Mention the Seychelles or Mauritius, and most people drift off in fantasies of the perfect holiday. It’s time to wake up! There is much more to these islands than beaches and palm trees. Madagascar, the Seychelles, the Comoros, Mauritius and Reunion together support such a diverse and unique assembly of animals and plants, that they are recognised as a global biodiversity hotspot. Unfortunately, faced with the usual problems of overharvesting, habitat destruction, and pollution, this region has not escaped the effects of the global extinction crisis that unfolds in plain sight..

Betsiboka River, Madagascar
Erosion is a great concern in Madagascar. Here you can see that the Betsiboka River carries a lot of sediment down to the sea, which has been mobilized by deforestation. Image: Oledoe (Flickr)

Freshwater ecosystems make no exception to this. Quite the contrary: Although many freshwater species provide important benefits to people, both direct (e.g. fisheries) and indirect (e.g. water purification), freshwater ecosystems are generally undervalued in terms of their biodiversity and the services they provide. This lack of concern for the conservation and sustainable use of inland wetlands has therefore led to alarming rates of freshwater habitat loss and degradation globally.

Ubiquitous degradation of freshwater habitats is taking a heavy toll among freshwater plants and animals in the Indian Ocean Islands. Now, the International Union for the Conservation of Nature (IUCN) has published the most comprehensive assessment ever produced on the conservation status of the freshwater biota in this part of the world.

The news isn't good.

Fourty-three percent of all 653 species of freshwater fishes, molluscs, decapods, dragonflies and damselflies, and aquatic plants were assessed against the IUCN Red List Categories and Criteria, 43% are found to be threatened. This level of threat is very high compared to other regions in the world.

This IUCN assessment is the product of a collaboration of many specialists, taxonomists, ecologists and conservationists. I specifically have assisted with assessing the conservation status of freshwater molluscs – snails, mussels and clams. Fortunately, the conservation status of freshwater molluscs is not quite as grave as that of other groups with at least 24% of all species being threatened. However, this still means that one out of four species is going to go extinct if the current population trends persist.

So, what can be done. Our assessment not only describes the dire state that many species find themselves in, it also makes specific recommendations for conservation actions that can help to stop the looming mass extinction. For example, we have identified key biodiversity areas that should be set aside to create a network of conservation areas.
While it is not too late to preserve most species, it won’t be possible without a dedicated and long-termed conservation strategy.

Frank Koehler, Senior Research Scientist, Malacology

More information

  • Máiz-Tomé, L., Sayer, C. and Darwall, W. (eds) (2018). The status and distribution of freshwater biodiversity in Madagascar and the Indian Ocean islands hotspot. Gland, Switzerland: IUCN. viii+128pp