Dangerous trees, phone this number now

I was up in Manchester last weekend, and on the Sunday we headed to a local park. Although a couple of trees had been uprooted, I couldn't help feeling that if the park was that dangerous, it would be shut with a bit more effort than posting up some A4 laminated sheets of paper on the otherwise open gates.

I was also puzzled by the appearance of a helpline for dangerous trees - "DANGEROUS TREES PHONE: 912 1154"

Why would dangerous trees need to phone anyone?