I think ecosystem balance is always needed. If lose that balance who knows what would happen to the ecosystem. I would hate to see what would happen if it was thrown off on a large scale. Its always about keeping things within the parameters of what they are suppose to be, ruining that balance in nature has consciences.
While it is true that over 99% of all species to have ever lived on earth went extinct, we should be very concerned now with disappearing species. The reason for this is because now we are causing these species to go extinct. And if it's out fault, we should stop it from taking place.
I believe species loss can be natural or it can be a human related problem. When we can directly correlate the cause to us, we should be concerned. The food chain is very important to all living things and if it starts to fall apart it will cause us major problems in the end.
Yes, we should be concerned about disappearing species, because losing a species could upset the food chain. Also, we lose a little bit of the earth and mother nature every time another species disappears. We never know what we could have learned from that species later on, if we let them go extinct.