While I think causing species extinction is a moral wrong, it is difficult for me to come up with a positive justification for this intuition. The most direct approach is perhaps through biodiversity. But I haven't come across a compelling argument for biodiversity as a moral good either. In fact my intuition appears very fragile on reflection (for instance not all species seem to be on a par, and the extinction of some may seem more devastating than the distinction of others). Any literature reference would be deeply appreciated.

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    If one doesn't find it morally wrong to kill a single lifeform for no reason other then the sole purpose of ending a life then I can't possibly see how one would be troubled with exterminating an entire species for no reason so that might be a good place to start with your argument.
    – Cell
    Aug 27, 2018 at 16:28
  • If there were a non-sentient species that was commonplace and dangerous to man (like a certain strain of bacteria for example), I don't see that it would be immoral to drive it to extinction (like we presumably did with polio, although that's a virus, so maybe technically not "living").
    – user935
    Aug 27, 2018 at 18:33
  • "I think causing species extinction is a moral wrong" - well, I wish mosquitos and bed bugs to die. I wish dangerous bacteria to die. Do you find these wishes immoral? Exactly the argument can be constructed that bacteria are causing deaths of animals and species extinction, so biodiversity does not work then.
    – rus9384
    Aug 27, 2018 at 19:43
  • @Cell, well, there is no "no reason". Explanation always exists: maybe just because someone likes it - killing animals. The real thing is how acceptable that reason is. Almost no one finds it normal for a serial killer being able to follow his killing wishes.
    – rus9384
    Aug 27, 2018 at 21:46
  • @rus9384 I disagree. You are using a different definition of reason than I used. I intended "no reason" to mean "lack of reasoning" i.e emotional. Not the more colloquial and trivial synonym for "explain". Animals, and generally all living things don't kill other living things merely for satisfication rather they kill for survival. I would consider the latter a reason for killing.
    – Cell
    Aug 27, 2018 at 22:02

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In terms of the morality, it's going to depend how you ground that. Suffering, systemic risk & systemic resiliance, irreversibility, are all specific things to consider. Is all, or some life 'sacred'? Or do we only judge by consequences?

Peter Singer argues that morality is the result of an expanding circle of concern, that we choose not to be gene-machines by expanding our concern from progeny, to family group, to tribe, nation, humanity, to non-humans, to ecologies. Each expansion dignifies us, makes us more fully developed and moral beings.

A case people talk about of extinction being maybe ok, or even good, is malaria/dengue/zika vector mosquitos. It's a good case to consider on 'pro extinction'. Male mosquitoes don't ever bite humans, they pollinate flowers. Mosquitoes are a key prey species for aerial & aquatic ecologies, and by supporting predators, other pest outbreaks are less likely to go to extremes - see the consequences of China's https://en.wikipedia.org/wiki/Four_Pests_Campaign Wider issues of mosquito extermination discussed here: https://www.bbc.com/news/magazine-35408835 How malaria also harms mosquitoes: http://www.sciencemag.org/news/2010/09/how-mosquitoes-fight-malaria Which seems to point toward win-win solutions..

Morals are more-or-less rules-of-thumb, which we allocate consequences to breaking based on a wide range of factors, though mainly risks & harms. It used to be that egg-collectors & other trophy hunters drove the most endangered large predators further towards extinction, and many countries got together to create https://en.m.wikipedia.org/wiki/CITES#Background_and_operation to deal with prosecuting these & other issues. The risks & harms to humans, and even ecosystems, of loss of large predators may be minimal. Yet 'charismatic megafauna', black rhinos, pandas, whales, polar bears, have recieved among the most enthusiasm to save. Many want a world with wild, that these symbolise. But reintroduction of lynx, wolves, bears & wild boar, & even beavers, to areas that lost them is invariably problematic. Many farmers & rural people don't want actual wild, actual physical threats, or even just ecological change (beavers).

David Attenborough talked about the importance he felt of preserving parasitic wasp species. Their macabre life cycles make us feel a bit quesy. Sometimes they have an ecological role, preventing too large or concentrated a population of some prey. Ethically though, conserving them is conserving that prey-hosts suffering. Attenborough argues we need to value and conserve as much complexity & dynamism as we reasonably can, out of wonder, in humbleness, and for posterity.

It is hard to take any argument for preserving smallpox seriously, now eradicated in the wild. Or ebola. Or viruses and their biodiversity. Though, viruses may hold keys to understanding life, and recently gave us CRISPR/Cas9 gene editing technology.

A final point is, biodiverse ecologies are generally more resilient. Long term studies of grasslands show the more species, the better range of climate they thrive in. Beavers & many other ecological elements slow water through landscapes, reducing flooding and drought. Small wildfires are part of many ecologies, and prevent huge fires. Coastal wetlands may be able to produce more food than conventional farming, while feeding masses of wildlife: https://www.youtube.com/watch?v=4EUAMe2ixCI Climax ecologies often maximise biomass for minimum inputs, & do so resiliantly. We should learn from them, before they are all gone. Potato & banana narrowed-genepool monocultures further highlight systemic risks of losing wild crop ancestors & diversity.

Morality cannot be limited to considering only 'ground level' concerns. We must engage with what kind of world we hope for, wish to live in, make ourselves part of developing. Megafauna are majestic, though they may mean humans retreating from some landscapes. Ecologies are complex & sophisticated, our record of intentional interventions terrible, we must learn more, and that means conservation. Biophilia is the idea we are drawn towards environments with more varied and flamboyantly-present life in them. "Growth for the sake of growth is the ideology of the cancer cell." (Edward Abbey). Maybe biophilia is an alternative master-ethic to growth ('progress'), one that places humans at the centre, as gardeners of what could be a new Eden. But the knowledge to do that, is dissappearing with rapid climate change, and total human alteration of landscapes and ecosystems, just as we are truly developing the means to understand them. How we feel about causing extinctions, is a microcosm of how we feel about the choice to become a kind of plague, or a kind of angels. So far our plague-nature is winning.

  • "Which seems to point toward win-win solutions.." - well, mosquitos still would suck blood causing pain to humans and other animals. Hardly win-win, especially if their amount will grow after curing them from malaria. And, btw, not only humans are causing extinctions. Other animals do it too. I'm not even sure that humans, taking their total mass (more than 200m tons) are causing more extinction than 200m tons of average animals.
    – rus9384
    Aug 28, 2018 at 0:41
  • Thanks so much for the reply! I was very much influenced by watching David Attenborough. I happened to sit in one of Singer's lectures whereby he defended the view that, from a utilitarian perspective (esp. minimization of pain), holding everything else equal it would have been a better world if there were no predators. That conclusion strikes me as absurd. But it was difficult for me to argue against my utilitarian friend, hence the original question. I wonder if cases like malaria should be evaluated based on separate moral considerations from ecological conservation.
    – Y.Z.
    Aug 28, 2018 at 2:29
  • @rus9384 We humans are not just driving some of the extinctions, but causing the fastest & worst mass extinction the planet has ever seen en.m.wikipedia.org/wiki/Holocene_extinction
    – CriglCragl
    Aug 28, 2018 at 22:36
  • @discretizer Why absurd? The Buddhist perspective, Mayana in particular, is for all beings to develop to states of not causing harm and suffering. Singer follows an old route.
    – CriglCragl
    Aug 28, 2018 at 22:40
  • Well, we caused so much extinction and the world was stable yet (prior to industrial age there already was much extinction caused by humans, right?). Therefore this argumentation is self-defeating. In either way, with further technological advances, we'll be able to create new species (or replicate extinct, but it does not worth it, take Jurassic park). If mosquitos gonna die, I guess there gonna be more flies, but flies, at least, do not suck blood.
    – rus9384
    Aug 28, 2018 at 22:46

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