Jeff Layman wrote:

It was an extrapolation. Once people find out that something can be
exploited, they start exploiting it from areas where it hasn't been
artificially planted. Just think of places like Bangladesh; if
mangroves were able to be exploited for charcoal, I am sure it would
have been done there, and goodness knows what would happen to that
low-lying land if the mangroves went.

OTOH, if they could be persuaded to grow on the coast (much of which is
pretty low-lying) they could be managed so that it would prevent erosion
and indeed, encourage silting, giving partial protection from storms and
tsunami, and provide a useful crop.

--
Rusty