Most living things live in simple ways, from the earthworm that works the soil to the whale that feeds on plankton. The complexity lies in the interactions between different organisms and contributes to their interdependence and biodiversity, so each link in the food chain contributes to the whole.Our human interrelationships are not so different, since we depend on each other too. Our daily gestures, our habits, our choices and our actions are not without consequences, whether on an individual or societal scale. Sustainable development means drawing on the natural resources necessary for our development without encroaching on those of future generations.