Here’s the summary of Environment topics in UPSC Prelims (2013–2023):

• Biodiversity & Protected Areas: Most consistent theme every year (national parks, sanctuaries, species-location matching, Ramsar sites).

• Basic Ecology Concepts: Food chains, succession, ecological pyramids—strong in early years, still asked but less dominant now.

• Climate Change & Global Treaties: Gained prominence after 2015 (Paris Agreement, COP summits, IPCC reports).

• Pollution & Waste Management: Shifted from basics (air, water, soil) to practical issues (plastics, benzene, solid waste).

• Renewable & Alternative Energy: Increasing focus on solar, biofuels, hydrogen, and energy efficiency.

• Indian Environmental Policies: Forest policies, CAMPA, NGT, eco-sensitive zones—moderate but steady presence.

👉 In short: Biodiversity is evergreen, climate change & renewable energy are rising, and pollution questions are more applied now. On average, 15–20 questions per year come from Environment, making it a high-weightage area in Prelims.