Review "Engineering: Worldwide ebb" by yi jing

It shows that humans consume resources equivalent to more than half production achieved by all the plants and other primary products on earth. Melanie Moses thought that humanity’s greatest challenge is how to reduce the demand for energy in increasingly complex, networked and energy-dependent societies. The article mentioned that it is crucial to need to detailed understanding structure of networks we have created, how networks change as they grow, and how networks constrain individual behavior.

Firstly, a question of size is introduced. Based on the Metabolic Theory of Ecology (MTE) which offers a way to understand the dynamics of flow through networks, a group of biologist and physicists experiment and compare between elephant and mouse. They figured out that the larger the animal, the longer its cardiovascular system takes to deliver resources to its cells, as a result that elephant grows systematically more slowly than a mouse, with a slower heart rate, a lower reproductive rate and a longer lifespan. Likewise, the rate at which a system processes energy drives much of its broad-scale behavior, whether that system is an organism, society or technology.

Secondly, a common trend mentions that decline in fertility rates that occurs with economic development. As societies consume more energy, people become wealthier but they also have fewer children. In addition, the proportion of energy available for reproduction declines. The same as the infrastructure grows, we get more out of it, but we must invest proportionally more into it.

The last, crucial messages are issued that human societies are complex systems that persist by consuming energy, but energy consumption cannot be lessened simply by reducing individual demand; and centralized networks, in which resources flow from a central place out to scattered destinations, deliver energy less efficiently when they transport goods over longer distances. These issues point out the importance of the efficiency drive. It mentions that it is better to increase in size more efficiently than purely centralized ones.