I think that environments must change/we must change environments to adapt to the following situations:
-Growing population; With the growing population, our cities are ever expanding due to the need for more homes, workspaces and places for people to live. Adelaide is a rapidly expanding city, there are new buildings being added on, more villages being built and it is busy most of every day.

-Climate chamge; Environments gradually change depending on what the climate is or where the environment is. Say for example a plant lives in a rainforest. It will usually have bigger leaves depending on how tall it is so it can catch more sunlight. We adapt to our environments by building environmentally stable and friendly buildings.
-Wars; depending on wether a country is usually at war, or is in an unstable circumstance, people will usually build an environment that can better protect them from the harm and damage that comes from war.
-Marketing and buisiness competition; people will build and make their buisinesses grow when the oppertunity rises. People most of the time want to do better than the 'other fast food store next door'. As humans we naturally have a love for competition.
There are other reasons that ar'nt as usual as the ones stated above like the fact that people dont know when to stop building.