Biodiversity consequences of replacing animal protein from capture fisheries with animal protein from agriculture

Abstract

Replacing animal protein sourced from marine capture fisheries with animal protein from agriculture will likely increase the threats to biodiversity given current human diets. Approximately half the Earth’s arable land surface has been converted from natural habitats to food production which has been identified as a key driver of biodiversity loss in terrestrial ecosystems, as have fisheries in aquatic environments. Reductions in seafood production arising from major reductions in access to fishery resources and consumption would affect the demand for agricultural land. Replacing all animal protein from marine fisheries could require almost an additional 5 million km2 of land - larger than the extent of intact rain forest in Brazil - if replaced by the current proportional combination of livestock and poultry. Replacing all fish in aquaculture diets would result in the need for over 47,000 km2 of new land converted to agricultural production. Concomitantly, data show that terrestrial and freshwater species are more likely to be threatened with extinction than marine species and that agriculture is the dominant cause of these extinctions. This paper suggests that extinction risks per million tonnes of animal protein produced are 2.6 times higher for agriculture than marine capture fisheries. Agriculture is the main driver of extinctions because it is predicated on the conversion of complex, natural ecosystem structures to simple, human-dominated systems, whereas well-managed fisheries seek to work within natural ecosystem structure and function. Available evidence suggests that relying even more on land-based animal foods by replacing marine with terrestrial protein sources may cause more biodiversity loss, not less. Policy makers need to consider the implications of restricting the use of fishery resources on planetary biodiversity beyond measures aimed at attaining sustainable use.