A tale of ancient sunlight energy with a dark end yet to come

Hartmann (2001) reveals how we humans lived on recent sunlight energy before the discovery of the 300-million-years-old deposits of ancient sunlight energy in the form of coal and then oil. This discovery led to increased production of human food, causing the human population to rise, initially gradually and then sharply. The problem is, these non-renewable energy resources are running out fast and oil is not expected to last another half a century. Without ancient sunlight energy, Earth can support a human population of a quarter of a billion to one billion, and the rest of the population, amounting to over five billion, risks starvation. Therefore, a devastating collision is inevitable between our rising human population (together with its increasing levels of consumption of ancient sunlight energy) and our ability to support this population.

(Retold by Asitha Jayawardena and entirely based on Hartmann (2001). For enhanced readability, the reference (i.e. Hartmann, 2001) is usually mentioned at the beginning of a section only.)

How ancient sunlight energy got stored in Earth

Hartmann (2001) begins the tale, describing how ancient sunlight energy got stored in Earth in the first place.

Around 410 million years ago, the Carboniferous Period began on Earth and it lasted for 70 million years. Those days, there existed only one land mass, called Pangaea (25% of Earth’s surface area) and life forms were limited to plants, fish, insects and small reptiles.

In the atmosphere the carbon dioxide content was very high, leading to trapping of more sunlight as heat. Carbon was available to plants in abundance, so they grew as a dense mat, sometimes rising hundreds of feet. The thick cover of rotting and dead plant material was in some places thousands of feet in depth.

In this period oceans (covering 75% of Earth’s surface) were home to plant matter, mainly simpler types, such as single-cell algae and other microscopic plants. Those near the ocean surface captured the sun’s energy to covert atmospheric carbon dioxide into plant matter carbon and, after death, settled to the ocean floors.

Around 300 millions years ago, a massive disaster struck and its cause is still unknown. It dissembled Pangaea and irrevocably changed the planetary environment. As a result, the thick mat of vegetation sank underground – together with its 70 million years’ worth of stored sunlight energy locked in carbon.

Again, around 205 million years ago, another disaster struck, pushing the ancient sunlight energy storage even deeper into Earth.

Meanwhile, unaware of these deeply buried stores of sunlight energy, life on Earth continued to evolve.

We are all made out of sunlight

Like all life forms on the planet, Hartmann (2001) continues, we humans are made out of sunlight. All life forms exist thanks to a plant somewhere that gathered sunlight and stored it in the first place.

Plants produce food (i.e. carbohydrates) and all other plant matter, from roots and fruits, using the energy of sunlight, carbon dioxide in the atmosphere and water from soil. This process, called ‘photosynthesis,’ releases oxygen as a waste gas. Plants, therefore, can be seen as a combination of sunlight, water and solidified air.

Unlike plants, animals – including us – cannot create tissues directly from sunlight, water and air. So, from the very beginning of the human history, the amount of readily available food (i.e. both plant food and animals-that-eat-plants food) limited our population.

However, in early days, all these plants and animals consumed sunlight in relatively recent years and the buried treasure of ancient sunlight energy remained hidden, unknown to us.

More sunlight energy from other animals and land

Hartmann (2001) turns to the methods we humans initially used to tap more sunlight energy by way of animals and land.

Around 40,000 years ago, we humans struck an important discovery with respect to sunlight energy. Until then, our food supply had been limited to the plants growing, and animals living, around us.

We observed that, although we couldn’t eat scrub brush and grasses, ruminant grazing animals (e.g. goats, sheep and cows) could eat them. By eating their flesh, we could consume the daily sunlight captured by such inedible plants. So we began herding and domestication of such animals and they provided us with useful energy, both as work animals and food animals.

Around this time we also realised that we could replace inedible plants with edible ones in order to increase our sunlight energy consumption. Thus began agriculture, which, however, gathered momentum only around 10,000 years ago.

These two methods – herding and agriculture – helped us convert the sun’s energy into human food more efficiently. Moreover, within a couple of millennia of that time, we started making tools out of metals and this helped us to become more productive farmers.

As food was abundantly available, our human population started growing faster. During the period from 8000BC to the time of Christ, our population grew from a mere 5 million to 250 million.

However, we were still using one year’s worth of sunlight energy every year. The deposits of ancient sunlight energy lay hidden, ‘waiting’ to be discovered.

Treasures of ancient sunlight energy – discovered!

Then Hartmann (2001) ventures into the tale’s climax – we humans discover the buried reserves of ancient sunlight energy!

It was only around 900 years ago that we discovered the 300-million-year-old treasure of ancient sunlight energy. Humans, in Europe and Asia, began using it for the first time, in the form of coal.

Thanks to coal, humans in the Northern climates no longer needed to maintain a certain acreage of forestland for fuel wood for winter. So they converted more forestland into croplands, producing more human food. As a result, our human population rose from 500 million around the year 1000 to the first billion in 1800.

The 1800s witnessed an even more important discovery – the ancient sunlight energy stored in plant matter that had sunk into the ocean floors, trapped below ground and compressed into oil. This discovery opened the door to a mass storage of ancient sunlight energy.

In farms oil replaced draft animals with tractors and machinery and the result was a dramatic rise in food production. Moreover, we realised that oil could be used for making clothing, so that the need for sheep-grazing and cotton-growing land went down. The result was the conversion of more non-food croplands into food production land. Consequently, our human population of one billion around the time of discovery of oil doubled to 2 billion in 1930.

Moreover, oil was a raw material for a variety of products such as synthetic fabrics (e.g. nylon, polyester), plastics and resins for construction. So we started spending the ‘oil version’ of ancient sunlight energy quite fast.

By 1930 we began using oil for food production in a variety of ways – ranging from farm machinery to pesticides – and human food production exploded! In 1960 our population hit 3 billion.

We became more efficient in extracting stored sunlight energy from oil and made more efficient engines for its consumption. Consequently, the food production soared. And so did our population! It hit 4 billion in 1974 and surpassed 5^th and 6^th billion marks in 1987 and 1999, respectively.

At this rate our population would hit 10 billion in 2030, 20 in 2070, and 80 in 2150. But we can’t expect this rate to simply continue because there won’t be enough food.

Without ancient sunlight energy, Earth could sustain a human population of between a quarter of a billion and one billion – the number it supported before the discovery of coal and oil. Today, if coal and oil are not available, the other five billion people would simply starve!

The tragic end yet to come

Hartmann (2001) winds up with a warning of a tragic collision yet to come.

Today, we heavily depend on the continued availability of stored sunlight energy, especially in the form of oil. The problem is, oil reserves are running out fast. Even according to the oil industry’s optimistic estimates, oil would not last for another half a century at the current rate of production.

A collision is therefore inevitable. On one side is our growing human population together with its increasing consumption of dwindling supplies of ancient sunlight energy. On the other side is our ability to support this population. The result is bound to be devastating.

Reference

HARTMANN, T. (2001) We’re made out of sunlight In: The last hours of sunlight: waking up to personal and global transformation, pp. 9-22. London: Hodder and Stoughton In: MAITENY, P. and PARKER, J. (eds.) (2002) Unit 6 Reader: Science and culture in education for sustainability. London: Distance Learning Centre, South Bank University.