Hey all! With the public walks coming up, BES Drongos have been going down every weekend to hone our guiding skills. It’s been hard work but fun at the same time.
This post will be slightly different as it will be both about the creatures that we saw and about invasive species. We hope not only to show what the BES Drongos are doing but also to show readers how nature works.
So, what is an invasive species?
As you can infer from the video, they are usually an exotic (not native) flora or fauna that has a negative impact on the local environment. They usually thrive in the introduced environment and can outcompete local species (which is a fancy way of saying they can snatch away precious food, water and other natural resources). It’s kind of like Planet of the Apes, only that highly evolved apes are more often than not highly evolved plants and smaller creatures and the people who are being terrorized are the local biodiversity, which might or might not include us.
A famous example of invasive species is the Hairy Clidemia (Clidemia hirta). This hairy leaf is commonly seen along the edges of our forest and is found throughout Singapore. While this plant might look innocuous, it has spread from its native continent (South America) to as far as Australia. Producing about 500 fruits in a single year, it is capable of outcompeting local plant species by sheer reproductive capacity. This has given it its nickname, Koster’s Curse. Koster, in fact, was the man who introduced this species to Hawaii. The plant wrecked such havoc on the coconut plantations there that it was considered a curse. Hence, Koster’s Curse, which in hindsight might not exactly be the legacy you want to leave behind.
However, as of the time this post is written, the Hairy Clidemia is not considered an invasive species in Singapore. This is because it is currently found only at forest edges and not within the forest itself. However, this does not mean it has no effect on the local ecosystem.
It’s not just plants that are invading our local forests, animals are too. The cause this time, are Red-eared Sliders (Trachemys scripta elegans). They don’t sound familiar? I’m pretty sure you have seen them before, just take a look at the picture below.
They’re the cute terrapins that you had as pets as kids. Small and placid, they were perfect when you were little. However, these terrapins live for up to 30 years and grow much bigger. They’re no longer able to keep them in those small, blue plastic tanks. These terrapins, more often than not, are released into reservoirs and ponds. They’re in their natural environment, right?
Wrong! These Red-eared Sliders originate from the Land of the Free, USA. They’re brought over here because they’re so popular as pets. When people release them into our ponds, they start competing with our local turtle species for basking and nesting sites. This has led to a great decline in numbers of local turtles. They’re so successful as an invasive species that places like Australia and Europe has banned the trade of them. Maybe it’s time for Singapore to do the same.
Another example of local species being outcompeted by invasive species is the displacement of the Green Crested Lizard (Bronchocela cristatella) by the Changeable Lizard (Calotes versicolor). The pictures are both Green Crested Lizards, native to Singapore. As you can see, they’re a brilliant green-bluish colour though (as seen above), prior to mating, the lizard has been observed to change into a dark brown colour (as seen below).
In Singapore, these lizards have often been displaced by the more aggressive Changeable Lizard, an exotic species. Now, Green Crested Lizards can rarely be found in urban areas and forest edges but are still frequently seen in our nature reserves and forests.
However, we cannot always blame the invasive species for the fall in local diversity. These species could simply be moving into abandoned areas, rather than outcompeting native species. What do I mean? Take for example the construction of a park. This would undeniably change the natural habitat from a forest to an urban area. Native species, unused to such an environment, would eventually leave because they cannot find food and other necessities. Hence, it would be inaccurate to say that the invasive species are the cause of displacement of native species when they are simply expanding into an abandoned area.
Habitat disruption as a matter of fact is far more likely to be a greater threat towards biodiversity than invasive species. Habitat disruptions is a global trend and occurs even in Singapore. A very recent example that its currently happening in the Johor straits would be the reclamation of land causing destruction of coral habitats, or the clearance of existing forests to build more housing. These are just some examples of habitat disruptions that have changed natural habitats to such great extent that native species can simply die out. This trend is so prevalent in our time that many scientists are now certain that we are going through the 6th Mass Extinction! This is frightening if you consider how the last Mass Extinction was the period by which the dinosaurs went extinct. So, here’s a short video that would tell you more about this event and why we should worry about this.
Well, all these issues might seem insurmountable and a problem best left to the authorities and experts. That’s not exactly true. This problem is our problem and sticking your head under the sand like an ostrich is not going to make it go away. Such large issues need both global and community action and your choice to be aware of such an issue can be a tipping point for your community. We encourage you to read, research, join our guided walks and watch more TED videos in order to, in the words of Jac the research officer, find out what you have to lose and then decide if you want to save it or not.
Well, we have more misadventures ahead of us whether on the Petai Trail or on the other roads of life. So, do continue to come back to read more about it!
Credit for the brilliant photos: Aw Jeanice, Ecology Asia, Jac and Rachel Lee.
For more fascinating photos, check out our Flickr account.