How do I, as a person who accepts the obvious reality of evolution, justify taking action to preserve the wiliwili - or any other species - when it is failing the test of natural selection? For that matter, how does anyone who understands and accepts evolution justify aiding organisms that do not seem to be fit to survive without our help? Why is there such a field as conservation biology, particularly if it is filled with "Darwinist" scientists?
The answer is simple, it is clear, it is obvious to anyone who understands science, and it is apparently incomprehensible to any number of creationists. Science can provide us with information about the world that we can use to inform moral judgments, but it does not provide moral guidance. Scientific knowledge can tell us what the situation was, what it is now, and what it may or may not be in the future. It does not tell us what we should or should not do.
People often use descriptive analysis as a justification for their actions. For example, economists who are too attached to their definition of efficiency. They find a solution to a mathmatical model that suggest the most efficient result (defined as creating the most dollar value) and then jump to the conclusion this is the best result (failing to take into account unequal distribution and diminishing marginal utility).