Because humanity can easily exhaust itself over a battle for resources as history has proven too. It was quite benificial to wage war for The British empire when it came to snagging diamonds from under the natives their nose, less so when it came to getting involved in 2 world wars. This example however is ony an analogy of a situation where "competing interrests ultimatly create an enviroment that proves detrimental for all". It's fairly simple to argue that people will act with more urgence if climate issue's as a result of collective greed increasingly affect them aswell. The only difference with that trend is that those on the green side will always argue that the people who already feel the consequences of climate change should expect things to worsen before they get better, which is never a fun thing to hear if one needs to be motivated into change.
