Humanity is on track to reach 11 billion people by the end of the century, according to recent reports. data provided by the United Nations. The problem is quite simple: humans are at the root of all "sustainability" problems. If humans did not exist, there would be no adverse human impacts. Assuming that you do not wish for the disappearance of the human race - a desire that some movements extreme environmentalists and Sir Hugo Drax, a villain seen at the James Bond - then the key question remains whether there is an optimal number of people for the Earth.
Ds soon as questions about population growth are raised, the work of the Anglican economist and pastor Malthus resurfaces. His Essay on the Population Principlepublished at the end of the 18th century.e century, has become a reference. According to Malthus, populations evolve according to three determining factors: fertility - the number of people born; mortality - the number of people who die; and migration - the number of people entering or leaving a given population.
A pastor named Malthus
Malthus observes that more births than deaths would lead to exponential population growth impossible to meet, even with intensified agricultural yields. This uncontrolled growth would inevitably lead to famine, resulting in mass disappearances. While Malthus was right about exponential growth, he was wrong about its disastrous impact.
Since we are thinking at the global level, let's leave aside the migration aspect, since there is no interplanetary population exchange at the moment. The considerable increase in the total number of human beings is therefore the result of an imbalance between fertility and mortality rates.
Increased farm yields
Putting ourselves on a long time scale, recent demographic developments make one dizzy. And this upward curve jeopardizes the planet's "carrying capacity". The figure of 11 billion could, however, represent a peak before starting to fall towards the end of the 21st century.e century.
This leads us to examine Malthus' first mistake: he did not see that the process of industrialization and economic development that had led to a decline in mortality could also be responsible for the fall in fertility. Improved living standards, access to quality education and empowerment, especially for women, had a strong impact on family size. This same demographic transition is observed, with variations, in most countries of the world.
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This may explain how populations manage to overcome unsustainable growth, but it is still remarkable that the Earth has been able to provide enough for a population that has grown by 700 % in just a few centuries. This was Malthus' second mistake. He simply could not design the incredible intensification of agricultural yields made possible by industrialization.
Seven billion people to feed
The "green revolution" that has quadrupled agricultural productivity since the mid-20th century.e century was made possible by irrigation, pesticides and fertilizers.
Whether we are omnivorous, vegetarian or vegan, in a sense, we are all consumers of fossil fuels, because most fertilizers are produced using the Haber process. This method makes it possible to obtain ammonia (necessary for the preparation of fertilizers) by reacting nitrogen with atmospheric hydrogen at high temperatures and pressures. However, anything that requires heat requires large amounts of energy; hydrogen is derived from natural gas, so the Haber process requires a lot of fossil fuels. If we include production, processing, packaging, transportation, marketing and consumption, it is easier to understand why the food system's share of total energy consumption is so high. more than 30 %while contributing 20 % to global greenhouse gas emissions.
Four major challenges
If industrialized agriculture can now feed seven billion people, what prevents us from thinking that it could be possible for 11 billion people? If famine does not intervene in this scenario, many other problems could arise.
Some research first suggests that production world food supply is stagnating. The green revolution is not out of breath today, but innovations such as GMOs, optimized irrigation or farms underground won't be enough.
Second, today's high agricultural yields require large and cheap supplies of phosphorus, nitrogen and fossil fuels, mainly oil and gas. While mineral or oil phosphorus shortages are not expected in the future, they are, however, increasingly difficult to get, which makes them more expensive. The chaos that affected the world food systems in 2007-2008 provides an indication of the impact that rising food prices can have.
Thirdly, the ground is threatened. Intensive agriculture that relentlessly exploits the fields leads to its inevitable erosion. The use of fertilizers can slow down this degradation, but not indefinitely.
Fourthly, it is not certain that we can maintain yields at current levels in a world that is facing climate change. It is at a time when we will have the greatest number of people to feed that floods, storms, droughts and other extreme weather conditions could have a very negative impact on food production. In order to avoid harmful climate change, we need to conserve the majority of the Earth's fossil fuel deposits in the soil...the same fossil fuels that our food production system is so fond of.
If humanity is to have a future, all these challenges must be addressed simultaneously. The goal is to minimize our impact on those natural processes that provide us not only with food, but also with the water we drink and the air we breathe. The stakes are much higher than those envisioned by Malthus at the time.
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James Dyke, Lecturer in Complex Systems Simulation, University of Southampton
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