New research in Frontiers in Systems Biology argues that land ecosystems are approaching functional saturation, meaning they can no longer absorb additional pressure or provide the same carbon storage and ecological functions. The review finds that 75 percent of land already shows measurable human pressure, and 24 percent of terrestrial ecosystems became more modified between 1990 and 2020. At the same time, local species richness has fallen by 13.6 percent on average in converted or degraded areas. The paper also pushes back on the idea that seaweed can replace what is being lost. While macroalgae can be highly productive, much of that biomass is quickly remineralized in the ocean, so it does not lock carbon away for the long term the way forests and soils do. Marine heatwaves and trophic shifts have already wiped out large kelp forests in places like northern California and Tasmania. For carbon markets and climate planning, the takeaway is that ocean carbon sinks are not a simple substitute for terrestrial protection. Projects that treat seaweed as a direct offset need to show where the biomass ends up and how long the carbon stays stored.
