That is, they focus on the reserve period. The only way to evade the constraints of the pulsereserve pattern involves some form of manipulation of the water input on a massive scale such as modern irrigation engineering. Such engineering requires investment beyond the means of the small local populations. Exogenous investment in the economy of arid lands is analogous to stochastic rain inputs in the ecology. This reasoning by analogy leads to insights into the relationships between populations and their environment that do not prejudice social theory.
Analogy serves as an integration mechanism at the level of the formulation of hypotheses.
A final example derives from the characteristic assessment of arid ecosystems as fragile. Analogy leads to the hypothesis that social systems in arid lands are similarly fragile. Examples can easily be found to corroborate this hypothesis, though not to prove it. But it is worth considering that deficiencies in human wellbeing generally are as much or more due to the fragility of cultural and social systems than of ecosystems. A solution to a desertification problem is not a solution unless it comprehends the problem of human welfare in a socionatural universe.