  SPICA is one of the key projects for the future. Not only its instrument
suite will open up a discovery window but they will also allow to physically
understand some of the phenomena that we still do not understand in the
high-redshift universe. Using new homogeneous luminosity functions (LFs) in the
Far-Ultraviolet (FUV) from VVDS and in the Far-Infrared (FIR) from Herschel/PEP
and Herschel/HerMES, we studied the evolution of the dust attenuation with
redshift. With this information, we are able to estimate the redshift evolution
of the total (FUV + FIR) star formation rate density (SFRD_TOT). Our main
conclusions are that: 1) the dust attenuation A_FUV is found to increase from z
= 0 to $z \sim 1.2 and then starts to decrease until our last data point at z =
3.6; 2) the estimated SFRD confirms published results to z \sim 2. At z > 2, we
observe either a plateau or a small increase up to z \sim 3 and then a likely
decrease up to z = 3.6; 3) the peak of A_FUV is delayed with respect to the
plateau of SFRD_TOT but the origin of this delay is not understood yet, and
SPICA instruments will provide clues to move further in the physical
understanding of this delay but also on the detection and redshift measurements
of galaxies at higher redshifts. This work is further detailed in Burgarella et
al. (2013).
