The main task of seismoecology – the forecast of strong earthquakes – is discussed in the paper. Based on known earthquake forerunners in the lithosphere and the atmosphere, we propose the spectral transmittance of the atmosphere to be treated as an earthquake forerunner. Variations in the statistical characteristics of the spectral transmittance before and after seismic events are analyzed. Space systems are proposed to be applied to monitor the atmospheric spectral transmittance.