Free The Knowledge: How to Rebuild Our World From Scratch by Lewis Dartnell

file that will last long after the collapse of civilization, is the Svalbard Global Seed Vault. This repository is built 125 meters into a mountainside on the Norwegian island of Spitsbergen. The 1-meter-thick steel-reinforced concrete walls, blast doors, and airlocks will protect the biological cache inside from the worst global cataclysm, and even with a loss of power the entombing permafrost (the site is well within the Arctic Circle) naturally maintains a subzero temperature for long-term preservation. Viable wheat and barley seeds will be safeguarded for more than a millennium.

PRINCIPLES OF AGRICULTURE
    The crucial question that you need to be able to answer is: How do I walk out into a muddy field with a handful of seed and make food come out of it before the winter sets in?
    This might seem like a no-brainer: seeds germinate naturally, and plants had been growing quite happily for millions of years before humans evolved. But that doesn’t mean by a long shot that cultivation and agriculture come easy. While plants grow naturally, farming is grossly artificial. You are trying to cultivate one particular variety of plant in monoculture, a pure and uniform crop isolated in a field to the exclusion of all other plants. (Any other plants that do begin growing in the field are by definition weeds and are competing with your food crop for sunlight and soil nutrients.) You are also trying to optimize the density of crop plants in your field, to get as much as possible out of the land and minimize the effort and energy expended in cultivating large areas. But you need to prevent this juicy target from being overrun by insects and other pests or fungal diseases that run riot under such ideal conditions (in the same way that cities are perfect breeding grounds for human pathogens). These two factors mean that a field of crops is a highly synthetic environment, and nature is constantly pushing back at you. It takes a great deal of careful control and effort to maintain this unstable situation.
    Yet you have an even more fundamental problem to overcome in agriculture. In a natural ecosystem such as a woodland, trees and underbrush plants grow by soaking up energy from sunlight, absorbing carbon from the air, and piping up a variety of mineral nutrients from the soil through their roots. These vital substances become incorporated into the leaves, stems, and roots of plants, and, when eaten, become part of an animal’s body. When the animal later excretes, or dies and decays, these nutrients simply soak back into the soil whence theycame. A natural ecosystem is therefore a healthy circulating economy of elements being transferred endlessly between different accounts. But the nature of farmland is fundamentally different: you are encouraging growth for the sole purpose of harvesting and removing the products for human consumption. Even if you spread much of the leftover vegetative matter back onto the fields, you’ve still removed the portion actually eaten, and year after year the land is steadily depleted. So the very nature of farming necessitates that you are progressively removing mineral nutrients, bleeding the soil of its vitality. And particularly with modern sewage systems—our waste is treated to kill harmful bacteria and then discharged into rivers or seas—agriculture today is an efficient pipeline for stripping nutrients from the land and flushing them into the ocean. Vegetation needs balanced nutrition just as much as the human body does, and the three major plant foods are the elements nitrogen, phosphorus, and potassium. Phosphorus is crucial for the transfer of energy, and potassium helps reduce water loss, but it is nitrogen, used in building all proteins, that is most often the limiting factor for crop yield. Unless you’re extraordinarily lucky, like the ancient Egyptians in the Nile valley, where the annual floods revitalize the land with fertile silt, you need to take action to address this fundamental