Questions on war

[busker]

When was the first world war, ma?
A century ago. 
Before there were no world wars, ma?
No they were too small. 

What's bigger than a world war, ma?
A war of worlds and hope,
a present killing future lives
destroying what's been known.

But why would people do that, ma,
't of greed or are they forced?
They simply do not think enough,
'bout what their actions cause.

What can I do to change it, ma?
The world is large and old,
to change the course of nature is
to change the stories told.

Both good and bad agree on that,
the difference lies of course
in what will be achieved with it, 
is't life and peace or war?

Good poem. It’s engaging, begins well, and ends well.

“The world is large and old,
to change the course of nature is
to change the stories told.”

Is clever.

Improvements:-

 I’d use something other than “nature”. You’re talking about human nature, not the natural world. But the line says “nature”, probably because you were trying to get it to fit.

So use a different two syllable word like “mankind” or “history” or something like that

A poem of this sort - with a repeating question and answer four line pattern - is better with rhyme and a regular meter. The rhyming here is irregular. Irregular rhyme is good in poems meant to sound like natural speech, but the sing song nature here isn’t natural speech, so the irregularity stands out.