I 
accidentally ran into this REM FAQ, which (supposedly) lists many unknown facts about the band REM. However, it misses details about Stipe’s collaborative works with (without doubt, controversial) rapper KRS-One.
Take for example the last time they worked together on an obscure album called ‘Civilization vs.Technology’ (‘H.E.A.L’): this album list so many conflicting arguments that it doesn’t surprise me that REM fans don’t want to hear about Stipe’s collaboration on the title track of that album. Which is a shame: that particular song is probably the only song worth listening to because of (both) KRS-One’s and Stipe’s well-meant concerns about the Greenhouse effect.
Not bad, if you think about that the song was produced in 1991.