An ecosystem is a just another word for a community: it is a group or community of organisms living in a particular environment. So whether it is a group of one-celled amoebas or a pride of lions, you can define all of those communities as an ecosystem. Almost all life forms are part of some sort of ecosystem. The members of that ecosystem sustain the balance of each ecosystem through processes that include the life cycle of those organisms, their food supply, the climate or health of the environment of the ecosystem and competing ecosystems.
When you understand that an ecosystem is a community of organisms, it becomes clear that the survival of that ecosystem is truly dependent upon the members of that community contributing to maintenance of the ecosystem. Human beings are a perfect example, because theoretically, humans are all working together to maintain their ecosystem so that they ensure the survival of their species. Community members typically are assigned different tasks according to their specialty, so in bacterial ecosystems, one may break down enzymes while in a human ecosystem, some people may be lawyers, doctors, artists or teachers.
Ecosystems are microcosms of a larger community of organisms. Acknowledging this fact helps you to see that while the bacterial ecosystem is virtually undetectable by the naked eye, it is dependent upon more evolved ecosystems above it in order to thrive. As a human being, you share a large responsibility as you are a part of one of the most highly evolved communities on the planet. However, destruction or disregard for other ecosystems can lead to a breakdown in community functioning and a denigration of natural resources. Without one-celled ecosystems or insect ecosystems, humans would be overrun with vegetation and thus the planet would be virtually uninhabitable.
As human beings become more aware of their interdependence with other ecosystems and the negative effects of an ecosystem's demise, it has become increasingly more important to promote the preservation of various ecosystems. Keeping the oceans, forests, rivers, lakes and mountains clear from human industrial waste and debris is more than just aesthetically pleasing but a step toward ensuring the survival of the organisms inhabiting those areas and thus helping to maintain their ecosystem.