What do lakes in Kerala have to do with the Caribbean false mussel

The species has wiped out native clams and oysters


Species such as the Caribbean false mussel are invasive species, introduced in new regions through human activities. While not all non-native species have negative impacts on biodiversity, local ecosystems and species, a number of them do and thus they are labelled ‘invasive’. 

About 6% of alien plants, 22% of alien invertebrates, 14% of alien vertebrates, and 11% of alien microbes are known to be invasive. They pose major risks to nature and people. Many such species have been intentionally introduced for their perceived benefits, without consideration or knowledge of their negative impacts, for example in forestry, agriculture, horticulture, aquaculture, or as pets. Others have been unintentionally introduced, for example as contaminants of traded goods or stowaways in ballast water.

A week-long plenary which opened on August 28 and was attended by representatives of the 143 member States of the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) has approved the Assessment Report on invasive alien species and their control.

Annual costs of invasive alien species have at least quadrupled every decade since 1970, as global trade and human travel increased. In 2019, the global economic cost of invasive alien species exceeded $423 billion annually. These trends are projected to accelerate as the global economy expands, land and seas are used more intensively, and demographic change takes place. Nearly 80% of the documented impacts of invasive species on nature’s contribution to people are negative. These species impact human health and wellbeing by reducing food supply, damaging health, affecting livelihoods, negatively impacting the natural world with cascading impacts on native species. 

In the future, climate change is likely to interact with other changes, profoundly shaping and amplifying the level of future threat. Warming temperatures are predicted to lead to changes in land and sea use in some regions. Human migration patterns—as well as more extreme events, such as droughts, floods and wildfires—could favour the expansion of invasive species. Climate change is also predicted to increase the competitive ability of some invasive alien species, extending the area suitable for them and offering new opportunities for introductions and establishment. 

Invasive alien species can also amplify the impacts of climate change. For example, invasive alien plants, especially trees and grasses, can sometimes be highly flammable and promote more intense fires. An example of this is some of the devastating wildfires experienced recently, which themselves then release more carbon dioxide into the atmosphere. 

Inger Anderson, Executive Director, United Nations Environment Programme, said: “Humanity has been moving species around the world for centuries. This practice has brought some positives, but when imported species run rampant and unbalance local ecosystems, indigenous biodiversity suffers… invasive species have become one of the five horsemen of the biodiversity apocalypse that is riding down harder and faster upon the world. While the other four horsemen – changing land- and sea-use, over exploitation, climate change and pollution – are relatively well understood, knowledge gaps remain around invasive species.” 

As for the Caribbean false mussel (Mytilopsis sallei), it was originally found in the Atlantic and Pacific coast of South and Central America. Researchers believe that it may have travelled to India via ships, later spreading to estuaries through smaller fishing vessels that travel frequently between coastal oceanic waters and the fishing harbours of Kerala. It’s possible that tropical cylone Ockhi which struck the Kerala coast in 2017 may have triggered the spread of the ‘Varathan Kakka’ (‘alien bivalve mollusc’ in Malayalam) across the State by carrying it into new waters.