  We use a K-selected (22.5 < K_AB < 24.0) sample of dwarf galaxies (8.4 <
log(M*/Msun) < 10) at 0.89<z<1.15 in the Chandra Deep Field South (CDFS) to
measure their contribution to the global star-formation rate density (SFRD), as
inferred from their [OII] flux. By comparing with [OII]-based studies of higher
stellar mass galaxies, we robustly measure a turnover in the [OII] luminosity
density at a stellar mass of M~10^10 Msun. By comparison with the [OII]-based
SFRD measured from the Sloan Digital Sky Survey we confirm that, while the SFRD
of the lowest-mass galaxies changes very little with time, the SFRD of more
massive galaxies evolves strongly, such that they dominate the SFRD at z = 1.
