He attended the College of Agriculture and Mechanical Arts (known today as the University of Puerto Rico at Mayagüez), obtaining a bachelor's degree in biology in 1952.
Caborrojeños pro Salud y Ambiente along with United States Fish and Wildlife Service were the primary promoters of a research and visitors center located at the Cabo Rojo salt mines.
The center is named Centro Intepretativo Las Salinas De Cabo Rojo don Efrén Pérez Rivera in his honor.
In a joint venture with the Puerto Rico Department of Natural and Environmental Resources, the committee had a major role in the restoration project of Isla de Ratones, a small key by the coast of Cabo Rojo that is rapidly losing its surface area due to erosion.
Pérez has occupied the presidency of Caborrojeños pro Salud y Ambiente several times from its inception through 2005 when he was succeeded by fellow professor Pedro Valle Carlo.