What effect does scarcity have on the choices people and countries make?

Before getting to the affects, lets see what Scarcity and Opportunity Cost means.

In simplest term scarcity means limited/less resources to fulfill the requirements of people.

On the other hand Opportunity cost means next best alternative foregone.

There are limited resources and the needs and wants of people are very high. Due to limited resources there is scarcity and opportunity cost takes place because everyone's wants and needs cannot be full filled. This leads to using best alternatives to serve the needs. Now these affects can both be positive (helpful in fulfilling needs) or negative, depending on the decisions and alternatives opted.