But throughout the aeons, a few plants -- mostly algae -- were neither consumed nor did they release their energy stores through decomposition when they died, for they experienced a different fate. By chance and uncommon circumstance, their bodies were exposed to an extremely rare combination of conditions that, over many aeons, transformed and greatly concentrated their substance and stored energy. They were turned into fossil fuels -- petroleum, coal, natural gas.
The process was uncommon, requiring unique and relatively rare combinations of events and circumstances. It was also extremely slow and gradual, requiring millions or billions of years. But in those (relatively) few pockets where it did take place, nothing was taking away or consuming the increasingly concentrated, buried stores of solar energy. So over time, they built up.
With geological change, some of the stores came near to the surface of the land, where human beings could find them. But for millenia, when we did encounter seeps of oil or layers of that peculiar kind of black rock, we made little use of them. The black rocks might burn, but dried dung and fallen branches were easier to collect and feed to the fires. Occasionally oil was used to waterproof items, or make torches, or somesuch.
Over time though, humankind's interest in the fossil fuels increased, with coal being the first to be used extensively. The industrial revolution was first fueled with coal as we used up forests, and discovered how concentrated a source of energy these black rocks were. Then came the increasingly rapid discoveries of petroleum and natural gas. We discovered they were more than just enormously concentrated sources of fuel energy. The fossil fuels had many, many uses! They were and are used to make fertilizers, medications, cloth, plastics, paraffin for candles, asphalt for roads, and more. Much more.
The energy in fossil fuels gave each of us cheap access to the equivalent of many, many working animals (even powerful ones like horses) and slaves -- and we didn't have to feed, clothe, or shelter them, train them, or put up with unwanted behavior from them!
The fossil fuels warmed us, relieved us of work, increased our capacity for producing things (and with that, our capacity to use up many more resources). They made it possible for us to irrigate and live on previously barren uninhabitable land. They allowed us to travel faster and farther than ever before. They restored and even increased the ability of depleted soils to produce crops (albeit of decreased nutritional value). They made it possible to transport food crops, even very perishable ones, and many other goods and products over great distances, even across oceans from one continent to another. They had more uses than these, more than I care to list here.
The proportion of carbon dioxide in our atmosphere increased at an unprecedented rate that mirrored with incredible precision our use of fossil fuels. After all, we were burning -- metabolizing -- the equivalent of millennia of algae growth in the space of only a couple hundred years. This increased the greenhouse effect of our atmosphere, decreasing the amount of heat the Earth radiates into space.
Our population increased enormously, exponentially -- an increase made possible by the unprecedented energy and resources supplied by fossil fuels. Our current human population is estimated to be 3 to 6 times the carrying capacity of Earth prior to the industrial revolution.
It was a heady ride. Our lives changed radically again and again -- steady, seemingly unending "progress". For a while -- a few generations, enough to forget the realities of previous human history -- it seemed that whatever we wanted, there would always be more. We could use up, consume, throw away, and never run out. We began to believe the myth of infinite growth.
But the rules of nature had not changed. We had just found an exceptional source of super-concentrated energy -- and failed to realize that it was finite. We were going through it fast.
We are at the peak of the steep mountain of growth now. Current supplies of petroleum can no longer meet current demand. Supplies of natural gas will soon be in the same boat, if they have not already reached their peak. Coal will follow suit, eventually reaching its peak production and beginning the downward slide - many say within this century (faster if we try to make it substitute for the dwindling supplies of petroleum and natural gas.) The demand for all these fuels is increasing. The discrepancy between supply and demand will grow larger.
What goes up, must come down.