His replacement, Tony Jones, has worked with Luscombe on the wildlife movement since the 1980s and is a Landlife trustee.
"Tony has vision, passion and commitment to the environment and community engagement," said a spokeswoman. "This will ensure we will continue to pioneer new approaches to benefit wildlife and people."
She credited Luscombe with driving the urban wildlife movement in the late 1970s and 1980s and shaping the trend for "re-wilding on a landscape scale" in the 1990s and 2000s.
"Grant's retirement is an important milestone and Landlife has sought a successor who understands its innovative, practical work and can keep it at the forefront of the environmental sector."