Inland waters are the most threatened systems globally, with dams, water extraction, pollution and invasive species as well as overharvesting of the fisheries themselves recognised as some of the biggest threats. It is imperative that the relationships we explored should be considered within freshwater and fisheries management; the protection and conservation of species diversity in freshwater systems is a win-win outcome for human food security and conservation efforts to preserve freshwater ecosystems.
At least two billion people depend directly on inland freshwaters for the provision of food. However, despite thousands of freshwater species contributing to food security, the relationship between biodiversity and yield remains poorly understood.
A new study from the University of Southampton and the International Union for Conservation of Nature (IUCN) now shows that freshwater environments with a greater fish biodiversity have higher-yielding and less variable fisheries. Using datasets from the Food and Agriculture Organization of the United Nations (FAO) and IUCN covering 100 countries in Africa, Europe and parts of Asia, the researchers have conducted the first large-scale test of the impact of freshwater biodiversity on fishery yields and the variability of yield over time.
After taking into account other factors that would be expected to have an effect on yield, such as fishing effort, the size of lakes, and temperature and precipitation, the colleagues found that fisheries with a higher number of species are also producing higher yields. In addition, they showed that in regions with a higher number of fish species there was also more stability in the year to year yield. Countries with such strong relationships were Tanzania, Democratic Republic of Congo, Vietnam and Thailand.
The results suggest that fish biodiversity may deliver benefits for human well being. As such, these results provide a powerful argument for placing biodiversity conservation centrally within fisheries management, particularly in countries with the highest yielding inland fisheries as these also tend to have high freshwater biodiversity.
Beyond food security, the researchers say that understanding the degree to which biodiversity underpins freshwater fisheries has particular policy relevance because freshwater systems are of major importance for the conservation of biodiversity. Freshwater habitats are disproportionately species rich given that they cover only 0.8% of the Earth's surface but contain 10% of all species described to date and as many as a third of all vertebrates.