Ecosystems can be of any size. A small pond in a forest is an ecosystem, and the entire forest is an ecosystem. A farm is an ecosystem, and a rural landscape is an ecosystem. Villages, towns and big cities are ecosystems. A region of thousands of square kilometers is an ecosystem, and planet Earth is an ecosystem.
Although humans are part of the ecosystem, it is useful to think of the interaction of humans and the ecosystem as the interaction of the human social system and the rest of the ecosystem. The social system includes everything about people, their population, and the psychology and social organization that shape their behavior. The social system is a central concept in human ecology because human activities that have some impact on ecosystems are strongly influenced by the society in which people live. Values and knowledge - which together constitute our worldview as individuals and as a society - determine how we process and interpret information and how we translate it into action. Technology defines our repertoire of possible actions.
These possibilities are limited by social organization, and social institutions that specify socially acceptable behaviors, transforming them into real actions. Like ecosystems, social systems can be on any scale - from one family to the entire human population on the planet.
Through the use of machines or human labor, people use energy to modify or create ecosystems by moving materials within them, or between each other. They transfer information from the social system to the ecosystem whenever they modify, reorganize, or create an ecosystem. The crop that a farmer sows, the spacing between crops, the alteration of the biological community of a field by weeding, and the modification of soil chemistry when applying fertilizers are not only material transfers, but also information transfers, since that the farmer restructures the organization of the ecosystem of his farm.