What does a quieter world mean for wildlife?
As life for many of us across the globe slowed down due to lockdowns as a result of Covid 19, it makes us wonder how was our environment affected from this stand still of life? The easing up of traffic has improved the problem of noise pollution for humans but also to animals.
The pandemic led to a quieter environment which had major impacts on birds and whales – some of the globe’s most vocal animals. Even though the ocean covers over 70% of the planet, we don’t often get to hear the sounds that are happening below the surface.
What is causing the noise?
Looking particularly at the oceans around the world, we can see that as a result of our more interconnected economies, there are more ships crossing oceans around the globe. This leads to an increase in underwater sound or acoustic fog making it more difficult for whales to communicate to each other.
Valeria Vergara, research scientist with the Ocean Wise Conservation Association in Vancouver, describes this like a group of people not being able to see or do things like driving or even walking due to a thick fog. There is of course the noise from wind and waves but there are also the human factors like cargo ships, commercial fishing vessels and container ships. Propellers slice through the sea that can make a rumbling sound which can travel hundreds or even thousands of kilometres.
Vergara ‘Sound is to whales like vision is to us.’
Another source of noise for the sea is seismic surveys. These are carried out as a way of mapping what lies beneath the ocean floor. It involves sending shockwaves that are fired from an airgun into the seabed. It can pierce miles into the seabed and then bounce back to the surface where they are detected by hydrophones. It can be used to indicate if there is for example, oil, below the rock. The noise can be described as an explosion and louder than a jet taking off that would rupture our ear drums.
The racket of oil and gas activity was described as ‘one big storm of noise’ by Christopher Clarke, a bioacoustics expert.
Researchers examined how less ships along the US-Canadian coast was linked to lower stress hormones within the species of baleen whale that can reach up to 15 metres and weigh up to 70 tons. Just like birds, whales also mask. This means they are required to sing louder to be heard over noise disturbances.
There are correlations found between noise and disruptions to mating and foraging patterns and behaviours. The increase in noise can also affect other sea creatures like fish and invertebrates such as crabs where they can be put off feeding for example. It is also suggested that seismic surveys cause significant mortality to zooplankton populations. Zooplankton are a vital part of supporting the health and productivity of global marine systems.
Sounds is of major importance to whales as it allows them to navigate, detect prey and predators and to sustain contact with each other. For Beluga whales, it is especially vital to their survival as they are located in the Arctic where it is dark for half the year. They are very sociable and migrate in pods from a few individuals to hundreds of whales. Beluga’s are known as the canaries of the sea. They were called this because early mariners could hear their chirps and whistles through the wooden hulls of ships. They are known to have 28 different types of sounds one of these being the contact call.
The contact call or the beluga’s ‘hello’ can be described as if a human was voicing their name in a dark room. It is how the whales locate each other even when they cannot see each other. Mothers can hear a calf call up to 500 metres away however, when noise is added into the equation from boats, this is reduced to 100 metres. Sound can also travel much faster and further in water as it is denser than air. If mother and calf get separated, this could lead to the mother calling louder and more frequently. If the calf does not find its mother it could mean they do not survive as they are entirely dependent on their mothers.
The Arctic ocean was once known as an ‘acoustic refuge’ due to the ice cover that capped the home of many marine animals. However, due to melting ice there has been an increase in shipping routes and an expansion of oil and gas exploration in the Arctic. This traffic is set to quadruple by 2025.
Marine ecologist Michelle Fournet explains that one of the major impacts noise can have on whales is that it can actually deafen them. It can be described like being at rock concert, but you never get to leave!
A quieter sea and its opportunities
Due to the Covid 19 pandemic, shipping has decreased, and whales could enjoy some peace and quiet for once. For whales, Fournet indicates that it is the first time in history they will be able to record a baseline and document what a quiet ocean sounds like and how whales behave within a quiet ocean. According to Dr. Cara Augustenborg, Environmental Policy Fellow at University College Dublin, this quieter time has led to an abundance of scientific data to help us better understand how the planet copes with human activities and to plan more effective solutions to environmental remediation.