Paul Currie

Why Day Zero Couldn't Happen!

See the amended version on The Conversation

When dealing with a complex crisis such as the Cape Town water situation, it is important to understand how proposed interventions would achieve the intended goals by using systems thinking. The world has zoomed its focus to Cape Town as the city faces an impending threat of “Day Zero” – albeit with shifting dates. Day Zero represents the point at which the municipality turns of water distribution system for much of the city except strategic and vulnerable areas. The big question is whether the measures in place to manage Day Zero on a day-to-day basis are robust or even feasible. The city has broadcast a disaster management strategy which includes establishing 200 water distribution points across the city, at which citizens can collect their 25 litre daily water allocation. This thought piece utilised system dynamics – a modelling approach - to simulate water collection in this manner over the course of a day (24 hours). Key assumptions were made: the population of Cape Town is estimated at 4 million people – 700 000 people who live in strategic areas or informal settlements will not have their taps turned off – 800 000 people within proximity of informal settlements will potentially source water there; 2 500 000 people will be required to collect water at designated water points; 200 distribution points are planned; an average of 50 taps per distribution site; water distributed is 25 litres per person – individuals are able to collect up to 100 litres a day to cover four day of consumption or share with other members of their household - this model assumes that the whole population must receive their allocation, but does not specify the hoarding or sharing behaviours which enable this; initial water pressure is assumed at a level which allows outflow of 10 litres per minute, which implies it requires 2.5 minutes to fill 25 litres or service one person; a waiting delay of half a minute (30 seconds) from changing between containers and people is assumed; equal distribution of people per water distribution point is assumed.

Insights and possible reactions
With the above assumptions, it would require 12.5 hours to provide water to the entire population per day, which can be cumbersome! Possible reactions to deal with the Day Zero water supply approach, illustrated in Figure 1, include: (i) doubling the number of distribution points (grey), which would require increasing the distribution points from 200 to 400, which will enable serving the population within 5 hours; (ii) changing water pressure to between 20 – 30 litres per minute (yellow), based on the population requiring to be serviced, which enables servicing the population within 8 hours; (iii) increasing the number of taps per distribution point to 75 or 100 per distribution point (blues), which would make it possible to service the population within 9 hours and 7 hours respectively. A combined scenario of 75 taps per site and increasing water pressure to 20 – 30 litres per minute, while maintaining the 200 sites (green), shows that the population are serviced much faster but within 6 hours. This appears more practical scenario, than doubling distribution points, with only one hour less time (5 hours) in servicing the population, in comparison with the combined scenario.

Figure 1_Population Serviced per Distribution Point Scenarios
Figure 1: Population Serviced per Distribution Point Scenarios

Socio-political dynamics of water crisis

Water crisis is a socio-political issue, and the insights discussed above could function perfectly as technical solutions. However, socio-political realities would quickly undermine these imagined, technical, plausible scenarios. For instance, how can the city ensure that people are taking the allocated amount of water? How would military order at a distribution point look in practice? What is the extent of conflict arising at the water points due to long queues and unmanaged behaviours, and how does this compromise the ability to service the people at a distribution point? To what extent can the water crisis contribute to some sort of social cohesion, given that water does not discriminate against anyone? How can water remain in the commons when those with means are able to develop private sources?

The aggregate impact of socio-political dynamics deviates from the well-organised technical solutions proposed above. They can be represented as random shocks, referred as ‘disruption noise’. This could dramatically increase the time required to service each person, implying that less people are serviced per hour (see Figure 2). It also means that, it will require 25 hours to service the population per distribution point, illustrated in Figure 3.

Figure 2_Average Population Serviced per hour due to Disruption Noise
Figure 2: Average Population Serviced per hour due to Disruption Noise
Figure 3_Comparison of Population Serviced per Distribution in Base and Disruption Noise Scenarios
Figure 3: Comparison of Population Serviced per Distribution in Base and Disruption Noise Scenarios

A key insight of the scenarios suggests that should Day Zero occur, the best technical intervention with less time required to service the population, would be doubling the number of distribution points to 400. However, a combined scenario of increasing number of taps per distribution point and increasing water pressure, while keeping the distribution points at 200, would be more practical. Further, the reality of conflict and water collection delays would increase the amount of time needed to service the whole population. These delays are unpredictable and incalculable and are the greatest indication for why Day Zero cannot be allowed to happen. The disaster management plan is unfeasible and would struggle to service people timeously while managing conflict.

A shared responsibility to become water cognisant

Water crisis in the city of Cape Town is a shared responsibility which faces a ‘tragedy of Commons’ systems archetype. What this means is that individuals may act in self-interest (such as water hoarding or wasteful water activities) at the expense of society. The availability of water resource, which may prevent the occurrence of Day Zero, is dependent on everyone acting in water-conscious manners, and being cognisant of how day-to-day activities, contribute to water efficiency and water availability for all.

Cape Town has for a long time, focused and relied, on water demand management measures, with limited interventions on the supply side management. Lessons from the Cape Town water crisis for other cities include better planning by focusing on the root cause of problems and not their symptoms, identifying high leverage intervention points, and understanding how best to affect these interventions. We hope the efforts to record how the many actors in Cape Town have contributed to water demand reduction as well as supply augmentation, will be used when future interventions are needed.

The Cape Town water crisis has been a result of the patterns and trends that systemic structures generated. Further, the variety and diversity of our understanding of how the system works, means that various actors in society (e.g. households, government, business, and academics) perceived and interpreted the systemic structures differently, and therefore acted differently.

This is a lesson that the City should take on: by more actively understanding, characterising, measuring, and communicating its dynamic metabolic patterns, which include not only water, but also energy, food, and wastes. There are many groups in the city that can improve the sourcing, utilisation and efficiency of the resource systems on which the city relies. After all, you cannot manage what you cannot measure.


the memory of water

This poem was presented by Paul at the Joint Conference of the International Society of Industrial Ecology and International Symposium of Sustainable Systems and Technology, hosted in Chicago from June 25-29 2017.

the memory of water
(or: cape town’s linear, unsustainable water metabolism and the lack of anticipatory planning which led to crisis)

August 2014

rain falls on the slopes of the berg river catchment
drops coalesce into streams
that meet the theewaterskloof dam
steady. waiting. evaporating

a pump pumps
(with lightning tamed from broken atoms 50 kilometres away)
with grav assist
water moves through harsh environs
of chlorine and lyme.

in darkness enters the city and
split and split and split again
till bright light opens it upon
hands and dishes – in toilet bowls – from showerheads
sprayed across flowering plants and gleaming mercs
from running taps down muddy roads past informal homes
in boilers and engines and cooling contraptions
reshaped and shifted. evapotranspirated

condensed. absorbed -
the lucky become clouds
free float and fly
or sink underground
to feed green crop
or recharge the aquifer.

while the rest, suds and all
reenter the pipes
darkens conveys through solids extraction
anerobic and aerobic trauma
and absorbed by salty surrounds of ocean water
where nutrients bloom
and biodiversity

ecoli wash past blue flag beaches
touching bathing tourists
city patrons who come to cape town
for natures beauty
and may not feel
the memory of water.

March 2017

No rain has fallen on the slopes of the theewaterskloof
and the city –
surprised by events it predicted in 20 oh 6
– calls for all:
reduce your use

so highway signs count down to the
end of water
ignored by urbanites who imagine
water comes only from taps
120 days left
no thought of the panic elicited
when a disgruntled public
see only
20 days left
so the signs much change
pipe pressure is dropped
and government states plainly its policy:
lets pray for precipitation

meanwhile the gardens die
cars lie conscientiously dirty
while the city’s gone from
green to beige
and blame is passed
from citizens to city
from rich to poor
to fire helicopters dumping dam water on an intense fire season
(predicted in 20 oh 6)

June 2016

no rain has fallen on the slopes of the theewaterskloof
though drizzles tickle eyes of
longing capetonians
looking for rain
a perhaps psychological balm to signal the end
of crisis
hopefully not ending the
3 daily toilet flush – the 2 minute shower – the limited laundry
all part of the 100 litre goal per person.
too bad drizzle isn’t drinkable

when the rain arrives
the waves arise
a storm of note
floods the city but
the dam levels rise

this crisis will last
reduce your use
says the mayor
unveils a new planned portfolio
on sustainable views
of how the city will change
and so ensues
that resource efficiency is finally
on the agenda

August 2030

rain falls on the slopes of the theewaterskloof
flows through pipes to the city
meeting water that’s
with the system it moves through
supports. hydrates

now toilet wash holds value
fueling gardens (indigenous)
and busses (electric)
no highway signs needed
as society’s conceded:
reduce your use – we’re water scarce!

our water adventures in circular fashion
now city’s caught-on
that’s a good pattern
expanding its works
water treatment reverts
to send back grey black blue
for an extra purpose

and throughout the system
pipes are lined with messages to keep
the crisis of cape town
in the memory of water

The 20 most resource intense African cities

Making the shift towards global sustainability requires direct focus on both cities as centres of resource consumption, economic activity, social upliftment and environmental threat, and resource flows and the infrastructure systems that conduct them. In order to compare the sustainability of cities, a resource consumption baseline is useful, particularly to draw out similarities between cities. This can then inform urban decision makers about which infrastructure interventions may be suitable in similar contexts to theirs, and thus find where partnerships may be formed.

The global typology of cities was produced in 2010i. However, when compared with multiple global cities, African cities show very low levels of consumption. This is often confused as being resource efficient, as opposed to lacking equitable access to resources. The agenda for urban practitioners in contexts of local resource deprivation and global calls for reductions in consumption, is to provide greater access to services in a resource efficient manner. The inquiry by Currie and Musangoii aims to draw our the subtleties of resource consumption in African cities which are lost in global comparisons.

1Africa Resource Consumption top 20sm
Figure a & b: 20 most resource intense African cities

Figures a and b represent one output of this inquiry and display the twenty most resource intense cities on the continent in terms of overall consumption (a) and consumption per-person (b). Both maps also show the proportions of biomass, fossil fuels and construction & industrial minerals consumed in each city. This is useful for speculating about the level of development of industry, as well as quality of life enjoyed in these cities, both of which are correlated to consumption of fossil fuel energy. A few insights are shared here:

Figure a shows most of the continents large cities, which are understandably the largest consumers of resources. Notably, Cairo, Alexandria, Algiers, Johannesburg, Tshwane, Durban and Cape Town consume larger proportions of fossil fuel and less biomass than most other cities, which relate to the strong economies and lower proportions of informal settlements seen in Northern and Southern Africa. Cities in Eastern, Middle and Western Africa show larger proportions of biomass consumption, suggesting that this may still be the predominant energy carrier and construction material. Notably, with the exception of Lusaka and Nouakchott (largely extractive economies) these cities are absent in Figure b. This suggests that, despite their size, citizens experience lower levels of resource consumption in these cities. Northern and Southern cities are widely present in this map, congruent with the stronger economies and higher quality of life. Zambian cities, Windhoek Libreville and Nouakchott show high material consumption, likely due to mineral processing and refining present therein.

High water consumption curiously takes place in cities in water scarce countries. This could reflect a larger need for industrial and residential water in dry spaces, or better tracking of water consumption due to only limited sources of water.

Only 31 of 120 cities examined are showcased here. The quantities of resource consumption are likely overestimates as they are scaled from national data. However, they prove useful for comparison between cities and as starting points for cities in which minimal city-level data is collected.


i. Saldivar-Sali, A. 2010. A Global Typology of Cities: Classification Tree Analysis of Urban Resource Consumption. Cambridge: MIT, September.
ii. Currie, P.K. and J.K. Musango. 2016. African Urbanization: Assimilating Urban Metabolism into Sustainability Discourse and Practice: African Urbanization. Journal of Industrial Ecology.

Differential African Resource Consumption

As part of an inquiry into the resource implications of rapid African urbanisation, we present 25 maps which depict differential population size, urban proportion and consumption of materials and energy, as well as carbon emissions for 53 of 54 African nations. Such maps are necessary tools for shifting discussion away from ‘a singular Africa,’ particularly in the context of urbanisation and resource requirements. What follows is a (by-no-means exhaustive) discussion of what we observe from these maps.

Africa has a population of almost 1.2 billion people, 30% of which is concentrated in five countries: the Democratic Republic of the Congo (64 million), Ethiopia (89 million), Egypt (79 million) Nigeria (164 million) and South Africa (51 million). Countries that have the highest proportion of urban dwellers, such as Algeria, Djibouti, Gabon, Gambia, Libya and Republic of the Congo, have smaller overall populations. The overall population of the country shows some correlation to the level of aggregate resource consumption, while the level of urbanisation shows direct links to the level of per capita resource consumption. This is partly due to our expectation that urbanisation typically promotes diversification and strengthening of economies, processes which require more resources. Whether urbanisation in Africa is driven by industrialisation or demographic shifts is a debate for another place – though it should be cognisant that each country will differ.

Africa Resources Currie May Consumption Metabolism uMAMA
click map for quality version

Comparing the aggregate consumption level of these countries is useful for global comparisons of consumption, as well as to understand which countries are most responsible for global environmental issues. Comparing per capita consumption may be a better for comparing the resource consumption as it relates to a country’s economy or the quality of life of its population.

Aggregate Consumption

When looking at energy, Northern Africa, Nigeria and South Africa show the highest consumption of fossil fuels and electricity, resulting in high carbon emissions. Due to investment in cheap, non-renewable electricity, Algeria, Egypt, Libya, Nigeria and South Africa show the largest emissions of carbon dioxide. In this way, as much as the global North must accept responsibility for climate change and historical atmospheric pollution, Africa too has its own continental reprobates. These high energy consumers have notably small proportions of renewable electricity generation compared to Middle and East African countries, who are utilizing available hydro-electric and geothermal resources. Egypt and Nigera may be exceptions: they produce a large amount of renewable electricity relative to other countries, but it still makes up only a small portion of their overall consumption. For countries with predominantly renewable electricity generation, their overall level of energy consumption tends to remain low - it will be important to continue to promote renewables here, perhaps through technology leapfrogging, instead of a transition to fossil fuel energy infrastructures. The lowest aggregate energy consumers are Saharan countries as well as Central African Republic, Namibia, Uganda, and Zambia.

Material consumption follows a similar pattern in which Northern countries, Nigeria and South Africa are the highest aggregate consumers of most materials except biomass. The highest biomass consumers are Ethiopia, Nigeria and Sudan, the highest construction material consumer is Egypt and the largest fossil fuel consumer is South Africa. Algeria, Angola, Botswana, Egypt, Mauritania, Egypt and South Africa show high consumption of Industrial Minerals and Ore. This may be a function of data availability, as it is unclear whether these countries show high consumption because they have large extractive industries or because they have strong industrial presence. It is likely a mix of both. The lack of infrastructure and institutions to process, refine and manage these resources represents a challenge described as Africa’s Resource curse, in which extractive economies remain entrenched and unable to diversify.

The levels of aggregate water consumption are somewhat curious as some of the highest consumers are notably water-scarce countries. This may be either due to water-scarce countries having more precise measurements of water consumption (as tracking scarce resources more prevalent, or a reflection of how warm, arid climates, prevalent in Northern and Southern Africa affect both household and industrial water needs.

Per Capita Consumption

South Africa, Egypt, Libya, and Algeria still dominate the consumption of Fossil Fuels, Electricity, Construction Materials, and Water even on per capita basis. They are still the biggest emitters of Carbon Dioxide. Nigeria is an exception as, even though it is a high aggregate consumer of resources, its share of its resources is diluted among a large population. Similarly, though Botswana and Namibia show low aggregate resource consumption, their share of resources is distributed over a small population, leading to quite high per capita consumption of resources.

If we equate resource consumption to quality of life, we might suggest that those living in Nigeria may enjoy a lower quality of life than those in Botswana. However, this does not necessarily take into account economic inequality in which most of the resources may be enjoyed by only a portion of the population, while the rest struggle to gain access to basic services. In this way, inequality measures would be important considerations for further investigation. This also highlights a challenge for promoting resource efficiency in much of the continent – the priority for national governments should be to provide resources those lacking basic services; however, it should be done in resource efficient manners to avoid lock-in to unsustainable infrastructure systems.

Per capita resource comparisons may also be useful for speculating about countries’ degree of progress along the socio-metabolic transition. This is the shift from agrarian economies, which primarily rely on biomass for construction and energy, to industrial economies which rely on fossil fuels for energy, make use of more industrial materials, and may make use of more energy intensive construction materials. Speculating thus, Northern and Southern African countries are farther along the socio-metabolic transition, with Kenya, Tanzania, Gabon, Angola, Ghana, Cote d’Ivoire, Nigeria and Senegal also in transition. Saharan and Middle African Countries show the least progress along the socio-metabolic transition. These are overall speculations and is by no means a rigid categorisation, as pockets of industry, affluence and high quality of life will be present in all African countries.

Data from 2010.

Habitat III


Habitat III, the United Nations Conference on Housing and Sustainable Urban Development, took the city of Quito, Equador, by storm from November 17 to 20, 2016, with attendees filling the Casa de la Cultura between Quito’s old city and the Mariscal. Paul Currie, a researcher with urban Modelling and Metabolism Assessment, the Centre for Complex Systems in Transition and the School of Public Leadership at Stellenbosch University, South Africa, participated in the conference and offers some reflections here:

Quito made a perfect setting for the conference, given its location in the global South, equipped with precarious cliffside housing, urban sprawl, limited highways, buses and cars spewing exhaust, an abundance of street vendors and a spectacular mountainous location in the midst of four active volcanoes. The concept of disaster resilience is quite apt, given the 1999 eruption of Pichincha volcano covered the city in ash. The city was also in the middle of it’s fiesta de la luz, drawing thousands of Ecuadorians to see the light shows projected on ornate churches – though such a description does no justice to the spectacle. As with any of these large events, the city takes on a new electric life and we’re left unsure if this is how it normally feels to wander Quito’s streets.


The conference drew together over 25000 single-day attendees of a rumored 45000 registrants. These attendees were united by a fascination with the form, processes and relationships of cities, and the starting point for most discussions was a unified acknowledgement that cities face challenges and that cities are the key to addressing global socio-economic and socio-ecological issues. From there, the points of divergence are the different language we use to describe these challenges, and the varied perspectives, approaches and agendas proposed to address them.


The 20-year latency between Habitat Conferences (The previous ones took place in Istanbul in 1996 and Vancouver in 1976), means that the global context has shifted drastically, and the world is in need of a renewed focus of its development priorities. This is seen by the recent concentration of mega-events that have resulted in the Paris Agreement, Sustainable Development Goals (SDGs) and the African Union’s Agenda 2063 to name a few.

Habitat III created a forum in which we could question together how cities have been developed, both as shining beacons of human ingenuity and creativity, and as structural enforcers of inequality and exclusivity. With this in mind, many note that the New Urban Agenda, the centerpiece of the conference, will not work if we overlook global and local inequity. The New Urban Agenda acknowledges a wide range of systemically discriminated groups including ‘women and girls, children and youth, persons with disabilities, people living with HIV/AIDS, older persons, indigenous peoples and local communities, slum and informal settlement dwellers, homeless people, workers, smallholder farmers and fishers, refugees, returnees and internally displaced persons, and migrants, regardless of migration status.’

While the NUA has a very clear desire to promote sustainable urban development, as visualised by the word cloud below, it is critiqued for not establishing its own targets or a means to measure the success of it’s many suggested interventions. What’s more, while it effectively stands as the embodiment of SDG Goal 11 to make cities and human settlements inclusive, safe, resilient and sustainable, it is very poorly connected to the goals and targets in the SDGs. This is highlighted as a missed opportunity by David Simon, of Mistra Urban Futures, in a conversation about the Habitat process. The power of cities as concentrators of people, welfare, innovation, as well as social diseconomies (crime, disease, poverty, inequality) and ecological impact, makes them the almost perfect levers for propelling global sustainability as embodied by many of the 17 SDGs. However, successful implementation of the NUA will be left to the interpretation of its broad rhetoric by local and national actors, many of whom are under-capacitated. Despite this, Simon explains that the NUA is the first UN document to ‘recognize the critical role of sub-national authorities and non-state actors’ – a major achievement for the UN system.

Screen Shot 2016-10-31 at 10.09.50 AM
word cloud of the key terms in the new urban agenda

The Sunday before the conference began, a Mayors assembly shared voices from the heads of cities, which I felt set the tone for the conference and highlighted the varied nature of urban challenges and priorities worldwide:

  • Ban Ki Moon, Secretary General of the United Nations, challenges the Mayors to raise their voices to speak for their people.
  • Ada Colau, the Mayor of Barcelona shared enthusiasm that ‘the right to the city’ was incorporated in the NUA
  • Tri Rismaharisni, Mayor of Surabaya shared that ‘gender equity works for all,’ saying that gender parity will be the foundation of sustainable development.
  • Dennis Coderre, Mayor of Montreal argued the importance of local government, which is more engaged with people’s daily lives and needs, and called on national governments to realize the importance of cities and local authorities.
  • Miguel Angel Mancera, Mayor of Mexico City suggested that cities should receive funds directly without intermediaries.
  • Gustavo Baroja, Prefect of Pichincha, argued that we must break through the binary distinction of urban or rural as both are inter-reliant.
  • Michael Muller, Mayor of Berlin, asserts that we must turn the NUA from a piece of paper into actions, citing his challenge of bringing refugees from the periphery into the city.
  • Emil Elestianto Dardak, the Regent of Trenggalek, encourages us to adopt sustainable patterns of production and consumption.
  • Kumar Rai Bipin, of the Urban Board of Delhi, declares healthcare as a fundamental right and urges that slum areas are upgraded and not relocated.
  • Daniel Martinez, the Mayor of Montevideo, argues that we need a radical declaration of economic realities: that we will not achieve justice if we cannot address the lack of resources. Fighting for a social economy which redistributes wealth is a requirement for sustainability.
  • Mohamad Baqer Qualibaf, Mayor of Tehran says that ‘nobody can be a mayor if they are not in love with their city’ and motivates that cities should be constructed for their citizens

These desires were voiced in the buzz-words plastered around the conference, calling for cities that were sustainable, resilient, smart, participatory, inclusive, and in the multitudes of presentation and exhibitions throughout the conference.


With the adoption of the NUA, the global urban reality is unquestionable, and along with it, the manifestation of all urban challenges, intrigues, speed bumps. This is specifically important for African nations as before the Habitat III process, there was a prevailing denial among many governments on the continent that urbanization is happening, that it is caused by natural growth, or that it could deliver social and economic benefits. This denial may have been the most limiting obstacle facing urban practitioners, as urban policies would be missing vital tools, or focus primarily on anti- or de-urbanisation mechanisms. With an urban reality accepted, what now remains is for governments, through engagement with other stakeholders, to embed the ideas of the NUA in national agendas and develop local targets for developing just, sustainable cities.

Urban Africa

by Paul Currie

Africa is described as 40% urban when comparing regions. This tends to generalise how to prepare for African urbanism, and many approaches fail to register that African nations span urbanisation levels from just over 10 per cent to 80 per cent. Clearly these countries will need differing policies and approaches.

Urban Metabolism of African Cities

by Paul Currie
first published on

I wander through cities and hear them humming around me. They are creatures, machines, fixtures, breathers, parts and pieces, relationships, conduits, conductors, caretakers and crushers. Each city has its own sounds and its own energies that draw my attention and set the rhythm of my feet. The unique vibes in different cities is unquestionable, but cities do follow very similar processes (see Radiolab Podcast). Each city has systems for moving people around, for bringing food from afar, for delivering electricity to our light bulbs, water to our mouths, and data to our phones. These actions or processes can be understood as flows, simple or complex, interwoven, and present in the thousands. These flows of materials, energy, people and information form the metabolism of the city and are responsible for its existence. Unfortunately we do not have enough information about how these flows are conducted within cities, particularly in the global south, which means decisions about service delivery or sustainability are often made without data to prove their efficacy.

Studying urban metabolism allows us to visualise and explain the complexity of socio-technical and socio-ecological processes by which flows of materials, energy, people and information enter and shape the city, service the needs of its people, and impact the surrounding environment. More simply, it shows how the city functions, what type and quantity of resources it uses, and how heavily the city impacts its environment. To aid exploration of urban metabolism, some conceptualise cities as organisms, while others as ecosystems. I prefer the suggestion that most contemporary cities behave as organisms, while the ideal city behaves as an ecosystem: An organism ingests food and water to power its body, to keep it living and thriving. Its wastes are then excreted, out of sight, out of mind. This is a typical modern city: resources come in, are used in processes of economic production (and hopefully human welfare), before the wastes are dumped in the surrounding environment. Cities tend to be located on key resources – most are on water and on fertile agricultural land. Of course there are those which defy a bioregional attitude and are placed on desert or on mineral wealth (Dubai, Las Vegas, Johannesburg). The wastes of cities have huge consequences for a city’s hinterland, undermining natural ecosystems or poisoning people downstream. The global trade apparatus is so established that nations can even export their wastes to poorer places. Thus, a simple goal of urban metabolism analysis could be to make more efficient use of the fresh materials coming into the city, and to properly reuse or recycle waste flows. This is how the ecosystem conception is useful. Ecosystems are defined by relationships between organisms and abiotic systems. In the same way that an ecosystem makes use of detritivores to break down biological wastes into reusable nutrients, so too could the perfect city use our wastes to power its systems. Stockholm powers busses based on biogas from its sewage system. Toronto’s wastewater system contains enough chemical energy to power itself (Bristow & Kennedy 2013). A cyclical metabolism is not only possible, but necessary for growing sustainable cities with low social and environmental impact.

It should be acknowledged that sustainability has multiple approaches. The mainstream sustainability discourse preaches resource efficiency. This is fine for developed spaces of the global north, where overconsumption is the daily routine. However, for countries in the global south, most people do not have access the basic resources they need, so the priority for these spaces is resource equity. The lack of formalised infrastructure in many of these spaces provides an opportunity to create infrastructure systems that are equitable as well as efficient.

Shaping infrastructures requires assessing how flows are conducted in these cities. Resource flows can be formally coordinated and regulated by city planners or government, or follow informal patterns where government is unable or unwilling to provide resources. This can be visualised as the distinction between networked water pipes and decentralized water tankers, bottles, boreholes or sachet water provision, or by comparing supermarket tomatoes to those bought on the streetside. Both systems effectively get water or tomatoes to people, yet informal systems are typically shunned as they do not fit the desired northern (America, Europe, Asian Tigers) image of a modern city. This is problematic as informal systems predominate in cities of the global south and in Africa. Tapping into the innovation and adaptability of informal systems can be useful for city practitioners in providing services or addressing necessary city functions. The successes of waste picking systems in Brazil, India, and Egypt are easy examples.

African cities predominantly function on informal systems as much of the networked infrastructure remains within the boundaries of original colonial settlements. Informality pervades public transport systems, water and food provision, energy generation and waste removal. Analysing these flows is difficult as they are hard to track and quantify. However, finding ways to do so is an important step for empowering city planners with more knowledge about the functions of their cities.

African cities may share attributes such as informal economies, slum dwelling, high youth unemployment, migratory citizens, precarious infrastructure systems (see the Nigerian fuel strike), resource and wealth inequality (see the Dumsor Report), and industrialisation within planetary boundaries. However, it is impractical to make singular recommendations about African urbanism when city practitioners in Arusha will be dealing with very different realities from those in Abidjan. More local urban metabolism studies would be invaluable.

Global urbanisation trends suggest that African cities will house one billion new urbanites by 2050. To aid studies of sustainability or urban metabolism in African cities, it is vital to make a shift from discussing African urbanism as a collective event. The oft-quoted statistic that Africa is 40% urban (the world purportedly passed 50% urban in 2008) overlooks the fact that 17 of 54 African nations are over 50% urban, 9 of which are over 60% urban, and 4 of which are over 70% urban: the African urban future is here. Meeting it with new visions for the sounds and energies of these cities will make all the difference.

Interesting Reads:

  • Bettencourt, L.M., Lobo, J., Helbing, D., Kuhnert, C. & West, G.B. 2007. Growth, innovation, scaling, and the pace of life in cities. PNAS. 104(17):7301–7306.
  • Bristow, D.N. & Kennedy, C.A. 2013. Urban Metabolism and the Energy Stored in Cities: Implications for Resilience. Journal of Industrial Ecology. 17(5):656–667.
  • Kennedy, C., Cuddihy, J. & Engel-Yan, J. 2007. The Changing Metabolism of Cities. Journal of Industrial Ecology. 11(2):43–59.
  • Krausmann, F., Fischer-Kowalski, M., Schandl, H. & Eisenmenger, N. 2008. The Global Sociometabolic Transition. Journal of Industrial Ecology. 12(5/6):637–656.
  • Pieterse, E. 2014. Filling the void: an agenda for tackling African urbanisation. In Africa’s Urban Revolution. S. Parnell & E. Pieterse, Eds. London: Zed Books. 200–220.
  • Turok, I. 2014. Linking urbanisation and development in Africa’s economic revival. In Africa’s Urban Revolution. S. Parnell & E. Pieterse, Eds. London: Zed Books. 60–81.