By: Cece Lin
As you leisurely stroll through a local Hong Kong park after an episode of rainfall, you’re most likely to encounter a typical sight: the domination of Giant African land snails (Fig. 1). This species of mollusk, although often encountered, serves as a striking example of an invasive species found not only in Hong Kong but also in various regions around the globe.
By definition, invasive species are non-native organisms that have been introduced into a new environment, where they proliferate rapidly and inflict harm on the local ecosystem, human health, and even the economy. Lacking natural predators in their adopted habitats, they would often outcompete native species for essential resources, alter habitats, and even cause the extinction of indigenous species. Consequently, the impacts of invasive species on conservation must not be overlooked.
What exactly are the implications of invasive species on conservation? Invasive species contribute to the decline of native populations through predation, competition, and disease transmission, thereby disrupting native ecosystems and their evolutionary functions. For example, the Giant African land snail has an extensive diet, consuming over 500 plant species, including crops and native flora, and even non-food materials such as concrete to source calcium for their shells. These feeding habits not only diminish crop yields but also damage native vegetation, resulting in significant economic losses in agriculture. Furthermore, female Giant African land snails lay over 10,000 eggs within their 9-year lifespan, facilitating rapid population growth and expansion. Last but not least, invasive species can alter essential ecosystem services, including habitat maintenance, crop provisioning, and soil retention, all of which are vital for ecosystem health and human well-being. For instance, the Giant African land snail modifies soil chemistry by neutralizing soil acidity through calcium carbonate from their shells, which adversely impacts native plant growth and alters soil ecosystem dynamics. Efforts to control and eradicate this invasive species have proven boat costly and labor-intensive. In Florida, for example, the removal of an infestation took over a decade and exceeded more than $1 million in expenses, ultimately preventing an estimated $11 million in crop losses.
So, what can we do to help? We can regularly collect and destroy snails and their eggs manually to reduce their population. Additionally, we can implement physical barriers such as copper or corrugated tin screens, strips of bare soil, or sand bands around infested sites to hinder snail movement. Finally, it is essential to prevent the introduction and spread of this invasive species by thoroughly inspecting plants, soil, equipment, and vehicles moving from infested to uninfested regions to avoid the accidental transport of adults or offspring.
Sources:
https://fcelter.fiu.edu/outreach/environmental-literacy/_assets/env-land-snails-reyes-suri-final.pdf
https://pmc.ncbi.nlm.nih.gov/articles/PMC4664396/
https://animaldiversity.org/accounts/Achatina_fulica/
