We 6 billion human beings are not the only inhabitants of this planet. We share it with billions and billions of animals, plants and single-cell organisms. And it is not merely a case of cohabitation: our very existence depends on our close links with these other organisms. Albert Einstein once predicted that if the honey bee disappeared, the human race could only survive for four years: without bees to pollinate their flowers, the majority of plants would fail to reproduce and would die out, along with all the animals that depend upon them for food, and that includes mankind.
All living organisms, including humans, are part of a complex web of relationships that connects them with one another and with their environment. This interdependence relates to the food chain, to the the balance of populations and to natural cycles. As a result of these relationships, all the basic elements circulate and are exchanged between living beings and the environment in a process that is constant and universal, occurring through us and all around us.
Carbon dioxide is collected from the air by plants which are, eaten by animals or humans, and then one day returns to the the air when the body of these living beings decompose. Oxygen, given off by plants in photosynthesisóthe process whereby plants synthesize organiccompounds from solar energy, carbon dioxide, and water is breathed in by animals or humans. Exertion will cause these to perspire and this perspiration will contain molecules of , water that may previously have been present in the sky, in the river, in the soil, in a fruit, in our brain. Understanding these relationships is the objective of what we call ecology.
What differentiates us from all other species is our awarenessof this interdependence between all living things and of the processes that sustain life. As Albert Jacquard put it, the nature of mankind is to “be aware that tomorrow will exist and that I can act upon it.“