That's what I read too.  The snails live high in the trees, and the
natives just cut down the trees to get the snails.  According to what I
read, nearly a third of the trees on Manus Island had already been
felled, for no other purpose than to get the snails from their upper
branches.  The economy on the island is pretty depressed, and the green
snails were one of the few exports they had.  But if the process was
allowed to go on unchecked, pretty soon there would be no trees left -
and no snails!

Paul M.