Spatial complexity

Tropical animals are usually adapted to take advantage of 3-dimensional

Spatial complexity is a big word, but in simple terms you could imagine it as the difference between a landed house and a condominium. If only one level is occupied like in the house, you get less room to live compared to if you build upwards and have multiple floors. 

Like a multi-storey building, spatial complexity means that space can be used more efficiently by living in higher structures. Higher spatial complexity also means higher resource density for animals using the area. Some animals use only one layer of the forest, while others can move through the layers depending on time of day.

Much of the activity of the forest can happen beyond the reach of humans at the upper levels of the canopy. Combined with dense understory layers, many animals are able to hide from humans, giving them room to carry on with their lives without having to encroach on humans.

How is spatial complexity accomplished? The easiest way is to mimic the natural rain forest and plant in layers, so that all the space from the soil all the way to the tree tops have space for animals to use.

With land being scarce in cities, we have to think about how to use what we have more efficiently. Increasing the amount of vertical space available is one way to do so.


Why plant introduced species?

Written by Thary Gazi Goh

Photo by Dr Saw Leng Guan (CC BY-NC-SA)

To be fair, here is why you should plant introduced plants, or rather when it is appropriate to plant introduced species.

  1. Often they are tough and easier to handle. Many commercial species are chosen because they are tough enough to be bred for hostile environments like cities. In some places native species might not be able to survive, but introduced plants can do fine.
  2. They have useful ecological functions. Just because a plant is not native doesn’t mean that wildlife can’t use it. Flowers will attract pollinators whether they are native or introduced. Oil palm is an introduced species, but often it supports fruit eating birds and mammals in the city.
  3. Easier to obtain. Many introduced species can be bought from nurseries, which is easier than looking for native plants which may be in forests and hard to identify. If you need plants fast, then it may be a feasible option.


Why plant native?

Written by Thary Gazi Goh

Setawar air (Costus speciosus). Photo by Syuhada Sapno.

Why should you go through the effort of planting native plants? It’s a good question that many people ask. Here’s 4 reasons:

  1. There is a higher diversity of native plants. Often these plants are able to coexist with local wildlife and integrated into the food chains and interactions of native wildlife.
  2. Native plants create more stable food chains. Many native plants can function as food or host plants for wildlife. This creates more stable and resilient food chains.
  3. More possibility. There is a larger variety of native plants, which means that these plants hold more possibility in terms of what habitats they can create in the future. They also hold in them many potential cures or useful compounds to humans in the future. To lose native plants is an act of destroying the biological legacy of future generations.
  4. This is their home. Where else do our native plants have to go if we remove them completely? It’s beyond cruel to destroy entire species and take their land from them.

Invasive species

Written by Thary Gazi Goh

A golden apple snail (Pomacea maculata) is laying eggs. Photo by Jpatokal (CC BY-SA 4.0)

An invasive species is a species that has been introduced by people and has gone somewhat out of control. These species come from other parts of the world, like South America or Africa.

Some invasive species are introduced by accident. For example, brown rats (Rattus norvegicus) were introduced through shipping. During the 70’s they were mostly confined to ports, but rapid urbanisation has allowed them to colonise the rest of the Klang Valley and Malaysia as well. 

Brown rats are larger than black rats, when older people comment that rats are growing larger they are just observing a larger rat species colonising more urban areas.

Other invasive species are brought in for a purpose and then something goes wrong and it unexpectedly becomes uncontrollable. Black cobras were introduced as a way to control rats in plantations, but they started to follow humans and rats into urban spaces as well and are now one of the most common poisonous snakes in cities.

Some invasive species are escapees from various projects that people do. Many animals escape from the aquarium trade into our waterways and become dangerous to our native wildlife. Others like the Giant African land snail were brought for experimental food programs during World War II and escaped into farm pests.

Not all introduced species are bad. Species like pineapple and papaya are relatively benign and have become staples of our village gardens. But often the line between invasive and introduced is vague.


Rain forests and rain

Written by Thary Gazi Goh
Photos by Goh Shang Ming

A carpet of dense, untouched forest

Ever wonder why it is called a rain forest? Rain forests are important controllers of the water cycle in tropical ecosystems.

Rain forests do 2 important functions with water:

  1. They control the intensity of water. This means that they control how much rain flows into rivers and floodplains. The root systems or rain forests allow water to pass into the soil instead of washing out as surface run off.
  2. They make rain. Rain forests can control how regular the rainfall is, in essence a rain forest produces its own rain. The tall trees of the rain forest take water from their roots and releases it from its leaves, often more than 30m off the ground.
Trees are closely arranged in a rain forest

These rise as fog and mist into clouds that come back down as rain. The rain forest is a living system. It can create more rain when it is too hot or put more water back into the air if there is too much in the ground.

You can actually observe this phenomenon near the forest patches in our cities, clouds of moisture can be seen rising from them, especially in early mornings and rainy days.

Rain forests are important infrastructure that carry out functions that make our lives more livable. We need rain forests to live stable lives.

If someone plans to cut down our power grid to harvest the copper and steel in it, we would think that they are an idiot. However, that is the kind of thinking that goes into our forest management. This is what happens when you view a utility as a single use resource.


Keystone species

Written by Thary Gazi Goh
Photo by Goh Shang Ming

Fig is food for bats, squirrels and many other animals.

Keystone species are species that cause the entire ecosystem to fall apart if they are removed. 

We can imagine an ecosystem to be a network of connections between various species. Some species are more connected than others, and they can be the ones holding the entire network together.

Keystone species take their name from the keystone in stone bridges, this is the stone that holds the entire bridge structure together, and if removed causes the collapse of the entire bridge.

The biggest problem with keystone species is that we are rarely able to identify them without close study, and sometimes we only understand how they function when we see the results when they are gone.

A cautionary tale of disaster caused by removal of a keystone species is China’s “War on four Pests”. One of those pests was the sparrow, which sometimes ate the grain of farmers. 

A quarrel of Eurasian tree sparrow (Passer montanus) roaming at the edge of a fountain

Farmers were given quotas to kill sparrows, believing that this will increase their crop yields. What happened was a great ecological tragedy of the modern world.

Without sparrows to control them, the population of grasshoppers and other insects exploded. These insects started destroying crops and a massive famine followed.

This case really illustrates the folly of removing species from ecosystems. We often have no understanding of their functions and removing the wrong species can cause collapses of ecosystems with horrible consequences.

This is one of the reasons why we have to try to protect as much of our native ecosystems as possible. We sometimes do not know what a keystone species is until it is too late.


Pioneer species

A palette of alpine pioneer plants

A pioneer species is a species that arrives at the start of a succession sequence. If you’re not familiar with succession, you can find an article about the concept here.

An example of a pioneer species is the Senduduk (Melastoma malabathricum), which breaks up poor soils with its extensive root system and lays down layers of dead leaves which become a carbon rich organic material for the topsoil. 

The purplish flowers of Melastoma malabathricum

It also blocks out smaller sun loving plants and provides shade for small saplings. By doing so it changes what species can survive in an area and it shapes the direction in which succession can proceed. This plant marks a shift from small herbaceous plants to small shrubs and saplings.

Letting plants take over through natural regeneration is one of the methods to recover soil quality and produce habitat. Being able to identify which pioneer species are there will tell you a lot about the progress of the regeneration.

Not all trees are equal, what, when and where play a very important role in determining whether a tree can support the ecosystem or if it cannot survive in it. Knowing which species act as pioneers is an important aspect of biodiversity enrichment, as it allows us to know when to plant something.



Written by Thary Gazi Goh
Photo by Goh Shang Ming

An island of trees standing amid roads and buildings

Imagine biodiversity as water, it can flow from one place to another, it can stagnate and it can seep out.

Some places have more biodiversity, some places have less. When conditions are right and there is a   pathway available, the biodiversity can flow from areas of high diversity to areas with lower diversity.

In ecology we usually call the places that can export biodiversity as “sources”, while places that accept biodiversity are called “sinks”. Like a spring of water, if you connect them the biodiversity can flow from a “source” into a “sink” until it fills up as much as it can hold.

When planning biodiversity enrichment in cities, it is important to be able to think about where your sources are. Planting a bunch of isolated trees is not the same as planting trees near a forest patch where wildlife can flow into it.

Also worth thinking about is the barriers that can prevent the flow of biodiversity. Is it a noisy road that crawling animals can’t get past? Or is it a row of buildings that block flying animals? Understanding where your pathways are can be just as important as identifying “sources” and making new “sinks”. 

Movement of urban-dwelling animals may be restricted by urban roads

A good example of a “sink” is an area that is large so it can be easily found by randomly moving wildlife and it has to have resources that the wildlife can exploit, so they decide to stay there. 

This analogy really helps when planning for wildlife intervention in the city. How we plan for the movement of wildlife can help us to have healthier ecosystems that are in less conflict with the humans around them.


Disturbance and movement

Tree falls can create gaps and disturbance in rain forests.

Written by Thary Gazi Goh
Photos by Thary Gazi Goh & Langur Project Penang

The natural world is chaotic. Accidental events can happen that can affect a whole ecosystem, for example a fire started by lightning or a disease that kills off a species. In the worst cases, random events can cause the collapse of entire ecosystems.

The effects of random events on ecosystems become stronger the smaller the area is. This means that small isolated forest patches will take more damage from accidents than larger areas. 

So why have our forests not been completely wiped out by random events? Two factors come into play: Movement between different ecosytems and heterogeneity. 

Movement of biodiversity between separate patches helps to recover damaged ecosystems. When all the vegetation was removed from Krakatoa after a massive volcanic eruption, the surrounding islands contributed to the recovery of the ecosystem there.

Natural rain forests are highly diverse.

Heterogeneity means more diversity of species. More heterogenous ecosystems are also more resilient. If a plant disease like fusarium wilt hits a monoculture banana plantation all the plants will be wiped out, if it hits a diverse rainforest there will be minimal damage.

This happens because there are more varied plants and they are far apart enough so disease doesn’t spread like a wildfire. In fact literal wildfires tend to spread less effectively in heterogenous forests because different plant species have different reactions to fire and some patches can act as natural fire breaks.

Canopy bridge stretches across roads with fast-moving cars
Malaysia’s first canopy bridge built by teams from Langur Project Penang and APE Malaysia

Photos credit to Langur Project Penang
Learn more on Malaysia’s road ecology and wildlife canopy bridge here

Canopy bridge provides a safer way for animals to cross a busy and dangerous road
Photos credit to Langur Project Penang

In terms of understanding how to apply this to our cities, it is really important to not just preserve forest patches, but to allow for some form of connection. This can be through bee lanes (margins planted with flowers to allow for pollinator movement), viaducts (tunnels that allow the movement of ground animals) or canopy bridges (rope bridges that allow movement of arboreal animals).

This is not just a matter of building structures, barriers can be removed through collective action like closing roads on certain days of the month or turning off non-essential lights during a migration or mating season.

In Kuala Lumpur most of our forest patches are abandoned rubber plantations, we can increase their resilience by planting a greater variety of tree species and slowly transitioning away from a monoculture plantation to diverse secondary forests.


Resources produced by plants for animals

Resources produced by plants for animals come in many forms. Some animals require the presence of water for reproduction like frogs. Others like butterflies require shade to prevent overheating. Some require very specific structures like rotting wood, or crevices to complete their life cycle.

When it comes to planting, plants produce resources for animals in several ways:

1. Food

Flowering plants are a food source for many pollinators.

Many plants produce food in the form of leaves for folivores (leaf eaters), seeds for grainivores (seed predators), fruits for frugivores (fruit eaters) or wood for xylophages (wood eaters). These in turn become food for other animals in the food chain. In tropical rain forests, figs and palms have more frequent fruiting cycles and are a staple of many frugivores diets. Dipterocarps and oaks, which make up the majority of trees in our lowland forest, fruit less frequently but produce large quantities of seeds every 2-12 years in a phenomenon known as “mast seeding”. Fallen leaves, logs and branches also provide food for invertebrate decomposers.

2. Host plants

Butterflies like this Drupadia ravindra need host plants to survive.

Many plants have chemical defences that make them poisonous to some animals (like tobacco and caffeine). However some animals have been able to overcome these and have adapted to solely feeding on a small variety of plants, these animals usually require the host plant to complete part of their life cycle. For example the tree Saraca thaipingensis is the host plant for the butterfly Drupadia ravindra. Planting larger varieties of plants usually leads to an increase in insect life due to a higher availability of host plants.

3. Shade

The majority of animals are not able to maintain their body temperature and must depend on their environment to heat up or cool down. Plants change the thermal environment by releasing water vapour into the air and reducing the amount of sunlight and heat below them.

4. Nesting space/nesting materials/shelter

 Plants with complicated structures are often good places to hide for many smaller animals. Larger animals such as monkeys also use trees to rest at night to avoid predators. Plants with large root systems or branching growth are especially good for animal nests. Some frogs have adapted to laying their eggs in epiphytes or bamboo. 

5. Mating space

Many animals use plants as a space for attracting the opposite sex. Birds often require trees to make mating displays. Some flies also use leaves for performance space, while beetles often need rotting wood as a place to attract mates. In some cases the loss of certain plant species leads to the loss of animals that use them for mating, like mangrove fireflies and berembang trees (Sonneratia caseolaris).