This study investigates the decreasing resistance of dark coniferous forests to adverse environmental factors, which are becoming increasingly pronounced yearly because of modern global climate change. Boreal coniferous forest degradation and dieback are observed in a large area of ​​Russian forest lands, including dark coniferous forests in the north of the European part of Russia. The research objects are dark coniferous forests of various condition categories in areas of intense drying out in the Arkhangelsk region and old trees growing in conditions with an expressed impact of a specific limiting factor. A study of dead and drying tree areas was carried out on the territory of the Sursky forest district (Arkhangelsk region), and a climate reconstruction was implemented for the Sursky forest district and the coast of the Unskaya Bay (Onega Pomorie National Park). Pine was chosen as an auxiliary species for dendroclimatic analysis since old pine trees grow on the Onega Pomorie territory and exhibit long-term climatic signals. The dendrochronological method was applied to determine the relationship between meteorological parameters and tree growth, and a forest pathological examination of trees was conducted. The determined fundamental causes of forest dieback were the trees weakening under the influence of adverse climatic conditions, droughts in particular, and subsequent tree damage by stem pests.