There is a lot of concern about species being close to extinction, especially if that is caused by human activities.
After all, species have been going extinct ever since life on earth started, with the mass extinction of the dinosaurs being the most notable. So, if humanity wipes out a few more, what does that really mean? For some, it may represent a failure of humanity to be a proper steward for the planet, but that presumes that it is humanity's job to do so. Many hold protests when species are under threat, and laws have been passed to protect the natural habitat of threatened species from development.
But is it fair to hold up potentially beneficial development projects just because the last few hundred or thousand members of a species will be adversely affected? It is a fair question, because humanity has no qualms about killing millions of animals for food, so why does it make a difference if those killed are the last remnants of a species?
To be a valid reason to hold up human development, threats to species need to be an indicator (canary) of problems greater than just the loss of that species, such as impending collapse of an essential ecosystem. The potential loss needs to outweigh the gains from the development, otherwise it is just a sentimental concern. That is, an impending species extinction needs to be shown to be an indicator of deeper damage to the environment by a development.
If environmental protection, including that of threatened species, is to be taken seriously, efforts need to be directed towards mitigating real threats to the earth or humanity. Of course, 'beneficial' must be more than just lining the bank accounts of a few businesses and workers, but result in the improvement of the living conditions of all the peoples in the society in which the development takes place.