Govt dun chop trees for nothing. From what I know, got ppl go
around th island to check the trees for diesease, infection, etc
for the trees.
Just like the bird flu, if a tree is infected by virus or
insects,etc they have to terminate it or risk infecting the whole
tree network in Singapore (as you know the HDB or road side
vegetation are ususally the same species).
Or the tree is just simply dying, in such case, they have to remove
it before it become a hazard( i.e. fallling branches,etc)