# AC transmission: Impact on the biosphere

Bird strikes, wildfires and a gas 24,300 times worse than CO2

Source page: https://www.materialinsights.org/energy/e_hvac/biosphere/

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).

Overhead AC lines take land, kill birds by collision, can start wildfires and leak a potent greenhouse gas from switchgear. Any effect of their magnetic fields on human health is uncertain and, if real, weak.
 Bird deaths from power-line collisions, US 8 to 57 million a year^[16](https://ideas.repec.org/a/plo/pone00/0101565.html) Camp Fire, California, 2018 85 deaths, 18,804 structures destroyed, 153,336 acres burned^[18](https://www.preventionweb.net/news/view/65486) Magnetic field level in leukaemia studies Above about 0.3 to 0.4 microtesla (time-averaged); IARC class 2B since 2002^[17](https://www.bfs.de/EN/topics/emf/lff/effect/who-risk/who-risk.html) SF6 global warming potential 24,300 times CO2^[19](https://www.syke.fi/en/about-us/news/transition-sf6-free-electrical-switchgear-will-begin-2026)

#### Effects over time

| Life affected | Short term | Medium term | Long term |
|---|---|---|---|
| **Humans**^[17](https://www.bfs.de/EN/topics/emf/lff/effect/who-risk/who-risk.html)^[18](https://www.preventionweb.net/news/view/65486) | Construction traffic, noise and land disputes along new corridors | Wildfire risk where lines fail in dry, windy weather (PG&E transmission lines caused the 2018 Camp Fire, which killed 85 people); low-frequency magnetic fields, with a weak, unproven statistical link to childhood leukaemia above about 0.3 to 0.4 microtesla | Corridors constrain land use for decades |
| **Animals**^[16](https://ideas.repec.org/a/plo/pone00/0101565.html) | Disturbance during tower and access-road building | Power lines of all voltages kill an estimated 8 to 57 million birds a year by collision in the US | Collision risk lasts as long as the line stands; marking lines reduces it |
| **Plants** | Clearing of trees along the right of way | Repeated vegetation cutting keeps corridors as grass or shrub | Little evidence of effect |
| **Fungi and soil life** | Soil compaction at tower foundations and access tracks | Little evidence of effect | Little evidence of effect |
| **Ecosystems**^[19](https://www.syke.fi/en/about-us/news/transition-sf6-free-electrical-switchgear-will-begin-2026) | Fragmentation where corridors cut through forest | SF6 leaking from switchgear has a global warming potential of 24,300 | Little evidence of effect |

#### How the effects are reduced

Routing lines away from forests and wetlands and reusing existing corridors (reconductoring) reduce land take. Markers on earth wires make lines more visible to birds. Utilities in fire-prone areas clear vegetation, harden equipment and switch lines off in extreme fire weather. The EU is phasing out SF6 in new switchgear by voltage class between 2026 and 2032.

#### Sources

1. [Refining estimates of bird collision and electrocution mortality at power lines in the United States (Loss, Will and Marra)](https://ideas.repec.org/a/plo/pone00/0101565.html) PLOS ONE (abstract via RePEc/IDEAS), 2014
2. [WHO risk assessment of low-frequency fields](https://www.bfs.de/EN/topics/emf/lff/effect/who-risk/who-risk.html) German Federal Office for Radiation Protection (BfS), 2024
3. [CAL FIRE investigators determine cause of the Camp Fire (CAL FIRE news release, reproduced by PreventionWeb)](https://www.preventionweb.net/news/view/65486) CAL FIRE via PreventionWeb (UNDRR), 2019
4. [Transition to SF6-free electrical switchgear will begin in 2026](https://www.syke.fi/en/about-us/news/transition-sf6-free-electrical-switchgear-will-begin-2026) Finnish Environment Institute (Syke), 2025

## Other sections

- [Summary](https://www.materialinsights.org/energy/e_hvac/index.md)
- [Overview](https://www.materialinsights.org/energy/e_hvac/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_hvac/correlation/index.md)
- [How it works](https://www.materialinsights.org/energy/e_hvac/explain/index.md)
- [Efficiency and losses](https://www.materialinsights.org/energy/e_hvac/efficiency/index.md)
- [Technology advances](https://www.materialinsights.org/energy/e_hvac/advances/index.md)
- [Value chain](https://www.materialinsights.org/energy/e_hvac/valuechain/index.md)
- [Geopolitics and regulation](https://www.materialinsights.org/energy/e_hvac/geopolitics/index.md)
- [Unit economics](https://www.materialinsights.org/energy/e_hvac/economics/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_hvac/links/index.md)