  We revisit the Schwinger effect in de Sitter, anti-de Sitter spaces and
charged black holes, and explore the interplay between quantum electrodynamics
and the quantum gravity effect at one-loop level. We then advance a thermal
interpretation of the Schwinger effect in curved spacetimes. Finally, we show
that the Schwinger effect in a near-extremal black hole differs from Hawking
radiation of charged particles in a non-extremal black hole and is factorized
into those in an anti-de Sitter space and a Rindler space with the surface
gravity for acceleration.
