CHAPTER 2
Human-Environmental Systems as
Complex Adaptive Systems
Interactions between humans and the environment are both extraordinarily
complex and constantly changing, with interacting feedbacks between
different parts of the system. The science of complex adaptive systems has
been developing to understand interactions like these. This chapter looks at
how the mathematics of complex adaptive systems can illuminate the
interactions between humans and their environment.
Sustainability science is hard!The problem is that answering the questions we care about – How can westop a new virus from spreading? How many tuna can we sustainably catch?
What will the climate be like in fifty years? – requires understanding systems that
are enormously complex and constantly changing.
Historically, science has tackled complex questions by breaking themdown into simpler components that can be understood separately. For example,
legend has it that Newton worked out his laws of motion by studying a falling
apple. Once he discovered those laws, he could use them to understand such
complex questions as how the planets wheel about the heavens. Predicting
planetary motion with perfect precision gets tough – after all, every object in the
universe is simultaneously pushing and pulling on the Earth, and Einstein’s
relativity theory tweaks the orbit as well – but Newton was able to get an
excellent approximation using the simple principles that govern the apple.
That’s not possible with many of the problems in sustainability, becausethe parts of the system interact in much more subtle ways, with changes that
feed back into one another. For example, when the planet gets warmer, sea ice
melts. The dark ocean that is then exposed absorbs more heat than the white
sea ice does. That makes the planet get warmer, which melts more sea ice,
which warms the planet, which melts more sea ice... As a result, to predict future
temperatures, it’s not enough to understand the isolated questions of how sea ice