I can understand part of the sentiment, but I'm a bit cautious of 1) the possibility of that happening 2) the impacts 3) the ethics.
One day –hopefully– humanity will have its shit together. Then the majority of suffering will be inflicted by (non-human) animals upon other animals. What do we do about that? I don't have an answer, but I'm pretty sure "let it continue" isn't it.
To bring the discussion back to the present: I think most people don't consider the morality of letting predators exist. If it was a disease or parasite that killed 10 people a year, we'd all agree on eradication. If it was a human being who killed 10 people a year, we'd all want to lock that person away until they died of old age. Nobody would make arguments like, "Your child is 1,000x more likely to be killed by a car than by a serial killer." But give the creature some fur and claws and have it roar or howl majestically... suddenly all manner of rationalizations are brought out in support.
That is nowhere near the same thing as a human killer that does it for non-survival reasons; anger, entertainment, sexual excitement, etc. Even if we say that human killers are driven by instinct, as animals are, they also have the ability to reason about the motivations, impact, and eventual consequences of those actions.
You should see my dog go after camel crickets, and how it plays with the dead bodies. It prefers them to tennis balls, for certain.
I wouldn't be surprised if other predators feel similarly about their prey, even if they also eat it.
Let me explain by way of an example that is close to home for me. In my country of birth we have many areas which normally used to have free roaming wildlife including predators like lions and leopards. These areas where subsequently taken over as farm land and the big cats removed. This allowed the pray, usually antelope and other herbivores, to breed out of control causing immeasurable damage to the vegetation and if left unchecked would cause these animals to die of starvation in the end. It might sound far fetched but these ever increasing herds do cause damage to the vegetation if their numbers become too big. Given this situation farmers and conservationists either have to organise regular culls of these animals or capture and relocate them. Unfortunately there is only so many place you can relocate them to before the natural environment cannot accommodate them anymore and starvation due to destroyed vegetation sets in.
Predators in these natural eco-systems serve a very necessary function.
I am not talking about Human predators here so please dont confuse the above example with justifying why some human beings prey on others. Human predators need to be removed from our society. We are not animals and have the ability to reason which sets a different standard for us.
What I am trying to illustrate is the logical conclusion of your very well intended desire to reduce suffering. I applaud your desire to reduce animal suffering, of which we humans have a lot of blame for, but to extrapolate that to natural eco-systems could have disastrous effects.
I think this is likely already the case. Most animals killed by humans are killed quickly and efficiently.
A typical kill in the wild, however, can be horrific. Especially when the predator does not dwarf the prey--coyotes killing a deer, for instance.
Diseases that are part of erradication programs used to kill or cause lifelong disability to millions. Diseases that kill thousands could be recommended to vaccinate aginst for those at risk. There would hardly be any research into a disease that kills 10 people a year.
For instance, see: http://www.bbc.com/news/world-australia-34513177 (which I may have come across from HN actually)
Note that they talk about 13 recorded deaths and none since the program began, but consider the effort involved.
And we do get pretty crazy about sharks and stuff when they kill less than a handful per year worldwide.
Yes. Let it continue. It is not your place to eliminate anyone else's suffering, in humans or otherwise.
I once read "Three Worlds Collide" by E. Yudkowsky. There are alternate endings to the story, that I won't spoil. But it is a tale intended to make you think about your own ethics. It is a long hypothetical that sets up the question, "What could it mean to have an ethical imperative to eliminate suffering?"
I didn't like the endings. I think it is unethical to project your own morality onto other species.
And that's the story that made me realize that those who practice veganism because they do not wish to inflict suffering upon other species for their own benefit are perfectly reasonable people, capable of coexisting with others, whereas those who would attempt to enforce that lifestyle upon others are a threat to me. When you cross over that line between "I don't" and "you shouldn't", I become wary. When you move a bit further to "no one should", you become my enemy.