Abandoned bicycles an eye-sore

The title explains it. It's not a hazard or anything to pedestrians,  but it's a breeding ground for mosquitos if people start throwing rubbish, such as soft drink containers or cups. The tyres could also trap water. But frankly,  picture of abandoned bikes is an eye-sore. They clutter walkways. 

These bikes are locked mostly beside poles, hand rails, trees, and some at bicycle stands. I'm curious as why owners abandon their bikes. Have they moved? Did they upgraded to a car or motorcycle? Did they forget where they parked their bikes? Were they victim of pranks? 

Some of the bikes/bicycles have been abandoned for more than a year. I'm clueless as how to inform the relevant authorities. If these bikes were to be recycled and distributed to the needy,  it would be more helpful than to see these bikes idly rotting away.

Just a thought.