At Payyanur, in 1972 he started a zoology club that would form the genesis of campus-based nature conservation activities.
He also set up the Society for Environment Education, Kerala (SEEK), which published an environment-focused magazine Soochimukhi.
Additionally, Jacob led the movement against the Silent Valley project in South Kerala.
The name of the plant Impatiens johnsiana is dedicated Prof. John C. Jacob who was popularly known as ‘Johnsi’, an ardent naturalist who had devoted his life to conserve the biodiversity of the Western Ghats.
The new plant is endemic to these parts of Western Ghats on densely clothed tree trunks in evergreen forests at an altitude of 1500-700 MSL.