As a native speaker of American English: "A case can be made that rich nations export environmental problems, the most graphic example being climate change." Breaking apart this three-part sentence: 1. A case (object) can be made (verb, passive) [subject is omitted by the passive verb] 2. Rich nations (subject) export (verb) environmental problems (object) 3. The most graphic example (subject) is* (verb, "to be") climate change *Basically the "being" is just a way of express the "to be"/"is"/"are" verb in that particular phrase structure. If sentence 3 stood on its own, you would NOT use "being" but rather "is." The sentence could also technically be written this way: "One can make a case that rich nations export environmental problems. The most graphic example of these environmental problems is climate change."