Eco-Sensitive Zones (ESZs) or Ecologically Fragile Areas (EFAs) are areas notified by the Ministry of Environment, Forests and Climate Change (MoEFCC), Government of India around Protected Areas , National Parks and Wildlife Sanctuaries. The purpose of declaring ESZs is to create some kind of “shock absorbers” to the protected areas by regulating and managing the activities around such areas. They also act as a transition zone from areas of high protection to areas involving lesser protection. [ Source – Wikipedia ]
ESZ has been notified in “Wildlife Conservation Strategy 2002” as “Lands falling within 10 km. of the boundaries of National Parks and Sanctuaries should be notified as eco-fragile zones under section 3(v) of the Environment ( Protection ) Act and Rule 5 Sub-rule 5(viii) & (x) of the Environment ( Protection ) Rules.”
You can refer to “Guidelines for declaration of eco sensitive zones around national parks and wildlife sanctuaries” at Ministry of Environment, Forests and Climate change (MoEFCC) website. or the pdf can be downloaded from link.