Biotic homogenisation is an underrated cost of large water infrastructure. How should India's EIA framework account for cross-basin biological risks?

Biotic homogenisation happens when artificial links let species mix between basins, so separate ecosystems lose what made them distinct. ATREE's Scientific Reports study warns that India's river-linking plan could become an "ecological highway" for invasive alien species (IAS). Current EIA practice barely measures this cost [1].

Why the cost is underrated

• Unique basins: India's basins evolved in isolation and hold many endemic species found nowhere else. Interlinking could "flatten" this unique biota [1].
• Source-to-sink spread: the Lower Ganga already hosts 13–15 IAS and could seed the Mahanadi. Aquatic pathogens can travel the same way [1].
• Irreversibility: a canal can be shut, but an invasive fish that is breeding in a new river cannot be removed. Drought losses, by contrast, can be recovered in a good monsoon.
• Missing from benefit–cost analysis: gains are counted, such as 10.62 lakh ha of irrigation from Ken–Betwa [3]. Losses to inland fisheries are not.

Gaps in the present EIA framework

• Project-by-project clearance: under the EIA Notification, 2006, each link is cleared on its own. Yet the National Perspective Plan (1980) envisages 30 links that together form one network [2].
• Focus on land: the Ken–Betwa review centred on flooding 4,141 ha of Panna Tiger Reserve core [4]. The biological risk at the canal's receiving end was never assessed.
• No freshwater-biodiversity watchdog comparable to the expert bodies that protect wildlife.

How EIA should account for cross-basin risk

• Network-level cumulative assessment: for every link, ask which basins become reachable for which species once it joins the grid.
• Mandatory IAS risk screening in NWDA's Detailed Project Reports, using basin-level maps of likely invaders [1].
• Sequencing by risk: build links within one river system first (the Ken and Betwa are both Yamuna tributaries) and defer links between separate basins.
• Safeguards and monitoring: fish screens and barriers, long-term biological monitoring, and adaptive-management clauses written into clearances.
• Equity: consult and compensate fishing communities in receiving States through public hearings.
• Global alignment: Kunming–Montreal GBF Target 6 calls for managing invasion pathways and cutting IAS introductions by 50% by 2030 [5].

Water security and freshwater biodiversity do not have to be traded against each other. A precautionary EIA that works at network scale would let India meet needs like Bundelkhand's. It would screen invaders before digging and order links by risk. That would honour Article 48A, Article 51A(g) and India's GBF commitments, and make river-linking truly sustainable.