I hope people stop downvoting you because this is an excellent question.
There is a number of species in that ecology today, let's call it N. It's a known good number of species: they work together, more or less, to stay alive as a group.
There are smaller collections of species which are nonviable. For example, if all species disappeared except elephants and tigers (2 species) the entire ecosystem would then disappear (the elephants would starve and then the tigers would) and eventually only inorganic material would remain.
There is a number of species, let's call it K, below which the probability of entire ecosystem collapse is nontrivial. We don't know what K is, but if we care about the existence of any ecosystem we must approach it carefully. And we won't know we've crossed it unless we go over.
We know K is somewhere between 2 and N. I think a good strategy is just to put the brakes on all extinction to try to buy us extra time to do science while we are approaching N=K.
As long as we keep N above K, we have a relatively easy problem: influencing a system at equilibrium. Once N drops below K we have a much harder problem: bootstrapping an ecology from nothing. Keeping N above K gives us more agency for less effort.
For that reason, I think the extinction of elephants would be bad.
It's also not just that the loss of a species is bad. It's that some species are especially important, and it's not necessarily known which these species are:
https://en.wikipedia.org/wiki/Keystone_species
Important also is the rate of species extinction. An ecosystem with some number of species in it can likely cope with a low rate of extinction (as species get outcompeted quicker than the my evolve), but can't cope with several species dying out in rapid succession.
The issue with humans is that we are rapidly increasing the rate of extinction, by pollution, poaching, exclusively occupying large tracts of land, clear-cutting forests, etc.
Surely an endangered animal would be the least likely to cause problems for us if it went extinct. Otherwise we would have noticed the ecosystem starting to go wonky as it neared extinction.
According to the National Parks Service website, only 41 wolves were released into Yellowstone and it had -major- impacts on fixing the ecosystem there.(Source: http://www.nps.gov/yell/learn/nature/wolves.htm )
It doesn't have to be " a lot" to keep an ecosystem in balance. A species that is there, even in low numbers(near extinction) could be the thread that ecosystem balance is hanging on by.
The issue with extinction is while it's natural for a few species to go extinct, due to human influence we are losing between 1,000 and 10,000 times higher than the natural extinction rate. (Source: http://wwf.panda.org/about_our_earth/biodiversity/biodiversi...)
We are part of the ecosystem we are damaging. You may take it for granted that animals continue to pollinate the plants you eat at dinner time. You make take it for granted that vultures cleaning up the dead prevent the spread of disease. There are many other cases of how the ecosystem is all tied together in a way that is integral to the human race's survival.
There is a number of species in that ecology today, let's call it N. It's a known good number of species: they work together, more or less, to stay alive as a group.
There are smaller collections of species which are nonviable. For example, if all species disappeared except elephants and tigers (2 species) the entire ecosystem would then disappear (the elephants would starve and then the tigers would) and eventually only inorganic material would remain.
There is a number of species, let's call it K, below which the probability of entire ecosystem collapse is nontrivial. We don't know what K is, but if we care about the existence of any ecosystem we must approach it carefully. And we won't know we've crossed it unless we go over.
We know K is somewhere between 2 and N. I think a good strategy is just to put the brakes on all extinction to try to buy us extra time to do science while we are approaching N=K.
As long as we keep N above K, we have a relatively easy problem: influencing a system at equilibrium. Once N drops below K we have a much harder problem: bootstrapping an ecology from nothing. Keeping N above K gives us more agency for less effort.
For that reason, I think the extinction of elephants would be bad.