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NASA’s Zero-Boil-Off Tank Experiments To Enable Long-Duration Space Exploration

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Thursday, March 14, 2024

Figure 1. The Gateway space station—humanity’s first space station around the Moon—will be capable of being refueled in space. Credit: NASA, Alberto Bertolin, Bradley ReynoldsNASA’s Zero-Boil-Off Tank experiments address the challenge of managing cryogenic propellants in space, crucial for future Moon and Mars missions, with potential Earth-bound benefits in hydrogen energy applications.Do we have enough fuel to get to our destination? This is probably one of the first questions that comes to mind whenever your family gets ready to embark on a road trip. If the trip is long, you will need to visit gas stations along your route to refuel during your travel.NASA is grappling with similar issues as it gets ready to embark on a sustainable mission back to the Moon and plans future missions to Mars. But while your car’s fuel is gasoline, which can be safely and indefinitely stored as a liquid in the car’s gas tank, spacecraft fuels are volatile cryogenic liquid propellants that must be maintained at extremely low temperatures and guarded from environmental heat leaks into the spacecraft’s propellant tank. And while there is already an established network of commercial gas stations in place to make refueling your car a cinch, there are no cryogenic refueling stations or depots at the Moon or on the way to Mars. Furthermore, storing volatile propellant for a long time and transferring it from an in-space depot tank to a spacecraft’s fuel tank under microgravity conditions will not be easy since the underlying microgravity fluid physics affecting such operations is not well understood. Even with today’s technology, preserving cryogenic fuels in space beyond several days is not possible and tank-to-tank fuel transfer has never been previously performed or tested in space.Propellant Management in Space: Overcoming Boil-OffHeat conducted through support structures or from the radiative space environment can penetrate even the formidable Multi-Layer Insulation (MLI) systems of in-space propellant tanks, leading to boil-off or vaporization of the propellant and causing tank self-pressurization. The current practice is to guard against over-pressurizing the tank and endangering its structural integrity by venting the boil-off vapor into space.Onboard propellants are also used to cool down the hot transfer lines and the walls of an empty spacecraft tank before a fuel transfer and filling operation can take place. Thus, precious fuel is continuously wasted during both storage and transfer operations, rendering long-duration expeditions—especially a human Mars mission—infeasible using current passive propellant tank pressure control methods.Introducing ZBO: A New Horizon in Fuel EfficiencyZero-Boil-Off (ZBO) or Reduced Boil-Off (RBO) technologies provide an innovative and effective means to replace the current passive tank pressure control design. This method relies on a complex combination of active, gravity-dependent mixing and energy removal processes that allow maintenance of safe tank pressure with zero or significantly reduced fuel loss.Zero Boil-off Storage and Transfer: A Transformative Space TechnologyAt the heart of the ZBO pressure control system are two proposed active mixing and cooling mechanisms to counter tank self-pressurization. The first is based on intermittent, forced, subcooled jet mixing of the propellant and involves complex, dynamic, gravity-dependent interaction between the jet and the ullage (vapor volume) to control the condensation and evaporation phase change at the liquid-vapor interface.The second mechanism uses subcooled droplet injection via a spraybar in the ullage to control tank pressure and temperature. While the latter option is promising and gaining prominence, it is more complex and has never been tested in microgravity where the phase change and transport behavior of droplet populations can be very different and nonintuitive compared to those on Earth.Although the dynamic ZBO approach is technologically complex, it promises an impressive advantage over the currently used passive methods. An assessment of one nuclear propulsion concept for Mars transport estimated that the passive boil-off losses for a large liquid hydrogen tank carrying 38 tons of fuel for a three-year mission to Mars would be approximately 16 tons/year. The proposed ZBO system would provide a 42% saving of propellant mass per year.These numbers also imply that with a passive system, all the fuel carried for a three-year Mars mission would be lost to boil-off, rendering such a mission infeasible without resorting to the transformative ZBO technology.The ZBO approach provides a promising method, but before such a complex technological and operational transformation can be fully developed, implemented, and demonstrated in space, important and decisive scientific questions that impact its engineering implementation and microgravity performance must be clarified and resolved.The Zero-Boil-Off Tank (ZBOT) Microgravity Science ExperimentsThe Zero Boil-off Tank (ZBOT) Experiments are being undertaken to form a scientific foundation for the development of the transformative ZBO propellant preservation method. Following the recommendation of a ZBOT science review panel comprised of members from aerospace industries, academia, and NASA, it was decided to perform the proposed investigation as a series of three small-scale science experiments to be conducted onboard the International Space Station. The three experiments outlined below build upon each other to address key science questions related to ZBO cryogenic fluid management of propellants in space.Figure 2. Astronaut Joseph M. Acaba installing ZBOT Hardware in the Microgravity Science Glovebox aboard the International Space Station. Credit: NASAThe ZBOT-1 Experiment: Self-Pressurization & Jet MixingThe first experiment in the series was carried out on the station in the 2017-2018 timeframe. Figure 2 shows the ZBOT-1 hardware in the Microgravity Science Glovebox (MSG) unit of the station. The main focus of this experiment was to investigate the self-pressurization and boiling that occurs in a sealed tank due to local and global heating, and the feasibility of tank pressure control via subcooled axial jet mixing. In this experiment, the complicated interaction of the jet flow with the ullage (vapor volume) in microgravity was carefully studied.Microgravity jet mixing data was also collected across a wide range of scaled flow and heat transfer parameters to characterize the time constants for tank pressure reduction, and the thresholds for geyser (liquid fountain) formation, including its stability, and penetration depth through the ullage volume. Along with very accurate pressure and local temperature sensor measurements, Particle Image Velocimetry (PIV) was performed to obtain whole-field flow velocity measurements to validate a Computational Fluid Dynamics (CFD) model.Figure 3. Validation of ZBOT CFD Model Predictions for fluid flow and deformation of a spherical ullage in microgravity by a subcooled liquid jet mixing against ZBOT experimental results: (a) Model prediction of ullage position and deformation and flow vortex structures during subcooled jet mixing; (b) PIV image capture of flow vortex structures during jet mixing; (c) Ullage deformation captured by white light imaging; and (d) CFD model depiction of temperature contours during subcooled jet mixing. (ZBOT-1 Experiment, 2018) Credit: Dr. Mohammad Kassemi, Case Western Reserve UniversitySome of the interesting findings of the ZBOT-1experiment are as follows:Provided the first tank self-pressurization rate data in microgravity under controlled conditions that can be used for estimating the tank insulation requirements. Results also showed that classical self-pressurization is quite fragile in microgravity and nucleate boiling can occur at hotspots on the tank wall even at moderate heat fluxes that do not induce boiling on Earth.Proved that ZBO pressure control is feasible and effective in microgravity using subcooled jet mixing, but also demonstrated that microgravity ullage-jet interaction does not follow the expected classical regime patterns (see Figure 3).Enabled observation of unexpected cavitation during subcooled jet mixing, leading to massive phase change at both sides of the screened Liquid Acquisition Device (LAD) (see Figure 4). If this type of phase change occurs in a propellant tank, it can lead to vapor ingestion through the LAD and disruption of liquid flow in the transfer line, potentially leading to engine failure.Developed a state-of-the-art two-phase CFD model validated by over 30 microgravity case studies (an example of which is shown in Figure 3). ZBOT CFD models are currently used as an effective tool for propellant tank scaleup design by several aerospace companies participating in the NASA tipping point opportunity and the NASA Human Landing System (HLS) program.Figure 4. White light image captures of the intact single hemispherical ullage in ZBOT tank before depressurization by the subcooled jet (left) and after subcooled jet mixing pressure collapse that led to massive phase change bubble generation due to cavitation at the LAD (right). (ZBOT-1 Experiment, 2018). Credit: Dr. Mohammad Kassemi, Case Western Reserve UniversityThe ZBOT-NC Experiment: Non-Condensable Gas EffectsNon-condensable gases (NCGs) are used as pressurants to extract liquid for engine operations and tank-to-tank transfer. The second experiment, ZBOT-NC will investigate the effect of NCGs on the sealed tank self-pressurization and on pressure control by axial jet mixing. Two inert gases with quite different molecular sizes, Xenon, and Neon, will be used as the non-condensable pressurants. To achieve pressure control or reduction, vapor molecules must reach the liquid-vapor interface that is being cooled by the mixing jet and then cross the interface to the liquid side to condense.This study will focus on how in microgravity the non-condensable gases can slow down or resist the transport of vapor molecules to the liquid-vapor interface (transport resistance) and will clarify to what extent they may form a barrier at the interface and impede the passage of the vapor molecules across the interface to the liquid side (kinetic resistance). By affecting the interface conditions, the NCGs can also change the flow and thermal structures in the liquid.ZBOT-NC will use both local temperature sensor data and uniquely developed Quantum Dot Thermometry (QDT) diagnostics to collect nonintrusive whole-field temperature measurements to assess the effect of the non-condensable gases during both self-pressurization heating and jet mixing/cooling of the tank under weightlessness conditions. This experiment is scheduled to fly to the International Space Station in early 2025, and more than 300 different microgravity tests are planned. Results from these tests will also enable the ZBOT CFD model to be further developed and validated to include the non-condensable gas effects with physical and numerical fidelity.The ZBOT-DP Experiment: Droplet Phase Change EffectsZBO active pressure control can also be accomplished via injection of subcooled liquid droplets through an axial spray-bar directly into the ullage or vapor volume. This mechanism is very promising, but its performance has not yet been tested in microgravity. Evaporation of droplets consumes heat that is supplied by the hot vapor surrounding the droplets and produces vapor that is at a much lower saturation temperature. As a result, both the temperature and the pressure of the ullage vapor volume are reduced. Droplet injection can also be used to cool down the hot walls of an empty propellant tank before a tank-to-tank transfer or filling operation. Furthermore, droplets can be created during the propellant sloshing caused by acceleration of the spacecraft, and these droplets then undergo phase change and heat transfer. This heat transfer can cause a pressure collapse that may lead to cavitation or a massive liquid-to-vapor phase change. The behavior of droplet populations in microgravity will be drastically different compared to that on Earth.The ZBOT-DP experiment will investigate the disintegration, coalescence (droplets merging together), phase change, and transport and trajectory characteristics of droplet populations and their effects on the tank pressure in microgravity. Particular attention will also be devoted to the interaction of the droplets with a heated tank wall, which can lead to flash evaporation subject to complications caused by the Liedenfrost effect (when liquid droplets propel away from a heated surface and thus cannot cool the tank wall). These complicated phenomena have not been scientifically examined in microgravity and must be resolved to assess the feasibility and performance of droplet injection as a pressure and temperature control mechanism in microgravity.Back to Planet EarthThis NASA-sponsored fundamental research is now helping commercial providers of future landing systems for human explorers. Blue Origin and Lockheed Martin, participants in NASA’s Human Landing Systems program, are using data from the ZBOT experiments to inform future spacecraft designs.Cryogenic fluid management and use of hydrogen as a fuel are not limited to space applications. Clean green energy provided by hydrogen may one day fuel airplanes, ships, and trucks on Earth, yielding enormous climate and economic benefits. By forming the scientific foundation of ZBO cryogenic fluid management for space exploration, the ZBOT science experiments and CFD model development will also help to reap the benefits of hydrogen as a fuel here on Earth.Project LeadDr. Mohammad Kassemi (Dept Mechanical & Aerospace Engineering, Case Western Reserve University)Sponsoring OrganizationBiological and Physical Sciences (BPS) Division, NASA Science Mission Directorate (SMD)

NASA’s Zero-Boil-Off Tank experiments address the challenge of managing cryogenic propellants in space, crucial for future Moon and Mars missions, with potential Earth-bound benefits in...

Gateway Space Station Full Configuration

Figure 1. The Gateway space station—humanity’s first space station around the Moon—will be capable of being refueled in space. Credit: NASA, Alberto Bertolin, Bradley Reynolds

NASA’s Zero-Boil-Off Tank experiments address the challenge of managing cryogenic propellants in space, crucial for future Moon and Mars missions, with potential Earth-bound benefits in hydrogen energy applications.

Do we have enough fuel to get to our destination? This is probably one of the first questions that comes to mind whenever your family gets ready to embark on a road trip. If the trip is long, you will need to visit gas stations along your route to refuel during your travel.

NASA is grappling with similar issues as it gets ready to embark on a sustainable mission back to the Moon and plans future missions to Mars. But while your car’s fuel is gasoline, which can be safely and indefinitely stored as a liquid in the car’s gas tank, spacecraft fuels are volatile cryogenic liquid propellants that must be maintained at extremely low temperatures and guarded from environmental heat leaks into the spacecraft’s propellant tank. And while there is already an established network of commercial gas stations in place to make refueling your car a cinch, there are no cryogenic refueling stations or depots at the Moon or on the way to Mars.

Furthermore, storing volatile propellant for a long time and transferring it from an in-space depot tank to a spacecraft’s fuel tank under microgravity conditions will not be easy since the underlying microgravity fluid physics affecting such operations is not well understood. Even with today’s technology, preserving cryogenic fuels in space beyond several days is not possible and tank-to-tank fuel transfer has never been previously performed or tested in space.

Propellant Management in Space: Overcoming Boil-Off

Heat conducted through support structures or from the radiative space environment can penetrate even the formidable Multi-Layer Insulation (MLI) systems of in-space propellant tanks, leading to boil-off or vaporization of the propellant and causing tank self-pressurization. The current practice is to guard against over-pressurizing the tank and endangering its structural integrity by venting the boil-off vapor into space.

Onboard propellants are also used to cool down the hot transfer lines and the walls of an empty spacecraft tank before a fuel transfer and filling operation can take place. Thus, precious fuel is continuously wasted during both storage and transfer operations, rendering long-duration expeditions—especially a human Mars mission—infeasible using current passive propellant tank pressure control methods.

Introducing ZBO: A New Horizon in Fuel Efficiency

Zero-Boil-Off (ZBO) or Reduced Boil-Off (RBO) technologies provide an innovative and effective means to replace the current passive tank pressure control design. This method relies on a complex combination of active, gravity-dependent mixing and energy removal processes that allow maintenance of safe tank pressure with zero or significantly reduced fuel loss.

Zero Boil-off Storage and Transfer: A Transformative Space Technology

At the heart of the ZBO pressure control system are two proposed active mixing and cooling mechanisms to counter tank self-pressurization. The first is based on intermittent, forced, subcooled jet mixing of the propellant and involves complex, dynamic, gravity-dependent interaction between the jet and the ullage (vapor volume) to control the condensation and evaporation phase change at the liquid-vapor interface.

The second mechanism uses subcooled droplet injection via a spraybar in the ullage to control tank pressure and temperature. While the latter option is promising and gaining prominence, it is more complex and has never been tested in microgravity where the phase change and transport behavior of droplet populations can be very different and nonintuitive compared to those on Earth.

Although the dynamic ZBO approach is technologically complex, it promises an impressive advantage over the currently used passive methods. An assessment of one nuclear propulsion concept for Mars transport estimated that the passive boil-off losses for a large liquid hydrogen tank carrying 38 tons of fuel for a three-year mission to Mars would be approximately 16 tons/year. The proposed ZBO system would provide a 42% saving of propellant mass per year.

These numbers also imply that with a passive system, all the fuel carried for a three-year Mars mission would be lost to boil-off, rendering such a mission infeasible without resorting to the transformative ZBO technology.

The ZBO approach provides a promising method, but before such a complex technological and operational transformation can be fully developed, implemented, and demonstrated in space, important and decisive scientific questions that impact its engineering implementation and microgravity performance must be clarified and resolved.

The Zero-Boil-Off Tank (ZBOT) Microgravity Science Experiments

The Zero Boil-off Tank (ZBOT) Experiments are being undertaken to form a scientific foundation for the development of the transformative ZBO propellant preservation method. Following the recommendation of a ZBOT science review panel comprised of members from aerospace industries, academia, and NASA, it was decided to perform the proposed investigation as a series of three small-scale science experiments to be conducted onboard the International Space Station. The three experiments outlined below build upon each other to address key science questions related to ZBO cryogenic fluid management of propellants in space.

Astronaut Joseph Acaba Installing ZBOT Hardware

Figure 2. Astronaut Joseph M. Acaba installing ZBOT Hardware in the Microgravity Science Glovebox aboard the International Space Station. Credit: NASA

The ZBOT-1 Experiment: Self-Pressurization & Jet Mixing

The first experiment in the series was carried out on the station in the 2017-2018 timeframe. Figure 2 shows the ZBOT-1 hardware in the Microgravity Science Glovebox (MSG) unit of the station. The main focus of this experiment was to investigate the self-pressurization and boiling that occurs in a sealed tank due to local and global heating, and the feasibility of tank pressure control via subcooled axial jet mixing. In this experiment, the complicated interaction of the jet flow with the ullage (vapor volume) in microgravity was carefully studied.

Microgravity jet mixing data was also collected across a wide range of scaled flow and heat transfer parameters to characterize the time constants for tank pressure reduction, and the thresholds for geyser (liquid fountain) formation, including its stability, and penetration depth through the ullage volume. Along with very accurate pressure and local temperature sensor measurements, Particle Image Velocimetry (PIV) was performed to obtain whole-field flow velocity measurements to validate a Computational Fluid Dynamics (CFD) model.

Validation of ZBOT CFD Model Predictions

Figure 3. Validation of ZBOT CFD Model Predictions for fluid flow and deformation of a spherical ullage in microgravity by a subcooled liquid jet mixing against ZBOT experimental results: (a) Model prediction of ullage position and deformation and flow vortex structures during subcooled jet mixing; (b) PIV image capture of flow vortex structures during jet mixing; (c) Ullage deformation captured by white light imaging; and (d) CFD model depiction of temperature contours during subcooled jet mixing. (ZBOT-1 Experiment, 2018) Credit: Dr. Mohammad Kassemi, Case Western Reserve University

Some of the interesting findings of the ZBOT-1experiment are as follows:

  1. Provided the first tank self-pressurization rate data in microgravity under controlled conditions that can be used for estimating the tank insulation requirements. Results also showed that classical self-pressurization is quite fragile in microgravity and nucleate boiling can occur at hotspots on the tank wall even at moderate heat fluxes that do not induce boiling on Earth.
  2. Proved that ZBO pressure control is feasible and effective in microgravity using subcooled jet mixing, but also demonstrated that microgravity ullage-jet interaction does not follow the expected classical regime patterns (see Figure 3).
  3. Enabled observation of unexpected cavitation during subcooled jet mixing, leading to massive phase change at both sides of the screened Liquid Acquisition Device (LAD) (see Figure 4). If this type of phase change occurs in a propellant tank, it can lead to vapor ingestion through the LAD and disruption of liquid flow in the transfer line, potentially leading to engine failure.
  4. Developed a state-of-the-art two-phase CFD model validated by over 30 microgravity case studies (an example of which is shown in Figure 3). ZBOT CFD models are currently used as an effective tool for propellant tank scaleup design by several aerospace companies participating in the NASA tipping point opportunity and the NASA Human Landing System (HLS) program.
Intact Single Hemispherical Ullage in ZBOT Tank

Figure 4. White light image captures of the intact single hemispherical ullage in ZBOT tank before depressurization by the subcooled jet (left) and after subcooled jet mixing pressure collapse that led to massive phase change bubble generation due to cavitation at the LAD (right). (ZBOT-1 Experiment, 2018). Credit: Dr. Mohammad Kassemi, Case Western Reserve University

The ZBOT-NC Experiment: Non-Condensable Gas Effects

Non-condensable gases (NCGs) are used as pressurants to extract liquid for engine operations and tank-to-tank transfer. The second experiment, ZBOT-NC will investigate the effect of NCGs on the sealed tank self-pressurization and on pressure control by axial jet mixing. Two inert gases with quite different molecular sizes, Xenon, and Neon, will be used as the non-condensable pressurants. To achieve pressure control or reduction, vapor molecules must reach the liquid-vapor interface that is being cooled by the mixing jet and then cross the interface to the liquid side to condense.

This study will focus on how in microgravity the non-condensable gases can slow down or resist the transport of vapor molecules to the liquid-vapor interface (transport resistance) and will clarify to what extent they may form a barrier at the interface and impede the passage of the vapor molecules across the interface to the liquid side (kinetic resistance). By affecting the interface conditions, the NCGs can also change the flow and thermal structures in the liquid.

ZBOT-NC will use both local temperature sensor data and uniquely developed Quantum Dot Thermometry (QDT) diagnostics to collect nonintrusive whole-field temperature measurements to assess the effect of the non-condensable gases during both self-pressurization heating and jet mixing/cooling of the tank under weightlessness conditions. This experiment is scheduled to fly to the International Space Station in early 2025, and more than 300 different microgravity tests are planned. Results from these tests will also enable the ZBOT CFD model to be further developed and validated to include the non-condensable gas effects with physical and numerical fidelity.

The ZBOT-DP Experiment: Droplet Phase Change Effects

ZBO active pressure control can also be accomplished via injection of subcooled liquid droplets through an axial spray-bar directly into the ullage or vapor volume. This mechanism is very promising, but its performance has not yet been tested in microgravity. Evaporation of droplets consumes heat that is supplied by the hot vapor surrounding the droplets and produces vapor that is at a much lower saturation temperature. As a result, both the temperature and the pressure of the ullage vapor volume are reduced. Droplet injection can also be used to cool down the hot walls of an empty propellant tank before a tank-to-tank transfer or filling operation. Furthermore, droplets can be created during the propellant sloshing caused by acceleration of the spacecraft, and these droplets then undergo phase change and heat transfer. This heat transfer can cause a pressure collapse that may lead to cavitation or a massive liquid-to-vapor phase change. The behavior of droplet populations in microgravity will be drastically different compared to that on Earth.

The ZBOT-DP experiment will investigate the disintegration, coalescence (droplets merging together), phase change, and transport and trajectory characteristics of droplet populations and their effects on the tank pressure in microgravity. Particular attention will also be devoted to the interaction of the droplets with a heated tank wall, which can lead to flash evaporation subject to complications caused by the Liedenfrost effect (when liquid droplets propel away from a heated surface and thus cannot cool the tank wall). These complicated phenomena have not been scientifically examined in microgravity and must be resolved to assess the feasibility and performance of droplet injection as a pressure and temperature control mechanism in microgravity.

Back to Planet Earth

This NASA-sponsored fundamental research is now helping commercial providers of future landing systems for human explorers. Blue Origin and Lockheed Martin, participants in NASA’s Human Landing Systems program, are using data from the ZBOT experiments to inform future spacecraft designs.

Cryogenic fluid management and use of hydrogen as a fuel are not limited to space applications. Clean green energy provided by hydrogen may one day fuel airplanes, ships, and trucks on Earth, yielding enormous climate and economic benefits. By forming the scientific foundation of ZBO cryogenic fluid management for space exploration, the ZBOT science experiments and CFD model development will also help to reap the benefits of hydrogen as a fuel here on Earth.

Project Lead

Dr. Mohammad Kassemi (Dept Mechanical & Aerospace Engineering, Case Western Reserve University)

Sponsoring Organization

Biological and Physical Sciences (BPS) Division, NASA Science Mission Directorate (SMD)

Read the full story here.
Photos courtesy of

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A career fair for middle school students mixes learning and entertainment to get them excited about working in the green economy.

At the 2025 Future Green Leaders Summit, middle school students designed fire-resistant homes using AI, learned about jobs that support the climate and environment, and cheered on superheroes dressed as “Wind,” “Solar,” “Ethanol” and other energy sources as they squared off in a rap and dance battle.The day-long event, held at San Bernardino’s Historic Enterprise Building on Wednesday, was organized by the Southern California Regional Energy Network, which is administered by Los Angeles County and paid for by California Public Utility ratepayers.The approximately 500 students in attendance came from the San Bernardino and neighboring Rialto school districts that have Title 1 status, meaning the schools receive supplemental federal funding because they enroll a high percentage of pupils living in low-income households. In both districts, Latino, Black and Asian residents represent more than 80% of the population, according to the U.S. Census.Organizers said the event was in part intended to confront a disconnect in the green economy. Although students from poor households and families of color are more vulnerable to the effects of rising global temperatures, pollution, and food and energy scarcity, people from their communities are less likely to be employed in green industries. Women are underrepresented too. AY Young, right, a musician, founder and CEO of the Battery Tour and former U.N. youth ambassador, powers his live shows with solar batteries while talking to middle school students at the Future Green Leaders Summit in San Bernardino on Wednesday. (Allen J. Schaben/Los Angeles Times) For instance, the U.S. solar workforce is 73% white and 70% male. The workforce overall is about 60% white and more than 50% female, according to the International Renewable Energy Council’s Solar Jobs Census.It’s hard for children to envision themselves in green careers when they don’t see people who look like them in those jobs, organizers said.“Kids, once they entered into high school, they have already made up their minds career-wise, and a lot of them are not going into STEM, especially females,” said Wendy Angel, referring to fields built on science, technology, engineering and math. Angel is the Southern California regional director for Emerald Cities, a nonprofit that works to bring diversity to the green economy. These imbalances were front of mind when Lujuanna Medina, the environmental initiatives division manager for L.A. County, came up with the idea to host a summit for middle school students four years ago.“We were like, ‘How do we reach them early on, before they reach high school? Let’s expose them to different parts of the green economy,’ ” Medina said. Golden Valley Middle School student Matthew Quintero looks through cards while learning about climate solutions and concepts of a game at the Future Green Leaders Summit in San Bernardino on Wednesday. (Allen J. Schaben/Los Angeles Times) The fair, with its mix of live entertainment, hands-on workshops and a career expo, was designed to make the green industry and the idea of sustainability more relatable, said Ben Stapleton, executive director of U.S. Green Building Council, an advocacy and workforce development group based in L.A.That’s especially important given a host of recent research showing that a fear for the future of the planet is taking a toll on young people’s mental health and making them feel powerless.One solution, said Stapleton, is to break big concepts like “climate change” down into more accessible components. “This is what it means in terms of air quality. This is what it means in terms of biodiversity, and access to plants and greenspace,” said Stapleton. “When you give kids those tools, they create the change and they understand that ‘I can be a part of this.’ ”During one workshop, Marcela Oliva, a professor at the Los Angeles Trade-Tech College, showed students how to use the latest digital visualization and 3-D simulation tools to design homes and landscaping that incorporate wildfire-resilient building materials and plantings. Students react as the energy superhero character “Ethanol” educates middle-school students in a rap-style “Energy Battle Royale” performance at the Future Green Leaders Summit on Wednesday. (Allen J. Schaben/Los Angeles Times) Elsewhere, students learned about energy-saving appliances, brainstormed solutions to problems such as the proliferation of plastic waste and deforestation and explored internship and professional job opportunities.Maximilian Valdovinos, 12, from San Bernardino, said that coming into the career fair, he was considering becoming a mechanic, but the event inspired him to consider possible careers in waste management.Thirteen-year-old Emily Zamora was a “maybe” on the idea of going into a green industry before the event’s end. But the activities she participated in made her reflect on the lack of tree cover and shade in the San Bernardino neighborhood where she lives and its potential effect on her health.“There’s very few trees where I live,” said Zamora, “and some of them are dead.”The organizers and workshop facilitators said they realize that not every student will leave the event wanting to pursue a green career. The idea is to plant a seed.

Climate
Energy
Forests

A Cartoonist Finds Hope Amid the Apocalypse(s)

In two powerful new graphic novels, Peter Kuper tackles climate change, disappearing insects, and other tough environmental topics — but gives us reasons to avoid despair. The post A Cartoonist Finds Hope Amid the Apocalypse(s) appeared first on The Revelator.

Peter Kuper has been publishing political cartoons and graphic novels since the 1980s, but his obsession with insects goes back even further, to when he was four years old and the cicadas emerged around his childhood home in Summit, New Jersey. “I keep this by my table,” says the cartoonist, holding a well-loved paperback copy of the classic Insects: A Guide to Familiar North American Insects up to his webcam. “This is my first insect book. All the pages are falling out.” Photo: The Revelator This year Kuper’s political cartooning and love of entomology intersected with the publication of two new environmental books — or maybe four, depending on how you count them. The first, Insectopolis: A Natural History (W.W. Norton, $35), is a graphic novel — five years in the making — about insects and the scientists who helped uncover their stories. Set after an apocalypse has wiped out all humans, the story follows the insects themselves as they travel through the New York Public Library, uncovering facts about their evolution, cultural importance, ecological roles, and more. It’s a fun, creative, colorful book that conveys Kuper’s fascination with insects and imparts more than a few lessons. Then comes Wish We Weren’t Here: Postcards From the Apocalypse (Fantagraphics, $19.99), a collection of wordless cartoons about climate change, plastic pollution, and other environmental issues originally published in the French satire magazine, Charlie Hebdo. Each one-page, four-panel strip starts with an image that slowly morphs into something more sinister and revelatory — like a drawing of an oil rig that becomes a dying junkie’s used needle. If that sounds confrontational and bleak, it is, but the book also turns the table a few times, transforming images of destruction into reasons for hope.   View this post on Instagram   A post shared by Peter Kuper (@kuperart) Kuper has also published two insect-themed coloring books this year, one based on Insectopolis, and another, Monarch’s Journey, adapting segments of his 2015 graphic novel, Ruins. The Revelator spoke with Kuper about these new books, the state of political cartooning, his new role as an insect conservation advocate, and what people can do to help insects and avoid despair. (This conversation has been edited lightly for brevity and style.) What’s it been like taking this insect conservation message on the road? You’re doing some book signings, some speaking tours. How are people reacting to it? It’s fulfilling the intent I had for the book, I believe, which is to get people who don’t know about insects or are afraid of insects, who generally will kill them first and ask questions later, to recognize that grocery stores would be empty of produce without insects. No chocolate, no coffee, no honey. I can tell every time I give a talk — I’ve seen the expression on people’s faces that something’s moved a little bit. In general, I try not to make my work a “scold.” I wanted to be easing people toward the correct door so that they choose the winning prize of survival. And you’re taking it to these new audiences with a Society of Illustrators show, and the bookstore audience, and the comics audience. Those aren’t necessarily always audiences who would get that conservation message. Right. And the form that it’s taking, I think, is making it a very easy pill to swallow. It’s sugar coated. I’m trying — even with Wish We Weren’t Here — to inject it with humor and have it take those kinds of mental leaps and connections that people can make in seeing something and recognizing it and maybe reconsidering something in a positive way.   View this post on Instagram   A post shared by Peter Kuper (@kuperart) After a lifetime of caring about insects, what did you take away from the five-year process of developing this book? My understanding of history and just coming to understand about the various extinction events that went on in the past, the essence of time and how little we humans can comprehend time. Also, just the miracle of evolution that has made the insects survive the way they have. Even something like the monarch butterfly, which I had learned about while working on Ruins — it goes through these three generations to travel 3,000 miles. The first generation’s one week, the next generation is two, and the last generation is six months. And they still don’t know how all the monarchs know how to get to this one forest in Mexico, which I also got to visit when I lived there. And there’s so many pieces of this history. I had no idea that dung beetles were the first animals — including humans — to navigate by the stars. And that they can follow the Milky Way at night to go in a straight line. And there’s so many fascinating aspects. The shine on apples comes from the lac bug, and 78 RPM records come from that same insect’s excretion. And one of the huge, fabulous aspects was reaching out to the entomologists. If I read a book, I would just look up the author online, reach out and say, “Hey, I’m working on this chapter on bees. Could you talk to me?” And every single one of them was wide open to it. In fact, slipped into Insectopolis are QR codes linking to interviews with four entomologists and the poet laureate from Mexico reading his poem about monarchs. With those interviews, I discovered that entomologists are like comic fans. The same way that comics were always considered low art, entomology was always considered low science. They were sort of put down by the people who were “all lab,” discovering DNA and poo-pooing E.O. Wilson, the ant expert at Harvard, because he was doing this dopey field work. Also, while I was at it, I was digging up entomologists and naturalists who were less known. It’s shocking how many of these people that made huge discoveries are essentially unknown. Margaret Collins, for example, was the first Black entomologist to get her Ph.D. She entered college at age 14. And she had to struggle with civil rights issues and racism and sexism to become the leading scientist on termites. I’m sure some people will be like, “Oh goody, termites.” But still, these are major areas. Architects have learned from the building structures that termites make. There are so many insects that we’ve learned from. The dragonfly has a nearly detachable head, and that’s how they figured out Velcro. Let’s shift and talk about Wish We Weren’t Here — which is a tough title to say. It twists the usual expression, “wish you were here,” and the brain does not want to go there. And I think that’s an interesting aspect of the book itself. You start with one image and twist it to another. How do you approach creating cartoons like that? My enthusiasm for wordless comics goes back to [Mad Magazine’s] “Spy vs. Spy,” which, I ironically ended up doing for 30 years. That and Sergio Aragonés’s wordless cartooning marginals and the books that he did. I get these images when I read an article. They sometimes form almost instantaneously. There’ll be a word in the article, something about “we’re gambling with climate change.” I start seeing the one-armed bandit. They just tend to form these flash images in my brain.   View this post on Instagram   A post shared by Peter Kuper (@kuperart) I just have to do these drawings. I read something in the paper, and I just feel like I need to have a response. And the way I can respond — aside from marching in the streets and knocking on doors, which I also do — is to do a drawing about it and share it. I was anxious to do Wish We Weren’t Here, because we’re right in the midst of even the term “climate change” being erased. So to do a whole book on climate change, it seemed like a rather vital time to do it. And though the comics in there are wordless, each page has the article that I referenced so that somebody could go and look more deeply into the subject. How does political cartooning like this compare to 10 or 20 years ago? Political cartooning has gone through such a contraction, but it’s still so powerful. Is there an audience for it? Is there an appetite for it? There’s a huge appetite for it. It’s just the delivery systems that have altered radically. You can use Instagram and social media to deliver things. I’ll post something, and, depending on the venue, it will get 100,000 likes. Or two. Do you have any advice for other people trying to use the arts or expression or protest as a way to get something out of themselves and to put some good into the world? Well, in every march I’ve been to, you get to see some of the most creative signs. They’re just people, clearly, they’re not professionals. They’re just coming up with a slogan, an image, sometimes a collage of a photo. It’s so powerful to go to a march with a sign that speaks your mind, especially if it’s with humor. Any given march is just loaded with that creative intervention, and I recommend that to everybody.   View this post on Instagram   A post shared by Peter Kuper (@kuperart) And please don’t stomp on insects every time you see them. Just help them out the door.  If you have a lawn, you can un-mow some of it. Don’t mow, and maybe plant the occasional pollinator — just make sure that they’re appropriate pollinators and not some kind of foreign specialty plant that actually is invasive or problematic. There’s just a lot of little actions that one can take all the time — and especially right now, not falling on fear to the point where you don’t get out and protest. That’s really important, because I really feel like what we’re being pushed toward is being scared enough just to stay home and disconnect. Previously in The Revelator: Comics for Earth: Eight New Graphic Novels About Saving the Planet and Celebrating Wildlife The post A Cartoonist Finds Hope Amid the Apocalypse(s) appeared first on The Revelator.

Climate
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Extinction

Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down.

The physics of mixing water layers — an interplay of wind, climate and more — makes lakes work. When it stops, impacts can ripple across an ecosystem. The post Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down. first appeared on Quanta Magazine

climate science Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down. By Rachel Nuwer November 14, 2025 The physics of mixing water layers — an interplay of wind, climate and more — makes lakes work. When it stops, impacts can ripple across an ecosystem. Katie Falkenberg for Quanta Magazine climate science Mixing Is the Heartbeat of Deep Lakes. At Crater Lake, It’s Slowing Down. By Rachel Nuwer November 14, 2025 The physics of mixing water layers — an interplay of wind, climate and more — makes lakes work. When it stops, impacts can ripple across an ecosystem. By Rachel Nuwer Contributing Writer November 14, 2025 animals biology climate science ecology physics All topics On a radiant July afternoon, a pair of scientists hung their heads off the side of a boat and peered into the brilliant blue water of a lake known for its clarity. They were watching for the exact moment when a black-and-white, dinner plate–sized object called a Secchi disc disappeared from view in the water column of Crater Lake in Oregon. The disc was being slowly lowered by crane, spinning lazily like a carnival prop. A minute or so after it hit the water, graduate student Juan Estuardo Bocel gave a shout to indicate that he could no longer see the disc: “I am out!” Seconds later, researcher Eva Laiti echoed: “OK, I’m out!” The crane operator, Scott Girdner, a lanky freshwater biologist who has spent most of his adult life at Crater Lake National Park, recorded the disc depth for each call. Then he slowly raised it until the junior researchers piped up again when it was back in view, and he recorded those depths, too. The mean of those readings, known as the Secchi depth, has been used as a simple and dependable measure of water clarity since 1865, when the Italian Jesuit priest Angelo Secchi invented it at the behest of the papacy. The value recorded that afternoon in 2025 — about 78 feet (24 meters), an unusually cloudy reading for Crater Lake — is now part of one of the world’s longest-running datasets on lake physics. The lake’s first Secchi reading was taken in 1886, and in 1983 scientists began to repeat the procedure several times per month every summer. When it comes to lake health, long-term data is treasure. Crater Lake’s size, natural beauty and otherworldly clarity — a reflection of its setting and isolation — make it one of the world’s most iconic freshwater bodies. With a maximum depth of 1,949 feet, it is the deepest lake in the United States. It’s also very likely the clearest large lake on Earth, with a vivid blue hue seldom encountered in nature. Share this article Copied! Newsletter Get Quanta Magazine delivered to your inbox Recent newsletters To measure water clarity, Scott Girdner and Taryn Weller, biologists at Crater Lake National Park, lower a black-and-white Secchi disc (right) and record the depth at which it vanishes. Crater Lake’s first Secchi reading was taken in 1886. Katie Falkenberg for Quanta Magazine “People are just amazed and wowed at the optical blue that you see from pure water itself,” said Sudeep Chandra, a limnologist at the University of Nevada, Reno, who collaborates with Girdner. “That blueness is the reflection of the hydrogen and oxygen hanging out together without any material in it.” Since 2010, however, Girdner and his colleagues have noticed an unexpected change in the Secchi data: Despite the day’s slightly cloudy reading, Crater Lake’s clear water is getting even clearer. This might sound like a good thing. After all, the lake’s remarkable, glasslike transparency and brilliant hue are major draws for the half-million tourists who visit every year. But it might also indicate that something is going wrong with the lake’s physics, chemistry and ecology, and it could be a harbinger of changes to lakes across the world in the age of climate change. As the planet warms, summers are growing longer and winter nights aren’t getting as cold as they used to. As a result, the surfaces of many deep, temperate lakes are warming even faster than the air. This shift to the energy flux of the top layer of water can set in motion a series of physical changes that add up to a breakdown of lake mixing — a fundamental process that acts like a heartbeat for deep, temperate lakes that don’t freeze in winter. Lake mixing is driven by physical properties such as wind, air temperature, water temperature and salinity, and on seasonal or annual cycles it circulates water between the surface and the depths. When mixing stops, oxygen and nutrients don’t get distributed throughout the water column, which can kill fish, trigger unsightly and dangerous algal blooms and invite invasive species to take over. “Many people visit Crater Lake because of its pristine water quality and blueness,” said Sudeep Chandra of the University of Nevada, Reno. “What happens if that changes?” Katie Falkenberg for Quanta Magazine From Italy to New Zealand and beyond, scientists have been alarmed to observe reduced lake mixing. In 2021, Chandra and his colleagues published evidence in Nature of greater stratification in the water column over time — an indicator of weaker mixing — in 84% of 189 temperate lakes for which they could find sufficiently long and robust datasets. Some lakes had stopped mixing altogether. “While each system is unique, the endgame is generally the same: a lack of mixing for these large, deep lakes,” Chandra said. Of the world’s millions of lakes, Crater Lake is one of very few with a monitoring program that stretches back more than 40 years. Scientists are now beginning to realize how crucial those datasets are for unraveling lake physics and how climate change is altering it. “Because local weather can be extremely variable from year to year, it takes many years to capture the range in conditions and measure ‘normal,’” Girdner said. “Hence the advantage of long-term datasets.” Crater Lake is therefore at the center of the first efforts by researchers, including Girdner and Chandra, to compare lake systems to get to the bottom of their breakdown, so they can prepare for the future and perhaps even ward off the most extreme impacts. “Historically, people have studied lakes one at a time,” said Stephanie Hampton, director of the Tahoe Environmental Research Center at the University of California, Davis. In light of how quickly things are changing, that siloed approach no longer works, she said. “We need to learn from each other and synthesize these data to understand what’s happening globally.” In July 2025, researchers journeyed to the remote research station on Wizard Island, the volcanic cinder cone near the western shore of Crater Lake. On the boat dock they ate their meals (including fresh-caught invasive crayfish) and slept out under the stars. Katie Falkenberg for Quanta Magazine Canary in the Lake   In 2006, five deep lakes in northern Italy — Iseo, Como, Garda, Maggiore and Lugano — stopped fully mixing. At first, scientists didn’t think much of it. They had been monitoring the lakes since the 1980s and 1990s, and it was normal for a few years to go by without complete mixing. But as time passed and the clear waters remained stubbornly in place, they began to fear that the pause might be permanent. Their fears seem to have been borne out. “It’s been 20 years that we haven’t observed any full mixing from the top to the bottom,” said Barbara Leoni, a freshwater ecologist at the University of Milan-Bicocca. “I don’t know that it will be possible to return to the past behavior.” While each system is unique, the endgame is generally the same: a lack of mixing for these large, deep lakes. Sudeep Chandra, University of Nevada, Reno Lake mixing is a function of the fact that water has different densities at different temperatures. In deep temperate lakes, this creates stratification in the water column: Lighter, warmer water floats on top, and colder, denser water sinks below. Any number of factors can influence mixing, but it is primarily driven by seasonal temperature changes, wind and waves. Because these features vary from place to place and from lake to lake, mixing does not follow a single formula. In many lakes, complete mixing occurs once or twice a year, usually in spring and fall. In very large lakes, mixing might happen in the shallow upper waters on annual or seasonal cycles, while full mixing to the deepest bottom layer may occur only every few years. By studying different lakes, scientists are hoping to find shared rules. Italy’s deep northern lakes previously achieved complete mixing on an approximately seven-year cycle. During the summer, the lake water would maintain distinct layers as surface waters warmed and remained light and in place. As surface temperatures dropped in autumn and winter, the layers would become closer in temperature; with a push from the wind, the lake would begin to mix. This redistributed heat, oxygen, nutrients and toxins throughout the water column. Researchers pull in a gill net to assess fish populations. Katie Falkenberg for Quanta Magazine That’s not how the Italian lakes work anymore, however. Now, the surface waters fail to get cool enough to sink and trigger mixing. As a result, oxygen is disappearing from the bottom of the stratified lake. It has already been depleted entirely in Lake Iseo. “We have 150 meters of water without oxygen,” Leoni said. This kills off oxygen-breathing life at depth and transforms the biological community. “In lakes where the deep waters have been oxygen-free for a long time, only bacteria survive,” she said. The hearts of Italy’s deep lakes have stopped and are no longer circulating nutrients; they show what can happen when lakes stop mixing. Crater Lake offers a different opportunity: to study how, exactly, warming temperatures can break the fundamental physics of a lake. Mixing Mix-Up On summer days, viewed from the rim of the ancient caldera that holds it, Crater Lake is a perfect mirror reflecting the procession of clouds and colors of the sky above. But beneath that glassy surface, dynamic processes are underway. Scott Girdner, a freshwater biologist at Crater Lake National Park, has run the lake’s long-term monitoring program since 1995. He will retire at the end of 2025. Katie Falkenberg for Quanta Magazine Compared to many other large lakes around the world, Crater Lake is close to pristine. It is surrounded by wilderness and protected as a national park. The air above it is mostly wind blowing off the Pacific Ocean, with few polluting cities or industries nearby. The lake lacks any rivers or streams emptying into it that could bring in pollution from elsewhere; it is filled by rain and melting snow. In July, Girdner and Chandra filled two large water coolers with lake water — enough to keep the team of around 13 visiting scientists, students and National Park employees, plus a journalist and photographer, hydrated overnight. The lake’s water tasted as pure as bottled water, and it maintained a natural, refreshing temperature under the blazing summer sun. Crater Lake has gained 33 additional days of summer weather per year over the past 60 years, as spring arrives earlier and earlier. The water purity does more than provide good drinking: It makes Crater Lake an ideal system for studying climate impacts. Without the confounding factors of agriculture, sewage, parking lot runoff and water withdrawals that tend to affect other lakes, Girdner said, “it’s easier to see the influence of climate change.” Girdner started working at Crater Lake in 1995 and has overseen the long-term monitoring program ever since. He often tells his staff that it’s not enough to just record change; they must also understand its drivers and its implications for the lake’s physics, chemistry and biology. To that end, every night at 8 p.m., a tube-shaped profiler instrument crawls along an anchored metal cable from a depth of 585 meters to Crater Lake’s surface and back down again. On this round trip, it tests twice a second for water conductivity, temperature, oxygen and salinity. Other sensors use light to measure chlorophyll fluorescence and phytoplankton particle density. That dataset and others tell the story of Crater Lake’s health across time. Like virtually all lakes around the world, it’s getting warmer: Average surface water temperatures have increased by 3 degrees Celsius since 1965. In summer, nighttime air temperatures are increasing faster than daytime ones; the coldest summer nights are not as cold as they used to be. And there are more summer nights: Crater Lake has gained 33 additional days of summer weather per year over the past 60 years, as spring arrives earlier and earlier. The remoteness that makes Crater Lake ideal for isolating climate change impacts also makes it a top location for stargazing. On average 98.6% of potentially visible stars can be seen at the site, according to NPS data. Katie Falkenberg for Quanta Magazine In the past, when summer nights grew cold, the lake released the day’s accumulated heat, causing surface water to become denser and sink. This phenomenon drives the shallow mixing that occurs in summer. As nights have warmed, however, this process has weakened, and mixing has slowed. Counterintuitively, as the layer of surface water has become warmer, it has also become thinner. “In the summer, there is half as much warm water floating on the surface now, on average, than there was in 1971,” Girdner said. This creates a sharper density difference with the cold water below, which in turn increases the amount of wind energy required to break through and mix the layers. I think about it like a vinaigrette. There’s resistance to mixing. Kevin Rose, Rensselaer Polytechnic Institute “I think about it like a vinaigrette,” said Kevin Rose, a freshwater ecologist at Rensselaer Polytechnic Institute in New York who collaborates with Girdner and Chandra. “There’s resistance to mixing.” So what does all of this have to do with the fact that the lake is getting clearer? That’s where biology comes in. In Crater Lake’s warm surface water lives a community of phytoplankton. A thinner warm surface layer means less habitat, so there are fewer phytoplankton, which means fewer particles in the water to scatter light. This boosts the water’s clarity overall and the depth to which light can penetrate. Crater Lake’s winter processes, which mix the lake all the way to the bottom, are undergoing their own profound changes. These transformations involve the weakening of a phenomenon called reverse stratification, in which a layer of very cold water, cooled by frigid winter air, forms on top of a slightly warmer layer that is around 4 degrees Celsius, the temperature at which water is heaviest. (At temperatures below that, water molecules begin to organize into lighter ice crystals.) When strong wind pushes the extra-cold surface water horizontally, as it approaches the lake’s edge some of it is forced down. If it is pushed down far enough, the increased pressure causes it to become denser than the 4-degree water layer. It then sinks to the bottom in a matter of hours, creating a mixing effect. Mark Belan/Quanta Magazine Historically, reverse stratification occurred during 80% to 90% of Crater Lake winters. As winters warm, it is becoming less common. “Crater Lake is sitting on a knife edge where it’s already really close to not being able to form reverse stratification,” Girdner said. This does not bode well for the lake’s future mixing. When Girdner’s colleagues used his data to simulate what might happen under a range of climate scenarios, the model predicted that reverse stratification will become rare within about 50 years. If the process stops entirely, Crater Lake will no longer mix to the bottom at all. Over decades, an oxygen dead zone will begin to form — similar to the ones in the northern Italian lakes. This risks significant ecological impacts, as well as a buildup of toxic compounds that could billow up to the surface if the lake does mix again. Crater Lake is just starting on the path toward such dramatic changes. Another iconic lake a few hundred miles away suggests what might happen next. A Trickle-Down Effect Lake Tahoe, the second-deepest lake in the United States, on the California-Nevada border, once rivaled Crater Lake in its clarity. In the 19th century, rocks glistened through its crystal-clear water. Then, rapid population growth in the 1950s polluted the water, causing algae to start growing offshore. In recent years, those algae have advanced into shallower waters. Secchi disc readings show that, since 1967, clarity in Lake Tahoe has been reduced by nearly 40 feet. The lake’s formerly rich blue hue is now diminished in some places. Jaden Bellamy, a biological science technician at Crater Lake National Park, monitors the lake’s wildlife, including invasive crayfish (left) and rainbow trout (right). Katie Falkenberg for Quanta Magazine These trends will likely continue as climate change advances, said Michael Dettinger, a hydroclimatologist at Scripps Institution of Oceanography at the University of California, San Diego. As Lake Tahoe’s mixing breaks down and summer waters get warmer and linger longer, phytoplankton enjoy an enhanced growing season and cloud the water. Over the next century, more intense and frequent storms are projected to increase water inflows, likely bringing “enormous spikes” of sediments and nutrients into the lake, Dettinger said. Smoke from wildfires also deposits particles, which can change the light structure and nutrient composition of the lake. Such events can affect a lake’s trajectory for years, Chandra said. When combined with altered lake mixing, they create a vicious ecological cycle. Algae blooms are a product of these and other disruptions. In addition to killing fish, the accumulation of oxygen-poor, nutrient-rich water that builds up in a stratified lake — especially one loaded with extra nutrients from runoff and wildfires — can leak to the shoreline, triggering nearshore algae growth that forms a green bathtub ring surrounding a clear center. “That’s one of the working hypotheses for what we think is happening in Lake Tahoe,” Chandra said. Crater Lake suffered its first bloom of shoreline algae in 2021. “It looked like someone took a massive bright green highlighter along the shore,” Girdner said. Because lake tours were closed due to the Covid-19 pandemic that summer, there was no public outcry. Had the bloom occurred during a normal summer — like July 2025, when tourists crowded the lake in passenger boats to marvel at the seemingly bottomless blue abyss around them — the situation might have made national headlines. Researchers process crayfish and fish to monitor the lake’s health. “You can measure vital signs of a human being and get some idea if something seems to be wrong or if things are changing,” Girdner said. “We do similar things in the lake.” Katie Falkenberg for Quanta Magazine When the green ring appeared, Girdner and his colleagues felt overwhelmed. At first they had no idea what could be driving the sudden growth. Then they noticed a telling detail: The greenest places were those with the highest numbers of invasive crayfish. When crayfish move into an area, the population of insect larvae and other aquatic invertebrates that graze on algae declines by about 95%. “They just hammer the insects,” Girdner said. In experiments, Girdner and his colleagues found that about seven times more algae grow in areas with crayfish compared to those without. Yet Girdner suspected there was more than crayfish at work. Those invasive predators had regrettably been introduced to the lake in 1915, but in the intervening century, no other major algae blooms had occurred. He and his colleagues found, instead, that record-breaking water temperatures during the exceptionally hot summer of 2021 had fueled the algae growth. Crayfish had just given it a boost. Milder winters have let the crayfish population grow and spread to new areas of the lake, further disrupting ecosystems. The Mazama newt (or Crater Lake newt), a subspecies found nowhere else in the world, has virtually disappeared. In addition to competing for the same invertebrate prey, the crayfish also capture newts in their pincers and devour the hapless amphibians alive. Similar climate-driven invasive species patterns have been seen in other lakes. These cascading impacts exemplify the fact that lake conditions are inherently and intimately tied to climate, Chandra said. “We cannot divorce the biological composition and interactions within a lake from the climatic conditions within the landscape.” The sun rises over the volcanic heap of Wizard Island on July 23, 2025. Katie Falkenberg for Quanta Magazine Teasing out the interactions between climate, lake mixing and ecology at Crater Lake will give research teams around the globe a blueprint for what to expect as the world continues to warm, and could be key to averting worst-case scenarios. An Uncertain Future Last year, Chandra, Leoni and other researchers were sitting in a cafe near Lake Iseo, comparing notes about climate change at their lakes, when the cafe owner interrupted. “Why do we even need to know this?” Chandra recalled him asking. “There’s not much we can do about it, so why even care?” It’s a sentiment that Chandra often encounters. He harbors hope, however, that some impacts to lakes can be slowed or avoided. While individuals cannot stop the juggernaut of climate change, he said, local interventions could make a difference. Those strategies would be context-dependent, but they could include working to balance a lake’s nutrients, controlling invasive species, cleaning up pollution, or restoring the forests and wetlands surrounding lakes. Collaborations between different groups of scientists could enhance such interventions, said Veronica Nava, a postdoctoral researcher in freshwater ecology at the University of Milan-Bicocca. “If one lake has already experienced what you’re observing, you can come up with better strategies,” she said. A buoy is attached to a mooring sensor, which measures optical chlorophyll fluorescence and turbidity. The NPS has six of these sensors around Crater Lake. Katie Falkenberg for Quanta Magazine Teamwork “is really where freshwater science is moving,” Hampton said. But such efforts are in their early days, as researchers have only started to think about comparing large lake ecosystems over the last few years. Now threats to U.S. research are rattling their newfound collaboration. “The cuts to research funding are going to hit large collaborations pretty hard,” Hampton said. The future of even Crater Lake’s exemplary scientific program is in jeopardy. After spending nearly his entire career at the lake, Girdner is retiring at the end of the year. The federal government has frozen hiring for the National Park Service, so his position will remain unfilled indefinitely. It’s unrealistic, he said, to expect his colleagues to continue the same research output on their own. “We’re going to have to pare down what we’re doing,” he said. Related: Nature’s Critical Warning System How Soon Will the Seas Rise? Simple Equation Predicts the Shapes of Carbon-Capturing Wetlands Until then, they’re focused on what they can do: adding another year’s data to Crater Lake’s history. After a busy day, Girdner steered the vessel back to the dock at Wizard Island, a volcanic cinder cone that juts out of Crater Lake like a pointy hat. In the cluttered boathouse, decades of signatures and sketches coated the wooden walls, bearing witness to the students and scientists who had made some contribution to a better understanding of the lake. Chandra boiled a few invasive crayfish until they were delectably tender, and the group ate them with dabs of hot sauce. They passed around a few bottles of prosecco to toast Girdner’s retirement. As the sun dipped low, the exhausted scientists unrolled sleeping bags on the dock. Girdner had spent countless nights on the island (more than his ex-wife had liked, he admitted). This would be one of his last. The sky’s soft gradient of pink, orange and gold slowly darkened, and the Milky Way twinkled into view. Voices faded, while bats skimmed the water’s still surface. The lake’s future was uncertain. But the urgency of protecting its natural splendor could not have been clearer.

Climate
Water
Animals

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Inside The Grand Canyon

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The Invisible Mammal - The Bat Rescuer

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Resilience

In 1998, a vast power grid serving 5 million people in Canada was destroyed by an ice storm. Twenty years later researchers of that disaster are developing a new kind of resilient power grid. Based in part on the book The Grid and the Village, the film explores how to protect grids and the people they serve from war, terrorist attack, and extreme weather.

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Reboot

Humans have exploited Earth to the point where it is no longer possible to live on it. Their only option is to relocate to Mars. When the last group of people has boarded the spaceship for the red planet, the Earth can finally breathe easy. Like an expressionist painting, Reboot depicts a world in which the absence of our species is the only chance nature has to recover its lushness and flourish once more.

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Cosmos

Chicken Soup for the Soil

Chicken Soup for the Soil follows the journey of North Carolina farmers Rachel Herrick and Suzanne Nelson Karreman as they work to rehabilitate farm soil ecosystems one pasture at a time. We learn that animals are not commodities and insects are not pests. They are partners in regenerating the soil. These are grassroots farms working with Nature to help Nature bounce back.

Land Use
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