evolution
Issue number6
Publication statusPublished - Jun 2022


Dive into the research topics of 'Potential negative effects of ocean afforestation on offshore ecosystems'. Together they form a unique fingerprint.

Cite this