Philosophically speaking, ethics is concerned with the evaluation of human actions – which attempts to understand the nature of morality and to define that which is right from that which is wrong(1).
From a professional viewpoint, ethics typically pertains to a code of professional standards that contain aspects of fairness and duty to the profession and to the general public.
A useful distinction between ethics and morals is that morals are influenced by established social customs (which may over time present ethical dilemmas).
As applied to sustainability, the consideration of ethics lies at the core of our business, governmental, and collective decision making. In many ways, choices revolving along sustainable concerns are simultaneously ethical as well.