This is addressed in their FAQ as well: "The general consensus among scientists is that the ecological impact of removing Aedes aegypti mosquitoes from urban environment would be small. They are not a significant food source for other animals and are invasive to many areas. The main ecological impact would be to restore the ecosystem to how it was before the mosquitoes invaded. Debug team is committed to working with communities and regulators to ensure the safety and acceptability of our field trials and releases."
In Indonesia for one they are. Every night, countless geckos come out, both indoors and outdoors, and start hunting for mosquitoes. Even lullabies sing about it [1].
The above song is so popular that it got an AI parody [2].
I'm curious what food chain reaction this will start if successful.
The extermination of sparrows – also known as the Eliminate Sparrows campaign – resulted in severe ecological imbalance, and was one of the causes of the Great Chinese Famine which lasted from 1959 to 1961, with an estimated death toll due to starvation ranging in the tens of millions (15 to 55 million).
Though that's unlikely to follow on from simply reducing mosquitoes in urban areas ... it absolutely warrants a close eye being kept on roll out and knock on effects.
The choice is between making one species of mosquito extinct or using traditional mosquito control methods such as removing standing water. The traditional methods affect many different insects not just mosquitoes. Attacking specifically the species that are vectors for disease is the more ecologically sound method.
If we could remove the insects that carry disease then the outcome could be more insects overall, because people will be more willing to have ponds, etc.