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“Snail Grass”  by Max Pixel under CC by 2.0

Molluscs is the second most diverse taxonomic group of animals, with arthropods being the first. This phylum includes univalves like snails, bivalves like clams, and cephalopods such as the octopus and squid.  These are soft bodied organisms that can live in marine, freshwater, or terrestrial environments.

Based on an increasing number of studies, there has been a local and global decline of the mollusc population, more specifically the non- marine species. It is hard to officially tell the population number, because these organisms are documented poorly and less then 2% of known species has had its conservation status properly assessed.

Why Are We Not Aware?

Recently there has been publications regarding the endangered and extinction of vertebrates such as rhinos, pandas and other furry creatures. Invertebrate extinction and endangerment does not receive any where near the amount of publicity that vertebrates receive. Why is this, when invertebrates comprise almost 99% of all animal diversity?  Molluscs have the highest number of documented extinctions of any major taxonomic group. 42% of the 693 recorded extinctions of animal species since the year 1500 are molluscs (260 gastropods and 31 bivalves). There has been a total of 708 freshwater and 1,222 terrestrial mollusc species were included in the 2002 IUCN Red List of Threatened Species list as of May 2003, and has increased sense then.

Why is the Population Declining?

Of the documented number of mollusc, 99% of the extinctions are non-marine. This may be surprising because of all the pollution being done to our oceans. There are two main human activities that researchers suggest for the decline of terrestrial species population:

Direct Habitat Destruction

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“Forest Destruction” by Wikimedia Commons under CC by 2.0

Terrestrial molluscs live in wetlands, forests, woodlands, and low tide levels. Events such as forest clearing for building, agriculture, and dam construction disrupt and destroy the mollusc habitat. Water pollution is certainly a threat to the species that live near rivers, wetlands, and low tides. With organisms like snails that have thin, permeable skin, it is easy for them to absorb the pollution in the water.

Introduction of Non-Native Species

The rosy wolfsnail was intentionally brought in to the Pacific Islands in hope that it would control the Giant African Snail population. This species needed to be controlled because it is a large crop pest that was also a non-native species to the area. The rosy wolfsnail did the job of reducing the population of the selected species, but unfortunately reduced the native snail population as well.

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“Rosywolf snail” by Wikimedia Commons under CC by 2.0

This was a human induced event that was not thought out completely, and ended up putting a huge decline of snails in the Pacific Island region. Human events like this one are not uncommon and whether they are intentional or not, they sill have a large impact on populations and ecosystems. Introductions of non-native species can also lead to diseases, competition of fast growing species, and predation on native species.

Why Should We Care?

Molluscs are crucial for healthy ecosystems. Terrestrial snails play a role in recycling forest nutrients back into the earth and provide food for a host of small mammals and birds, freshwater snails are important recyclers of plant and animal waste which helps keep the water they live in healthy for themselves and other organisms. Molluscs are considered “ecological indicators” meaning that they provide a window into the health of the entire ecosystem and give early warning of habitat changes. In the medical field, molluscs provide biotoxins and metabolites used for research.

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“Siphon” by Wikimedia Commons under CC by 2.0

What We Can Do To Stop The Decline

  • Follow regulations about bringing foreign foods, animals or other items to different regions
  • Get involved with organizations that help regulate water pollution
  • Teach children its not acceptable to pour salt on snails

There needs to be more regulation and protection for molluscs in their natural habitat. Just because they are not as furry and cute as other animals, they are very important. more research needs to be done on the exact populations and the endangered species. Organizations such as FMCS (Freshwater Molluscs Conservation Society), and OCEANA have done work to help conserve these important organisms.

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“Mussel Heart” by Static Pixels under CC by 2.0



One thought on “Molluscs on the Decline

  1. I loved learning more about terrestrial species importance in this post. My main focus on mollusca are the marine calcifying types. Seeing how important these species are to terrestrial ecosystem is a nice portion to add to my future research.

    Liked by 1 person

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