Combining options 1 and 3
Point taken about the importance of the ecological roots. Here's a re-working, re-inserting that:

Sustainability, in a very general sense, is the capacity to maintain a certain process or state indefinitely. However, over the last 50 years or so in recent years the concept has been applied more specifically to living organisms and systems, and to humanity in general. As applied to the human community, sustainability has been expressed as This is sometimes expressed through the idea of meeting the needs of the present without compromising the ability of future generations to meet their own needs.

Sustainability requires that human activity only uses nature’s resources at a rate at which they can be replenished naturally. The term has its roots in ecology as the ability of an ecosystem to maintain ecological processes, functions, biodiversity and productivity into the future. There is now clear scientific evidence that humanity is living unsustainably by consuming the Earth’s limited natural resources more rapidly than they are being replaced by nature. Consequently, for many people, sustainability has come to mean a call for action, for a collective human effort to keep human use of natural resources within the Earth’s finite resource limits.

Sustainability has become a controversial and complex all-purpose term  that is widely applied in many different ways: to different levels of biological organization (e.g.sustainable e.g.,wetlands, gardens, prairies, forests), to different levels of human organization (sustainable households, (e.g., ecovillages, eco-municipalities, sustainable cities) towns, sustainable countries) and to human activities and disciplines and more {e.g., (sustainable agriculture, sustainable architecture sustainable economics).

I sure hope that this one passes muster for all.