Why Preserve The Species Facing Possible Extinction?

Because each & every creature in this world relies on other species for its survival. If we remove one out, then it will effect the whole ecosystem. Especially eliminating a keystone species can have seriously nasty results.

Think of the american grey wolf for example. Once their population started to fall in the yellow stone national park(World's First National Park) the numbers of the elks started to rise dramatically. Which only resulted in a lots of tummies that needed to be filled with willows, aspens and other trees that provided shade for the water in the park & kept it cool. With the shade gone the water became too hot for the local trout fish, which in turn took the breeding areas away from the migratory birds that fed on those trouts.

After gray wolves were brought back into the park, they kept a check on the elk population and system came back to normal.