What is the meaning of the phrase "as they relate to..."?

This section presents recent developments in climate change as they relate to oceans.

Climate change affects many things, including, but not limited to, rivers, lakes, soil, animals, crops, the economy, and on and on.

However, the section in question (i.e. "This section") only describes (or "presents") the part of climate change (or the "recent developments" thereof) where it concerns oceans. Nothing but the oceans. No lakes, no crops, no economy - just the oceans.

Which is why the phrase can be changed to:

... where oceans are concerned.

Or:

... pertinent to oceans.

Etc.

In your second example, the activities in question can relate to any number of things, but the two publications are only concerned with that part of said activities that affects, or is affected by, the "Articles of the Charter."

In your third example, the scope of said effects can be huge, but the section under the title will only discuss the part that's relevant to traveler's diarrhea. I.e. "where traveler's diarrhea is concerned."

I hope this helps.