When intentional introductions go wrong

Sometimes species are released, or escape, and then havoc ensues.
05 March 2019

Interview with 

Angela Cano, Cambridge University Botanic Garden


Lionfish in sea


In the main show, we heard about accidental introductions but what happens when an introduction isn’t an accident? Mariana Campos headed back to Cambridge University Botanic Garden to visit assistant curator Angela Cano to explore why these intentional introductions happen.

Mariana - there are a few reasons for which species get released outside their native range. Alien, or non-native, species can be introduced for the food, for their local, for other useful reasons such as as biocontrol, and for malicious purposes. If they become invasive then things can not quite go to plan.

Here’s Angela Cano, assistant curator of the botanic garden with an example…

Angela - maybe one of the most striking ones is the guava cherry. This is a shrub that was introduced from Brazil into different islands such as Mauritius or Hawaii and it was introduced because it produces edible fruits. The problem is that it became invasive; it forms big clumps of forest and local flora cannot grow any more in those environments. And an additional problem is that a species of pigs, that was also introduced intentionally, is helping the guava cherry to spread because it eats the fruits and disperse the seeds, so it’s two species really changing completely the environment of these highly diverse islands.

Mariana - Not only was the cherry guava pushing out native plants you then introduced another pesky species - the pig. Their combined traits cause damage to the environment, plus there’s a big risk of losing biodiversity.
Then there’s also the problem of when an introduced species, which is originally kept secure, escapes.

Angela - There’s the case of the lionfish that was intentionally introduced in Florida. It was supposed to be confined in aquariums, but because of Hurricane which is something completely unpredictable the aquarium was destroyed and the fishes were released to the Caribbean Ocean. This fish was originally from the Pacific and it basically started invading all the Caribbean islands and preying on the local fishes and the young of local fishes. And it’s unpredictable what can happen in the future with the populations of those reefs and of the people as well because if the fish preys upon the local fishes then the fishermen wouldn’t be able to find their traditional food and this will affect the local economy.

Mariana – Right. So pretty things that we bring in, be them beautiful lionfish or ornamental plants can also, so to say, jump the fence and become a big problem. And we not done yet! Part of the problem of invasiveness can be caused by the lack of a predator; sometimes a solution is to introduce one - that’s called biocontrol. But, you guessed it, it can go wrong…

Angela - There was an invasive species in the Pacific Islands. It was a snail so they try to fight it using another species, flatworm, and after introducing it became also invasive. So it not only preyed on the invasive snail but also on endemic and rare snails that were originally from those islands.

Mariana - But biocontrol shouldn’t get a bad reputation because it is a very powerful tool. In recent times the risk assessment of introductions has vastly improved so that accidents like that don’t happen again.

Another type of introduction little talked about are the malicious introductions. Unfortunately, living species have been used in the past as a method of bioterrorism, usually pests and diseases that are introduced to a new area where the mechanisms to deal with these haven’t evolved.

One case in South America was the attack to the cocoa trees, the vital plant to give you your chocolate fix. A fungus that causes the disease called Witches Broom infected the trees in the Amazon, which had adapted to survive this, but it was intentionally taken from there to plantation somewhere 3000 km away which couldn’t fight off this fungus. But what happened, is the disease spread so fast and thoroughly but the cocoa bean production more than halved driving down with the exports, economy, and job security. It was allegedly a political attack from poor farmers to fight big plantation owners. Almost 30 years later, the country’s cocoa exports still haven’t recovered to the levels before the witches broom introduction.
So whether something’s been released, escaped or otherwise there are multiple ways to tackle the problem of intentional introductions.

Angela - Education is very important so if people know that they that they can play a role where they should know. So, for example, people like buying exotic pets because when they are small, they are cute and look interesting but then these animals can grow quite big. And then people don’t know what to do with them and they release them into the wild. If people know that they shouldn’t do that then I guess they won’t do it.
And also if you organise authorities of different countries and make them work together to have a network of information that can also prevent species from spreading because if you find, if you detect an invasive species in the Mediterranean coast of France, if the Mediterranean countries are aware of these they can start thinking of strategies to prevent the invasion of the species.

Mariana - And what about prevention itself? Is there much done on the side of keeping things before they come in?

Angela - Yes. So for example here in the Botanic Garden we participate in expeditions across the globe, but we just don’t bring the species directly into our collection. I recently was part of an expedition to South Africa where we collected beautiful succulent plants and to be sure that we didn’t bring any pests with the plants we had to remove all of the soil in South Africa bring the plants only. But anyway, they have to stay in quarantine for a year before we can bring them to the garden; that’s to prevent invasive species to spread.


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