Opening this meeting devoted to the. ecological aspects of nitrogen fixation, I would like to emphasize the global significance of the problems discussed. The biospheric nitrogen pool is known to be maintained by the activity of nitrogen-fixing bacteria. According to the FAO estimates, 70% of the total planetary nitrogen yield is of biological origin. In recent years, the dynamic equilibrium of nitrogen circulation in nature has been subjected to constantly increasing anthropogenic pressure. This pressure arises from the processes of artificial irrigation, drainage of marshes, extensive application of fertilizers, utilization of nitrogen, humus, peat, coal and eutrophication of the water bodies. Along with this, the release of gases into atmosphere has increased. Of primary concern is nitrous oxide, which is known as one of the main factors enhancing the greenhouse effect and exhausting the atmospheric ozone layer. More intensive use of biological nitrogen fixation through agricultural systems, which are optimized to protect nature, is one of the main ways for preventing disastrous ecological changes resulting from the unbalanced nitrogen budget of the Barth. And release of the gaseous forms of nitrous oxide and ammonia into the atmosphere has the severest ecological consequences.