Short answers, pulled from the story.
The Volga Delta is the largest river delta in Europe, located in Russia's Astrakhan Oblast where the Volga River drains into the Caspian Sea. The far eastern part of the delta extends into Kazakhstan, and it lies approximately 60 km downstream from the city of Astrakhan.
The Volga Delta covers 27,224 km2 today and is approximately 160 km across. In 1880 it measured only 3,222 km2; its dramatic growth during the 20th century resulted from changes in the level of the Caspian Sea.
Baer's mounds are linear ridges of clayey sands in the Volga Delta, named after researcher Karl Ernst von Baer. They range from 5 to 22 m in height and between 0.4 and 10 km in length. Their exact origin is still debated, though the early theory attributing them to wind action has been discredited.
The Volga Delta is a major staging area for water birds, raptors, and passerines, including breeding squacco herons, great white egrets, and Dalmatian pelicans. It is best known for its sturgeons, with catfish and carp also present in large numbers; much of its local fauna is considered endangered.
The Astrakhan Nature Reserve was established in 1919, making it one of the first Russian nature preserves. It was created to protect the delta's diverse and endangered wildlife.
Between 1984 and 2001, the Volga Delta lost 277 km2 of wetlands, averaging roughly 16 km2 per year. The losses came from both natural causes and industrial and agricultural modification of the delta plain, compounded by the Volga discharging large quantities of industrial waste and fertilizers into the shallow northern Caspian Sea.