Drewe, who has been volunteering with the Kent Wildlife Trust since becoming semi-retired, comes from a musical family.
While he composed the music, the lyrics were written by his brother, Olivier Award-winning lyricist Anthony Drewe.
Together the pair created an uplifting song which has sparked off a fundraising initiative which began with a choir from the Farrington School in Chislehurst.
“With the contacts I have got, I saw how I could make this work, and the school jumped at it,” he said.
All funds from this performance have gone to Butterfly Conservation, and now, Drewe is planning a mass singalong for the autumn.
He explained: “The plan is to get a number of schools to sign up to the Sing2Save website and record the song, which they will all perform at the same time, or in the same week.”
The cost to take part is a suggested donation of £1 per pupil, with the composer hopeful of raising a significant sum for a charity close to Sir David’s heart.
“I have the time, and I have the inclination, to want to do more for wildlife conservation,” he added.
Drewe is planning to make the song available online on 5 June for World Environment Day.