Submit Similar Content to Two Conferences Assuming that I have some methodology for monitoring ecological behavior that I wish to publish on, how much overlap is acceptable between an ecological paper and a computational algorithm paper, published at different times?
Actually, think, rather, in terms of how much is unique in the two papers. If each has sufficient novelty and each is independently interesting, then you should be fine. 

This is a judgement call, of course, and it might be best to make it a bit conservatively so that no one thinks you are just padding a CV. Likewise, ask yourself if people would think that you just split things that should be said together into two papers for padding the CV. 

And remember that it is your judgement call to make, but others will make it also. 

In the example you cite, of course, it seems as if one paper is focused on an application and the other on methodology. That seems (to an outsider like myself) to be fine, especially if a deep explanation of the methodology is both interesting on its own and not essential to the application.