2023 Author: Bryan Walter | [email protected]. Last modified: 2023-05-21 22:24
An assessment of the biodiversity of freshwater fish in 2,456 river basins showed that in half of them taxonomic, functional and phylogenetic diversity is deeply influenced by anthropogenic impact. Such rivers are found mainly in the temperate zone of the northern hemisphere, while the rivers of Australia and the African tropics, on the contrary, have suffered the least. The article was published in the journal Science.
Rivers and lakes occupy only about a percent of the planet's area, but they serve as habitat for 18 thousand species of freshwater fish, that is, a quarter of the planet's vertebrates. These species support the sustainability of ecosystems: they produce biomass, regulate food webs and provide the cycle of nutrients. They are also important for people, because in a number of regions of the world it is river fish that plays the role of the main food resource. Over the centuries, the biodiversity of freshwater ecosystems has been declining due to anthropogenic activities. Humans changed land use and flow patterns in river basins, polluted soil and water, and brought invasive species into rivers.
Scientists led by Guohuan Su of the University of Toulouse have estimated the biodiversity of freshwater fish in 2,456 river basins around the world. They took into account not only their taxonomic biodiversity (the number of fish species in the basin), but also functional (the number of different ecological groups and guilds to which these fish belong), as well as phylogenetic (the abundance of fish families and orders in the basin). The data were taken from the FIP databases, BioFresh project and scientific publications. Their study covered 14 thousand species. To illustrate the results of the assessment, the authors introduced the index of cumulative change in biodiversity (CCBF), which can range from 0 to 12, where 0 corresponds to no effect, and 12 - to maximum oppression. These scores are composed of six indicators: three indices of taxonomic, functional and phylogenetic diversity, as well as three indices of taxonomic, functional and phylogenetic similarity (similarity indicates the overlap of biodiversity between neighboring rivers in the region).
Scheme for the assessment of cumulative changes in freshwater fish biodiversity. The index value equal to 0 corresponds to the absence of significant damage, equal to 12 - to the maximum damage.
It turned out that the biodiversity of freshwater fish in more than half (1297) river basins is deeply affected by anthropogenic impact: CCBF for them exceeded six points. Most of these rivers are located in the temperate zone of the northern hemisphere. At the same time, biodiversity in about one third (878) of river basins has been minimally reduced. This was typical mainly for small reservoirs, occupying no more than 13.4 percent of the world's river area. They are located mainly in Australia and the African tropics.
Changes in six global freshwater fish biodiversity indices.
According to the authors of the study, the most important factors undermining biodiversity in rivers of temperate latitudes are the operation of dams, the introduction of alien species into rivers, the intake of water for the needs of industry and agriculture, as well as its pollution.
Scientists recently found that anthropogenic activities have already had a strong impact on a third of the world's lakes and on 610 of the 710 lakes located in key biodiversity zones.
