What is the best strategy for Environment and Ecology in UPSC Prelims — the fastest-growing and most unpredictable section?

Environment and Ecology has undergone the most dramatic growth of any subject in UPSC Prelims over the last decade. In the 2014-2016 era, 8-10 environment questions per paper was standard. By 2021-2025, the range has climbed to 13-19 questions, with the 5-year average sitting at approximately 16.4 questions — making it the second-largest contributor to GS Paper I after Current Affairs. Any aspirant treating Environment as a peripheral subject is mispricing what is now approximately 32 marks of the paper.

The core resource: Shankar IAS Academy's Environment book (11th edition, October 2025) is the single most widely used and most exam-aligned source. It is organised into six parts: Part I — Environment Ecology (ecology basics, food chains, biogeochemical cycles), Part II — Biodiversity (hotspots, protected areas, species conservation), Part III — Climate Change (UNFCCC, Paris Agreement, carbon markets), Part IV — Legislations, Conventions and Organisations, Part V — Sustainable Development, Part VI — Annexure (India-specific data). For Prelims, Parts II and IV generate the highest question frequency and should be studied with extra rigour. Supplement Shankar IAS with the UPSC official syllabus checklist and your NCERT Class 11 Biology Chapter 15 (Biodiversity) and Chapter 16 (Environmental Issues) — these two chapters are direct NCERT sources that Shankar IAS abstracts from.

Biodiversity conventions — the exam's perennial sub-topic: International conventions tested repeatedly include:

• Ramsar Convention (1971): Focuses on wetlands of international importance. India has 99 Ramsar sites as of April 2026, the highest count in Asia. Tamil Nadu leads with 20 sites. Frequently tested: definition of a Ramsar site, Montreux Record (Ramsar sites in critical condition — Keoladeo National Park and Loktak Lake are on it), and the Ramsar Criteria (nine criteria, not all need to be met).
• CITES (1963/1975 in force): Regulates trade in flora and fauna. Appendix I (trade banned), Appendix II (regulated trade), Appendix III (country-specific). UPSC frequently asks which species are in which Appendix.
• Convention on Biological Diversity (CBD, 1992): Three objectives — conservation, sustainable use, benefit-sharing. Nagoya Protocol (2010) operationalises access and benefit sharing. Kunming-Montreal Global Biodiversity Framework (2022) set the '30x30' target.
• Convention on Migratory Species (CMS/Bonn Convention, 1979): Covers migratory species crossing international boundaries. Appendix I (endangered migratory species), Appendix II (species requiring cooperative agreements).
• Bonn Challenge (2011): Not a convention — a voluntary pledge to restore 150 million hectares of deforested land by 2020 and 350 million hectares by 2030. Frequently confused with the Bonn Convention (CMS); UPSC tests this distinction.

IUCN Red List categories: Nine categories in order of extinction risk — Extinct (EX), Extinct in the Wild (EW), Critically Endangered (CR), Endangered (EN), Vulnerable (VU), Near Threatened (NT), Least Concern (LC), Data Deficient (DD), Not Evaluated (NE). UPSC regularly asks candidates to arrange these in order or identify where a specific species falls. Important species to know by IUCN status: Great Indian Bustard (CR), Gharial (CR), Indian One-horned Rhinoceros (VU), Snow Leopard (VU), Indian Tiger (EN at subspecies level, but Bengal Tiger is EN).

India's Protected Area network: As of 2025, India has 106 National Parks, approximately 567 Wildlife Sanctuaries, 18 Biosphere Reserves (13 in UNESCO World Network of Biosphere Reserves), 58 Tiger Reserves (under Project Tiger/NTCA), and 33 Elephant Reserves. Questions frequently test which category a specific area belongs to, since the same geographic area can be simultaneously a National Park, Tiger Reserve, and Biosphere Reserve (e.g., Sundarbans is all three).

Study strategy: The environment section rewards a 'convention-by-convention' and 'species-by-species' approach more than comprehensive reading. Create a one-page reference sheet for each major convention listing: year, headquarters (if any), what it protects, India's specific obligations, and key Indian sites/species relevant to it. For PYQ analysis, environment questions from 2015-2024 show that approximately 40 percent of environment questions relate to international conventions and agreements, 30 percent to India's own protected area network and legislation (Wildlife Protection Act 1972, Forest Conservation Act 1980 as amended 2023, Environment Protection Act 1986), and 30 percent to ecological concepts (ecosystem services, biomes, biogeochemical cycles). Allocate revision time in this proportion.