What we are doing to the planet we are living on?

Hi everyone, I have a question and would like to see where everyone stands on this.
Lets compare the world as a whole to a smaller place in an ecosystem. Lets say the maximum amount of deer in particular alloted, closed off forest, is 200. This forest supports 200 deer stability for a long period of time because of the self supporting ecosystem. Lets say a huge amount of food is dumped in that forest that only the deer eat. So the deer breed out of control and eat all the food, that food is gone and with a population of 2000 deer all the rest of potential food will be gone also. So the deer starve and die in huge quantities and after the damage they did on the environment, it supports only 20 deer now.

Since this same logic can be applied to humans and the world, why would we be worrying about something as seemingly trivial as abortion being legal or not? shouldn't space exploration be a bigger priority? Or at least more of an attention to what we are doing to the planet we are living on?

I really ask this because I do not understand your positions on this. Please help me here.