20 Roubles Berezinsky Biosphere Nature Reserve. Beaver

The Berezinsky Biosphere Reserve, established in 1925 in what is now northern Belarus, was added to UNESCO's World Network of Biosphere Reserves in 1978 — one of the first Soviet sites to receive that designation. The Eurasian beaver (Castor fiber) had been hunted to near-extinction across Europe by the early twentieth century, and Berezinsky played a direct role in its recovery as a protected breeding population within the reserve helped anchor regional reintroduction efforts across the continent.

Belarus issued several silver pieces in this nature reserve series through the early 2000s, with KM#45 among the first strikes.