How urban soundscapes affect humans and wildlife — and what may have changed in the hush of lockdown

Kurt Iveson, University of Sydney and Dieter Hochuli, University of SydneyThe dull roar of traffic, the barking of dogs in backyards and the screeching of cockatoos at dusk. The shattering of early morning quiet by the first plane overhead or the garbage truck on its rounds. The squealed delights and occasional fights of a children’s playground.

These sounds and many more create what Canadian composer R Murray Schafer famously called a “soundscape”. Schafer, who passed away last month, helped us realise we experience cities with our ears as well as our eyes.

In recent years, studies have confirmed these soundscapes affect the well-being of urban inhabitants — both human and non-human. But with much of the country back under lockdown, urban soundscapes have changed, sometimes bringing delight, but sometimes causing new distress.

So let’s take a moment to consider how soundscapes influence our lives, and the lives of urban wildlife.

When sounds become ‘noise’

Whether it’s housemates, traffic, or construction, we tend to respond to many urban sounds by defining them as “noise”, and try to shut them out. We do this using a range of techniques and technologies: building regulations on soundproofing, controls on the times for certain activities like construction, and planning measures.

But noise mapping efforts show such regulations tend to produce uneven urban soundscapes — some people are more exposed to loud or annoying sounds than others.

Housing quality is a major factor here, and noise problems are likely exacerbated under lockdown. A recent study of pandemic housing inequality in Sydney found increased exposure to noise during lockdown is significantly contributing to poor well-being.

For example, sounds travelling across internal and external walls of apartments were frequently a source of tension in pre-pandemic times. Now, with so many more people spending more time at home, these domestic sounds inevitably increase.

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Read more:
Coronavirus reminds us how liveable neighbourhoods matter for our well-being

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It’s not just humans whose lives are disrupted by city noise, as many animals use sound to communicate.

The ever-vigilant New Holland honeyeaters of Australian cities use their alarm calls to warn their friends and neighbours of danger, while the iconic chorus of banjo frogs in wetlands are the hopeful calls of males seeking mates.

This is the sound a banjo frog makes.

Noisy environments can dramatically change how these animals behave. In some cases, animals adapt to their noisy environment. Some frogs, for example, overcome traffic noise disrupting their sex lives by calling at a higher pitch. Likewise, populations of bow-winged grasshoppers in Germany exposed to road noise sing at higher frequencies than those living in quieter areas.

For other animals, such as microbats in England, disruptive noise changes how they forage and move around their environments.

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Read more:
How noise pollution is changing animal behaviour

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In extreme cases, these human-associated noises can drive animals away from their homes, as the disruptions to their lives becomes untenable.

Urban black-tufted marmosets in Brazil have been shown to avoid areas with abundant food where noise may interfere with their vocal communication. And research shows intruding noise in stopovers for migratory birds in the United States reduces their diversity by 25%, with some species avoiding the stopovers altogether.

Black-tufted marmosets in Brazil avoid noisy habitats even when there’s plenty of food.
Shutterstock

A new quiet?

The soundscape of cities in lockdown can be dramatically different from what we have come to accept as normal.

First, there are new noises. For example, in Sydney’s areas of concern subject to tighter lockdown restrictions, people are living with the frequent intrusive noise of police helicopters patrolling their neighbourhoods, making announcements over loudspeakers about compliance.

But in other cases, as our movements and activities are restricted, some city sounds associated with a negative impact on well-being are significantly reduced. People who live near major roads, aircraft flight paths, or construction sites will certainly be noticing the quiet as road traffic is greatly reduced and non-essential construction is paused.

But of course, while this silence might be golden for some, for others the sound of silence is the sound of lost work and income. This quietude may even be considered as unwelcome or even eerie — the sonic signature of isolation, confinement and loss.

The bow-winged grasshopper adapts to noisy soundscapes by singing at higher frequencies.
Quartl/Wikimedia, CC BY-SA

Just as many animals adapt to or avoid noisy urban environments, there is a chance many will respond to this natural experiment playing out. Quieter urban environments may see the return of some of our more noise sensitive species, but this depends on the species.

The Brazilian marmosets mentioned earlier didn’t return to those locations even during quieter times, suggesting the noise left a disruptive legacy on their habitat choice, well after it was experienced. On the other hand, other experiments show some species of birds rapidly returned to sites after noise was removed from the landscape.

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While it’s too early to confirm any early speculation about nature returning to quieter urban environments during lockdown, there is compelling evidence many people will benefit from engaging with local nature more actively than they did before.

Birdwatching increased tenfold in lockdown last year.
Matthew Willimott/Unsplash

Many more Australians are acting as urban field naturalists. Birdwatching, for example, increased tenfold in lockdown last year.

It’s clear people are seeing novelty and wonder in animals and plants that have survived and even thrived in our cities right beneath our noses the whole time. Our increased use of local greenspace during the pandemic has created new opportunities to find the extraordinary in the ordinary.

Rethinking post-pandemic soundscapes

What might we learn from this natural experiment about the soundscapes we take for granted and the soundscapes we actually want?

This is an invitation to think about whether we ought to do more to control sounds we consider “noise”. Yes, decibel levels of activities like car and air traffic matter. But it’s also an opportunity to think beyond controlling sounds, and consider how we might create soundscapes to enhance human and non-human well-being. This is easier said than done, given there’s no universal measure of what sounds give pleasure and what sounds are perceived as noise.

This aligns with the growing body of evidence on the need to reduce noise pollution and protect biodiversity when planning and managing our cities.

Like just about every other dimension of urban life, envisioning and creating an improved urban soundscape requires careful attention to spatial inequality and diversity – including of species – and a capacity to work through our differences in a fair and just way.

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Read more:
Where the wild things are: how nature might respond as coronavirus keeps humans indoors

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Kurt Iveson, Associate Professor of Urban Geography and Research Lead, Sydney Policy Lab, University of Sydney and Dieter Hochuli, Professor, School of Life and Environmental Sciences, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Climate explained: how particles ejected from the Sun affect Earth’s climate

Earth’s magnetic field protects us from the solar wind, guiding the solar particles to the polar regions.
SOHO (ESA & NASA)

Annika Seppälä

CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

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When the Sun ejects solar particles into space, how does this affect the Earth and climate? Are clouds affected by these particles?

When we consider the Sun’s influence on Earth and our climate, we tend to think about solar radiation. We are acutely aware of the skin-burning dangers of ultraviolet, or UV, radiation.

But the Sun is an active star. It also continuously releases what is known as “solar wind”, made up of charged particles, largely protons and electrons, that travel at speeds of hundreds of kilometres per hour.

Some of these particles that reach Earth are guided into the polar atmosphere by our magnetic field. As a result, we can see the southern lights, aurora australis, in the southern hemisphere, and the northern equivalent, aurora borealis.

Aurora australis observed above southern New Zealand.
Shutterstock/Fotos593

This visible manifestation of solar particles entering Earth’s atmosphere is a constant reminder there is more to the Sun than sunlight. But the particles have other effects as well.

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Solar particles and ozone

When solar particles enter the atmosphere, their high energies ionise neutral atmospheric nitrogen and oxygen molecules, which make up 99% of the atmosphere. This “energetic particle precipitation”, named because it’s like a rain of particles from space, is a major source of ionisation in the polar atmosphere above 30km altitude — and it sets off a chain of reactions that produces chemicals that facilitate the destruction of ozone.

The impact of solar particles on atmospheric ozone was first observed in 1969. Since the early 2000s, thanks to new kinds of satellite observations, we have seen growing evidence that solar particles play an important part in influencing polar ozone. During particularly active times, when the Sun releases large amounts of particles into space, up to 60% of ozone at altitudes above 50km can be depleted. The effect can last for weeks.

Lower down in the atmosphere, below 50km, solar particles are important contributors to the year-to-year variability in polar ozone levels, often through indirect pathways. Here, solar particles again contribute to ozone loss, but a recent discovery showed they also help curb some of the depletion in the Antarctic ozone hole.

How ozone affects the climate

Most of the ozone in the atmosphere resides in a thin layer at altitudes of 20-25km — the “ozone layer”.

But ozone is everywhere in the atmosphere, from the Earth’s surface to altitudes above 100km. It is a greenhouse gas and plays a key role in heating and cooling the atmosphere, which makes it critical for climate.

In the southern hemisphere, changes in polar ozone are known to influence regional climate conditions.

Solar particles ionise nitrogen and oxygen molecules in the atmosphere, which leads to other chemical reactions that contribute to ozone destruction.
Shutterstock/PunyaFamily

Its depletion above Antarctica had a cooling effect, which in turn pulled the westerly wind jet that circles the continent closer. As the Antarctic hole recovers, this wind belt can meander further north and affect rainfall patterns, sea-surface temperatures and ocean currents. The Southern Annular Mode describes this north-south movement of the wind belt that circles the southern polar region.

Ozone is important for future climate predictions, not only in the thin ozone layer, but throughout the atmosphere. It is crucial we understand the factors that influence ozone variability, be it man-made or natural like the Sun.

The Sun’s direct influence

The link between solar particles and ozone is reasonably well established, but what about any direct effects solar particles may have on the climate?

We have observational evidence that solar activity influences regional climate variability at both poles. Climate models also suggest such polar effects link to larger climate patterns (such as the Northern and Southern Annular Modes) and influence conditions in mid-latitudes.

The details are not yet well understood, but for the first time the influence of solar particles on the climate system will be included in climate simulations used for the upcoming Intergovernmental Panel on Climate Change (IPCC) assessment.

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Solar weather has real, material effects on Earth

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Through solar radiation and particles, the Sun provides a key energy input to our climate system. While these do vary with the Sun’s 11-year cycle of magnetic activity, they can not explain the recent rapid increase in global temperatures due to climate change.

We know rising levels of greenhouse gases in the atmosphere are pushing up Earth’s surface temperature (the physics have been known since the 1800s). We also know human activities have greatly increased greenhouse gases in the atmosphere. Together these two factors explain the observed rise in global temperatures.

What about clouds?

Clouds are much lower in the atmosphere than where most solar particles penetrate. Particles know as galactic cosmic rays (coming from the centre of our galaxy rather than the Sun) may be linked to cloud formation.

It has been suggested cosmic rays could influence the formation of condensation nuclei, which act as “seeds” for clouds. But recent research at the CERN nuclear research facility suggests the effects are insignificant.

This doesn’t rule out some other mechanisms for cosmic rays to affect cloud formation, but thus far there is little supporting evidence.

Annika Seppälä, Senior Lecturer in Geophysics

This article is republished from The Conversation under a Creative Commons license. Read the original article.

I’ve always wondered: do nuclear tests affect tectonic plates and cause earthquakes or volcanic eruptions?

A detection station for seismic activity at Bilibion, a remote corner of Russia.
The Official CTBTO Photostream (Copyright CTBTO Preparatory Commission) , CC BY

Jane Cunneen, Curtin University

This is an article from I’ve Always Wondered, a new series where readers send in questions they’d like an expert to answer. Send your question to alwayswondered@theconversation.edu.au

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Do underground nuclear tests affect Earth’s tectonic plates, and cause earthquakes or volcanic eruptions? – Anne Carroll, Victoria

Apart from escalating global fears about conflict, North Korea’s recent nuclear tests have raised questions about geological events caused by underground explosions.

Some media reports suggest the tests triggered earthquakes in South Korea. Others report the explosions may trigger a volcanic eruption at Paektu Mountain, about 100km from the test site.

So can an underground test cause an earthquake? The short answer is yes: a nuclear explosion can cause small earthquakes. But it is unlikely to affect the earth’s tectonic plates or cause a volcanic eruption.

Although a nuclear explosion releases a lot of energy in the immediate region, the amount of energy is small compared to other stresses on tectonic plates.

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Read more: What earthquake science can tell us about North Korea’s nuclear test

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What are tectonic plates?

Tectonic plates are slabs of the earth’s crust which move very slowly over the surface of the earth. Mountain ranges form at the edges of the plates when they collide, and ocean basins form when they move apart.

Tectonic plates are slabs of the earth’s crust.
Designua/shutterstock

Volcanoes occur mostly where plates are colliding. One plate overrides another, pushing it down to where it may partly melt. The partially melted rock – also known as lava – then rises to the surface, causing a volcano.

The movement of tectonic plates also causes earthquakes, which is why 90% of them occur at the plate boundaries. All but the deepest earthquakes occur along faults, which are breaks in the crust where rocks can move past each other in response to stress. This stress can be from both natural events and human activities.

Human induced earthquakes

“Induced seismicity” is the term used to describe earthquakes caused by human activities.

Human induced earthquakes can be caused by anything that changes the stresses on rocks beneath the surface. These include processes that add or remove great loads from the surface, such as mining, building dams or tall buildings.

Other processes that change the amount of pressure on rocks can include fluid injection from drilling, or extraction of water from aquifers.

Human-induced earthquakes have been reported from every continent except Antarctica. Induced earthquakes only occur where there is already some stress on the rocks. The human activity adds enough stress to the rocks to reach the “tipping point” and trigger the earthquake.

Nuclear explosions can induce small earthquakes along existing faults near a test site. Some underground nuclear tests have fractured the ground surface above the explosions, causing movement on faults adjacent to explosion sites.

Earthquakes from nuclear testing

The 3 September 2017 North Korean nuclear test generated shock waves equivalent to a magnitude 6.3 earthquake. Eight minutes later, a magnitude 4.1 event was detected at the same site. This may have been linked to a collapse of a tunnel related to the blast.

Several small earthquakes measured since the event may have been induced by the nuclear test, but the largest is only a magnitude 3.6. An earthquake of this size would not be felt outside of the immediate area.

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Read more: North Korea tests not just a bomb but the global nuclear monitoring system

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The largest induced earthquake ever measured from nuclear testing was a magnitude 4.9 in the Soviet Union. An earthquake of this size can cause damage locally but does not affect the full thickness of the earth’s crust. This means it would not have any effect on the movement of tectonic plates.

Historical data from nuclear testing (mostly in the USA) shows that earthquakes associated with nuclear testing typically occur when the explosion itself measures greater than magnitude 5, 10–70 days after the tests, at depths of less than 5km, and closer than around 15km to the explosion site. More recent studies have concluded that nuclear tests are unlikely to induce earthquakes more than about 50km from the test site.

Volcanic eruptions

Concerns have also been raised about the risk of volcanic eruptions induced by the nuclear tests in North Korea. Paektu Mountain is about 100km from the test site and last erupted in 1903.

Mount Paektu is an active volcano on the border between North Korea and China.
Google Maps

In the 1970s, the USA conducted a number of nuclear tests in the Aleutian Islands, a volcanic island arc chain containing 62 active volcanoes.

One of the blasts, named Cannikin, was the largest underground nuclear test ever conducted by the USA. There were fears that the blast would cause a huge earthquake and tsunami. The blast did result in some induced earthquakes, but the largest was a magnitude 4.0 and there was no increase in volcanic activity.

Based on this evidence, it seems unlikely a nuclear test by North Korea will trigger an eruption of Paektu Mountain. If the volcano was on the verge of erupting, then an induced earthquake from a nuclear blast could influence the timing of the eruption. However, given the distance from the test site then even this is not likely.

Monitoring nuclear tests

The Comprehensive Nuclear Test Ban Treaty Organisation (CTBTO) has a global monitoring system to detect nuclear tests, including seismometers to measure the shock waves from the blast and other technologies.

Global network of seismic monitoring stations.
CTBTO / The Conversation, CC BY-NC-ND

Seismologists can analyse the seismic data to determine if the shock waves were from a naturally occurring earthquake or a nuclear blast. Shock waves from nuclear blasts have different properties to those from naturally occurring earthquakes.

Testing was much more common before the CTBTO was formed: between 1945 and 1996 more than 2,000 nuclear tests were conducted worldwide, including 1,032 by the USA and 715 by the Soviet Union.

Since 1996 only three countries have tested nuclear devices: India, Pakistan and North Korea. North Korea has conducted six underground nuclear tests at the same site between 2006 and 2017.

Jane Cunneen, Research Fellow, Curtin University

This article was originally published on The Conversation. Read the original article.

Noise from offshore oil and gas surveys can affect whales up to 3km away

Migrating humpback whales avoid loud, nearby sounds.
BRAHSS, Author provided

Rebecca Dunlop, The University of Queensland and Michael Noad, The University of Queensland

Air guns used for marine oil and gas exploration are loud enough to affect humpback whales up to 3km away, potentially affecting their migration patterns, according to our new research.

Whales’ communication depends on loud sounds, which can travel very efficiently over distances of tens of kilometres in the underwater environment. But our study, published today in the Journal of Experimental Biology, shows that they are affected by other loud ocean noises produced by humans.

As part of the BRAHSS (Behavioural Response of Humpback whales to Seismic Surveys) project, we and our colleagues measured humpback whales’ behavioural responses to air guns like those used in seismic surveys carried out by the offshore mining industry.

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Read more: It’s time to speak up about noise pollution in the oceans

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Air guns are devices towed behind seismic survey ships that rapidly release compressed air into the ocean, producing a loud bang. The sound travels through the water and into the sea bed, bouncing off various layers of rock, oil or gas. The faint echoes are picked up by sensors towed by the same vessel.

During surveys, the air guns are fired every 10-15 seconds to develop a detailed geological picture of the ocean floor in the area. Although they are not intended to harm whales, there has been concern for many years about the potential impacts of these loud, frequent sounds.

Sound research

Although it sounds like a simple experiment to expose whales to air guns and see what they do, it is logistically difficult. For one thing, the whales may respond to the presence of the ship towing the air guns, rather than the air guns themselves. Another problem is that humpback whales tend to show a lot of natural behavioural variability, making it difficult to tease out the effect of the air gun and ship.

There is also the question of whether any response by the whales is influenced more by the loudness of the air gun, or how close the air blast is to the whale (although obviously the two are linked). Previous studies have assumed that the response is driven primarily by loudness, but we also looked at the effect of proximity.

We used a small air gun and a cluster of guns, towed behind a vessel through the migratory path of more than 120 groups of humpback whales off Queensland’s sunshine coast. By having two different sources, one louder than the other, we were able to fire air blasts of different perceived loudness from the same distance.

We found that whales slowed their migratory speed and deviated around the vessel and the air guns. This response was influenced by a combination of received level and proximity; both were necessary. The whales were affected up to 3km away, at sound levels over 140 decibels, and deviated from their path by about 500 metres. Within this “zone”, whales were more likely to avoid the air guns.

Each tested group moved as one, but our analysis did not include the effects on different group types, such as a female with calf versus a group of adults, for instance.

Our results suggest that when regulating to reduce the impact of loud noise on whale behaviour, we need to take into account not just how loud the noise is, but how far away it is. More research is needed to find out how drastically the whales’ migration routes change as a result of ocean mining noise.

Rebecca Dunlop, Senior Lecturer in Physiology, The University of Queensland and Michael Noad, Associate Professor, The University of Queensland

This article was originally published on The Conversation. Read the original article.

Copenhagen Summit Fails to Deliver

In news that has delighted the ears of climate change sceptics the world over, the Copenhagen summit on climate change has failed to deliver anything of real value that will actually make a difference. It is truly disappointing that even in the face of a massive environmental disaster that will affect the entire planet, global leaders have failed to lead and work together in finding solutions to the major issues we face over the coming decades and century.

Newspapers in Australia have reported the failure of the summit and are reporting on the leader of the opposition gloating over the failure of the summit. His solution is to ignore the real issue and hope that the Australian people prove to be as oblivious to climate change as the coalition he leads.

Typically, the usual anti-Kevin Rudd biased journalists and climate change sceptics of the newspaper (The Sunday Telegraph) I read this morning, were also quick to pour further scorn on the Prime Minister and the problem of climate change itself (which they deny). One particular vocal climate change sceptic in the Sunday Telegraph has very little credibility with me and I find his obsessive anti-Rudd tirades more than a little tiring. This self-opinionated buffoon is little more than an embarrassment for both the Sunday Telegraph and the Daily Telegraph for which he also writes. His columns are becoming more of a personal vendetta against Kevin Rudd than anything resembling real journalism.

I’ll be finding a better way to become acquainted with the daily news than continuing to read the biased diatribes that continue to be put forward by these papers in future. I’ll also be hoping that our leaders can overcome the various preoccupations each have with self-interest (whether it be personal or national) in order to reach a real workable agreement on dealing with the growing threat of climate change