The problem with this argument is that it's throwing out some big numbers and bad outcomes, without making any attempt to quantify the likelihood of those outcomes.
Without quantification, this position is basically unfalsifiable. Plus, there's a trivial contrapositive that is just as valid: "what if allowing mosquitoes to live causes an outbreak of a new disease that is transmitted by mosquitoes and kills billions?". Sure, that could also happen. As with total food-chain collapse from reduction of population of a non-keystone species, it seems very unlikely. Contrast that against the almost-certain probability that 0.5m will die next year (0.1 Holocausts per year, or one Holocaust per decade) from malaria.
If we don't attach a probability to these outcomes there's no way of having any sort of meaningful conversation about them.
Without quantification, this position is basically unfalsifiable. Plus, there's a trivial contrapositive that is just as valid: "what if allowing mosquitoes to live causes an outbreak of a new disease that is transmitted by mosquitoes and kills billions?". Sure, that could also happen. As with total food-chain collapse from reduction of population of a non-keystone species, it seems very unlikely. Contrast that against the almost-certain probability that 0.5m will die next year (0.1 Holocausts per year, or one Holocaust per decade) from malaria.
If we don't attach a probability to these outcomes there's no way of having any sort of meaningful conversation about them.