To show the relationship between global warming and a smaller koala population.
Explanation:
A cause-and-effect organizational structure is when an author talks about how something came to be and also presenting the consequences of that act. In other words, the organizational structure of a text shows how something came to be and what that resulted in.
In the given passage, the author talks about how koalas in Australia are affected by climate change. The passage also shows how their survival is affected by the need to look for additional food. Therefore, the author uses the cause and effect pattern to show how the global relationship is related to the decreased population of the koalas.
