Ecosystems are complex networks of interacting and interdependent species. These could be predator-prey interactions (who eats whom), symbiotic interactions (co-habitation with mutual benefits), accommodating interactions (this tree provides nest space for that bird), and so on. Healthy ecosystems generally consist of a large diversity of species, with many such interactions and dependencies.
Furthermore, many ecosystem networks contain so-called keystone species: important nodes in the network which, if they would disappear, could cause the entire network (i.e., the whole ecosystem) to change significantly, or even collapse. This notion of keystone species was introduced in 1969 in a short paper by American ecologist Robert Paine. He observed that when a top predator (a species of starfish) was removed from a marine ecosystem, the biodiversity of this ecosystem would reduce significantly.
Starfish feed on mussels, thus keeping the mussel population in check, and allowing other species to co-exist within the same ecosystem. However, after removing the starfish the mussel population explodes and crowds out other species, reducing the ecosystem’s biodiversity and thus its overall health.
In tropical regions, biodiversity is generally richer than anywhere else due to the relatively warm and moist conditions all year round. For example, Singapore has around 400 bird species and more than 1500 plant species, all on an island of just over 700km2, located about one degree north of the equator.
Unfortunately, because of human development much of this biodiversity is at risk. With Singapore’s rapidly increasing urbanization it has already lost 95% of its original forests. Moreover, more than half of the naturally occurring flora and fauna is currently only present in protected nature reserves. But luckily the government has realized this precarious situation, and is actively engaged in creating more green spaces and preserving the country’s precious natural diversity and keystone species.
The Bukit Timah Nature Reserve retains one of the few areas of primary rainforest left in Singapore. It was one of the first forest reserves that was created on the island, and the only one that was saved from depletion by logging. The park also happens to contain the highest point on the island, Bukit Timah Summit. Although at only 163.6m above sea level it’s an easy walk up to the top.
Adjacent to Bukit Timah is the Hindhede Nature Park. This much smaller park contains an old mining quarry that is now filled with water, giving rise to a fresh-water ecosystem including fish and turtles.
The MacRitchie Reservoir Park is a nature reserve area bordering Singapore’s first water reservoir (of the four currently existing). This close proximity to fresh water makes it an important biodiversity reserve. The northern section of the park contains a treetop walk, a suspended walkway that allows visitors to walk along the forest canopy and observe a unique part of the ecosystem that you normally don’t get to see from that close by.
These forests are also home to monkeys, in particular long-tailed macaques. It is always a delight to see them in their natural habitat, free to roam around as they wish.
The Sungei Buloh Wetland Reserve contains one of the last original mangrove forests in Singapore. Mangrove trees are considered a keystone species. They firm up shorelines, reduce erosion, and provide safe feeding areas for fish and nesting space for birds, among others. In other words, they create a perfect environment for many species to thrive, including large birds such as the impressive painted stork. The wingspan of these birds can reach to over 1.5m.
One of the most peculiar species here is the mudskipper, an amphibious fish that spends a good part of its life out of the water. It uses its fins to “walk” (or skip, rather). It represents a modern-day equivalent of the original vertebrate water-to-land evolutionary transition in the late Devonian, some 360 million years ago (more on this in a future post).
These forests are also home to the draco, or flying lizard. Dracos have a membrane attached to their extendable ribs that can be used to glide through the air, from one tree to another. Seeing them actually “fly” is simply amazing.
But there is one species in Singapore that is truly unique to this island: the merlion. Half fish (like a mermaid) and half lion, it is the country’s national symbol. A large statue of it is on display under the impressive downtown Singapore skyline.
So, even though it may take a little bit of an effort to find it, there is still plenty of biodiversity to be enjoyed on this highly developed island. That is, if you don’t mind sweating it out in one of the hot and humid protected rainforest areas for a couple of hours. But it does provide a good example of how we can deal with biodiversity preservation, including an ecosystem’s keystone species, even in extensively urbanized areas.
In fact, complex networks like ecosystems are no strangers to Singapore. Hosted by Nanyang Technological University, its Complexity Institute aims to become Asia’s leading institute for complexity research. The rich local ecosystem networks certainly provide a stimulating environment for such important work.
All photographs © Wim Hordijk
This article is part of the Beauty and Science of Nature series.