Nature knows how to avoid network collapse

By | March 16, 2021

Ruth DeFries writes:

Sometime in the first billion years of the planet’s 4.5-billion-year history, a cell emerged in a primordial stew of chemicals brewing in liquid water. At that moment, the predictable chemistry and physics of the early Earth gave way to seething, roiling complexity. Primitive life thrived in the deep sea, where underwater volcanoes vented heat and spilled a cocktail of chemicals into seawater. Once life was underway, the course of the planet and the life it supported became a single, intertwined system. The Earth’s interacting oceans, atmosphere and life developed into what’s known as a complex adaptive system, in the nomenclature of scientists who study such phenomena. Once its parts were connected and able to respond to their surroundings, feedback loops of cause and effect allowed the system to constantly adjust.

For around a billion years, simple bacteria dominated life – producing sugars by extracting hydrogen from hydrogen sulfide and combining it with carbon and energy from the Sun or from deep-sea vents. Then a switch in bacteria’s survival strategy set off cascading feedbacks that changed the course of all life that followed. Not only could bacteria extract hydrogen from hydrogen sulfide in swamps or in the sea, but some now expanded their repertoire to use the hydrogen from water. They could live anywhere, so long as it had water and energy from the Sun. The effect reverberated into blue-green algae that transformed the atmosphere.

With oxygen as the by-product of blue-green algae’s ability to extract hydrogen from water, oxygen levels built up in the atmosphere about 2.5 billion years ago. Those bacteria accustomed to low-oxygen conditions retreated to airless, stagnant waters, but life as a whole overcame the problem and prospered. Photosynthesising plants thrived as atmospheric oxygen shielded them from the harmful radiation of the Sun. Over the course of billions of years, sponges, corals and jellyfish flourished in the oceans, followed by insects, reptiles, dinosaurs, mammals and other animals on land.

The proliferation of life forms created both problems and opportunities. Many kinds of life couldn’t survive the bombardments from space and the swings in climate from erupting volcanoes. About 250 million years ago, ashes and gases from colossal volcanoes blocked out sunlight and obliterated most forms of life, including trilobites, corals and other marine creatures. Another potential disaster occurred around 66 million years ago, when a comet collided with the Earth. The massive collision ejected dust into the air, which blocked the Sun’s energy once again. Many organisms didn’t survive, including nearly all of the dinosaurs. But the range of life within the Earth’s complex adaptive system meant that some could adapt and life persisted. Without a diversity of life forms, a diversity of species within life forms, and a diversity of individuals within species, life on Earth might not have recovered 250 million years ago, 66 million years ago, or at any other time throughout geological history when an existential onslaught threatened life itself.

The life-saving benefits of diversity don’t just apply to ancient forms of life. In the current day, diversity is humanity’s insurance against the uncertainties of a changing climate. While our food supply depends increasingly on a homogeneous stew of a handful of crop species, nature’s experience shows the wisdom in keeping variety alive. The principle applies not just to plants and animals that humans eat, but to languages, world views, cultures, and forms of knowledge that the modern world overlooks as old-fashioned. In finance, the benefits of ‘portfolio diversity’ are well known, while ‘design diversity’ in engineering creates failsafe mechanisms by creating slightly different parts for the same function. Investments in seed banks and an awareness of the value of non-Western ways of thinking suggest we’re slowly absorbing the principles that allowed evolution to overcome inevitable calamities. [Continue reading…]

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