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I present an H-alpha survey of z~1 galaxies, to determine star formation rates (SFRs), with the near-infrared multi-object spectrograph CIRPASS. I present robust detections of H-alpha in z~1 galaxies, demonstrating the first successful application of this technique to observing high redshift galaxies. Stacking the spectra in the rest-frame to infer a total SFR for the field, I find a lower limit (uncorrected for dust reddening) on the star formation rate density at redshift z=1 of 0.04 Msun/yr/Mpc^3. This implies rapid evolution in the star formation rate density from z=0 to z=1 which is proportional to (1+z)^{3.1}. Comparing to star formation rate estimates from the UV, it appears that star formation rates inferred from H-alpha are, on average, a factor of two higher than those based on the UV continuum alone.