Low earth-orbiting satellites: do these affect animals that respond to celestial cues?
Low earth-orbiting satellite technology has promised to improve internet connections worldwide, even in the most wild and remote places. But will this come as a cost to wildlife?
Illustration by Caitlin Noble.
Last year, Space X’s Starlink program launched more than 700 low earth-orbiting satellites into orbit. A low-earth orbit (LEO) as the name suggests, orbits close to the Earth’s surface, often between 160- 1000 km altitude above the earth. Traditional satellites, by contrast, are positioned much higher, at above 35,000 km. The main reasons for sending these satellites into space was to provide a high bandwidth and low communication latency. This is the time delay for data to be passed from one point to another. Additionally, this type of satellite requires the lowest amount of energy for satellite placement. SpaceX were aiming for a latency of 20 milliseconds and hope in the future to be able to half this. But there is a race, as other companies such as OneWeb backed by Richard Branson also want their name on the prize; to be the 1st to decrease latency between space and Earth. But the question is, could this increasing number of satellites come at a cost to wildlife?
Scientists are worried that increasing the numbers of LEO satellites in the sky will have detrimental impacts on wildlife, specifically those animals which use celestial cues for navigation and movement during migrations. This means that they use the sun, moon and or stars for navigation and movement. Wildlife that use celestial cues come in a range of forms from the small-sized dung beetle to the harbour seal.
Indigo Bunting. Image by Patrice Bouchard, Unsplash
Migratory birds such as the indigo bunting (a small seed-eating bird) use the stars and their centre of orientation in navigation. In a well-known study carried out by Stephen Emlen, the buntings have been found to become disoriented when all of the constellations within 35º were blocked from view.
Harbour Seal. Image by C Hollingsworth, Flickr.
The majority of pinniped species are not migratory, although they may conduct long journeys foraging for many days and nights. It has been found that seals, in particular harbour seals, can detect simulated and real bright stars, so may use celestial orientation.
Dung Beetle. Image by Bernard Dupont, Flickr
When there is no light, a species of dung beetle are thought to navigate using either the moon or sun. They use these cues to help roll balls of dung in a straight line.
Those animals which navigate using the stars, such as birds, use what is called a centre of rotation. This helps them to identify a configuration of bright stars in the sky which is associated with the pole star. In the northern hemisphere, the pole star points towards the north. But having large numbers of satellites in the sky, which reflect the sunlight back towards the Earth could result in confusion. These bright satellites could cause disorientation, and as a consequence cause migration to occur in the wrong direction.
This has been shown in sea turtle hatchlings who use the moonlight reflecting off of the tops of waves to navigate towards the sea. Bright artificial light at night has left them disorientated and as a consequence, many have been observed to wander into roads. Other impacts have been associated with these bright, artificial lights. For example, bird song time changing. Song birds including the European robin, common blackbird, great tit and blue tit have earlier dawn and later dusk song when exposed to light pollution. This reflected light will be most visible just before dawn, and just after dusk, which is often the time when nocturnal animals such as bats are out foraging. This could potentially cause a change in time of foraging and commuting, especially to those species which are light adverse such as the lesser horseshoe. Thus, if the satellites do reflect light towards the earth it could cause implications across the whole ecosystem.
It must be noted that Elon Musk has issued a statement on Twitter, assuring that SpaceX has worked closely with astronomers to minimise the potential for the reflection of the satellites, but it is still unknown as to if LEO satellites will impact animals relying on celestial cues.
Thank you to Caitlin Noble for her wonderful illustration. You can find more of her work on her Instagram @caitlinniamhillustrations
Elen Peel
Elen is a BSc and MSc Conservation Biology student at the University of Exeter, based in Cornwall. She is interested in ecology, conservation and climate change. During her spare time she enjoys hiking, photography and playing the saxophone.