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Palms as keystone species

Like figs, palms produce fruit several times throughout a year. In between the fruiting seasons of other trees, palms make up a large portion of the diet of many urban fruit eating animals, especially birds.

Many palm fruit are adapted to be eaten by birds, these are usually small in size, round and dark blue black to red in colour. The seeds of these palms are often spread by the birds that feed on them, making them very common in wild patches all over the city. 

Even invasive palms such as oil palm can have ecosystem function for bird and mammal life. Fruiting trees are often visited by starlings, green pigeons, tree shrews and squirrels.

Palm flowers are also beneficial to many pollinators. These flowers grow in large pollen-rich clusters that often attract pollen feeders such as stingless bees. Coconut palms are often grown near stingless bee farms because of the food that they supply to the bee colonies.

These features make palms a keystone species in supporting wildlife in urban environments. Fortunately, many palms are grown as ornamental plants, and in many wild patches throughout the city they are sown by birds and make up large portion of our urban forests.

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Succession

Succession is the process in which the plant community changes over time. A forest goes through several stages where different plants become established and in turn change the environment of the forest. Note that this isn’t straightforward process, each stage can have many different species of plants and a very high number of possible combinations of species. Sometimes it can even move in reverse due to disease, fire or human disturbance. However, understanding the succession process can help in choosing the planting strategies.

Fig 2: Early succession annual herb dominated community

From bare ground, small herbs and shrubs are the first to establish themselves. These plants help to build up organic material in the soil and change the soil from a bacterial dominated community to a fungal one. Shade intolerant trees and plants that can survive in areas with high heat and unstable microclimates begin to take over in the following stage of succession. Once these trees become large enough to produce shady environments, forest species start to establish themselves.

Fig 4: Young shade intolerant trees.

Old agricultural trees like rubber can create shade and allow shade tolerant forest trees to grow. This allows some of these areas to skip the shrubby community and shade intolerant stages of succession, but generally these agroforests have less diversity than natural forests due to isolation (native tree seeds cannot reach these forests) and competition from the existing population of agricultural trees. Replanting these areas with forest trees may help to restore the plant diversity while taking advantage of the more stable shaded environments created by existing trees.

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Spatial complexity

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

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.

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Pioneer species

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 <LINK>.

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. 

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.

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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).

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Environment

The average urban animal

We tend to view our species as average, that cannot be further from the truth

As humans we view ourselves as nothing special. This thinking causes all sorts of problems for the wildlife around us, because humans are in fact quite extraordinary creatures, and when we design our spaces for extraordinary creatures we exclude the average animal.

If I was to describe the average animal species, it would be cold-blooded, it has a narrow diet, it is very small in size, likely it can fly and it would be negatively affected by artificial light.

Humans are fantastic at sweating and warming ourselves up. We have one of the best heat regulation systems in the natural world, and it is so good that we rarely think about it. 

We can heat ourselves up when we are cold and sweat off any excess temperature. Many animals have to depend on their environment to be able to do so.

The average urban animal is closer to a small insect than a human.

But this leads us to build cities that are designed for amounts of heat that humans can handle, but many other animals cannot. We also carelessly use materials like concrete and glass that reflect a lot of heat, creating areas that are bearably hot for humans but lethal to some animals.

We eat a lot of things. Our diets are very wide, and we take food from many different levels of the food chain. Compare that to the limitations that most animals face: predators usually have a small set of prey that they can hunt or some herbivores are limited to only single host plant.

When designing habitat, we should consider that many animals have a limited set of items that they can feed on. Many butterflies need host plants to survive, and without these plants you can’t have enough caterpillars to sustain a population of insect feeding birds. 

Many birds are limited by the design of their beak, if there isn’t the right types of fruit or seed available they might not be able to survive in an environment.


We are very much in the upper limits of animal size. We usually compare ourselves to megafauna we see on National Geographic, but considering that the smallest animals are smaller than specks of dust and most animals are actually less than a few centimeters in length, we’re really big. And this is a problem when we think about habitats, we assume that animals need as much space as us. In many cases they can do with less. 

Frogs can live in a system that consists of a few ponds or streams, millipedes can spend their entire lives in a single log and populations of butterflies can survive in small parks or patches of forest. 

Most animals are capable of flight.

The modern human lives in a 2-dimensional world, we rarely need to move upwards or downwards unless we are changing the level that we are on. Therefore we rarely think about 3-dimensional space, especially space that can be reached through flight.

Most species of animals can fly. Most insects are able to fly at least at one point of their lives, birds are capable of flight, mammalian bats can fly, even reptiles and amphibians have evolved the ability to glide. 

This means that they can move in ways that humans can’t. Roads with heavy traffic may be an obstacle to humans, but not a bird. The ledges of buildings and the rooftops of our cities are all fair game for animal habitat. 

We can create light and it doesn’t have a seriously negative effect on us. This is not the case for many animals with strict activity periods. 

Artificial light can extend the activity of birds, causing them to use up more energy or become more stressed. It can be downright lethal to many insects since it affects their navigation and causes them to fly about lights until the die of exhaustion or get eaten by predators.

Humans are a special class of our own. And when we consider the needs of animals we need to consider that animals are very different from us, so we need to design with their need in mind as well. When we do that, there is a surprising amount of space for us and our animal neighbours.





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Heat

To survive in urban environments, many organisms need to deal with extreme heat.

Most animals are what we would call “cold-blooded” (This is not a proper scientific term, it is more accurate to say they are exothermic and poikilothermic). Unlike humans, they can’t generate their own body temperature and depend on outside heat.

They are also less capable of dealing with higher temperatures, it can cause them to overheat. This means many of the hotter zones in our cities are barriers to their movement. 

Concrete and asphalt are thermal barriers that can block the movement of biodiversity.

Our obsession with concrete, steel and glass, the modern designs of our cities don’t take into account the thermal environment. Combined with the tropical heat, our architecture creates an environment that is hostile to life. 

Our cities are often too hot for invertebrates, except for hardy pest species. And when there are no other animals to control them, these pests can multiply out of control. But they often are not enough to sustain viable food chains. 

Imagine a city where controlling the temperature is a goal, and biodiversity is one of the indicators of whether you can achieve that goal. Living things such as trees, rain gardens, green spaces and green walls can greatly help to dissipate heat. 

Not only would it be healthier for all living things, but for humans as well.

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What is urban biodiversity?

Biodiversity is the variety of animals, plants and fungi in an area. It is also the variety of genes within each species.

One of the thousands of species of butterflies found in Malaysia.

Many don’t know that Malaysia is country with mega biodiversity, which means that compared to the rest of the world we have many times more diversity. For example in Malaysia we have 6000 species of moths, 2000 species of bees, 8000 species of ants and 200 species of dung beetles.

The ubiquitous banyan growing out of a  concrete structure.

Of course in cities there are far fewer species. The study of urban biodiversity is about what can survive in our cities and the unique new ecosystems that emerge in them.

An example of urban biodiversity is the patches of pavement plants that grow next to our pathways, or the banyans that take over buildings as soon as they are abandoned. These become the foundation for food chains that allow pollinators or fruit eating birds to live in our cities. 

In terms of genetic variety, a good local example is the different breeds of banana that we enjoy. Malaysia has a wide variety of wild and domesticated banana species, and these allow us to have a wide selection of pisang goreng as well as the genetic diversity to breed more resilient crops in the future. 

Even a garden can seem like a forest to small animals like toads.

There are practices that we can do to make our cities more friendly to wildlife, this website is a repository of information on how we can create cities that can serve more than just humans.

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Pollinator series

Pollinators: Flies

This is a continuation of our series on pollinators. In this article I will cover flies, often overlooked pollinators of many plants.

As usual, keep in mind that a lot of the plant examples are not exclusively pollinated by a single pollinator. Often there can be several different pollinators visiting the same type of flower. For example anything that a fly can pollinate is usually also visited by bees.

Large Flies

I’m generalising larger flies into a single guild, and it is likely this group can be divided up into several sub-groups, but fly pollination is so poorly studied that we do not have a very broad picture of what flies are doing on flowers.

Flies usually feed on nectar when they land on flowers. Since they aren’t as fuzzy as bees, they don’t pick up as much pollen, but some are hairy enough to transfer pollen. Mango farmers take advantage of flies by putting prawn shells around their farms. This attracts carrion flies which then also pollinate the mango flowers.

Hoverflies are sometimes mistaken for bees. An easy way to tell hoverflies from bees is their flight pattern – they fly less frantically than a bee. They are not as fuzzy as bees and usually spend more time on flowers. They also tend to have shorter antenna compared to bees.

While pollinating they hunt for smaller insects and are good natural pest control.

Examples: Hoverflies (Syrphidae), Carrion flies (Calliphoridae), Flower flies (Anthomyiidae)

Flower structure: Fly-pollinated flowers tend to be shallow and grow in clusters.

Plants that they pollinate: mangoes

Small flies and midges

Small flies are very important pollinators of important crops, without them we wouldn’t have cempedak, nangka or chocolate.

Some are very small and can hardly be seen while flying. These flies typically are attracted to downward facing flowers that are close to the ground. Some plants like Aristolochia have elaborate trap flowers that trap the flies for a while until they pick up enough pollen.

Examples: Small fruit flies (Drosophila spp.), Scuttleflies (Phoridae), Midges (Nematocera)

Flower structure: Usually not brightly-coloured, tube shaped flowers

Plants they pollinate: nangka, cempedak, cocoa, Aristolochia

Carrion feeders

This group of insects feed on carrion and other rotting material. Some plants take advantage of this by pretending to be rotting meat with foul-smelling and dark reddish or purple flowers.

While the confused insects, (usually carrion flies or carrion-feeding scarab beetles) crawl around the flower in search of food, sticky pollen gets all over them. When they give up and leave the flower, they bring the pollen to other flowers for pollination. Our famous Rafflesia flower uses this pollination system.

Examples: Carrion feeding scarab beetles (Onthophagus deflexicollis), Carrion flies (Calliphora spp., Chrysomya spp., Lucilia spp.)

Flower structure: The structure of these flowers is surprisingly varied, but they have similar traits of foul smells and dark coloration

 Plants they pollinate: Amorphophallus, Rafflesia, Tacca

References:

Ssymank, A., Kearns, C. A., Pape, T., & Thompson, F. C. (2008). Pollinating flies (Diptera): a major contribution to plant diversity and agricultural production. Biodiversity, 9(1-2), 86-89.


This article is supported by The Habitat Foundation Conservation Grant

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Pollinator series

Pollinators: Bees and Wasps

Often people ask me about how to make their gardens pollinator friendly. This is a tough question, because there are so many different types of pollinators. Guides usually don’t have all of them in one place.

Here, I’ll explain the categories of pollinators that visit plants, as well as the characteristics of the flowers that they pollinate. But be warned that a lot of the plant examples are not exclusively pollinated by a single pollinator. Often, there can be several different pollinators visiting the same type of flower.

To do this, I dug up a bunch of scientific papers and tried to summarise all of it in simple language here. Some of these categories correspond to categories used by scientists, while some have been simplified and combined for the general public.

Since there are so many pollinators I’ve split this up into a few different articles. This one will discuss bees and wasps.

Bees

Bees collect pollen on their hairy bodies and legs. There are 265 valid bee species in Malaysia. 62 species have been recorded in Kuala Lumpur alone (some of these may be undescribed).  Bees can be divided into two guilds: large bees and small bees.

Large bees

These are your typical bees, locally called lebah or sometimes kumbang*. Only honey bees tend to sting, and only if aggressively disturbed. 

They vary greatly in size, from 10mm to 40mm in length. Large bees tend to travel quite long distances in search of flowers, and due to this prefer flowers with more nectar.

Many of these bees are long tongued bees, they have long mouthparts that lets them suck up nectar that is deep in flowers. A subgroup of large bees are the very large carpenter bees, which tend to prefer larger flowers that can support their weight.

Examples: Honey bees (Apis spp.), carpenter bees (Xylocopa spp.), Blue banded bee (Amegilla spp.)

Flower structure: Usually these are not round and are somewhat tube shaped, often with a petal where the bee can land. However they also pollinate or steal pollen from round, shallow flowers by crawling around inside them.

Plants that they pollinate: tomatoes, eggplants, begonia, Senduduk, Coromandel, many wildflowers.

*In the Malay language, carpenter bees are kumbang kayu, although kumbang is also used for beetles.

Small bees

This is a more diverse group of bees, but easily missed due to their small size (2-12mm). They include bees that live in colonies like stingless bees or solitary bees like sweat bees.

These bees are slower fliers with less range than larger bees. Some of these bees have shorter mouthparts and cannot harvest nectar from very deep flowers. They feed primarily on pollen, and therefore tend to prefer shallow round flowers that they can walk in and collect pollen.

Examples: Stingless bees (Heterotrigona spp.; Lepidotrigona spp.; Tetragonula spp.), Sweat bees (Halictidae)

Flower structure: Shallow round flowers which are not tube shaped.

Plants that they pollinate: Basil, lotus, water lily, Lantana, sunflowers, Beggarsticks,

Wasps

Wasps are less furry and much thinner than bees. They can be identified by their thin “wasp waist”. While many are predatory, they sometimes pollinate flowers when they opportunistically feed on nectar or pollen. However they pollinate with less efficiency than bees because they lack the fuzz to trap pollen.

But there are flowers that are adapted to being exclusively pollinated by wasps, although a lot is still unknown about this type of interaction.

Examples: Hover wasps (Liostenogaster spp.), paper wasps (Ropalidia spp.)

Flower structure: Usually these flowers communicate with their pollinators by smell and taste of nectar (some of which cannot be detected by humans).  Some orchids mimic wasps and transfer pollen as the wasp tries to mate the flower.

Plants they pollinate: Some species of Orchids such as Coelogyne sp., usually these have greenish-yellow colours.  At the moment I can’t find any records of Malaysian plants being pollinated by non-fig wasps. (Any help on this would be appreciated)

Fig wasps

Fig wasps are an example of a keystone species that nobody thinks about. Without fig wasps the fruiting events of figs which sustain most birds in urban settings would not be possible. The reason being that fig wasps are the exclusive pollinator of figs.

Fig flowers grow inwards, forming round structures called synconium. The synconium has a small hole in it that is just big enough for a fig wasp to enter. Female fig wasps lay eggs within fig flowers, while also pollinating the flower so it produces a fruit structure that the larva can feed on. The new females emerge, mate with wingless males, pick up pollen and escape the fig fruit to continue the cycle.

Examples: Fig wasp (Ceratosolen spp.)

Flower structure: Synconium. Flowers that grow inwards and look like round fruit.

 Plants they pollinate: Figs

References:

Cheng, J., Shi, J., Shangguan, F. Z., Dafni, A., Deng, Z. H., & Luo, Y. B. (2009). The pollination of a self-incompatible, food-mimic orchid, Coelogyne fimbriata (Orchidaceae), by female Vespula wasps. Annals of Botany, 104(3), 565-571.

Weiblen, G. D. (2002). How to be a fig wasp. Annual review of entomology, 47(1), 299-330.

Ascher, J.S., and Pickering, J. 2020. Discover Life bee species guide and world checklist (Hymenoptera: Apoidea: Anthophila). Available from http://www.discoverlife.org/mp/20q?guide=Apoidea_species [accessed 8 May 2020].


This article is supported by The Habitat Foundation Conservation Grant