This territory has been of interest to nature protection bodies for many years and part of the territory was first declared a reserve by the Ministry of Education, Science and Culture in 1949. The peaks of Velký and Malý Bezděz were protected as dominant features in the otherwise flat landscape. Malý Bezděz Hill was declared a state nature reserve by the Ministry of Culture in 1988. The territory was expanded and declared as the Velký and Malý Bezděz Nature Reserve by the Česká Lípa County in 1993.
The reserve is also included in the Českolipsko-Dokeské pískovce a mokřady SPA – Bird Area and is also included as a proposed Site of Community Importance within the Natura 2000 network of protected areas.
The Velký a Malý Bezděz Nature Reserve lies on the slopes of the Large and Small Bezděz Hills. The summit of Velký (Large) Bezděz (603m) is dominated by the Bezděz Castle, which was built by Přemysl Otakar II between 1264 and 1278 AD. After the Battle of Bílá Hora (White Mountain) the castle passed into the ownership of Albrecht from Valdštejn, who converted it into a monastery. The castle was later occupied by invading Swedish forces, but was re-opened as a monastery from 1662 until it was abolished by Josef II in 1785. The ruined castle became a tourist attraction from the 19th century onwards and was partially re-built. After the Second World War the castle was closed to the public for several years as a secret military airfield was being built nearby and military exercises were carried out on the military training ground, which could be seen from the summit of Bezděz. When the castle was re-opened to the public, the works to rebuild it were resumed. Advance fortifications were also built on the summit of Malý Bezděz. We do not know exactly when, but they are mentioned in connection with the period of the Hussite Wars in the 15th century.
The majority of the nature reserve on both peaks is covered by acidophilous beechwoods, which cover 84% of the territory and grow on the oligotrophic and rocky brown soils. Other forest communities which are represented in the reserve include lime-beech communities with a rich herb layer, which includes the protected martagon lily (Lilium martagon). Talus and ravine forests (oak-hornbeam stands) can be found on the southern slopes of Velký Bezděz and in the warmest positions there are fragments of subxerophilous oak-hornbeam groves. Protected plant species which grow in the reserve include northern rock-cress (Cardaminopsis petraea), the Cheddar pink (Dianthus gratianopolitanus) and the garlic Allium strictum as well as the rare tree species - juniper (Juniperus communis) and common whitebeam (Sorbus aria).
The most significant animal species and the main subject of the protection in the nature reserve is the rare Alpine longhorn beetle (Rosalia alpina). The larvae of this striking beetle develop in semi-dry and dry wood of the branches and trunks of the beech trees (Fagus sylvatica). The adult beetles lay their eggs in the dry wood of standing tree stumps, broken trees or branches. The larvae feed in the dry wood and overwinter in their final larval phase, then turn into chrysalis at the end of May or in June just under the surface of the dry wood. The development of the beetle larvae takes at least three years and the adults live from the beginning of June until September (maximum numbers occur in July) and they are especially active in warm, sunny weather.
The long-term target for nature protection in Velký a Malý Bezděz NR is to maintain the forest stands with a near-natural tree species composition and also to ensure the occurrence of rare communities and plant and animal species, especially the population of the critically endangered Alpine longhorn beetle (Rosalia alpina). In parts of the reserve where it will not endanger the presence of rare organisms or specific communities which are bound to specific stages of forest development, management activities will be limited to modifying the species and spatial structure of the forest and supporting the self-regulating capability of the forest stands.