Beneath the surface of the world’s cooler coastal waters, a forest grows. Kelp — the largest and fastest-growing of all algae, capable of extending six inches in a single day under ideal conditions — creates three-dimensional underwater habitats of extraordinary complexity and productivity. A single hectare of healthy kelp forest supports more species than a comparable area of tropical rainforest, providing shelter, food, and nursery conditions for fish, invertebrates, marine mammals, and seabirds in a vertical ecosystem that stretches from the seafloor to the sunlit surface.

Beyond their ecological function, kelp forests represent one of the most promising natural mechanisms for carbon sequestration that the ocean provides. As kelp grows, it absorbs carbon dioxide through photosynthesis. When it dies, fragments sink into the deep ocean, carrying their stored carbon with them into storage that can persist for centuries. Scientists are now investigating whether the deliberate cultivation and restoration of kelp forests at scale could contribute meaningfully to climate stabilisation — a genuinely hopeful finding in a field that too rarely produces them.

The threat to existing kelp forests is real and largely driven by the same forces affecting terrestrial ecosystems: warming seas, pollution, and the disruption of the predator relationships — particularly the decline of sea otters — that keep the grazing urchin populations that consume kelp in check. Restoration projects are underway on multiple coastlines, with early results suggesting that with sufficient protection and the return of keystone predators, these forests can recover with extraordinary speed.