  (abridged) The Carina Nebula (NGC 3372) is our richest nearby laboratory in
which to study feedback through UV radiation and stellar winds from very
massive stars during the formation of an OB association before supernova
explosions have influenced the environment. This paper takes inventory of the
combined effect from all the known massive stars that power the Carina Nebula.
The present-day total ionizing photon luminosity produced by the 65 O stars and
3 WNL stars in Carina is about 1e51/s, the total bolometric luminosity of all
stars earlier than B2 is 2.5e7 Lsun, and the total mechanical luminosity of
stellar winds is about 1e5 Lsun. The total ionizing flux was about 25 per cent
higher when eta Car was on the main sequence, before it and its companion were
surrounded by its obscuring dust shell, and when the 3 WNL stars were on the
main sequence. For the first 3 Myr, the net ionizing flux of the 70 O-type
stars in Carina was about 150 times greater than in the Orion Nebula. About
400-500 Msun has been contributed to the region by stellar wind mass loss
during the past 3 Myr. The net ionizing flux and mechanical luminosity are also
given for the individual clusters Tr14, 15, and 16, and Bo10 and 11, which are
relevant on smaller spatial scales.
