Malthus is still wrong: energetic limits to human systems

image_3“Large amounts of energy will be required to fuel economic growth, increase standards of living, and lift developing nations out of poverty.” (Brown et al., 2011; see Figure at left).

A key message from Brown et al. in their must-read empirical and theoretical summary of relationships between energy and economic development. The paper reveals a hard fact of human systems: increasing development is coupled with increasing energy use and both of these are going in the same direction- up! Though whether one causes the other will probably remain a chicken and egg discussion forever, they show that Kleiber’s 3/4 power law, a foundational discovery in understanding the evolution of higher organisms, populations, and even ecosystems also applies to human systems (as it does to social insects; eg Hou et al., 2010). Perhaps this is not surprising given the resemblance between the network structures needed to support urban systems (roads, etc. eg. Bettencourt et al 2007), and the veins and other distribution systems needed to support the metabolism of higher organisms that are thought to give rise to these power laws.

Brown et al.’s empirical and theoretical summary of the human predicament- to move forward means to use more energy- is solid, useful, and I agree with it. On the other hand, their jump to a Malthusian argument seems uninspired and typical. Just because energy is required for human systems to develop does not mean that this is a limit to development. Does energy limit the evolution of organisms? It certainly constrains the opportunities and shapes the evolution of organisms, but it is equally an opportunity- it shows that organisms and human systems (like other living systems) have a clear path towards development- by using more energy.

The power law relationships revealed by Brown et al. indicate that to support the world population in 2050 in the current US lifestyle would require 16 times the current global energy use. This is a huge number- and not much better if we substitute Switzerland’s per capita energy use (about half that of the USA). It is also true that our use of carbon-based energy is already changing global climate, fossil fuel use is ultimately unsustainable, the alternatives are expensive, and that in the process of using more energy we humans will change the world even more (Smil 2005). But who would have imagined 300 years ago that humans could fuel a developing society without using more wood and horses, or the changes in living standards and longevity associated with the move to more energy-rich societies? While we are changing the world forever, the evolution of human systems is just beginning.

Media links:

A Physicist Solves the City:

Doomsayers Beware, a Bright Future Beckons:

References cited

Bettencourt, L. M. A., Lobo, J., Helbing, D., Kühnert, C. & West, G. B. (2007) Growth, innovation, scaling, and the pace of life in cities. Proceedings of the National Academy of Sciences, 104, 7301-7306.

Brown, J., Burnside, W., Davidson, A., Delong, J., Dunn, W., Hamilton, M., Nekola, J., Okie, J. & Mercado-Silva, N. (2011) Energetic limits to economic growth. BioScience, 61, 19-26. <download>

Hou, C., Kaspari, M., Vander Zanden, H. B. & Gillooly, J. F. (2010-in press) Energetic basis of colonial living in social insects. Proceedings of the National Academy of Sciences. <link to paper>

Kleiber. Max (1932). “Body size and metabolism”. Hilgardia 6: 315–351.

Smil, V. (2005) Energy at the crossroads: global perspectives and uncertainties, edn. The MIT Press.