There are a confirmed 16 trees in the world that produce 40 types of fruit each year.
1 Answer
There are a confirmed 16 trees in the world...
This construction is common in reportage contexts.
What is being confirmed is the quantity, here 16. That factuality is not plural, hence a.
A quantity qua Quantity is singular: How many is that again? Is 16 rather few?
a confirmed modifies the quantity 16. are and trees agree in number.
We can have confirmed quantities and unconfirmed quantities.
When a number is not absolutely confirmed, we would hedge with something like this:
There are some 16 trees in the world that...
or we can say
An unconfirmed 16 people were injured when the bus and truck collided.