In addition to the well-known “Red List”, the International Union for Conservation of Nature (IUCN) has now also published a “Green Status” for the first time. It supplements the information on the population of endangered animal species. The example of the gharial – a harmless crocodile species with cult status in South Asia – shows how this works. The river crocodiles are “endangered” and their populations are “critically decimated” because humans have largely destroyed their habitat in India and Nepal.
The gavial (Gavialis gangeticus), native to South Asia, is harmless to humans but is of great interest to biologists. “Gharials, also known as gharials, are very special crocodiles due to their long snouts and the bulbous ‘ghara’ structure at the end of the snout of the adult males,” explains senior author Phoebe Griffith from the Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB) in Berlin. The function of this bulbous nose is still unknown.
From an evolutionary and ecological perspective, this species of crocodile is quite unique. Not only does it have an unusually narrow and long mouth, it also split off from other crocodiles more than 40 million years ago and feeds primarily on fish. In addition, the river crocodiles, which are up to six meters long, have a remarkable social life. The reptiles maintain communal nurseries in which up to 1,000 young animals from different females live. But such large gatherings have become rare today because there are fewer and fewer gharials. It is estimated that only 300 to 900 individuals remain alive worldwide.
Green status: “critically decimated”
To track the development of these and other ecologically important animal species, the International Union for Conservation of Nature (IUCN) recently introduced the “Green Status of Species”. The expert assessment, now published for the first time, supplements the well-known “Red List”. This regularly updated list serves as a standard reference worldwide for assessing the extinction risk of individual species. In addition, the “Green Status” assesses in the future how far the species is from a complete recovery. The successes of previous conservation efforts as well as the potential for future recovery in various regions of the world are taken into account. The associated “Green List” also serves as an appreciation and certificate for successful nature reserves.
In this first-ever “Green Status” assessment, the gharial was classified as “critically decimated”. The crocodile is listed as “critically endangered” in the Red List. According to the researchers, the reason for this is that there are hardly any free-flowing rivers left in the gharials’ homeland, in India and Nepal. The crocodiles have a long history there. Asian artworks from the last 5,000 years depicting swimming gharials show that the animals were previously widespread. “This species is an important part of the cultural heritage with which people have safely shared the rivers for thousands of years. Only with the advent of large-scale river infrastructure since colonial times did the gharial go into decline,” explains Griffith. Accordingly, gharial populations have been decimated by man-made changes to the river courses, such as the removal of sand and rocks and the construction of dams. As a result, the crocodiles lack sandbanks for sunbathing and laying eggs.
Greater protection of habitats needed
According to the researchers, more measures are needed to protect the remaining natural habitats of gharials in South Asia and to renaturalize changed river landscapes in India and Nepal. This would also benefit many other species in the rivers. Measures taken so far show that such protective efforts are effective. Protected areas have already been set up in some places, for example in the Chitwan National Park in Nepal. In the local Rapti and Narayani rivers, populations are now slowly recovering, as Griffith’s team reports in a current study. In addition, fishing with gill nets, in which crocodiles often end up as bycatch, has been banned in many places. Hunting and collecting gharial eggs are also prohibited there. Without these measures, the gharial would most likely have already become extinct, the researchers emphasize.
However, in order to achieve further success in species protection, future protection measures must be more strategic and targeted. The “Green List” and the “Green Status” of the IUCN, among others, are now helpful in assessing how and where gharials can be protected particularly effectively. “The assessment helps us identify existing populations whose recovery could be supported by innovative, evidence-based conservation measures,” says Griffith.
Sources: IUCN “Green List”Leibniz Institute for Freshwater Ecology and Inland Fisheries (IGB); Specialist article: Reptiles & Amphibians, doi: 10.17161/randa.v31i1.21018