All ecosystems are local, and local eradication has been a thing since the first shovel was invented, and nothing too bad has happened.

If there's an abandoned lot and you eradicate the mosquitoes by removing the water filled abandoned car tires, the existing ecosystem does pretty well. In a similar way you can willfully decide to make a livestock pond either a mosquito factory or mosquito free and mosquito free has not resulted in any problems.

Local eradication programs have successfully worked for centuries, at least. What makes this story interesting is its very wide ranging and likely very expensive.