HVDC links: Impact on the biosphere
Narrower corridors than AC, but birds and seabeds still notice
What this tab covers Effects on human, animal, plant, fungal and microbial life and on whole ecosystems: in the short term (construction and early years), medium term (operating life) and long term (decommissioning and legacy).HVDC needs fewer and narrower corridors than AC for the same power, but overhead lines still affect birds and land, converter stations occupy land at each end, and subsea cables disturb the seabed during laying.
Right-of-way width versus 765 kV AC About 50 ft narrower6 Bird collisions with power lines, US 8 to 57 million a year19 Expected CO2 saving, Viking Link first year About 600,000 tonnes8Effects over time
| Life affected | Short term | Medium term | Long term |
|---|---|---|---|
| Humans | Construction of converter stations, landfalls and cable trenches; land access disputes | Converter station noise and visual impact near homes | Corridors and stations constrain land use; cables and stations must be removed or left in place at end of life |
| Animals19 | Seabed trenching disturbs bottom-living animals along the route | Overhead lines of all types kill an estimated 8 to 57 million birds a year by collision in the US; little evidence of population-level effects of subsea cable fields on marine life | Little evidence of effect |
| Plants6 | Clearing for the right of way, about 50 ft narrower than for 765 kV AC | Vegetation managed under overhead lines | Little evidence of effect |
| Fungi and soil life | Disturbance at tower bases, cable trenches and station sites | Little evidence of effect | Little evidence of effect |
| Ecosystems8 | Seabed habitat disturbed along cable routes | Interconnectors displace fossil generation: Viking Link was expected to save about 600,000 tonnes of CO2 in its first year | Fewer corridors than AC for the same transfer reduce fragmentation |
How the effects are reduced
Routing through existing corridors, burying cables under sensitive coasts and drilling under beaches at landfalls reduce disturbance. Subsea cables are buried in the seabed where possible, which also protects them from anchors. Markers on overhead lines reduce bird collisions. Choosing one HVDC line instead of several AC lines for the same power reduces total land take.
Sources
- HVDC Transmission: Multi-Value Planning Considerations and Experience The Brattle Group (for MISO), 2023
- National Grid announces commercial operations of Viking Link, the world's longest land and subsea interconnector National Grid, 2023
- Refining estimates of bird collision and electrocution mortality at power lines in the United States (Loss, Will and Marra) PLOS ONE (abstract via RePEc/IDEAS), 2014