The combined impact of fisheries and climate change on future carbon sequestration by oceanic macrofauna

Although the role of marine macrofauna in the ocean carbon cycle is increasingly understood, the cumulative impacts of fisheries and climate change on this pathway remain overlooked. Here, using a marine ecosystem model, we estimate that each degree of warming reduces macrofauna biomass and carbon export by 4.2% and 2.46%, respectively. Under a high emission scenario (SSP 5-8.5), this translates to a 13.5% ± 6.6% decline in export by 2100, relative to the 1990s. Fishing further amplifies this reduction by up to 56.7% ± 16.3%, creating a sequestration deficit of 14.6 ± 10.3 GtC by 2100. On average, a 1% biomass loss from fishing results in a 0.8% decline in carbon export. However, sequestration durability (~600 years) remains unaffected. While measures restoring commercial macrofaunal biomass could yield carbon benefits comparable to mangrove restoration, multiple uncertainties limit their inclusion in the Nature-based Climate Solution portfolio, highlighting the need for further research.