Scientific News

Freshwater megafauna in sharp decline according to study

Freshwater animals represent about one-third of all vertebrate species in the world, presenting a highly respected variety. However, it is unfortunate that life itself in the rivers, lakes and all the bodies of freshwater in the world is in sharp decline, as confirmed by new research published in Global Change Biology.

The research, in particular, has focused on freshwater megafauna, which is all those animals of a certain size that weigh at least 50 pounds. We speak, therefore, of crocodiles, large fish such as sturgeons, giant tortoises, and so on.

By gathering data on 126 species of freshwater megafauna from various parts of the world, researchers have concluded that from 1970 to 2012 these populations even decreased by 88%.
This is a double decrease compared to the heavy defections affecting terrestrial or marine vertebrate populations.

Sonja Jähnig, a researcher at the Leibniz-Institut für Gewässerökologie und Binnenfischerei (IGB), lead author of the study, talks about alarming results that confirm the already very strong concerns before this study regarding freshwater biodiversity.

The most important decreases occurred in the Indo-Malaysian ecozone (India and neighboring countries plus south-east Asia), with a 99% decrease, and in the Palearctic eco-zone (almost all of Asia, Europe and North Africa), which saw a 97% decrease.

Among the most affected species are those related to large fish such as sturgeons, salmonids and giant catfish that show an average drop of 94%. These species are followed by reptiles that show an average decrease of 72%.

The main reasons behind the decrease in the populations of these animals are due to the excessive exploitation by human beings and the loss of the flow of the rivers, a phenomenon that occurs especially when the flow of water is blocked by the dams, as recalls Fengzhi He, first author of the study and expert in freshwater megafauna.