Various approaches in multiple scales (temporal and spatial) are required in monitoring the rapidly changing local/global ecosystems. Those approaches, including ground observation, numerical simulation, and aerial/space remote sensing, can be powerful only if they collaborate with each other. This is the starting point of the "JJJJ" community which started in 2008. "JJJJ" means a group of four networks/institutes: JapanFlux, JaLTER, JAMSTEC, and JAXA. JapanFlux is a study network for carbon/water/energy transfer between ecosystem and the atmosphere, with a particular focus on ground measurement of CO₂ flux. JaLTER (Japan Long-Term Ecological Research Network) aims at gathering long-term records on various ecosystems in Japan. JAMSTEC (Japan Agency for Marine-Earth Science and Technology) studies earth-system with numerical models, observation, etc. JAXA (Japan Aerospace Exploration Agency) operates earth-observation satellites. JJJJ is working on sharing ideas, information, data, and future plans to make ecosystem observation more systematic and synthetic than ever.