Study and long-term prediction of orbital debris environment in low Earth orbits are urgent needs for secure human space development and exploration. This paper introduces some results of Low Earth Orbital Debris Environmental Evolutionary Model (LEODEEM) being researched at Kyushu University with collaboration from JAXA for the purpose of discussing problems of space environment conservation. The model calculates LEO debris evolution (less than 2,000 km altitude of perigee) taking into account collisions, and future launch traffic. It becomes possible to predict a long term LEO environment and investigate future mission hazard evaluation by using this model.