Why are Orangutans important?

The power of orangutans in ecosystems

Have you ever asked, or answered the question ‘why are orangutans important?’ Because for most people it may never have occurred to them, yet it’s so fundamental to why we do conservationWhy is animal conservation important? Animal conservation is important, because animals are the only mechanism to create biodiversity, which is the mechanism that creates a habitable planet for humans. Without animals, the energy from today’s plants (algae, trees, flowers etc) will eventually reach the atmosphere and ocean, much of it as carbon. The quantity of this plant-based waste is so More. Nonetheless, it’s rare to encounter many people who search deeply for an answer. Among the exceptions is Ian Redmond who recently sent me a copy of his article in Primate Eye [7]. Therein he discusses orangutan nest-building, and considers their role in forest ecology.

I don’t know many scientists even, who have an innate awareness of the power of animals in ecosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More. Those who do, have usually spent an inordinate amount of time among animals. Without this, the rigidity and constraints of pure scientific research, tends to obscure the obvious: that ecosystems cannot exist without animals – and our own survival depends on that.

It’s rarely possible to directly describe this significance though. Instead, biodiversityWhat is the definition of biodiversity? When we ask, what is the definition of biodiversity? It depends on what we want to do with it. The term is widely and commonly misused, leading to significant misinterpretation of the importance of how animals function on Earth and why they matter a great deal, to human survival. Here I will try to More experts will infer this from the ‘magnitude’, ‘scale’ and ‘intensity’ of an effect. If you do this for an animal, you get a measure of what I have coined ‘Animal Impact’. That is to say, the impact animals have on ecosystems.

Orangutans are dynamic forces

It’s true that animals, primates included, disperse seeds, pollinate flowers and prune vegetation. But these are linear traits that describe function(Of an ecosystem). A subset of ecosystem processes and structures, where the ecosystem does something that provides an ecosystem service of value to people. More. Biodiversity, however, is defined by structure, function and process.

If you create a new wetland and make it a uniform bowl-shape, it won’t be diverse. It’s the structural diversity that underpins life on Earth.

Stable structures are complex but to remain so, they need to be dynamic … and this is a process. It’s the animals that create ecosystem structure and to maintain that, the processes have to be complex, continuous and large-scale. They have to respond to changes in the outside world. Take animals away and you get a less resilient world that supports fewer animals, including humans.

As a tourist you might see an orangutan sitting for a moment in a tree. But this belies the true nature of a community of animals that together, create the biodiversity of entire nations. Once you realise the magnitude, scale and intensity of these effects, you cannot deny their significance on soil, water and climate. Orangutans, like all animals, are key to building and maintaining a habitable Earth.

Orangutan nest building

Building nests is a function of orangutan ecology and most primates, including humans, prepare their bed before nightfall. In this instance, orangutans find a location to rest, and gather leaves to create a comfortable place to sleep. It’s common to see these structures dotted along the river banks where orangutans live.

As humans we live in a single house but for orangutans, the whole forest is their home.

Ian Redmond has added up the number of these structures throughout an orangutan’s life:

“… each adult orangutan builds a new nest every evening, and by constructing it, creates a light gap in the canopy – 365 days per year. Nest construction is a bit like folding an umbrella – it makes a light-gap by bringing leaves at the tip of each branch used into a tight ball of vegetation which forms the sleeping platform, like a giant bird’s nest. An orangutan might live for 40-50 years, so if we take 40 years as a reasonable age, he or she is likely to be making nests for 32 years or more. This equates to more than 11,000 such gaps in the canopy per orangutan.

Ian Redmond, Primate Eye October 2021.

With that knowledge, we can look further at the implications of orangutan behaviour on the forest.

What was the natural occurrence of orangutans?

In the 1980s there were an estimated 21,000 orangutans in forest reserves and state parks in Malaysian Borneo. This is an area of about 29,000 km² [2]. However, orangutan territories are only a proportion, as they overlap and are patchy [3]. Males can even have territories of 100 km². Plus, orangutans are more common in lowland forest below 500m.

In prehistoric times orangutans would have been more abundant and widespread [4]. However, their population contracted after the appearance of another primate species – humans. People became a substitute for orangutans. Indigenous humans were (and still are) part of ecology.

In recent years however, half of the remaining orangutans in Borneo have been killed. This is because humans extract value from forest ecosystems now, rather than being part of building them. If anything, our absence should mean there are more orangutans, not fewer.

#1 The magnitude of orangutan impact

As Ian describes, an orangutan will create about 11,000 nests in its lifetime and each of these is about a metre in diameter. To build a nest, the animal breaks branches and weaves them together, furnishing it with leaves. Nest-building is a big chore as one has to be constructed every night [5].

Seeds dropped beneath a night-nest have the added advantage of being in a pool of sunlight, as well as being in a package of nutrient-rich manure, far from the parent plant. 

Ian Redmond, Primate Eye October 2021.

#2 The scale of orangutan impact

A paper written in 2012 [1] looked at nest density of orangutans in Malaysian Borneo (Sabah). Using aerial surveys, they looked at the distribution of nest sites. Lowland forest reserves and sanctuaries remain the most important. However, even low-density regions are significant, because orangutans do some much of the heavy lifting in forest ecology. The following figures show how widespread orangutans are and how they can impact the land on the scale of an entire country.

#3 The intensity of orangutan impact

A new nest is constructed each night and orangutans use multiple nest areas but rarely use the same nest twice. There are no fixed number of nests per orangutan as it’s very site-specific. However this paper [6] implies that there may be as many as 300-600 nest sites per orangutan. These nests are in various stages of degradation, depending on how long since the branches were broken, after which rot and wood-boring insects begin to affect the nest strength.

This makes sense when you consider that orangutans live throughout the forest and individual trees only fruit now and again. Orangutans have to be on the move constantly, following cultural patterns of behaviour, in order to feed themselves and survive. So, any night they can find themselves in a different place.

As I’ve discussed often in this blog, animals not only harvest food but they cultivate it too. It’s the animals that create the ecosystem, not the plants alone. The intensity of animal impact by orangutans is clearly significant, as would be expected for such a big-bodied animal, with a sophisticated society.

The biodiversity value of orangutans

Orangutans influence forest ecosystems at scale, with populations that cover the majority of naturally-forested landscapes. The magnitude of effect from just a single animal is bewildering as the function they perform at great intensity, building hundreds of nests. Every one of these is a dynamic process that creates light and transforms plant energy into food, enabling orangutans to support a huge biomassThe weight of living organisms. Biomass can be measured in relation to the amount of carbon, the dry weight (with all moisture removed) or living weight. In general it can be used to describe the volume of energy that is contained inside systems, as the size of animals relates to their metabolism and therefore, how much energy they contain and More of other animals. Added together, this food chainA single thread in a food web illustrating the chain of animals that eat each other. At the base of the food chain are small high-energy (fast metabolism) animals and at the other end large low metabolism animals. An example would be whales eating krill that eat plankton that eat algae. Or lions that eat gazelles that eat grass. More structure allows forest ecosystems to diversify and stabilise. This inevitably amplifies all nutrientA substance that contains the raw materials for life. At a chemical level, these are contained inside compounds that are absorbed into the body and essential energy-containing molecules are extracted, so that energy can be transformed into other chemical processes that use the energy for living. More processes and creates concentrations of nutrientsEnergy and nutrients are the same thing. Plants capture energy from the Sun and store it in chemicals, via the process of photosynthesis. The excess greenery and waste that plants create, contain chemicals that animals can eat, in order to build their own bodies and reproduce. When a chemical is used this way, we call it a nutrient. As we More in the soil.

In conclusion, orangutans are one of the key components of the forest ecosystem, without which, it collapses.

Orangutans are amplifying and concentrating their effect around feed areas and large emergent trees with uniform canopy. Those spots act like nutrient ‘sources’ and then other animals will transfer(of nutrients) the thing that sets animals apart from plants, is that they can move. Some of the biggest migrations on Earth every day, are the movement of insects like caterpillars, from the stem of a plant to a leaf and back, before turning into butterflies and transferring the energy elsewhere. Large-scale migration of grazing animals and migratory songbirds moves More these out radially into the rest of the forest, which become nutrient ‘sinks’. If you remove the source, the nutrient energy runs dry – which is why tropical forests don’t withhold their nutrients without megafaunaThe largest animals that represent the top of the trophic pyramid. These are the final building blocks in ecosystem structures for maximum entropy production. Megafauna can be measured at any spatial scale. The largest animal that ever lived on Earth is the Blue Whale. In a grassland, spiders could be considered megafauna The term is generally reserved for animals larger More.

There is more than ample evidence now, for the fact that soil nutrient cannot be replaced, without the presence of wild animals. You can see for yourself the decline in soil quality in palm oil plantations. To have any chance of maintaining farmland of any sort, wildlife has to be integrated throughout. There is no human substitute, including fertiliser, that will ever replace animal impact.

Conservation biologists need to start telling the right story

Orangutan nests tend to be associated with taller trees and more uniform canopy structure. But it is wrong to assume that it’s the trees that build this structure!

Orangutans have been around for millions of years. For all that time, they have been creating light gaps, so the dominant trees and uniform structure are created by the orangutans.

For instance, this article by the Orangutan Conservancy is titled ‘How canopy structure affects orangutan nesting sites‘. It should really be titled: ‘how orangutan behaviour effects canopy structure’.

Plants do not create ecosystems. By denying animals the thanks they deserve, for how they create ecosystems, undermines our recognition of their importance for human survival. If we can turn the conversation around to how animals create habitable ecosystems, we will stand a far better chance of protecting them. It’s for our own sake.

This is the story about wildlife that gives me greatest hope of reversing the declines we have seen over the past 50 years. Now we need to create a change in human values and attitudes to wildlife.

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References

1. Gregory, Stephen & Brook, Barry & Goossens, Benoît & Ancrenaz, Marc & Alfred, Raymond & Ambu, Laurentius & Fordham, Damien. (2012). Long-Term Field Data and Climate-Habitat Models Show That Orangutan Persistence Depends on Effective Forest Management and Greenhouse Gas Mitigation. PloS one. 7. e43846. 10.1371/journal.pone.0043846.
2. Simon D, Davies G, Ancrenaz M (2019) Changes to Sabah’s orangutan population in recent times: 2002–2017. PLoS ONE 14(7): e0218819. https://doi.org/10.1371/journal.pone.0218819
3. Singleton, I., van Schaik, C.P. Orangutan Home Range Size and Its Determinants in a Sumatran Swamp Forest. International Journal of Primatology 22, 877–911 (2001). https://doi.org/10.1023/A:1012033919441
4. Spehar, Stephanie N. et al. “Orangutans venture out of the rainforest and into the Anthropocene.” Science Advances 4 (2018): n. pag.
5. van Casteren, Adam & Sellers, William & Thorpe, Susannah & Coward, Sam & Crompton, Robin & Myatt, Julia & Ennos, Roland. (2012). Nest-building orangutans demonstrate engineering know-how to produce safe, comfortable beds. Proceedings of the National Academy of Sciences of the United States of America. 109. 6873-7. 10.1073/pnas.1200902109.
6. Spehar, Stephanie & Mathewson, Paul & Nuzuar, & Wich, Serge & Marshall, Andrew & Kühl, Hjalmar & Nardiyono, & Meijaard, Erik. (2010). Estimating Orangutan Densities Using the Standing Crop and Marked Nest Count Methods: Lessons Learned for Conservation. Biotropica. 42. 748 – 757. 10.1111/j.1744-7429.2010.00651.x.
7. Ian Redmond OBE. Primates, Biodiversity and Climate. Primate Eye. The Primate Society of Great Britain. No. 135. OCTOBER 2021