The division is expected to lose 57 of its 180 staff members and see about $24 million slashed from its budget of $73 million, the Times of London reported.
"With cuts of that size, you simply can't continue the same level of output, or if you do, you are going to replace it with something very skimpy," veteran broadcaster David Attenborough told Radio Times.
Attenborough narrated the wildly popular "Planet Earth" series, which was broadcast around the world and sold on DVD, and he will soon be seen in the new high-definition reptile and amphibian series, "Life in Cold Blood" on BBC One.
Andrew Jackson, managing director of Tigress Productions, the maker of nature programs, told the Times of London the cutbacks would result in "the depletion of the BBC talent base."
But a BBC representative defended the downsizing, promising, "The big landmark pieces and events such as 'Springwatch' are continuing on the BBC and quality will in no way be compromised."