February - March 2021 (14:3)

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Editor’s note: Anthropogenic noise in the ocean – from ships, sonar, construction, oil wells, windfarms, seismic surveys, and other activities – harms marine animals ranging from marine mammals to fish to invertebrates. Ocean noise has been documented to:

As the Skimmer is covering various way that the COVID-19 pandemic has impacted marine ecosystems and communities, a likely reduction in ocean noise is one possible bright spot. As we collected news and research articles on this topic, however, almost all reports that we found related to ocean noise and marine mammals off the West Coasts of the U.S. and Canada in the first half of 2020. To help broaden our understanding, we asked scientists from Applied Ocean Sciences, a collective of ocean consultants with expertise in ocean acoustics, to share what they have learned about noise trajectories over a longer timescale and in other areas of the world. Below is our Skimmer-style summary of news and research articles and an interview with Chris Verlinden, a senior scientist and chief technology officer at Applied Ocean Solutions.

Part 1: “An unprecedented pause in ocean noise that probably hasn’t been experienced in decades”: A summary of ocean noise news from the COVID-19 pandemic

Part 2: “In many parts of the ocean a whale might be audible twice as far away in 2020 as in 2019”: Interview with Chris Verlinden of Applied Ocean Sciences

Skimmer: We know the pandemic led to some dramatic decreases in ocean noise in the first half of 2020, but many noise-producing ocean uses have picked back up (e.g., shipping, fishing) since then. What can you tell us about changes in the ocean soundscape from before the pandemic to now – one year in?

Verlinden: Great question. The financial shutdown associated with the COVID-19 pandemic led to a dramatic decrease in certain types of shipping activity all over the world. It is important to note that this decrease was not uniform geographically or across vessel types. Cruise ship traffic all but disappeared during the height of the pandemic and has not yet returned to its pre-pandemic numbers. Similar reductions occurred in some passenger ferry routes where the number of vessels required to fill the needs of the community decreased during the height of the pandemic. Ferry routes, at least in the U.S., have now largely returned to pre-pandemic levels. Recreational fishing traffic (charters, sport fishing, deep sea fishing, etc.) decreased dramatically in the U.S. early in the pandemic, while most commercial fishing traffic continued at its pre-pandemic levels. Traffic from military vessels remained fairly constant, as did survey and research vessel traffic. Tanker traffic experienced a drop from the second half of March into April of last year but then steadily rose to pre-pandemic rates by the end of the year. Container vessel traffic experienced a similar trend in March and April 2020 but is only now starting to increase. Interestingly, bulk carrier traffic along certain areas on the U.S. West Coast decreased dramatically in March and April 2020, more than container traffic. This traffic included cargo such as gravel, chemicals, and bulk agricultural goods such as wheat and lumber. This made certain areas, such as the mouth of the Colombia River, substantially less trafficked and thus quieter than usual.

These trends by vessel type were roughly similar across the U.S. So in areas where much of the vessel traffic was cruise ships (such as parts of south central or southeast Alaska), ocean noise decreased significantly during the COVID-19 pandemic. Below are several plots of the number of vessels underway in a few different areas of U.S. waters during March-April 2019 and 2020. You can see that it varies dramatically with regard to geography. Most of this traffic is expected to return to usual pre-pandemic levels, with the possible exception of the cruise ship industry.


So in a nutshell, changes to shipping traffic depends on the type of traffic and location. But for the most part, shipping levels dropped dramatically in most places in the U.S. in the latter half of March 2020 into April and have increased to nearly pre-pandemic levels in most places for most types of vessels.

Now let’s talk about the acoustic implications. It is important to note that the acoustic impact of a ship depends on a lot of variables such as the vessel type and speed as well as local oceanographic characteristics, bathymetry, and ocean bottom properties. Sound propagates differently in deep water versus shallow water and in cold water versus more temperate waters. For these reasons, the changes in ambient ocean noise from ship traffic do not mirror the changes in shipping density. Also, there are other sources of noise in the ocean including wind, waves, industrial activity, seismic disturbances, ice, and biologics such as whales, fish, and shrimp. All these things taken together are referred to as the soundscape. So, the changes in the global soundscape are a more nuanced discussion than the changes in shipping activity. Below are some figures that illustrate this. The figures on top show global ship densities (from Spire Inc. global AIS data) in 2019 (top) and 2020 (bottom). You can see a subtle reduction in density in the major lanes in 2020.


Now let’s look at figures with the average modeled global shipping noise from 2019 (top), 2020 (middle), and the difference (bottom).


Our models predict that most of the ocean was quieter in April 2020 than April 2019, an average of about 3 dB quieter. That might not sound like a lot, but decibels are logarithmic so 3 dB represents a doubling of intensity. This means that in many parts of the ocean a whale might be audible twice as far away in 2020 as in 2019. That’s a big deal.

Also, not all areas are impacted the same. Below are plots of what a fictional grid of 16 ships will sound like at the surface of the ocean in the South Pacific compared to the Arctic. The cold water at the surface in the Arctic traps sound near the surface because of a phenomenon known as surface ducting. So if you reduce the number of ships in the Arctic by a couple of ships, the average noise level near the surface will decrease dramatically, while reducing the number of ships in the tropics will not have as big of an impact.



So, long story short: many areas of the global ocean were quieter in 2020 than 2019 due to the reduction in shipping associated with the COVID-19 pandemic. The average difference was about 3dB, which is significant for marine mammals and other organisms. In most locations, the difference was most pronounced in April 2020. Since that time, vessel traffic and thus the soundscape have been returning to pre-pandemic levels. The acoustic impact is not uniform and does not follow trends in shipping perfectly due to oceanographic and environmental factors. I expect ship noise to return to pre-pandemic levels by the end of 2021 and then continue the trend of increasing. Most literature reports that the ocean gets louder by an average of 3 dB per decade, although some recent research suggests the current trend may be closer to 1-2 dB per decade. I expect this rate of increase to continue for the foreseeable future with our increasingly globalized economy driving more shipping, and by extension, more shipping noise.

That being said, this rate of increase will likely not occur uniformly, and I am most concerned about noise levels in the Arctic. With the cold surface temperatures, surface ducting, and organisms evolved for a very quiet region, the continued increase in vessel activity in the Arctic will make it a lot louder over the next couple decades and have a significant negative impact on the native marine mammal populations.

Skimmer: What upcoming data are you most interested in seeing to help us better understand how changes in ocean uses during the pandemic are altering ocean soundscapes and ecosystems?

Verlinden: Model and observational data comparison. The Arctic. Marine mammal stress hormones.

The pandemic gave us a rare opportunity to study the impact of reducing ship traffic on the global soundscape. It is rare that we, as scientists, can see precisely how these knobs are being adjusted. Let’s not waste it. Let’s see what happened during 2020 and how it impacted the marine organisms that rely on sound to survive. Applied Ocean Sciences’ approach has been to model the global ship noise, but that is only part of the story. We need to compare these models to actual observations and adjust our model parameters until we can reproduce the observed data. We can then use those models to estimate and infer the soundscape everywhere. If our models can reproduce the changes that occurred during the COVID-19 pandemic, it will improve our confidence in our ability to model the soundscape everywhere in the world under a variety of circumstances. This includes forecasting the soundscape under projected future shipping and industrial activity levels. I’d particularly like to apply this knowledge to the Arctic to predict soundscape changes over the next 10-50 years.

Finally, I’d love to see what the marine mammal stress physiology community comes out with over the next few years. After the 9/11 terrorist attacks, marine biologists recorded a reduction in stress hormones such as cortisol and aldosterone in marine mammals in the Bay of Fundy. This directly correlated with the reduction in ship traffic that followed those attacks. I am interested and excited to see if this is observed on a global scale during the COVID-19 pandemic and see what we can learn about the impact of ship noise on marine mammal population health using these observations. The COVID-19 pandemic and resulting changes in shipping and ship noise has provided us with an amazing opportunity to understand how ship noise impacts marine mammals so that we can better address the challenges faced by these animals in the future.

For additional background, we encourage you to check out Applied Ocean Science’s excellent StoryMap on COVID-19 and Ship Noise.

Editor’s note: Climate change is the greatest threat to the health of marine ecosystems worldwide, and the COVID-19 pandemic has the potential to alter the world’s climate change trajectory, for better or for worse. Numerous, diverse relationships between the two crises have arisen. These relationships have proven enormously changeable over the course of the pandemic and by location, and the net impact of the pandemic on climate change and society remains to be seen. This article briefly characterizes a number of the diverse intersections and parallels between the two crises.

Do you have updated information or a new or different perspective? We would love to get your thoughts and additions. You can add them to the Comments section below or send to The Skimmer editor at skimmer [at] octogroup.org.

#1: Greenhouse gas emissions went down in 2020, but not by as much as initially expected, not for all that long, and not for the “right” reasons. Without systemic changes, the COVID-19 pandemic is unlikely to have a significant long-term impact on global emission trajectories.

From the experts:

  • Ethan Zindler of BloombergNef: “The amount of pain we’ve had to go through for a relatively modest drop shows that there needs to be more smart policy and smart thinking about emissions. The emphasis has to be not on how to reduce demand, but how to make supply more green.”
  • Kevin Book of ClearView Energy Partners: “This is the way it feels to cut emissions in the worst way possible. [Cutting emissions through a worldwide pandemic] still isn’t enough to change the atmospheric stock of carbon.”

#2: The massive economic stimulus spending going on right now by nations around the world will be “make or break” for addressing climate change and is unfortunately trending toward carbon-intensive measures.

From the experts:

#3: Stimulus spending aside, the COVID-19 pandemic may have helped speed the shift in global energy production away from fossil fuels and towards renewables.

From the experts:

  • Fatih Birol of the International Energy Agency: “[The sharp decrease in oil demand has] fast forwarded some power systems 10 years into the future suddenly giving them levels of wind and solar power that they wouldn’t have had otherwise without another decade of investment.”
  • Valentina Kretzschmar of Wood Mackenzie: “The oil and gas sector is already a very much unloved sector by investors and in this kind of oil price environment, it becomes low return, high risk and high carbon. It is not a very attractive proposition.”
  • Christoph Bertram of the Potsdam Institute for Climate Research: “The events of 2020 could accelerate transformation trends in the power sector, and thus enable faster emission reductions in that sector than previously anticipated.”

#4: The COVID-19 pandemic gave governments an excuse to ease environmental safeguards, potentially offsetting some of the reductions in greenhouse gas emissions from reduced travel and commercial/industrial activity.

From the experts:

  • Gina McCarthy of the Natural Resources Defense Council and former US EPA administrator: “This is an open license to pollute. Plain and simple. The administration should be giving its all toward making our country healthier right now. Instead, it is taking advantage of an unprecedented public health crisis to do favors for polluters that threaten public health. We can all appreciate the need for additional caution and flexibility in a time of crisis, but this brazen directive is an abdication of the EPA's responsibility to protect our health."

#5: The COVID-19 pandemic has led to cancellations/delays in critical climate change negotiations and research.

These delays have slowed international climate change negotiations and may be allowing countries to put environmental and climate concerns on hold for a while, including ignoring the incorporation of low-carbon strategies in their economic stimulus packages. Disappointingly, a new analysis found that the new pledges announced so far for the UN COP26 to be held in November (from 75 countries representing about 30% of global greenhouse gas emissions) are vastly inadequate and would only reduce global emissions by less than 1% (from 2010 levels) by 2030. To limit global warming to 2°C, emissions would need to decrease by 25% (from 2010 levels) by 2030.

From the experts:

  • Emily Darling of The Wildlife Conservation Society: “We know so much about the inequity of scientific resources and training, where Western researchers can travel and fly and do ‘helicopter science.’ That’s not a model that’s sustainable, and it’s not a model that’s ethical. So this new reality gives us a chance to develop online tools for collaborations, for conferences, for workshops, and identify where we really need to travel and be face-to-face with our work.”

#6: Despite early fears, the COVID-19 pandemic does not appear to have drawn public concern away from climate change long-term, although it may have hurt the ability of some countries and communities to implement mitigation and adaptation measures.

From the experts:

#7: THE COVID-19 pandemic is having other large-scale societal impacts that will have greenhouse gas emissions implications, including changes to where people live, how they get around, and how they do their work.

#8: Last but not least, climate change is making epidemics and pandemics of zoonotic diseases such as COVID-19 more likely because it is increasing interactions between wildlife, domesticated animals, and humans.

Parallels between the COVID-19 pandemic and climate change

In addition to intersections, there are a number of parallels between the COVID-19 pandemic and climate change.

#1: For starters, although it seems a bit facile to even write this, both the COVID-19 pandemic and climate change are catastrophic public health and economic crises.

#2: As with climate change, denialism and misinformation about COVID-19 have worked to prevent effective action to prevent and mitigate the disease in some areas, notably in the US and Brazil.

#3: As with climate change, the COVID-19 pandemic is hitting low-income communities hardest. Mitigation and recovery efforts need to promote social and racial justice to help address these disparities and the systemic inequities that caused them.

#4: There is generational conflict in how society is responding to the two crises.

From the experts:

  • Audrey, 18 year old: "We haven't seen the government or adults as passionate about the things we really care about, like mental health and climate issues."
  • Jamie Margolin, 18-year-old climate justice activist: “[The pandemic] has exposed how government leaders, and the American public, actually can make immediate, dramatic behavioral changes – even when those changes have serious consequences for the economy and our quality of life. It’s just that, until now, they haven’t been willing to. But the way the coronavirus disproportionately affects older people is the exact way the climate crisis disproportionately affects young people. When it comes to the climate crisis, most of the statistics are flipped: Young people will suffer the most. You want young people to sacrifice – to stop socializing, to shut ourselves inside so older people can live. But many older people aren’t sacrificing so the youth can live.”

#5: “Shifting baselines syndrome” is affecting societal response to both crises.

From the experts:

  • George Loewenstein of Carnegie Mellon: “There is a tremendous amount of research showing that we tend to adapt to circumstances if they are constant over time, even if they are gradually worsening. Fear tends to diminish over time when a risk remains constant. You can only respond for so long. After a while, it recedes to the background, seemingly no matter how bad it is … Once the fear is gone, the willingness to take measures is also gone.”

#6: Finally, both the COVID-19 pandemic and climate change crises are “collective-action problems.”

  • The best chance at minimizing the health and economic impacts of both was/is early, big, global, and coordinated government response. Early government responses to the COVID-19 pandemic showed that governments can take quick, dramatic action (e.g., stay-at-home orders, travel restrictions, mask mandates) with good citizen compliance in response to a crisis. However, later pushbacks (e.g., premature elimination of and large-scale non-compliance with mask wearing and physical distancing mandates) in some countries have shown that collective action, even for a fast-moving threat, has its limits in today’s world.
  • So, ultimately, has the global response to the pandemic so far been a reason for hope or despair on the climate change front? It is too early for a final verdict to be rendered, but most would probably agree that the global response to the COVID-19 pandemic has been mixed at best. Some countries such as South Korea, Taiwan, and Lithuania have excelled at controlling the virus and blunting the financial impacts of the pandemic, but – similar to the global response to climate change – a lack of resources, tribalism, and misinformation have stymied efforts across much of the globe.

From the experts:

  • May Boeve of 350.org: “We’ve seen that governments can act, and people can change their behavior, in a very short amount of time… And that’s exactly what the climate movement has been asking governments and people to do for years in the face of a different kind of threat—the climate crisis—and we don’t see commensurate action.”


Editor’s note: Stanford economist Paul Romer coined the phrase “a crisis is a terrible thing to waste” in 2004.

Some more climate change-related news and resources:

Some more plastic pollution-related news and resources:

And some other recent news articles that caught our attention:

Editor’s Note: From the Archives calls attention to past Skimmer/MEAM articles whose perspectives and insight remain relevant.

As professionals in the marine conservation and management field, Skimmer readers are hyperaware of large scale and global changes to marine ecosystems. Research is now examining the emotional and psychological toll that these changes are having on people. This article synthesizes the seminal research on “ecological grief” and how society can address it at both policy and personal levels.