War is different, all sorts of things happen due to necessity during wartime. People accept all sorts of limits for the duration of a war.
"It's better to keep people poor, so they can be more environmentally friendly." Is that a fair summary of what you're trying to say ? This is generally not true poorer countries are generally not as environmentally friendly as rich ones.
It is the bigger economy, the stronger economy which is better capable of adaptation. See the difference between floods in say Katrina and floods in Pakistan. A richer country could afford to spend more on gas, and also more on alternate sources of energy, if and when peak oil occurs.