Megafauna usually means mammoths, furry rhinos, giant sloths, and other Tertiary extinct vertebrates. But the megafauna still lives on our planet. Unlike the terrestrial and marine vertebrates, the large vertebrate of rivers and lakes was somewhat forgotten. Now scientists are trying to fix it.
Bison and buffalo, elephants, large African ungulates, or giant beasts are similar in size to mammoths, furry rhinos, or giant sloths. But many of them are at risk of extinction. A range of conservation organizations, scientific institutions, and research are therefore dedicated to their protection.
30 kgs and More
However, little attention is paid to living in freshwater. Maybe because they cover only 1% of the Earth’s surface, but a third of the world’s vertebrates live there. Among them, we can find representatives of the megafauna. However, since rivers and lakes provide relatively small space for their inhabitants, they cannot grow to land-like dimensions. In this environment, scientists consider all animals weighing 30 kilograms or more to be megafauna.
Not Just Freshwater Fish
Freshwater megafauna does include not only fish but also reptiles and amphibians and many aquatic mammals. Many of them are included in the list of species threatened with extinction. Their global population was only recently evaluated for the first time. The results of the study are alarming: from 1970 to 2012, it fell by a full 88%. This is a double loss against vertebrate populations on land or in the oceans.
Hunting and Dams
According to scientists, there are two main causes of this enormous slump. The first is excessive hunting – large aquatic vertebrates are often a sought-after source of meat, skin, or eggs. The second is the loss of free-flowing unregulated watercourses. The Cascades of dams on large rivers block many species of big fish from reaching the spawn places.
Rivers in Danger
Although most of the world’s great rivers are already divided by dams into small isolated sections, about 3700 large dams are planned or even under construction to divide river flows. The study results could become one of the basic measures that would coordinate their construction with the protection needs of freshwater vertebrates.
Source and credit: https://www.nytimes.com/2020/01/21/science/freshwater-megafauna-endangered.html, wikipeda.org, pixabay.com