Climate change exacerbates nutrient disparities from seafood

Seafood provides essential micronutrients, particularly in low-income countries where it is an affordable source of iron and zinc, vital for development. Globally, fish consumption is promoted for its health benefits. However, marine fisheries production peaked in the 1990s, with overexploitation affecting a significant portion of fish stocks. Aquaculture has expanded rapidly to meet demand, but climate change impacts both fisheries and mariculture through altered species distributions, productivity, and increased disease risks. The impact of these historical changes and future climate change on the availability of important nutrients for human consumption is unclear, making this research critical for mitigating climate risks to food security and human health.

Existing literature highlights the importance of seafood as a source of essential micronutrients, particularly in low-income countries where dietary deficiencies are prevalent. Studies have shown the health benefits of fish consumption, including protection against heart disease and type 2 diabetes. However, research on the historical trends in seafood nutrient production and the projected impacts of climate change on nutrient availability is limited. This study addresses this gap by combining reconstructed fisheries databases and predictive models to assess nutrient availability from both fisheries and mariculture, considering past trends and future climate change scenarios.

This study quantifies past and future nutrient availability from global fisheries and mariculture, focusing on calcium, iron, omega-3 fatty acids, and protein. Global databases of fisheries catches and mariculture production were combined with taxa-specific nutrient content estimates. Projections from climate, fisheries, and mariculture production models were integrated to assess the impacts of climate change and mitigation scenarios. Two Earth system models (GFDL-ESM4 and IPSL-CM6A-LR) under two emissions scenarios (SSP1-2.6 and SSP5-8.5) were used. Edible portion estimates were derived from various sources, accounting for variation across species and geography. Nutrient content was estimated using a trait-based Bayesian model for fish and by assigning values based on available data for invertebrates. The Dynamic Bioclimate Envelope Model (DBEM) projected changes in potential catches, and the Global Mariculture Production Model (GOMAP) projected mariculture production potential. Changes in nutrient availability were calculated by multiplying projected production changes with nutrient content estimates. Monte Carlo simulations accounted for uncertainties in nutrient content and edible portion estimations. Coastal population data were used to assess per capita nutrient availability changes.

Globally, the total availability of the four key nutrients increased until the early 1990s before declining. This decline is largely attributed to decreased finfish fisheries production and the diversion of a substantial portion of catches for fishmeal and fish oil. Focusing on nutrients available for direct human consumption (excluding those used for fishmeal and oil), iron, calcium, and omega-3 availability increased, while protein stagnated. Invertebrate fisheries and mariculture showed the largest increases, but these were insufficient to offset the overall decline due to their smaller contribution to total production. Climate change projections indicate decreases in nutrient availability from fisheries across all four nutrients by 2050 and 2100, with larger declines under the high-emission scenario (SSP5-8.5). Minerals (calcium and iron) show the largest projected declines, particularly in the tropics. The relative declines in mineral micronutrients from fisheries are largely due to projected decreases in pelagic fish catch potential. Mariculture is projected to increase calcium and protein availability by 2050 but may decrease omega-3 fatty acids. The projected increases in mariculture are insufficient to compensate for the losses from fisheries. Regional disparities are significant, with tropical regions experiencing much larger declines than extra-tropical regions. These declines are particularly concerning for low-income tropical countries, which are highly dependent on seafood-sourced nutrients and also face population growth. Nutrient availability declines scale linearly with global warming levels, with low-income countries experiencing a much faster rate of decline than the global average.

The findings reveal that past nutrient availability from capture fisheries has stagnated and future availability faces significant challenges from climate change, particularly impacting low-income tropical countries heavily reliant on seafood. The study highlights the need for effective mitigation strategies to limit global warming and protect vulnerable populations. Reducing the use of fishmeal and fish oil in aquaculture, adapting fisheries management to account for species range shifts, and prioritizing sustainable aquaculture of nutritious species can help mitigate the negative impacts. The potential for mariculture to compensate for fisheries losses is limited, and strategies for increased sustainable mariculture should be further investigated. International cooperation is crucial to address the inequities in nutrient availability under climate change.

This study demonstrates the substantial and unequal impacts of climate change on seafood-sourced nutrient availability, emphasizing the urgent need for global mitigation efforts to limit warming. Strategies such as sustainable aquaculture development, reduction in fishmeal and oil usage, and nutrition-sensitive fisheries management are crucial for ensuring food security and nutritional equity. Future research should further investigate sustainable and climate-resilient aquaculture practices, explore alternative sustainable feed sources, and refine models to better capture the complex interactions between climate change, fisheries, mariculture, and nutrient availability.

The study relies on model projections, which involve inherent uncertainties. The nutrient content estimations may also contain uncertainties due to limited data on some species. The study primarily focuses on established mariculture production areas, neglecting potential future expansion in other regions. The model does not fully capture all aspects of complex ecological and socioeconomic factors, such as potential technological advances in aquaculture and changes in consumer preferences. Future studies could incorporate additional species, improve parameterizations of existing models, and further explore the role of regional and international trade in shaping nutrient availability.