Bowdoin Science Journal

Environmental Science and EOS

The role of info chemicals in seabird plastic ingestion

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Short-tailed Shearwater (Puffinus tenuirostris), Ryan Shaw (2009)

Plastic debris is widespread in our waters with more than a quarter of a billion metric tons of plastic suspended in its global oceans. This abundant plastic pollution is being consumed by hundreds of organisms, ranging from tiny zooplankton to giant baleen whales. Seabirds are especially at risk, with a projection model concluding that over 99% of all seabird species will have ingested plastic debris by 2050. The consumption of plastic is incredibly harmful to seabirds as it reduces the storage volume of the stomach which ultimately leads to starvation and death. In the last few years, it has been discovered that the plastic problem is much more complicated than we thought before as many seabirds rely on their sense of smell to locate their prey instead of just visually. A 2016 study has brought to light this common misconception of marine organisms consuming plastic debris solely based on visual cues and has introduced a new factor: dimethyl sulfide (DMS). 

DMS is an infochemical used by foraging organisms as a way to find prey in marine environments. The production of DMS is from the enzymatic breakdown of its chemical precursor, dimethylsulfoniopropionate (DMSP), which increases when zooplanktons eat, letting other marine organisms know of the presence of a new meal. Plastic debris is an excellent substrate for biota that produce these infochemicals due to its convenience in biofouling, which is the accumulation of organisms on a surface. Since plastic debris can be easily fouled by DMS-producing organisms, then the debris can also produce a DMS signature that is significant enough to lead seabirds and similar organisms to consume it. 

To prove this, scientists examined the sulfur signature of plastic beads from the most common types of plastic found in the ocean. These plastic beads were tested for sulfur signatures after either being exposed to marine conditions or never being exposed to these conditions. The beads exposed to marine conditions were deployed off the coast of California at the Bodega Marine Laboratory and Hopkins Marine Station at oceanographic buoys and then retrieved after approximately three weeks. After examining each plastic bead, it was found that the samples not exposed to marine conditions did not produce any DMS signature. However, every sample that was tested after marine exposure was found to have produced a DMS signature. Even after less than a month of marine exposure, these plastic samples were found to produce DMS signatures that were significant enough to be detected by seabirds.

Additionally, the study was able to predict the importance of DMS and plastic ingestion patterns within seabirds through data analysis. Plastic ingestion data was analyzed from 55 studies among 25 procellariiforms––the order under which seabirds fall––to determine that DMS responsiveness has a significant positive effect on the frequency of plastic ingestion. Additionally, plastic ingestion patterns were predicted through calculations using data from previous studies to find that DMS-responsive species ingest plastic five times as frequently as non-DMS-responsive species.

The study has challenged the frequent assumption that marine organisms consume plastic because it is visibly mistaken for prey, suggesting rather that chemical cues like DMS play a role. This plastic ingestion has many implications, one such being that the semiannual movement patterns of seabirds between the Southern and Northern Hemispheres can create contact with plastic on a global scale rather than just a regional one. Although the primary focus of this study was on seabirds, they are not the only species that respond to DMS––sea turtles, penguins, and various other organisms have been shown to use DMS and DMSP as foraging compounds and could be impacted similarly. We must start mitigating the plastic waste we produce and work towards cleaning up our oceans. While this is a huge step to take, we can begin by looking for alternatives to plastic that are safer for the environment and reduce the amount of plastic that we use in our everyday lives.


References:

Savoca, M. S., Wohlfeil, M. E., Ebeler, S. E., & Nevitt, G. A. (2016). Marine plastic debris emits a keystone infochemical for olfactory foraging seabirds. Science Advances, 2(11). https://doi.org/10.1126/sciadv.1600395 

Eriksen, L. C. M. Lebreton, H. S. Carson, M. Thiel, C. J. Moore, J. C. Borerro, F. Galgani, P. G. Ryan, J. Reisser, Plastic pollution in the world’s oceans: More than 5 trillion plastic pieces weighing over 250,000 tons afloat at sea. PLOS ONE 9, e111913 (2014).

Wilcox, E. Van Sebille, B. D. Hardesty, Threat of plastic pollution to seabirds is global, pervasive, and increasing. Proc. Natl. Acad. Sci. U.S.A. 112, 11899–11904 (2015).

Ocean plastics pollution. Ocean Plastics Pollution. (n.d.). Retrieved April 2, 2023, from https://www.biologicaldiversity.org/campaigns/ocean_plastics/?adb_sid=71bc9f17-356c-492f-9204-f0e22e2752b6

Mercury, Contaminating Our Oceans and Your Food

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Mercury, you may know it as the solar system’s smallest planet or as the “red stuff” in old thermometers. You may have even heard of its toxic effects on people if exposure occurs. However, you may not know that mercury is significant outside of the realm of toxic thermometers and astronomy. The chemical element mercury is a contaminant that is being pumped into the atmosphere at an alarming rate and is poisoning aquatic environments. Mercury is becoming an increasingly common pollutant in our oceans and lakes and its toxic effects are causing harm to marine life and creating an imbalance in our marine ecosystems.

Before mercury can enter aquatic environments, it is released in large quantities by anthropogenic sources. Mercury can enter the atmosphere through natural sources such as volcanoes or forest fires, but it is primarily released through the burning of fossil fuels and small-scale gold mining (Montes 287). The release of mercury is problematic because it is very easily transported through the atmosphere. Mercury is a volatile element, which means that it evaporates at low temperatures (mercury can even evaporate at room temperature) and easily enters its gaseous state to be carried long distances through the air (Pollet 860).

After mercury is transported through the atmosphere and enters aquatic environments, it is transformed into its more toxic state, methylmercury (CH3Hg or MeHg). Mercury is transformed into methylmercury through the process of mercury methylation when Hg incorporates CH3, making it into CH3Hg (or MeHg). In the ocean, methylation of mercury is carried out by bacteria. Essentially, bacteria that are present in aquatic environments absorb mercury and perform the methylation reaction before releasing methylmercury back into the ecosystem (Poulain 1280-1281).

Once organisms ingest methylmercury, they experience detrimental effects on their function and, ultimately, their survival. For example, seabirds with more than 0.2 μg (micrograms) of mercury in their blood per gram of wet weight have observed negative effects on their bodies’ systems and their function. An approximately equivalent concentration can be represented by one person out of the entire state of Alabama, which has a population of 5.04 million. At this level or greater, birds experience detrimental effects on their nervous and reproductive systems as well as changes to their hormonal makeup and trouble with motor and behavioral skills (Pollet 860). 

Another interesting observation of mercury contamination is its differing distribution of concentrations among populations. The methylmercury concentration in seabirds was explored between 2013 and 2019 when egg and blood samples were taken of Leach’s storm petrels along with the GPS tracking of foraging petrels. By comparing measured mercury concentration in blood and eggs to ocean depth of foraging locations, a correlation was found. The study concluded that the water depth had a significant effect on the methylmercury levels measured in Leach’s storm petrels. Storm petrels who foraged in deep waters had higher methylmercury concentrations in their blood than storm petrels who forage in shallow or coastal waters. The positive correlation between ocean depth and mercury concentration is likely due to differences in diet based on foraging location. This could also be related to the fact that mercury methylation is most efficient in deep water (Pollet 860).

These negative effects on seabirds also have broad effects on the entire ecosystem that they are a part of. This is because methylmercury biomagnifies up the food web. As the methylmercury moves up trophic levels in a food chain, its concentration in a given organism increases. This increase in concentration is dramatic. In fact, measured mercury concentrations in predator species can be millions of times greater than the concentration observed in surface waters. The problem of biomagnification is even more dramatic in Maine because of its latitude. While the phenomenon is not entirely understood, ecosystems located at higher latitudes have been observed to be more susceptible to biomagnification than tropical regions (Lavoie 13385-13394). 

Other than affecting our Maine wildlife, mercury contamination could have a negative impact on human health. Mercury is not only a problem for seabirds, but fish are also just as susceptible to contamination. This can become a major problem for commercial fisheries because the seafood they produce for our consumption have the potential for mercury contamination. In fact, there was an incident in Japan in 1956 when people who consumed contaminated seafood became severely ill or died. Over the course of 36 years after the incident, 2252 people were infected 1034 people were killed in relation to the initial methylmercury contamination (Harada 1-24). While this level of contamination is an anomaly, a 2018 study projected that approximately 38% of countries experience some level of human exposure to mercury due to contaminated seafood consumption. There are steps that can be taken to prevent this. For example, setting stricter regulations on mercury content limits, applying proper culinary treatments, or updating fishing practices could all diminish the probability of mercury exposure to humans (Jinadasa 112710). 

That being said, addressing the root of the problem is the only way to most effectively diminish mercury exposure for marine organisms and people. Mercury contamination is a problem that has a dramatic domino effect beginning in our atmosphere and ending in human consumption. It is an issue that is often forgotten in discussions of the environmental impact of burning fossil fuels. However, considering its impact on marine life and eventually human life, it is a byproduct that cannot be overlooked.

 

Works Cited

da Silva Montes, C., Ferreira, M. A. P., Giarrizzo, T., Amado, L. L., & Rocha, R. M. (2022). The
legacy of artisanal gold mining and its impact on fish health from Tapajós Amazonian
region: A multi-biomarker approach. Chemosphere, 287, 132263.

Harada, M. (1995). Minamata disease: methylmercury poisoning in Japan caused by
environmental pollution. Critical reviews in toxicology, 25(1), 1-24.

Jinadasa, B. K. K. K., Jayasinghe, G. D. T. M., Pohl, P., & Fowler, S. W. (2021). Mitigating the
impact of mercury contaminants in fish and other seafood—A review. Marine Pollution
Bulletin, 171, 112710.

Lavoie, R. A., Jardine, T. D., Chumchal, M. M., Kidd, K. A., & Campbell, L. M. (2013).
Biomagnification of mercury in aquatic food webs: a worldwide meta-analysis.
Environmental science & technology, 47(23), 13385-13394.

Pollet, I. L., McFarlane-Tranquilla, L., Burgess, N. M., Diamond, A. W., Gjerdrum, C., Hedd, A.,
… & Mallory, M. L. (2023). Factors influencing mercury levels in Leach’s storm-petrels at
northwest Atlantic colonies. Science of The Total Environment, 860, 160464.

Poulain, A. J., & Barkay, T. (2013). Cracking the mercury methylation code. Science, 339(6125),
1280-1281.

Ecology, Policy, and Science Communication: The Story of Biologist and Activist Erika Zavaleta

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Erika Zavaleta is an interdisciplinary scientist that has worked her career to make her research accessible, has broken down barriers for biologists of color, and is seen by many to be a trailblazer in her field. Zavaleta is a community and ecosystem biologist at the University of California Santa Cruz (UCSC) that focuses on global and regional environmental change, ecosystem functioning, and effective stewardship. She uses environmental policy, economics, anthropology, and outreach as tools to communicate her research to a larger audience as a scientist that aims to make the field accessible. She received her bachelor’s and master’s in anthropology and Ph.D. in biological sciences at Stanford University. Dr. Zavaleta is a Howard Hughes Medical Institute Professor in the Ecology and Evolutionary Biology department at UCSC. She is an appointed California Fish and Game Commission science advisor, an Ecological Society of America (ESA) “Excellence in Ecology Scholar,” ESA fellow, and a fellow of the California Academy of Sciences. Dr. Zavaleta has also co-authored over 75 papers and book chapters in the fields of conservation, ecology, and social sciences. In 2021, she received the Commitment to Human Diversity in Ecology Award from ESA due to her devotion to highlighting the voices of low-income, Indigenous, Black, and Latino backgrounds in the ecology and conservation field.

Dr. Zavaleta’s Conservation Science and Solutions Lab is interested in questions related to ecological responses to climate change, changes in biodiversity due to environmental variability, and conservation-based approaches to mediate these impacts. Some research projects currently taking place by her lab members are the impacts of land and water use changes on bat ecological communities, the impacts of community-led forestry conservation efforts in Brazil and Nepal, and the effectiveness of current conservation efforts in response to climate change. Through this research, Zavaleta’s group works to act as a link between ecology theory and research to develop and recommend effective conservation and management practices. The lab places an emphasis on collaborating with community partners, approaching research through a multidisciplinary lens, and furthering initiatives that promote inclusivity in the field of conservation and biology.

Zavaleta’s lab has supported initiatives that she founded at UCSC that provide mentorship and support for historically excluded scientists including the Doris Duke Conservation Scholars Program and the Center to Advance Mentored, Inquiry-Based Opportunities (CAMINO) in 2013 and 2017 respectively. The Doris Duke Conservation Scholars Program (DDCSP) is a national fellowship that aims to increase accessibility to the conservation field, mainly focusing on providing training and research experience for underrepresented students in science. DDCSP is carried out by five partners including the DDCSP Collaborative, the University of California at Santa Cruz, the University of Michigan, the University of Washington, and the Yale School of the Environment. CAMINO works directly with students at UCSC and provides academic and professional assistance from graduate and faculty mentors. The center pairs CAMINO scholars with funded internships where they can gain research experience regardless of their previous internships in the ecology and conservation field. Dr. Zavaleta currently serves as a faculty director for both of these programs.

Most recently, Zavaleta established a training called FieldFutures with biologist Dr. Melissa Cronin that emphasizes the importance of field-based education and research that prevent sexual harassment for scientists in the ecology and conservation field. As said on their website, “studies have shown that 64% of surveyed field researchers experienced harassment—and one in five experienced assault— while conducting fieldwork. Women, people of color, LGBTQIA+ people, and people with other marginalized identities are more likely to experience these problems.” Since fieldwork directly places scientists of all genders at greater risk of sexual violence, FieldFutures works to provide workshops that identify ways to increase prevention, provides a space for scientists to get hands-on experience in dealing with these situations, and offers protocols that can be used in the field. The “Futures” component of their name symbolizes their vision of a future for fieldwork free of sexual assault and harassment—and they are working towards getting closer to this prospect with each training.

I write about Dr. Zavaleta as a fellow Latina and future conservation biologist who not only admires her research and intellectual contributions to the field but also her dedication to making the field one that welcomes people like me. During my first and second summers as an undergraduate, I spent them as a Doris Duke Conservation Scholar at the University of California Santa Cruz (UCSC). I have heard first-hand Dr. Zavaleta’s passion for finding climate solutions, diversifying the field, and using public policy to enact impactful environmental legislation. She has not only shown her commitment to increasing diversity in the field, but she has also asserted her support for social movements around the country and pledged to incorporate their missions in her own work. In 2020 in a letter as director of DDCSP, she contended that

Science and conservation have long marginalized Black and brown voices, faces, and talents. The demographics of our country tell us that there should be five times as many scientists and professionals of color in ecology, evolution, and conservation as there are. The absence of diverse leadership in our field sustains this gap unless all of us work for change. We all have to speak up and act when we see racial inequities affect our peers, colleagues, students, and communities.

As a beneficiary of the initiatives she has passionately poured time and energy into, I can attest that programs like DDSCP have helped me and my peers realize that scientists like us—first-generation college students and people of color— can thrive in this field and use our experiences to connect to a greater audience in the scientific field. I wish to be as intentional and inclusive as Dr. Zavaleta moving forward as a scientist, educator, and science communicator and I hope that more people in this career follow her lead.

Living in Beaverland: The Ecology and Biogeochemistry of Beavers

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Next time you’re flying up to the Portland Jetport and the third rerun of Endgame just isn’t cutting it, look out the window. Much of the northern half of the continent is a sprawling landscape dotted with kettle lakes, winding rivers, and other vestigial scars of a world once drowned in ice. Certainly, of the processes that shaped the bedrock Bowdoin sits on, none are as immediately evident as the glaciers that covered it for seventy thousand years. Today, however, a much tinier (and cuter) force gnaws away at the landscape of modern Maine. Our waterways are a record of glaciers, true, but they’re just as much a record of the furry engineers that now inhabit them: Castor canadensis, the North American beaver. 

 

NPS / Neal Herbert, Public Domain.

 

Calling beavers “ecosystem engineers” isn’t science mumbo-jumbo: beavers quite literally show an understanding of the forces of hydrology that backdrops their dams. When a stream encounters a thin opening in bedrock that constricts its flow, its waters gurgle and bubble as it narrows through the gap. It is this gurgling that first allures a beaver to build its dam. In essence, beavers can “‘hear’ the geometry of the river basin.” There, a pioneering beaver colony lays the first branches of speckled alder that they consider too bitter for food, pointing the branches upstream to catch and anchor sediment as part of this keystone layer of wood. Layer upon layer of mud and stick convexes upstream, like the shape of the Hoover Dam, to combat increasing pressure from the pond when the dam plugs more water. As the colony gets larger, beavers build secondary and tertiary dams upstream to relieve pressure on their lodge, so that within generations, the colony will have terraformed their entire forest environment with ponds and meadows along a stairway of rivers and dams.

This process of familial expansion has impacted nearly all of the waterways in the northern United States, especially following their bounce back to pre-colonial populations. For instance, in the North Woods of Minnesota, 90% of streams flow through at least one dam, and overall, 15% of land is covered by beaver ponds or meadows. In the process, beavers unknowingly change the ecology, hydrology, and chemistry of their ponds— often by simply slowing down water. 

At its simplest, slower water cannot carry as much sediment, and in beaver habitats, this has incredible repercussions. Regions that experience alarming rates of erosion benefit from dams because streams cannot carry away soil. So, if rivers cannot carry sediment, they must deposit it instead of erode: beaver ponds carry much more sediment than other streams, increasing the amount of organic matter stored in its pond bottoms. When abandoned dams are broken through, this standing stock of nutrients encourages plant growth and a more biodiverse wet meadow after flooding settles. In the Colorado River, for instance, the distribution of sediment deposited in a dam flood influenced where a diverse plant community was able to grow.

By the same token, beaver habitats are essentially wetlands, critically changing the biogeochemical conditions around dams. Deeper waters and deeper soils foster denitrification, a form of bacterial activity that filters waters affected by nitrate pollution from things like fertilizers. Depositing more sediment also increases the carbon found in beaver ponds. Altogether, these wetland conditions increase biodiversity by a third of what’s found without beaver habitation. Because slower, sediment-laden streams downstream of dams are more likely to curve and branch, more beaver colonies can use them. With these prolific changes, the continent might truly, as environmental journalist Ben Goldfarb puts it, “better be termed Beaverland.”

Scientists have kept log (pun intended) of these benefits for quite some time— the foundational study on their role as geomorphic agents was published in 1938— but attempts to work together with the rodents in structures called beaver dam analogs (BDAs) have only caught on in recent years. In one of its earlier uses, ecosystems analyst Michael Pollock worked on the restoration of a stream that steelhead trout used in their migration inland. Before long, “beavers came and set up shop” on Pollock’s somewhat ad-hoc dams, and the results his team saw were incredible: BDAs increased habitat and reared more than three times more steelhead than an undammed stream nearby.

Despite its happy ending, Pollock argues that their study isn’t the paper to end all papers. How effectively BDAs can mimic and aid beaver dam construction still requires much more testing, and whether it’s worthwhile to reintroduce beavers at all is still debated. Nonetheless, some local governments and farmers alike who benefit from their application have begun to consider the idea of a true BDA Beaverland, so long as regulators get on board too. Whether the costs of building and maintaining BDAs are worth a beaver dam’s biogeochemical and ecological benefits are still up for talk among officials hesitant to rely on these furry rodents. But with all its controversy, you can’t deny that the impacts of Beaverland truly seem to be giving glaciers a run for their money.

Seismic Songs and Slinkies

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            In 1970, a 34-minute album was released by bio-acousticians Katharine and Roger Payne composed entirely of humpback whale songs. A few minutes into the album, phrases begin to coalesce into conversations with voices rising and falling in a strangely familiar rhythm. Some phrases sound like whining teenagers. Others like an elder beginning a story or a family on a trip. At times, though, the songs sound completely otherworldly.  The album is called Songs of the Humpback Whale, and it turned people’s ears towards the sounds of the oceans.

           Today, whale songs have caught the attention of a different audience: geophysicists studying the ocean floor. Our modern understandings of bathymetry – or underwater topography – have largely come from studies using instrumental acoustic waves onboard ships. As a ship travels through the ocean, an instrument called a transducer sends sound waves through the water and receives the signals that bounce back. Imagine standing at the railing of a ship and flinging one end of a slinky down to the seafloor: when the slinky hits the bottom, it sends a pulse back up to your hand. Now imagine your slinky reaches a layer of mud on the seafloor. It will send a very different signal back to your hand than if it penetrated to a denser material, like the ocean crust. That return pulse can be analyzed to produce profiles of seafloor texture and thickness.

           As powerful as this method – called the echo sounder method – is to the study of bathymetry, it comes with a major problem. Roger Payne and others helped us understand that marine mammals use sounds to socialize, navigate, find food, and identify mates. These are just a few possible interpretations of marine mammal vocalizations; it’s still a language we have yet to fully translate. What happens, though, when the ambient noise of the ocean from shipping increases? Global ship density increased by a factor of four from 1992 to 2012 which was linked to a 3 decibel per decade increase in ambient marine noise. That might not seem like a lot, but studies have found that maritime noise negatively interferes with marine mammals.  As some biologists describe it, maritime noise is like smog; “it shrinks the perceptual world of whales, fish, and other marine life.” And it turns out, the echo sounder method and other acoustic methods used to study the seafloor can also be detrimental to marine mammals and cause temporary hearing loss, disorientation, and behavioral changes.

           Is there a solution? Can geophysicists and oceanographers simultaneously study the seafloor while minimizing the impacts on marine life? From Science, authors Václav Kuna and John Nábĕlek introduce an innovative and less invasive technique for studying ocean seafloor structure by harnessing fin whale songs. 

Fin whales (Balaenoptera physalus) are the second largest whale in our oceans, growing up to 75-85 feet long. Fin whales use baleen – hair-like plates made of keratin that hang inside whales’ mouths – to filter feed on krill and small fish. The most important characteristic of fin whales for Kuna and Nábĕlek’s research was their powerful vocalizations – often reaching up to 189 dB, which is louder than a jet engine. These vocalizations have been picked up at ocean-bottom seismometer (OBS) stations which monitor underwater earthquakes. Kuna and Nábĕlek discovered that these OBS stations were not only recording songs directly from fin whales but also the secondary waves reflected up from the seafloor.

           Kuna and Nábĕlek studied six fin whale song recordings collected from three OBS stations located near an active fault in the north east Pacific, about 150 km off the coast of Oregon. The authors determined the whales’ paths and distances from the stations based off of the difference between the arrival times of two wave types – the direct wave, registering first at a higher velocity, and the waterborne multiple wave, a series of waves that bounce off the seafloor and sea surface before registering at an OBS station.

           In addition to sound waves, the authors identified four distinct seismic waves based on their unique subsurface reflection patterns. The arrival times of these seismic phases at the OBS stations varied because their velocities differed depending on the composition of the layers they penetrated. Again, think of the slinky interacting with seafloor layers that have differing densities. Based on the arrival times of the seismic phases relative to the arrival times of the waterborne wave types, Kuna and Nábĕlek determined that the seismic velocities of the whales’ calls corresponded with wave interactions at sediment, basaltic, and lower crustal layers. These findings aligned well with geophysicists’ previous maps of the bathymetry in the region.

           The significance of these results is nothing short of remarkable. Kuna and Nábĕlek harnessed a natural phenomenon – fin whale songs – to better understand geologic features of the seafloor that are completely unrelated to whales. They created a link between two distinct spheres of Earth that no one knew existed. Now as Songs of the Humpback Whale comes to an end, I’m left with an image of whales sharing secrets of the seafloor as they travel across ocean basins. 

 

 

 

An Ozone Success Story

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As a child, news of the hole in the ozone layer terrified me. I pictured green aliens covered in slime sliding through the dark hole into the skies above us, casting murky shadows over entire continents. Standing below the ozone hole I wanted to know could you see their tentacles reach through the clouds?  I was convinced the ozone hole was a portal to a frightening and unknown world. 

The stratospheric ozone layer, 15-35 km above us, acts like sunscreen. Ozone refers to O3 gas – three oxygen atoms bonded together. The layer protects our (and every other living thing’s) DNA from harmful levels of ultraviolet (UV) light from the sun that pelt our planet. Here’s the catch: ultraviolet light also kickstarts chemical reactions in our atmosphere that cause oxygen atoms to break off from ozone. This leaves ozone continually crumbling and combining in a balanced cycle that maintains the layer’s UV repellency. In the 1980s, however, a geophysicist and two meteorologists began noticing that the ozone layer was thinning each spring, particularly over Antarctica. 

Thus, the ozone “hole” was discovered. Here’s what the scientists concluded. The thinning ozone layer represented a history of accumulating aerosols and chlorofluorocarbons – a kind of gas known as CFCs. At the time, CFCs were used as refrigerants in air-conditioners and cars, as cleaning products, and as foaming agents for insulation. Even hairspray aerosol cans contained CFCs. One ingredient in CFCs is chlorine which, as a gas, erodes away the ozone layer faster than it can be created. As gaseous CFCs accumulated in the upper atmosphere, the ozone layer was gradually eaten away and higher levels of ultraviolet light began to be recorded in the Southern Hemisphere. These findings mobilized scientists to act. 

The Montreal Protocol from 1987 is one of a few examples of multinational cooperation on environmental regulations. The treaty banned production and international trade in a number of ozone-depleting substances, CFCs included. As the only UN Treaty in history to receive universal ratification, the signatories collaborated around a common objective to protect the ozone layer and the animals and plants who live beneath it. The ozone hole contributed to an awareness of the capacity of human behavior to mangle natural processes. 

This story does not end in 1987. In 2013, the decline of CFCs unexpectedly slowed from 0.85% between 2002-2012 to 0.4% after 2013. This was a sign that newly produced CFCs — 13,000 tons, to be precise — were entering the atmosphere, and scientists didn’t know where it was coming from. That might not sound like that much – given that in 2019 the US alone emitted 5.1 billion tons of CO2 – but any new CFC production contributes to a reservoir of CFCs that still exists in discarded items, like refrigerators and air conditioners. That pool hasn’t been released yet, but its effect on the atmosphere has been accounted for. These newly produced CFCs contribute to a 6-45% increase in the global reservoir and future cumulative emissions. We might see aliens yet. 

Eventually the CFCs were traced to eastern mainland China through monitoring stations in Japan and Korea. The Chinese government questioned the source of the emissions but agreed that improved atmospheric monitoring was needed. China, as a signatory of the Montreal Protocol, was obligated to take action in the face of these findings and they did just that. Their atmospheric testing stations now record CFC levels in the atmosphere, labs were built to test for CFCs in suspect consumer products, and hefty fines were placed on any factories producing CFCs. 

Like so many emissions, the effects of CFCs aren’t limited to the current moment but to many years in the future. That being said, the Montreal Protocol worked. The damage to the ozone layer will be negligible and China took firm action. We can apply our sunscreen peacefully knowing the thinned ozone layer is still on track to recover fully with no aliens in sight.