SUMMARY
Reliability is one of the main characteristics of ecosystem, its ability to effectively maintain its structure and perform functions without fail when environmental conditions change due to natural or anthropogenic negative impacts. It is shown that in the assessment of ecosystems, the leading role belongs to environmental monitoring to determine the condition of ecosystem components and identify the possibility of ensuring reliability. Methodical approaches to environmental monitoring have been developed. Mechanisms of ensuring and principles of reliability assessment of different types of ecosystems are considered. The main attention is paid to the recovery, reservation and conditioning of ecosystems under the influence of negative factors. To quantify the ability of ecosystems to recover, it is proposed to use appropriate criteria, which are determined by certain calculation formulas. With insufficient reliability of ecosystem elements due to the actions of negative factors, its reliability is ensured by reservation at the expense of additional means and capabilities. In the case of agroecosystems, which are artificially created biotic groups of organisms that are supported by humans, it is an integrated approach using the theory of ecosystem reliability that expands the range of means to study their effective functioning. It is noted that the increase in the reliability of the agroecosystem is provided by the use of its reliable elements, as well as special systems for ensuring recovery and reservation. It is emphasized that the application of reliability theory in the study of agroecosystems contributes to the management of their functional efficiency for obtaining environmentally safe products