connection between words in a sentence

[Klpno]

Hi, everyone.
Sometimes I find it somewhat difficult to figure out the connection between words in a sentence. Here is an example.

The security of states was also affected by other developments in world history. The rapid rise in population since the eighteenth century, together with the gigantic increases in energy consumption and industrial output were creating new problems. Deforestation, desertification, pollution spreading beyond national boundaries and, worst of all, the destruction of the ozone layer and global warming, were all world dilemmas which affected the security of every state and which none could counter on its own.

As far as I understand the word 'spreading' relates only to the word 'pollution'.
Am I right? And are there any rules for such cases?

[Conor]

[Klpno]

Thank you very much, Conor.