Ecology and Environmental Impact Assessment: Structure, Indices and Process
Ecology questions test ecosystem function, biodiversity measurement and biogeochemical cycles; EIA questions test the procedural sequence from screening to post-clearance monitoring. Expect index calculations and process-ordering items.
Core rules and concepts
- Energy flow: gross primary production, net primary production (GPP minus respiration), and roughly 10% transfer between trophic levels; ecological pyramids.
- Biodiversity indices: Shannon H' = -sum(pi ln pi); Simpson D = sum(pi^2). Richness counts species; evenness describes how abundance is distributed.
- Ecosystem concepts: keystone species, carrying capacity, ecological succession, resilience and resistance; biogeochemical cycles (C, N, P, S).
- EIA sequence: screening, scoping and terms of reference, baseline studies, impact prediction, mitigation, environmental management plan (EMP), public consultation, appraisal and clearance, then compliance monitoring.
- Indian framework: EIA Notification 2006 categorises projects as A (central appraisal) or B (state appraisal); Category B may require only an EMP.
Worked example
Two communities each contain four species. Community 1 has equal abundances of 0.25: H' = -4(0.25 ln 0.25) = ln 4 = 1.386. Community 2 has abundances 0.7, 0.1, 0.1, 0.1: H' = -(0.7 ln 0.7 + 3 x 0.1 ln 0.1) = 0.250 + 0.691 = 0.941. Richness is identical, but the Shannon index is lower because evenness is lower. The reasoning point is that diversity indices combine richness and evenness; richness alone does not measure diversity.
Traps that cost marks
Equating species richness with diversity; confusing EIA with EMP (the EMP is the implementation and monitoring plan); mixing screening (whether EIA is needed) with scoping (what it covers); and assuming public hearing applies to every project category.