More plants and animals mean a healthier ecosystem, right? Well, this is not necessarily so. Plants and animals in the form of invasive species are actually causing global biodiversity loss. What are invasive species? Invasive species refer to animals or plants that are non-native and introduced. During my recent field trip to the Singapore Botanic Gardens (SBG), I saw quite a few invasive species.

First, let me introduce to you the Keppel Discovery Wetlands which is a freshwater wetland ecosystem restoration project. By examining the historical maps which showed where freshwater swamp forest wetlands were once located and more recent maps of this area, the SBG reconstructed this lost habitat by creating ponds and swamp forest on the edges. This ecosystem is important as it is one of Singapore’s most endangered natural habitats. The interactions between the organisms living in the wetland and its environment contribute to its unique biodiversity. However, invasive species can upset this balance and lead to biodiversity loss.

Map of The Learning Forest housing the Keppel Discovery Islands (Credits: NParks)

Hydrilla

Take a close look at Figure 2 and you will notice “brown leaves” floating on the water surface. Those are Hydrilla, a submerged plant introduced from the aquarium trade. It grows very quickly, making population management difficult if it is not maintained regularly. It can outcompete native plants and take up excess nutrients from the water. Large infestations can also cause algae blooms and deplete oxygen while causing fish kills. Here, cost plays an important role in restoration planning because the lack of maintenance in these unnatural ponds led to the growth of the hydrilla.

Hydrilla verticillate (Hydrilla), IUCN listed as Least Concern; shelter at the Orchid Island overviewing the wetlands (Credits: Lydia Sing)

Javan myna

The Javan myna is frequently spotted not just around SBG but everywhere around us. With deforestation and urbanisation, the population of Javan myna has increased in urban spaces. The Javan myna’s droppings are a hygiene problem and they have also been competing for nesting cavities. Fun fact! According to the International Union for Conservation of Nature, the conservation status of the Javan myna is vulnerable and its population trend is decreasing although it is considered an invasive species in Singapore.

Acridotheres javanicus (Javan Myna), IUCN listed as vulnerable (Credits: NParks)

Red-whiskered bulbul

Another invasive species I spotted around Keppel Wetlands at SBG was the Red-whiskered Bulbul, recognised by its black crest on top of its head and a red patch behind its eye. It is believed to be introduced through escaped pets. The red-whiskered bulbul has been found to damage plants, compete with, and displace native birds, prey on native young birds and arthropods, and spread invasive plant species (NParks, 2019).

Pycnonotus jocosus (Red-whiskered Bulbul), IUCN listed as Least Concern; resting on a tree (Credits: Lydia Sing)

What can be done?

Be it the accidental or deliberate introduction of invasive species, human activities are the leading causes of these issues in Singapore. However, we can also be part of the solution. Public outreach on the potential impacts of invasive species can minimise their introduction. Prevention is better than cure and it is much cheaper to prevent than to clean-up after the invasive species. Let’s all do our part to prevent the introduction of invasive species!

 

Written by: Lydia Sing Ying Wei