I thought this was an interesting question, so spent some time digging. It is worth browsing the ngram usages here. The goal is not so much to look at the frequency but at the actual usages. For example:
An understanding of the translation of The New Testament
Which is plainly very different than understanding the translation of the New Testament.
The Child's Understanding of Emotion
Which is also plainly quite different from the child understanding emotion.
However, a bit of a confounding factor here is that these two examples are actually titles of books, and consequently the grammar is a bit compromised. And I think that is a key observation here. I think the problem is that your second sentence is not correct. I think it should be:
... is crucial for an understanding of population dynamics.
The key point here is that "understanding" in this context is a noun not a verb, and so the genitive is adjectival in nature.
So "understanding xyz" is the process or comprehending it, whereas "an understanding of xyz" is the result of that comprehension.
To put it another way: the information about survival and recruitment is crucial to understanding. Understanding what? Well "an understanding of population dynamics."
So too, with the titles above. The first book contains the result of someone understanding the translation of the New Testament, it is not the process of doing so, but the result of doing so. And also the second contains a description of the result of a child's comprehension of emotion rather than the actual process of a child acquiring that understanding.