I was reading up on the extinction phases and dinosaurs, what stands out repeatedly is a gradual reduction in size of organisms due to lower oxygen levels in the atmosphere through each extinction phase. Apparently the earth atmosphere was more oxygen rich before and is slowly declining. That and combined with pollution thats already affecting the atmosphere, we may be heading toward extinction when we think the threat is out there where it is more insidious and subtle, the air we breathe or lack thereof. Even if we did away with fossil fuels and used just clean energy, this decline in atmospheric oxygen may be the real ticking time bomb to life on this planet, not necessarily our sun dying or a rogue asteroid etc.
I'm not sure that is entirely right. There have certainly been periods, most famously the Carboniferous, at which oxygen levels were greater than today, but as I understand it the picture is not one of continuous decline. More here: https://en.wikipedia.org/wiki/Geological_history_of_oxygen
We don't preserve , we are in process of deforestation , See Brazil , Indonesia, Philippine, Siberia. England and Spain empire are finished . they have to resort to coal and other petroleum product . The only one which is replanting tree reclaiming desert is ISRAEL.
Widespread planetary husbandry is relatively new. The next generation will do better than we, and subsequent generations will follow.
