Very nice post @bitminter!
I totally agree that plants are making the air more clean.
We canot live without them in our lifes but many people forget this SMALL detail.
We are trying to evolve and touch the stars ....and many people are giving so many good ideeas.
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Meanwhile in our Planet...forests are burned
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Scientist think about teraforming planets and on ways to travel to other planets faster.
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Meanwhile here pollution increases
Well my ideea on this matter is a simple one and is not needed to change or terraform a planet.
In Philip K. Dick's Total Recall he writes about making a dome that would function with recycled air.
But to this we can add inside the "dome" a small forest with all the plants, trees and animals too.
Because it is proven that inside a forest the air is more clean then outside of it and animals keep maintain the balance, not to forget about the bees who ensure the polenisation of plants.
So.. even that I wrote about sci fi litle bit , I am agreeing with you @bitminter that we need plants and that we will be dead without them.