I tend to think of this problem as akin to other forms that impact global warming. There are those who drive a hummer by themselves to get to work everyday, driving 100 miles round-trip and even one-way. Many factories aren't bound by intense environmental restrictions and dump tons of toxic chemicals. There are families that have 6+ children.
However there are also people who drive a Prius, have 1-2 children, and factories that abide by environmental groups' suggestions on waste. Now all of those "good" examples still contribute to global warming, even if it is small: a Prius still puts out CO2 and other gases, 1-2 children still adds to the overpopulation problem, and any toxic waste produced by a factory still pollutes the surrounding ecosystem.
However, if most people drove a Prius and bought from environmentally sound companies and had small families, I think we'd be fine. To put it another way: if we removed the small producers of environmental destruction, it WOULD lessen the impact, but hardly enough to make a dent in the problem. If we remove the producers of the large amounts of waste and destruction, we would be fine. I tend to think of those of us that make conscientious decisions about the corals and fish that we buy as no overall problem to the oceans and reefs. If most aquarists out there were like us, and factories didn't pollute their nearby reefs, and cyanide fish catching was a thing of the past, but people still kept aquarium fish, it would be all right. We have to learn to lessen our impact, not necessarily remove it. Just by living, you contribute to the overall impact on the planet, no matter how good of a lifestyle you have. A person's gotta eat, breathe, go to the bathroom, shower...all of those things impact the Earth, its just the extent to which you do it.