"Each of us counts, each of us has an impact on the planet, every day. And we have a choice, like choosing what difference we are going to make" (Dr. Jane Godall, 2018).Despite an ecological consciousness reflected in people's beliefs and attitudes, and the existence of public consensus on the need for environmental action, there is sometimes a sense that little and slow progress is being made.Individual practices remain weak and actual behaviors remain weak.In order to understand this phenomenon of inaction, this work proposes to study the ecological crisis at its root and to explore the underlying causes of our behaviours at the origin of the latter. It is based in particular on environmental psychology studies. A field of research that studies the complex set of interactions between the environment and individuals and is interested in the environment in its socio-physical dimensions.This book therefore endeavours to highlight an essential element to be taken into account in order to better understand what we experience, and the actions to be taken to move forward: the human being and his psychology.