Then, I claim that if we abandon a speciesist viewpoint we should change completely the way in which we should intervene in nature. Rather than inter… - Oscar Horta

This means that the number of animals that come into existence only to die shortly after is extremely high. On average, if we consider a context in which populations remain stable at least in the mid term, for each animal that reproduces, only one of her or his offspring survives (otherwise animal populations would grow exponentially very fast, and would become massive with just one generation). This means that all the rest of the animals die. Many of them die shortly after coming into existence. These animals starve to death, are eaten by other animals, or die for other reasons that usually entail a great deal of suffering. This means that an enormous number of animals come into existence only to suffer. Their lives contain virtually no enjoyment, since they die shortly after they start to exist. However, their lives do contain significant suffering, because of the painful ways in which they die. They thus live lives in which disvalue outweighs value. Living their lives causes them more harm than good. In fact, in many cases it causes them great harm and no good at all.

It is commonly believed that animal ethics entails respect for natural processes, because nonhuman animals are able to live relatively easy and happy lives in the wild. However, this assumption is wrong. Due to the most widespread reproductive strategy in nature, r-selection, the overwhelming majority of nonhuman animals die shortly after they come into existence. They starve or are eaten alive, which means their suffering vastly outweighs their happiness. Hence, concern for nonhuman animals entails that we should try to intervene in nature to reduce the enormous amount of harm they suffer. Even if this conclusion may seem extremely counter-intuitive at first, it can only be rejected from a speciesist viewpoint.

What do we consider disvaluable and valuable in our own lives? Some people say negative and positive experiences, others say thwarted and satisfied preferences, others say a list of things such as ignorance and knowledge, meaningless or meaningful relations, pain and pleasure, etc. All these different things require that we're sentient. We don't consider that what is valuable in our lives is just being the members of a certain species or living in some ecosystem as such. Abstract entities such as species and ecosystems cannot feel pain and other affections, and therefore don't have interests, while sentient beings do. This is why we should be concerned with what happens to sentient individuals, rather than abstract groups.