When did Horizon Season 16 Episode 21 air?
Horizon Season 16 Episode 21 aired on November 12, 1979.


Horizon tells amazing science stories, unravels mysteries and reveals worlds you've never seen before.
Horizon investigates how the British landscape is changing its appearance with native trees being replaced by imported species.
Direct answers for episode-level questions and details.
Horizon Season 16 Episode 21 aired on November 12, 1979.
This episode runs for approximately 60 minutes.
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