Invasive alien species may sound like something from another planet but in Bermuda and around the globe, they are a real-world threat. In fact, the International Union for the Conservation of Nature (IUCN) has named them the biggest threat to biodiversity after habitat loss. Interestingly of the ‘100 of the world’s worst invasive alien species’ catalogued by the IUCN, 24 species occur in Bermuda.

What is an

invasive species?

Most species introduced into a new place do not cause problems in their new location. In fact many bring considerable benefits, such as in agriculture, horticulture, and the pet industries. However some species do not. These are known as invasive species. An invasive species refers to any species that becomes established in a new environment, then proliferates and spreads in ways that are destructive to native ecosystems, the economy, human health, and ultimately human welfare.

Invasive alien species, often referred to simply as ‘invasives’, can be a mammal, bird, insect, fungi, plant, virus or bacteria. We as humans tend to notice the ones that impact us the most such as rats, disease carrying mosquitoes, garden pests, weedy plants and domestic animals or pets gone feral such as pigeons, chickens and red eared sliders.

The challenge is identifying the characteristics that distinguish invasive from harmless introduced species. Every species taken out of its natural environment has the potential to become invasive. However some traits appear to make a species more likely to become invasive, such as having few predators, the ability to adapt and outcompete other species for food and habitat, quickly reproduce and thrive in disturbed systems.

Why do we care?

Invasive species are now recognised as one of the greatest biological threats to the environment, affecting biodiversity and ecosystem functioning, with harmful impacts that are considered second only to those caused by habitat loss. Impacts can be broken down into three main categories. Economic impacts include loss of crops due to predation or damage, increased cost of production and control. Social impacts include human health and safety problems but also interference with traditional lifestyles, aesthetic values and the enjoyment of natural areas. Harder to quantify are ecological impacts that include competition, predation, habitat modification, transmission of disease, hybridisation, disruption of ecosystem function and changing trophic dynamics (the position an organism occupies in the food chain).

The impacts caused by many invasives often fall into more than one category, affecting the ‘pocket book’, human health and Bermuda’s natural environment. For example the feral pigeon which causes damage to crops, is a vector of disease and a competition of threatened species such as the longtail. Other examples include the Brazil pepper (asthma, habitat destruction), feral chicken (toxoplasmosis, salmonella, bird mites and feather allergies); feral cat (toxoplasmosis, salmonella, feline leukaemia and feline HIV). Potentially the giant land snail (salmonella, rat lungworm parasites in both the animal and slime that if ingested can cause meningitis like symptoms).

How do we manage the invasive issue?

Prevention is the first line of defence. Species proposed for importation are vetted in order to limit negative impact to Bermuda’s economy, its society and the environment. This is followed by early detection and rapid response. Regular inspections are made of transport hubs such as the airport, docks, mail sorting areas to identify potential introductions. In this the public can also assist if they see something unusual by e-mailing conservation@gov.bm. Once identified the suspect is captured and quarantined. Unfortunately some species have and will continue to escape and thrive, necessitating control. While the ultimate goal might be to eradicate, it might not be possible. Therefore the goal might be to reduce their population density to a tolerable level or contain them in a certain area. While daunting, control can be effective. It is very notable that Bermuda does not have a problem with feral dogs, which is a major problem in the Caribbean, due to strong legislation and controls. Mitigation and restoration: when control has failed, strategies have to be developed to learn how to live with the problem species and minimise their social, economic and environmental impact. Often the strategy is to designate areas to be kept free of invasives and work to restore those areas back to their original condition. This works best on remote islands like Nonsuch Island.

What are we doing

about them?

Mother Nature is complicated. A newly introduced species can become a problem in a matter of weeks like in the case of a virus or in the case of plants more likely decades from when it was first introduced. Management is likely to require the cooperation of Government, the private sector, non-government organisations and the public to effectively control the problem. With this in mind the Department of Conservation Services has been tasked with developing a National Invasive Species Strategy that is intended to organise Bermuda’s effort to combat and prevent biological invasions.

***

For further information or to nominate an invasive species, contact conservation@gov.bm.