Due to high ecological risk and questionable storage durability, work related to which historical concept is now primarily focused on modeling failure rather than scaling deployment?

Answer

Ocean fertilization (adding nutrients like iron).

Historical methods involving the addition of nutrients to stimulate plankton blooms are currently met with caution, meaning current research on them largely focuses on assessing potential risks and failure modes.

Due to high ecological risk and questionable storage durability, work related to which historical concept is now primarily focused on modeling failure rather than scaling deployment?
technologyoceanclimateremovalcarbon