It’s the carrying capacity, stupid!
Dakhla, September 19th, 2017
The Easter Island (Rapa Nui) is one of the most isolated inhabited islands in the world, being over 2,000 kilometers away from its closest neighbor the Pitcairn Island. By the time of European arrival in 1722, the island had no trees, a poor population of about 3,000 people, and a few hundred Moai statues scattered along the coastline. The famous statues, each carved from a single massive stone, were puzzling to the European discoverers, because the islanders that were met by the Europeans seemed unable to support an artisan class, let alone move the monolithic statues of up to 86 tons. The mystery of the Moai statues invited some wild origin stories over the years, with some speculating that they were remnants from a civilization of the mythical sunk continent Atlantis, or even that they were extraterrestrial, but the most plausible version is that the statues were created before Easter Island’s civilization collapsed. Carbon dating of soil samples indicates that the first settlers arrived around 400 A.D. on an island covered with palm trees.1 The same technique shows a noticeable forest reduction from 900 A.D. and complete deforestation coinciding with the island’s population peak at 10,000 people around 1400 A.D.. Not long thereafter the island's first weapons appear in the archaeological records.
This grim history of the Easter Island can be explained with a theory that was introduced by Thomas R. Malthus in 1798. In his Essay on the Principle of Population Malthus describes that: “Population, when unchecked, increases in a geometrical ratio [that is, exponential]. Subsistence increases only in an arithmetical ratio [that is, linear]. A slight acquaintance with numbers will shew the immensity of the first power in comparison of the second.”2 Malthus warns that, if population growth is not kept under control with preventive measures lowering the birth rates, the population will outgrow the carrying capacity of its environment and collapse through higher death rates; the latter mechanism is also known as the Malthusian catastrophe. His theory led the UK to keep census data through the British Census Act of 1800 and is said to have influenced both Darwin and Russel Wallace, the pioneers of evolutionary biology.
However, more recently, Malthus seems to have fallen from grace in mainstream economics.3 Critics of Malthus point out that the assumption of linear growth in food production is flawed and that the assumption that the population increases exponentially does not hold as countries get richer. Indeed, countries with high incomes have lower birth rates, and during the last two centuries food production has grown faster than the population (although not without adverse effects, for example, claiming more land for agriculture and industrial fishing both contribute to the loss of biodiversity). Some critics of Malthus go as far as to claim that we have never observed a Malthusian catastrophe; obviously, they must be unaware of the above example. I reckon that we would have observed more Malthusian catastrophes, if it wasn’t for migration.4
The bus from Agadir to Dakhla qualifies as one of the least comfortable nights I’ve ever had. Even with my legs folded underneath my seat, my knees were jammed against the seat in front of me for about twenty hours. The monotone desert on my left-hand-side and either desert or ocean on my right-hand-side offered little distraction, and neither did my fellow passengers. If anything, the stares I received in the bus and during the stops along the way seemed less friendly the further I moved south, but this probably just reflected my less than cheerful state of mind. The only consolation was that I still had enough battery to listen to music, and on the tunes of Tiken Jah Fakoly my mind wandered back to Essaouira.
Alef decided to wait for my conference to finish, so we could visit Essaouira together. We did a little souvenirs shopping, visited several galleries, and after a short stop at our hotel to change into our new djellabas, we were just in time to catch the sunset overlooking the silhouette of the city walls and dozens of seagulls playing in the wind. On her penultimate day in Morocco, we went back to Agadir, as she had to catch a flight from there. By now, it seemed that the butterflies were mutual, as she told me that she was wanted to extend her travels and join me to Dakar. Unfortunately, the visa policies of many African countries are as unwelcoming as the European. So instead, the next day we said our goodbyes, wondering if we’d ever see each other again.
Just before entering Dakhla, the bus was stopped at a checkpoint by the local police, and being the only (obvious) foreigner, I was pulled off for a chat. The officer wearing a black leather jacket and opaque sunglasses asked me why I was visiting Dakhla. My reply, that I was planning to rest for a night or two before travelling onward, didn’t seem to satisfy him. Neither was he convinced by my answers to his follow-up questions where I was planning to stay and whether I knew anyone in Dakhla, because I could only give him the first name of my contact. Only after inspecting my passport and collection of visas, he started to believe my earlier answers, but still seemed puzzled. I figured that it would be fastest to tell him that I’m travelling by bus because I’m afraid of flying.
In explaining Malthus’s theory, I used the concept of the carrying capacity of an environment. Even though the term may not be attributed to Malthus directly, it is in line with the spirit of the theory.5 The notion that every environment can only sustain a population of a certain size implies that we face some level of absolute scarcity. In case you wonder what the carrying capacity of our planet is, several have tried to estimate it, but in my opinion, this is a rather pointless exercise.6 Although the concept of carrying capacity implies absolute scarcity, there is no reason for it to be fixed over time: Economic development through technological progress can increase our global carrying capacity, while imprudent resource consumption, like the consumption of trees on the Easter Island, can deteriorate our carrying capacity.7
The notion of absolute scarcity is at odds with how neoclassical economics treats scarcity. In neoclassical economics – the largest school of thought within economics today – resources are assumed to be scarce relative to one another only. That is, one can substitute one scarce resource for another less scarce resource. This view on scarcity has led to many insights (some discussed in later chapters) and for long the assumption seemed harmless, because it was inconceivable that human consumption could have a global influence. However, it is becoming increasingly clear that we do change global natural processes. Recently, the scientific community started adopting the term Anthropocene to describe a new geological epoch during which human activity has a measurable global impact.8 With the arrival of the Anthropocene, it is becoming increasingly dangerous to ignore that we face absolute scarcity. On top, ignoring absolute scarcity allows for the absurd idea that we can grow our economy forever.9
Malthus’s ideas had a revival when Donella H. Meadows and her colleagues published a study called Limits to growth in 1972. This group, also going by the name ‘The club of Rome’, performed simulations of the consequences of exponential growth with finite resources. Their simulations included relations between the world population, food production, industrialization, resource depletion, and pollution. Their baseline – business-as-usual – scenario predicted that population overshoots the global carrying capacity and starts to collapse in the next decade, unless we would take serious action on controlling our resource consumption. This prediction may come as a surprise, since we have never had higher average incomes and life expectancy.
A little over forty years after their publication, we can assess how well their baseline scenario matches the data so far. Figure 3.1 plots the predicted values in dotted lines together with estimates of the realized values in solid lines. In general, the simulation of the business-as-usual scenario seems to match the observations rather well so far, with the simulations often being somewhat on the pessimistic side. Yet, the real test of these predictions comes only in a few years, and we should aim to prevent the occurrence of this collapse on a global scale.
Figure 3.1: Comparison of the Limits to growth ‘business as usual’ scenario (dotted line) and realized values (solid line)
Source: Turner and Alexander (2014)
In the latest contribution in the Malthusian tradition, Johan Rockström and his colleagues propose to establish planetary boundaries for the impact of our economic activity. Their 2009 article, called A safe operating space for humanity, identifies eight such boundaries and suggests parameter values where possible. For example, the proposed threshold for climate change is set at an atmospheric CO2 concentration of 350 parts per million.10 Rockström and his colleagues argue that transgressing these boundaries carries unacceptable risks of irreversible damage to the global carrying capacity. The authors find that three out of eight of these boundaries are currently transgressed (that is, climate change, biodiversity loss, and the nitrogen cycle), see Table 3.1 that is taken from their article.11
Table 3.1: Proposed planetary boundaries to human activity.
Source: Rockström et al. (2009, p.473)
Despite its relevance, the transition to the Anthropocene and its implications have hardly permeated the economics literature and curricula so far. Economic policy in the Anthropocene should give a more central role to improving the carrying capacity of our planet rather than blindly chasing economic growth. Regrettably, even in the wealthiest nations, the desirability of further economic growth is rarely questioned in the political arena. The promise that a ‘rising tide floats all boats’ is politically more appealing than battling poverty through income redistribution, unless we take the rising tide literally.
Unless you practice kitesurfing, there is little to do in Dakhla, and since the winds were unsuitable for beginners, I spend my day surfing online and talking with the staff of Dakhla Evasion instead. Perhaps it was simply the less romantic side of travelling alone, but I started wondering what I was doing here, and Lagos – my envisioned destination – never seemed as far away as it did today. Back home, many people had already expressed their worries about my itinerary through West Africa, and while I was aware of some safety risks, I expected that much of these warnings would be more nuanced once I got closer to Mauritania. Instead, both the Mauritanian and Senegalese staff I met here echoed the same warnings even stronger: Unless I’d travel with a local guide, I’d better not do it.
I slowly started to feel ill-prepared for the rest of my travel and wondered whether my anxiety could be a side-effect of the malaria pills I started taking. Just when I had gathered the courage to buy my bus ticket to Noaukchott, I received text from Alef: “I miss you.” I miss her as well. Should I break my self-imposed no-fly policy and change my plans by following her? It seems like a crazy idea to do so after meeting her only a week ago, but she was willing to change her plans as well.
I’m thinking back on what the Tuareg nomad I met back in Marrakech told me: “You only need two days of desert to clear your mind.” I have been here only for a day and a half, but I could use a bit of clarity right now! Would I regret it more if I’d end the travel I’ve been looking forward to for months after only two weeks, or would I regret it more if I don’t join Alef to Mexico?
“I sincerely hope, for the sake of posterity, that they will be content to be stationary long before necessity compels them to it.”
John S. Mill (1857, p. 750-751)
1. I base my description of Easter Island’s history on Brander and Taylor (1998), who in turn refer mostly to the archaeological work by Van Tilburg (1994).
2. I added the clarification between brackets to the quote from Malthus (1798, p.4) just in case you are acquainted with numbers, but lack some mathematical vocabulary. Although his work is best known for the Malthusian catastrophe, Brander and Taylor (1998, p.119-120) point out that: “Malthus was not a fatalist. He believed that enlightened public policy could reduce population growth, contemplating both contraception and “moral restraint” as mitigating factors.”
3. For example, The Economist published “Malthus, the false prophet” in 2008 and Reuters ran an article by Hadas (2011) entitled “7 billion reasons why Malthus was wrong”. I considered calling this letter ten billion reasons why Malthus is right.
4. Ghost towns around the globe provide suggestive evidence; e.g. the abandonment of seaside villages such as Great Harbor Deep in Canada, where overfishing led to a reduction in the carrying capacity. Myers (2002) estimates that we may expect 200 to 250 million climate refugees by 2050; that is, unless these regions can adapt to rising sea levels (for example, by switching to floating homes and saline agriculture) or mitigate desertification through reforestation projects. For the Maldives, a country of almost four hundred thousand people and maximum elevation of 2 meters, floating cities may offer the only possible adaption strategy as an alternative to migration.
5. Verhulst (1838) introduced the concept of a carrying capacity mathematically, while Sayre (2008) traced back the first use of the term to a report by the US Secretary of State in 1845.
6. In “How many people can the Earth support?” Cohen (1996) reviews 65 estimates ranging from below 1 billion to above 1.000 billion, and the median estimate is 12 billion.
7. To illustrate the point that the carrying capacity is conditional on behavior further, take the example of the documentary film Cowspiracy: The Sustainability Secret (2014, 1h05m): “The human population drinks 5.2 billion gallons of water every day and eat 21 billion pounds of food, but just the world’s 1.5 billion cows alone, drink 45 billion gallons of water every day and eat 135 billion pounds of food. This isn’t so much a human population issue, it a human-eat-animals population issue.”
8. Crutzen (2002) introduced the term by referring to our impact on land use, the prevalence of river diversion, and the share of the fish stock used for human consumption, among other impacts. Waters et al. (2016) add that the stratigraphic signature of humanity is sufficiently distinct to recognize this new geological epoch by reviewing evidence on the growth of new materials, such as concrete and plastics, and the transformation of land and ocean surface by mineral extraction and trawler fishing.
9. Daly (2013) recommends to distinguish between economic growth and economic development, where growth refers to an increase in the quantity of economic activity, and development refers to an increase in quality. I intend to follow this recommendation.
10. During the Copenhagen summit of 2009, the former Malidivian president Mohamed Nasheed argued for this boundary that gives an estimated 1.5 degrees Celsius global warming, see the 2011 documentary film The Island President.
11. Lewis (2012, p. 417) points out some inconsistencies of the proposed planetary boundaries, among which: “Rockström’s published planetary boundary suggests that we could expand croplands by 400 million hectares before reaching the threshold — something that would seriously harm biodiversity.”