AsianScientist (Feb. 12, 2013) – Imagine 6.9 million people living in Singapore in 2030, or put another way, about one person per 100 square meters if we are not stacked on top of one another. As the White Paper on Population went into parliamentary debate last week, the biologist in me wondered how this issue could be examined using ecological principles.

Looking at the Total Fertility Rate (TFR) of Singapore, or the number of children a woman has during her lifetime, it is clear why we should be worried. The TFR has dropped to a historic low of 1.2, way below the 2.1 number that is needed to replace everyone in the population.

Across Oriental Asia – in Hong Kong, Taiwan and Singapore – we are observing a similar trend of slowing birth rates. Later marriages, delayed reproduction in the 30s, and an increase in education levels have all fostered lower fertility rates.

Singapore is greying, and the only recourse seems to be an increase in immigration to make up for the shortfall in numbers. But is immigration a band-aid solution to a deeper problem?

According to Belgian mathematician Pierre Verhulst, lower childbirth rates should be observed in highly dense populations like Singapore. He explains that the rate of population increase declines as the population closes in on the natural ‘carrying capacity’ of the land – the maximum number of individuals which the environment can support.

This phenomenon is true in nature, where populations evolve towards the most efficient reproductive strategy, a mechanism known as Darwinian fitness.

In a small ‘kampung’ (village) where competition is scarce, the best reproductive strategy is often to produce as many babies as possible and as quickly as possible, but provide less parental care. In a highly crowded and competitive city, however, the best strategy may be to produce fewer babies and nurture them more closely.

Hence, the animal kingdom has very simple principles at its core. Place Singaporeans in exceedingly competitive and dense environments and child bearing rates take a plunge. It worries me that if the population density were to rise any further in Singapore, the National Population and Talent Division (NPTD) will find it more difficult to raise fertility rates even with its enhanced package of maternity leave and cash gifts.

We may also want to consider whether having 6.5 to 6.9 million people living in Singapore is sustainable set-up. In 1968, the ecologist Garrett Hardin published a thought-provoking piece in Science called “The Tragedy of the Commons” that considers the economic problem of finite resources in a fixed space.

Hardin describes a pasture open to all, where each herdsman seeks to maximize his income by buying and raising more cows for sale. Adding more cows leads to overgrazing of the commons, but because the field is shared by everyone, the negative impact of overgrazing is divided among all of them. Here, the only sensible course of action for an individual herdsman is to add another animal to his herd, at the expense of the rest.

Putting Harding’s model into context, if there are 6.9 million ‘herdsmen’ in Singapore, each trying to eke out a living in a resource-strapped city, will he or she make independent decisions that lead to a net benefit for the country?

But is overpopulation – through immigration or childbirth – all that bad? Not always, according to the Allee effect, which says that individual fitness increases as the population density of a species increases. This phenomenon is observed in nature, such as in the increased availability of mates, increased success of pollination in plants, and the aggregation of animals such as fish shoals and bird colonies for protection against a predator.

Human populations also benefit in dense cities such as Manhattan and Seoul. Not only are there economies of scale, a critical mass of talent often leads to innovation and breakthroughs, which in turn draws others in, leading to a vibrant economy.

At some point, however, we surely must ask: Is there a limit to population growth for Singapore, and for our planet?

Projections by the United Nations Department of Economic and Social Affairs (UN DESA) places the world population at somewhere between 7.5 and 10.5 billion by 2050. A major reason for increasing population growth is breakthroughs in medical care, such as the introduction of antibiotics which has prolonged lifespans. Various estimates have placed the world’s carrying capacity in the range of 4 to 16 billion, although the latter figure would eventually result in the loss of all wildlife and the use of every drop of freshwater available.

As for an individual city’s carrying capacity, let’s take a look at the most remarkable story of human population density in recent history – Kowloon Walled City in Hong Kong. After the Japanese Occupation, the city’s population increased dramatically until it contained a staggering 33,000 residents within the size of about five football fields in 1987. The city was demolished in 1994 after it became too unsanitary and unsafe for living.

Given that Singapore is about 710 square kilometers wide, a simple calculation reveals that if we removed all the roads and parks in Singapore, and if we built on every surface like in Kowloon Walled City, we could fit as many as 886 million people into Singapore. And you thought 6.9 million was bad?

But this is no laughing matter. Singapore is already the second most densely populated sovereign nation in the world, with a population density of about 7,500 people per square kilometer.

As the pressures on space and other limited resources intensify, several questions remain to be answered. Will we exhaust the carrying capacity of our little island with a population of 6.9 million? More worryingly, will Singaporeans stop reproducing if and when that figure is reached?

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Copyright: Asian Scientist Magazine; Photo: Kenny Teo (zoompict)/Flickr/CC.

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