The article analyzes the current efforts to combat climate warming by moving towards the ultimate goal announced by many countries as the complete decarbonization of their economies by 2050. The main trends in reducing harmful effects on the natural environment by replacing fossil fuels with renewable and environmentally friendly (“green”) sources — hydrogen, wind, solar, and water energy are considered. Promising developments of atomic energy in this context are also described. The state of affairs in the field of thermonuclear power plants is noted. It is shown that “green” energy sources, in the strict sense, do not exist today, and the designated ways to achieve zero emission of harmful substances are quite contradictory and therefore look difficult to implement so far. At the same time, it was noted that it is vital to develop “green” energy not only from the point of view of nature protection, but also due to the fact that traditional fossil energy sources will sooner or later be exhausted. It is indicated which problems will need to be solved. It is shown that there are a lot of them and they are very complex. It is concluded that the level of modern technologies and the ideas existing here let to suggest that carbon fuel as a primary energy source will remain in demand by 2050. And since the achievement of decarbonization is also associated with problems whose solutions have not yet been found or tested in practice, the path in this direction is likely to be longer.

The most effective measure for the protection of karst caves is to establish a conservation status for the most valuable of them, which regulates the order of visits to caves and their use. In this regard, an important task of preserving caves and their components is to determine their value on the basis of uniform principles for assessing the scientific and applied significance, as much as possible excluding subjectivity. A method for determining the scientific and applied significance of karst caves is presented, taking into account the frequency of commonly and rarely found components of the cave environment in the region by groups: geological (karst rocks and cave deposits), morphometric, morphological and recreational parameters, water manifestations, cryogenic and microclimatic complexes, biotic and memorial-historical components. On the basis of a point rating of the value of the caves, the conservation status of the region’s karst caves can be ranked: cadastral registration, a state natural monument, a nature sanctuary [zakaznik], a component of a national park and reserve.

The article is dedicated to the famous Russian paleolimnologist and diatomist Natalya Naumovna Davydova (6.07.1931–23.07.2014) and opens a series of publications prepared for her 90th birthday. N. N. Davydova devoted her life to studying the lakes history. The geography of the lakes she has studied is wide: from the Kola Peninsula to Central Asia and from the Baltic Sea to Western Siberia. However, the main objects of her research have always been the largest lakes in Europe: Ladoga, Onega, Peipsi. N.N. Davydova stood at the origins of the Ladoga Expedition of the Laboratory of Limnology, founded by S.V. Kalesnik. She has developed methods for reconstructing the stages of small and large lakes evolution based on diatom analysis, as well as assessing the natural and human factors, which determine the rate and direction of lake ecosystems evolution.

Diatoms are traditionally applied in studies of the evolution of the Lake Ladoga ecosystem in the late- and postglacial times. The diatoms possess siliceous frustules that are well-preserved in sediments, which enables studying the sedimentary diatom assemblages composition and its variations in time. Cysts of the golden algae (chrysophytes) constitute the second most abundant group of siliceous microfossils in the Ladoga sediments. However, they have not been used in paleoreconstructions until recently. In the present study, we compare the diatom record in the sediment core obtained from the central part of the Lake Ladoga with the absolute and relative abundances of chrysophyte cysts. The study is aimed at reconstruction of the Holocene paleoenvironments in the Lake Ladoga and assessment of the indicative value of the chrysophyte cysts in the studies of the Lake Ladoga evolution. We also maid an effort to interpret the information of the diatom assemblages composition and abundances of the siliceous microalgae in terms of the changing duration of hydrological and hydrobiological seasons resulted from the Lake Ladoga level changes and climatic shifts in the past.

Samples of surface sediments and sediment columns from various sections of the Lake Imandra were collected for diatom analysis. Histograms of diatom complexes species proportions were constructed. Two types of graphs of the natural (undisturbed) diatom complexes structure were distinguished. The first one, in its outlines, is close to an exponential dependence, and the second one has a certain similarity with the logistic dependence. Both types of histograms change their shape when a negative external influence takes place. The degree of their distortion reflects the overall level of anthropogenic load on a particular section of the water area. The third type of graphs — linear graphs was distinguished for the displaced and redeposited diatom complexes. The research allowed to identify the lake’s water areas where paleoreconstructions are the most efficient. Water areas where the interpretation of the obtained results is difficult, and paleoreconstructions are not recommended, have been identified as well.

The results of diatom, palynological and radiocarbon analyses have shown that bottom sediments have been accumulating in the lake Yuzhnoe Haugilampi for the last 13–12 000 cal. years. Terrigenous sediments (sand, clay) formed in the lake in the Late Glacial Period and organic sediments (gyttia) began to form in Pre-Boreal time. The vegetation reconstructions of the area cover the period from Younger Dryas until present. After the retreat of the glacier of the last Valdai glaciation, periglacial vegetation (Artemisia-Chenopodiaceae), tundra and forest-tundra birch communities spread over the study area. In Pre-Boreal, tundra and forest-tundra vegetation had been changed by birch open forests. Later, in the Boreal period, middle taiga pine forests reached their maximum development. In Atlantic period, middletaiga forests were replaced by south-taiga pine and spruce forests with thermophilic species. The forests began to acquire a middle-taiga character in the Late Holocene. In the Late Glacial Period, no diatom flora evolved in the lake. Sediments from that period contain the scarce, possibly redeposited valves of marine diatoms and small quantities of pioneer epiphytes and bottom species. In the Pre-Boreal period, a rather scarce diatom complex (regarding the abundance and diversity of species) developed in the lake, represented by pioneer forms typical for many northern water bodies: Ellerbeckia arenaria, Pseudostaurosira brevistriata, etc. The mass vegetation of diatoms began in the Boreal Period. The dynamics of the development of the lake from the Younger Dryas to the Subboreal time is traced.

The work is devoted to the Caucasus lakes study which is the most promising for the application of the taxonomic proportions graphical analysis method in diatom complexes. Previously, seven lakes were studied, in which this method was confirmed as informative. Studies of the bottom sediments of the lake Bolshoe Dzitaku were carried out using a similar algorithm. A layer-by-layer analysis of the diatom complexes taxonomic structure is carried out. A brief description of the method and the results of its application are given. It was found that the diatom complexes formed in the central part of the lake were not subjected to significant processes of redeposition. The obtained results allow us to include the lake Bolshoe Dzitaku in the list of lakes of the Caucasus that are promising for further ecological and paleoclimatic reconstructions of the Late Holocene. Further studies on the lake’s water area involving a wide range of biological and physico-chemical methods, including age dating of lake sediments by isotopic methods, are recommended.