When Gaylord Nelson stepped up to the podium in April 1970, his voice rang with powerful purpose. The Wisconsin senator set forth a challenge for America—a call to arms that he declared a “big concept”: a day for environmental action that would go beyond just picking up litter.

“Winning the environmental war is a whole lot tougher than winning any other war in history,” he said. “Our goal is not just an environment of clean air and water and scenic beauty. The objective is an environment of decency, quality and mutual respect for all other human beings and all other living creatures.”

In the half-century since concerned people all across the United States took steps to repair a world rife with pollution, litter, ecological devastation, political apathy and wildlife on the brink, great strides have been made and major setbacks have been recorded. An estimated 20 million Americans volunteered their time and energy to live up to Nelson’s goal. Inspired by man-made disasters like the burning of Ohio’s Cuyahoga River and an oil spill in Santa Barbara, California, environmentalists of the day pushed the nation and the world to recognize the damage they were inflicting on the planet and to change course. Social justice lawyers and urban city planners took up the hard effort of bringing this vision to the impoverished, the hungry and the discriminated.

Today, when not battling a deadly pandemic that has shut down the world economy, Earth’s citizens continue that struggle, challenged by the consequences of global climate change in the form of increasingly catastrophic natural disasters, a depletion of necessary resources, and humanitarian crises on an unprecedented scale. At the same time, scientists, innovators and younger generations are fighting back against these forces and offering reasons for hope and optimism.

In honor of the 50th anniversary of Earth Day, and the 50th anniversary of Smithsonian magazine, the staff of Smithsonian magazine challenged scientists, historians, researchers, astrophysicists, curators and research scholars across the Smithsonian Institution to identify something about the planet that has been revealed over the past 50 years. Read on and be inspired—and sometimes saddened—by their responses—the things achieved and the struggles still ahead.

The Age of Humans

Aerial view of plastic corralled by a floating booming as two birds fly over
Microplastics infiltrate the food chain as animals inadvertently consume plastics. Tiny deep ocean filter feeders have been found with microplastics in their bodies, as have fish, birds, humans and other animals. Luis Acosta / AFP via Getty Images

Humans Created a New Epoch

Our improved understanding of the geological history of Earth helps us understand how the atmosphere, oceans, soils and ecosystems all interact. It also gives us a new perspective on ourselves: We are pushing the Earth to depart radically from the state it has been in for several million years or longer. Our models show that our use of energy and resources will have side effects that persist for hundreds of thousands of years into the future. These realizations have given rise to a new term—the Anthropocene, or Age of Humans. We lack the ability to destroy the Earth, thank goodness, but if we want to leave it in a condition that is pleasant for humans, we have to learn to work within the limits and constraints that its systems impose. Our scientific understanding tells us what we need to do, but our social systems have lagged behind in helping us implement the needed changes in our own behavior. This little essay is being written from self-quarantine because of the worst global pandemic in a century. The human tragedies of COVID-19 should remind us of an important principle. It is difficult or impossible to stop exponential processes like the spread of a virus—or, the growth of human resource use. Global change is generally slower and more multifarious than this pandemic, but it has a similar unstoppable momentum. The sooner we flatten the curve of our resource consumption, the less harm we will cause to our children and grandchildren. If we bring our consumption of resources and energy into line with the ability of the planet to replenish them, we will truly have inaugurated a new epoch in Earth history. —Scott L. Wing, paleobiologist, National Museum of Natural History

The Polar Ice Caps Are Melting

The Arctic that existed when I was born in 1980 was more similar to the one that 19th-century explorers saw than it will be to the one my children will know. Each year since 1980, winter sea ice has steadily dropped, losing more than half its geographic extent and three-quarters of its volume. By the mid-2030s, Arctic summers may be mostly free of sea ice. The Arctic is undergoing a fundamental unraveling that has not happened since it first froze over more than three million years ago, a time before the first bowhead whales. These filter-feeding whales are known as the one true polar whale for good reason—they alone have the size and strength to deal with the vicissitudes of ice, including the wherewithal to break it up should it suddenly begin to close up around a breathing hole. Mysteriously, bowheads can live up to 200 years. A bowhead calf born today will live in an Arctic that, by the next century, will be a different world than that experienced by all of its ancestors; as the Arctic unravels within the scale of our own lifetime, some of these bowheads may still outlive us, reaching a bicentenarian age in an Arctic Ocean with far less ice and many more humans. Nick Pyenson, curator of fossil marine mammals, National Museum of Natural History. This passage is adapted from his book, Spying on Whales.

Feedlot Cattle Increase Methane Emissions

In 1978, the U.S. raised almost twice as many bovine animals as it had in 1940. The emergence of industrial feedlots made this explosion possible. The country’s nearly 120 million ruminant animals, increasingly being fed a diet of grains laced with hormones and antibiotics, were concentrated into industrialized feeding operations. The tremendous population growth that feedlots made possible, however, came with an unexpected consequence: a dramatic rise in methane emissions. In 1980, atmospheric scientist Veerabhadran Ramanathan discovered that trace gases such as methane were extremely potent greenhouse gases, with a warming potential on an order of magnitude greater than CO2. And in 1986, climate scientist and Nobel laureate Paul Crutzen published an article that put the burden of increasing methane emissions on the cattle industry in unequivocal terms. Crutzen explained that 15 to 25 percent of total methane emissions were of animal origin, and “of this, cattle contribute about 74 percent.” Crutzen and others, thus confirmed that growing bovine numbers, were one of the largest factors behind the rise of methane emissions. —Abeer Saha, curator of engineering, work and industry division, National Museum of American History

Parasites Can Hitchhike Around the World in Ships

In the last decade, we’ve discovered that parasites move around the world’s oceans faster and in far larger numbers than we thought. Commercial shipping is the main way goods move from place to place, transporting millions of metric tons of cargo a year. In two studies published in 2016 and 2017, my colleagues and I used DNA-based methods to search for parasites in ballast water (the water that ships take on board and hold in special tanks for balance). We’ve discovered that ballast tanks are full of parasites known to infect many different marine organisms. In our 2017 study, we found some parasite species in all of our samples, from ships docking in ports on the East, West and Gulf Coasts of the U.S. This signals a huge potential for parasite invasions. Knowing these ships are unwittingly ferrying parasites means we can act to limit the future spread of parasites and the diseases they cause. —Katrina Lohan, marine disease ecology laboratory, Smithsonian Environmental Research Center

The Arctic Is Now at the Center of Global Interests

The year 1970 was a good one for the Arctic. Northern regions buried in snow with lots of winter ice. Polar bear populations were high, and the seal hunt was producing a good income for Inuit hunters before French actress Brigitte Bardot’s protest killed peltry fashion. Meanwhile, scientists studying the Greenland ice cores were predicting the Holocene was over and the world was headed into a new ice age. What a difference 50 years can make. Today the Arctic is warming at a rate twice that of the rest of the world; summer pack ice may be gone by 2040 with trans-Arctic commercial shipping and industrial development soon to begin, and Arctic peoples are now represented at the United Nations. In 50 years, the Arctic has been transformed from a remote periphery to center stage in world affairs. Bill Fitzhugh, curator and anthropologist, Arctic Studies Center, National Museum of Natural History

Plastics Are Not the Savior We Were Looking For

The first Earth Day may have been observed 100 years after the invention of the first synthetic plastic, but it took place just three years after Dustin Hoffman’s character in The Graduate was advised, “There’s a great future in plastics.” Though criticized in the 1970s as a technology of cheap conformity, plastics were nonetheless sought out as unbreakable, thus safer for packaging hazardous materials; lightweight, thus environmentally beneficial for transportation; easily disposable, thus reducing disease spread in hospitals; and suitable for hundreds of other applications.

But synthetic plastics were designed to persist, and now they are present on every square foot of the planet. If uncaptured by reuse or recycling streams, a significant amount degrades into small bits called microplastics, which are smaller than five millimeters and can be as small as a virus. These small pieces of plastic circulate in waterways, air and soils around the world. Microplastics infiltrate the food chain as animals inadvertently consume plastics. Tiny deep ocean filter feeders have been found with microplastics in their bodies, as have fish, birds, humans and other animals. By one estimate, the average American will consume or inhale between 74,000 and 121,000 particles of microplastics this year. So far, we do not know the full implications of our microplastic-filled world. Chemical leaching from plastics can affect reproductive systems in organisms. Small bits of plastics can accumulate enough to cause blockages. The challenge ahead is to invent new materials that have properties we need—lightweight, flexible, able to block disease transmission, and so on—but that do not persist. Arthur Daemmrich, director, Lemelson Center for the Study of Invention and Innovation; —Sherri Sheu, environmental historian, research associate, National Museum of American History

Flora and Fauna

Golden Lion Tamarin
Thanks to a network of Zoo-ICUs, some species—including golden lion tamarins—were saved from the brink of extinction. Photo by EyesWideOpen/Getty Images

Giant Pandas Can Be Saved

Ever since the groundbreaking work of conservation biologist George Schaller and his colleagues in the 1980s, we have known the key ingredients required for bringing giant pandas back from the brink. They need mature forest with a bamboo understory, adequate birthing dens for raising their precocial young, and protection from poaching. Leaders within the Chinese conservation community, such as Pan Wenchi, used this knowledge to advocate for a ban on forest cutting and the creation of a national reserve system focused on giant pandas. The unprecedented outflow of funds from the Chinese government and the international NGOs has resulted in the creation, staffing and outfitting of more than 65 nature reserves. Taking place every ten years, the National Giant Panda Survey involves hundreds of reserve staff and documents the return of this species to much of its suitable habitat. Meanwhile, zoos throughout the world cracked the problems of captive breeding, and now sustain a population of more than 500 individuals as a hedge against collapse of the natural populations. In 2016, this massive effort paid off. The IUCN Redlist downgraded giant pandas from endangered to vulnerable conservation status, proving it is possible with a few critical advocates and an outpouring of support to put science into action. —William McShea, wildlife ecologist, Smithsonian Conservation Biology Institute

Critical Mangrove Habitat is Thriving Again

A bridge between land and sea, mangrove forests are among the most productive and biologically complex ecosystems on Earth. Found throughout the tropics and subtropics, mangroves provide critical habitat for numerous marine and terrestrial species and support coastal communities by slowing erosion, cleaning water and much more. In 2007, after decades of rampant losses, scientists sounded the alarm: Without action, the world would lose its mangroves within the next century. In just ten years, concerted, coordinated global efforts have started to pay off. Improved monitoring and increased protections for mangroves have resulted in slower rates of loss. Governments and communities around the world have begun to embrace and celebrate mangroves. A member of the Global Mangrove Alliance and partner in conservation and restoration throughout the American tropics, the Smithsonian is contributing to ambitious goals aimed at protecting and conserving these important habitats.—Steven Canty, biologist, Smithsonian Marine Station; Molly Dodge, program manager, Smithsonian Conservation Commons; Michelle Donahue, science communicator, Smithsonian Marine Station; Ilka (Candy) Feller, mangrove ecologist, Smithsonian Environmental Research Center; Sarah Wheedleton, communications specialist, Smithsonian Conservation Commons

Animals Can Be Brought Back From Near Extinction

In the 1970s, only 200 golden lion tamarins (GLTs) existed in their native Atlantic forest, located just outside of Rio de Janeiro, Brazil. Centuries of deforestation had reduced their habitat by a whopping 98 percent, and that along with their capture for the pet trade had decimated their numbers. In an unprecedented collaboration, Brazilian and international scientists led by the Smithsonian’s National Zoo accepted the challenge to rescue the species from certain extinction. Zoos genetically managed a captive breeding population and soon 500 GLTs were being cared for across 150 institutions. From 1984 to 2000, descendants of the reintroduced zoo-born GLTs flourished in the wild and Brazil’s dedicated GLT conservation group, Associação Mico-Leão Dourado, led an environmental education program that sought an end to illegal deforestation and the capture of GLTs. By 2014, 3,700 GLTs occupied all remaining habitat. In 2018, yellow fever reduced that number to 2,500. A painful setback, but the conservation work continues. —Kenton Kerns, animal care sciences, National Zoo

Pollinators Are a Critical Part of Our Ecosystems

The first report demonstrating major pollinator decline in North America was published in 2006 by the National Academy of Sciences. Over the past 50 years, habitat degradation has had an enormous impact on pollinators and the native plants that support them, but the public can help reverse this trend by creating native plant gardens. Tools such as Pollinator Partnership’s Ecoregional Planting Guides and National Wildlife Federation’s Native Plant Finder can help individuals select appropriate plants that help pollinators. The Million Pollinator Garden Challenge helped connect a network of approximately five million acres, from tiny yards to public gardens, to restore and enhance landscapes to benefit pollinators. It is with hope that these collective efforts will help the populations of bees, butterflies, moths, flies, beetles, birds and bats, which sustain our ecosystems, help plants to reproduce, and are responsible for bringing us one out of every three bites of food that we eat. —Gary Krupnick, head of plant conservation, botany, National Museum of Natural History

When it Comes to Trees, Size Matters

Large-diameter trees are disproportionately important to the Earth’s carbon budget. All trees absorb carbon dioxide as they photosynthesize, but a 2018 study using data from 48 Smithsonian ForestGEO research sites across boreal, temperate, tropical and subtropical forests found that the largest one percent of trees made up about 50 percent of aboveground live biomass, which has huge implications for conservation and climate change mitigation strategies. If we lose big trees to pests, disease, other degradation, and deforestation, we lose significant carbon stores. —Caly McCarthy, program assistant, Lauren Krizel, program manager, ForestGEO

Some 'Extinct' Species Weren't Gone for Good After All

Some 200 million years ago, well before the first Earth Day (and humankind for that matter) dinosaurs were dining on a coniferous tree on what is now the Australian continent. Only known to humans from the fossil record, Wollemia nobilis from the family Araucariaceae was thought to have gone extinct a couple of million years ago, until a lucky explorer brought back some interesting pinecones from an excursion in New South Wales. The ancient, Wollemi pine was rediscovered in 1994. Black-footed ferret, a big-eared bat, a fanged ‘mouse-deer’, and a cliff-dwelling Hawaiian hibiscus are more examples of Lazurus taxon—species that seemed to have been resurrected from the dead. While we are thought to be on the precipice of a sixth mass extinction, stories of species discovered after they were once thought lost forever are welcome glimmers of hope. It’s stories like this that we love to share as part of the Earth Optimism movement to maintain an inspired sense of enthusiasm for our planet and the progress and discoveries we can make in conservation. —Cat Kutz, communications officer, Earth Optimism

Fungi Are Fun to Have Around

Fungi are best known for their fruiting bodies—mushrooms—but most of their structure is hidden underground in a network of microscopic threads called mycelium. People once thought that fungi were harmful parasites that “stole” nutrients from plants so that they could thrive. Today we better understand the ancient relationship between mycorrhizal fungi and the plants they connect. Tiny fibers play an outsized role in the Earth’s ecosystems: 90 percent of land plants have mutually beneficial relationships with fungi. They break down organic materials into fertile soil, help plants share nutrients, and communicate through chemical signals. Plants supply fungi with sugars from photosynthesis; in exchange, fungi provide plants with water and nutrients from the soil. —Cynthia Brown, manager, collections, education and access, Smithsonian Gardens

Animal Species Need ICUs Just Like Humans

Confronting an extinction crisis starts at home: Field conservation, right in animals’ home habitats, is public health for endangered species. But when public health fails? Just as Intensive Care Units (ICUs) have to be at the ready for humans, since 1970 biologists have learned that zoos and aquariums must serve as “ICUs” for the extinction crisis. When field conservation isn’t possible, sometimes the only alternative is to safeguard endangered species in captivity for a time, and restore them to the wild when conditions improve. In 1995, Smithsonian scientist Jon Ballou provided the first complete description of how to accomplish this, empowering networks of “Zoo-ICUs” to rescue dozens of species from extinction, including the Golden Lion Tamarin and the Scimitar-Horned Oryx. This research into population management means that Earth did not lose some of its most critically ill patients in the last 50 years. —Kathryn M Rodriguez-Clark, population ecologist, National Zoo and Conservation Biology Institute

Earth Is Populated by More Than Three Trillion Trees

Trees are found on every continent except Antarctica and in all the major habitats of the world. How many trees are there? Until 2015, we did not know. Now, the global number of trees across the entire Earth has been calculated to exceed three trillion individuals. But the number of trees on the planet has continually changed over the 400 million years since trees first evolved. Between 10,000 to 12,000 years ago, before the accelerated growth of human populations, however, twice the number of trees existed than are present today. Now, the number of trees is decreasing because of human activity, including forest destruction, tree exploitation, climate change, pollution and the spread of invasive species and diseases. More than 15 billion individual trees are lost each year due to human action. Humans have had a tremendous impact on trees and will continue to do so into the foreseeable future. —John Kress, botanist, National Museum of Natural History

Bees Must Be Saved

Bees are hugely influential organisms on humans and have, throughout history, had almost mythological qualities placed on them. (The ancient Greek writer Homer called honey the food of the gods.) The many species of bees may differ in some physical characteristics, but one thing they share is a pollinator role in our ecosystems. Along with other insects, bees travel from plant to plant, pollinating flowers that wind up being essential to human life. Their contributions to human societies are invaluable. I argue that contemporary awareness and activism surrounding conserving bee populations is a massive highlight in environmental history. Without our pollinators, we will experience crop failures and food shortages, so their survival and longevity is in our collective best interest. Organizations like the Honeybee Conservancy work to protect our flying friends and new research, including using fungi to protect bees against disease, gives us hope and optimism. — Zach Johnson, sustainability intern, Conservation Commons

Justice and Human Rights

1982 Warren County Landfill Protest
Photographed in October 1982, residents of Warren County, North Carolina, unite in protest against a landfill in their community. Bettmann / Contributor via Getty Images

Latinos and Other Communities of Color Are Hit Harder by Climate Change

Poor and minority communities are more likely to be impacted by the consequences of climate change, they are also less likely to contribute to its underlying causes. Their carbon footprint is smaller—they purchase fewer goods, drive and fly less, and reside in smaller housing units. Impoverished communities have limited access to health care, making inhabitants more susceptible to infectious diseases, malnutrition, psychological disorders and other public health challenges caused by disasters. Due to rising energy costs, working-class Latinos may have limited access to air conditioning and because many live in urban areas, their residences are impacted by the “heat island” effect. They have less mobility, limited access to warning systems and language barriers may result in a slower response to looming dangers. Because many Latinos do not have homeowners' insurance or depend on inefficient public housing authorities, their period of recovery is typically longer. Experts are noticing increasing numbers of Latinos among the class of “environmental migrants,” sure signs of displacement and attendant economic decline and social stress. It is clear that environmentally challenged Latino communities must continue to inform a more collaborative, solutions-oriented science driven by community-directed research. Active community participation in scientific research can produce better solutions to address public health challenges and to manage natural resources during disasters. It can also create new employment opportunities for community members, strengthen social networks and build lasting, functional partnerships between research institutions and impacted communities. These approaches and outcomes are key in creating the resilience needed to withstand and thrive in the face of natural and human-induced disasters. —Eduardo Díaz, director, Smithsonian Center for Latino Studies (adapted from this column)

Environmental Racism Is a Problem in Need of a Solution

It’s the Same Old Game is a color 16mm film released in 1971 by the Emmy-award winning producer and director Charles Hobson. This 20-minute documentary examines the consequences of poor urban planning and its impact on the environment and people in communities of color. At the time, environmentalism had grown as a political and social justice crusade across the United States. It’s the Same Old Game, however, confronted racism in urban planning, where city planners approved of dumps in poor and minority communities, demolished housing to build highways, and built industrial plants in the middle of neighborhoods, where rumbling trucks and smokestacks spewed noise and air pollution. As an exploration of a nascent justice movement, environmental racism, the film reflects the concerns of a new generation of African American activists following the Civil Rights Movement and Martin Luther King Jr.’s death in 1968. —Aaron Bryant, curator of photography, National Museum of African American History and Culture

Women Are at the Center of the Green Revolution

Research from the United Nations has shown that women will be the most affected by the consequences of climate change. However, women like Wangari Maathai are also at the forefront of the fight for climate action and environmental conservation. In 2004, she became the first black woman and only environmentalist to win the Nobel Peace Prize. Rural Kenyan women, like many females in the Global South working as subsistence farmers, are both the caretakers of their land and their families. Maathai founded the Green Belt Movement in 1984 to give women resources and compensation income for planting and tending to trees, helping them gain financial independence. Meanwhile, their communities would reap the ecological benefits of reforestation. Wangari's grassroots movement showed that it’s possible to tackle gender equality and climate change simultaneously through sustainable development. —Fatima Alcantara, intern, American Women’s History Initiative

Environmental Justice Cannot Be Achieved Without a Diverse Movement

Nearly two decades of community-led efforts to address environmental inequality and racism came to a head at a gathering in Washington, D.C. in October 1991. Over the course of four days, more than 500 participants at the First National People of Color Environmental Leadership Summit challenged narratives that communities of color were neither concerned with nor actively combating environmental issues. Those present, representing civil rights, environmental, health, community development, and faith organizations from across the U.S., Canada, Central and South America, and the Marshall Islands, had been living with and organizing against the impacts of years of environmental inequality and racism. Conversations, negotiations and moments of solidarity produced the 17 Principles of Environmental Justice that have defined the Environmental Justice Movement in the years since. The declaration made almost 30 years ago proclaimed: We “do hereby re-establish our spiritual interdependence to the sacredness of our Mother Earth; to respect and celebrate each of our cultures, languages and beliefs about the natural world…; to ensure environmental justice; to promote economic alternatives which would contribute to the development of environmentally safe livelihoods.” The summit forever transformed notions of “the environment” and “environmentalism,” energizing and supporting the work of Environmental Justice networks and precipitating reflection within mainstream environmental organizations who sought to address charges of exclusivity and a lack of diversity. —Katrina Lashley, program coordinator, Urban Waterway Project, Smithsonian’s Anacostia Community Museum

Rivers Have Rights, Too

In 2017, the Whanganui River in New Zealand was granted legal personhood. Environmental personhood is a legal status that gives natural entities rights, like the ability to be represented in court. In this river’s case, a committee of indigenous environmental defenders were designated as the river’s “legal guardians,” effectively giving the waterway a voice in court in case of future pollution or harmful development. Could granting legal personhood to vulnerable ecosystems be another tool for modern conservation? Over the past two decades, examples of environmental personhood have spread to Bangladesh, Ecuador and the United States. Rivers, lakes and mountains in those countries can now claim legal standing. Though the practice has yielded mixed results in protecting environmental resources, hope persists. Granting personhood to natural resources may spark a change in public and political opinion of ecosystem conservation, with indigenous leaders at the forefront. —Fatima Alcantara, intern, American Women’s History Initiative

Policy Decisions Made Without Scientific Backing Can Have Serious Consequences

The water crisis in Flint, Michigan, forced environmental injustice to the forefront of public discourse. It also demonstrated the importance of environmental impact studies. In 2014, facing a budgetary crisis, officials of this poor, majority-black city economized by changing its water source to the Flint River. Yet they failed to consider how the water’s chemistry could affect infrastructure. Pipes corroded and leached lead and water turned foul, yet authorities dismissed residents’ complaints. Officials could have averted catastrophe by commissioning a study—or even speaking with scientists—before making this change. Poor and minority communities are more likely than others to shoulder burdens of environmental contamination. Sometimes these are legacy problems. Flint’s case involved deliberate obfuscation of facts and attempts to discredit a pediatrician who cried foul. Those children in Flint who were poisoned by lead will pay for this injustice for the rest of their lives. —Terre Ryan, research associate, National Museum of American History

Kids Can Make a Difference

Curtis Bay in Baltimore, Maryland, has historically been a center for industrial development. It is also one of the most polluted areas in the United States, with one of the highest rates of air pollution-related deaths. In 2012, the nation’s largest trash incinerator was planned to be built less than a mile from a high school. Experts projected the plant would emit two million tons of greenhouse gases and about 1,240 tons of mercury and lead into the atmosphere every year. High school student Destiny Waterford and her grassroots organization, Free Your Voice, campaigned for years to stop the building of the incinerator. They employed creative strategies to win community support: everything from knocking door-to-door, to presenting songs, speeches, and videos to committees and boards. In 2016, their efforts paid off and the energy company ended all plans to continue building the plant. In recognition for her work, Destiny Watford received a Goldman’s Environmental Prize the same year. —Fatima Alcantara, intern, American Women’s History Initiative

The Way Way Back (or Beyond)

Iconic 1968 Earthrise Image
The visceral sense of Earth’s fragility against the vastness of space came home to many humans shortly before the first Earth Day, when Apollo 8 astronaut William Anders shot the iconic image of our planet hovering over the surface of the moon. The profound question arose: “Are humans alone?” NASA

The Search For Life Beyond Earth Reminds Us How Unique Our Home Planet Is

The visceral sense of Earth’s fragility against the vastness of space came home to many humans shortly before the first Earth Day, when Apollo 8 astronaut William Anders shot the iconic image (above) of our planet hovering over the surface of the moon. The profound question arose: “Are humans alone?” The 1975 Viking mission to Mars gave us the first chance to search for life on another planet. Half-a-century on, we have now confirmed the existence of water on Mars and determined its past could have been life-sustaining. We are now finding exoplanets in habitable zones around distant stars, too. Yet, each discovery, most importantly, confirms the preciousness of life here, the uniqueness of our home planet, and the importance of ensuring a healthy future. —Ellen Stofan, director, National Air and Space Museum

The Secrets to the Beginning of the Solar System Lie in Antarctic Meteorites

Since the first Earth Day in 1970, teams of scientists have discovered regions in the mountains of Antarctica that can contain thousands of meteorites stranded on the surface of the ice. These meteorites fell to Earth from space over tens of millions of years and were buried beneath new ice forms. As the ice of the polar cap flows with gravity, the ice gets stuck against the massive Transantarctic Mountains and, as very dry winds erode that ice away, meteorites are left exposed on its surface. Teams of scientists from a number of countries have collected nearly 45,000 meteorites over the past 50 years, including the first recognized meteorites from the Moon and Mars. While the vast majority (more than 99 percent) of these meteorites come from asteroids, many new types of meteorites have been discovered, each filling in more pieces of the puzzle of how our solar system formed. —Cari Corrigan, Curator of Antarctic Meteorites, Department of Mineral Sciences, National Museum of Natural History

The Dinosaurs Died From a Meteorite Crashing Into Earth

In 1980, the father and son team of Luis and Walter Alvarez, digging into a roadcut outside the town of Gubbio, Italy, discovered a layer of rock enriched in the element iridium. Rare in the crust of the Earth, iridium is common in meteorites, suggesting that this layer was deposited after a major impact about 65 million years ago at the boundary between the Cretaceous and Tertiary geologic periods. The Alvarezes and their colleagues suggested that impact caused the extinction of dinosaurs. Ten years after that, a crater was identified in what is today the Yucatan Peninsula of Mexico. While impacts on Earth were well-known, these studies suggested the remarkable idea that impacts of material from space altered not just the geologic history of Earth, but the biologic history of our planet. —Tim McCoy, curator of meteorites, National Museum of Natural History

In Some Ways, the Earliest Years of Earth Weren’t All That Different From the Planet of Today

The Earth and environment we have today are the result of billions of years of cosmic good fortune. The Earth is 4,567 million years old, and the first roughly 500 million years of this is known as the Hadean Eon. This eon is named after Hades, the Greek god of the underworld because we used to think that Earth’s early years were an inhospitable period of doom and gloom, with oceans of churning magma blanketing the surface. Now, thanks to the discovery of microscopic crystals of the mineral zircon from Australia, some of which are as old as 4,400 million years old, we have a different story of the early Earth. From these crystals, geologists know that the early Earth had liquid water oceans and continents that may have resembled the continents of today—critical steps in laying the groundwork for the emergence of life and setting our world on its path to today. —Michael R. Ackerson, curator of the National Rock and Ore Collection, National Museum of Natural History

For Millions of Years, Earth Thrived With Higher Biodiversity Than Today

In the past 50 years, scientists have learned an enormous amount about the evolution of Earth’s ecosystems, and we can now understand human impact on biodiversity from the perspective of Deep Time as never before. The fossil record provides a look at historic biodiversity by comparing recent communities of plants and animals with ancient ones. In 2016, a team of paleobiologists and ecologists at the National Museum of Natural History discovered that ancient species tended to occur more often together rather than separately, and these positive associations shaped ancient communities. Amazingly, this pattern of species “aggregation” lasted for 300 million years—strong evidence that it was important to sustaining biodiversity. About 6,000 years ago, however, these bonds began to break apart, and the dominant pattern today is more like “every species for itself.” Human impact, particularly agriculture, may have caused the shift because it disrupts natural habitats and drives species to compete for resources. A Deep Time perspective shows how profound this change is for life on our planet, and it also gives us valuable insight into the kind of community structure that helped sustain biodiversity for hundreds of millions of years. —Kay Behrensmeyer, paleobiologist, National Museum of Natural History

Ancient Humans Dealt With Big Shifts in Climate

Fifty years ago, anthropologists assumed they knew all about the environment in which humans evolved. Arid grassland and barren ice-age landscape presented the critical survival challenges that transformed our ancestors, impelling them to control fire and invent new technologies, for example. But a quarter-century ago, research on ancient climate began to tell a different story. Environmental records from the deep past proved that we inhabit an amazingly dynamic planet. Early ancestors encountered huge swings between wet and dry in our African homeland, and between warm and cold as populations ventured to higher latitudes. Humanity’s history of confronting Earth’s climate swings helps explain our exceptional adaptability—a species evolved to adjust to change itself. This revised understanding of human evolution, however, implies that our survival in the world depends on altering it. The runaway result is an unprecedented transformation of Earth —a new survival challenge of our own making. —Rick Potts, director, Human Origins Program, National Museum of Natural History

Life on Earth Requires Atmospheres With Lots of Oxygen

As scientists improve their ability to examine distant planets, the number of potentially habitable worlds has increased exponentially. However, it has become apparent that a better understanding of the intricate dynamics between environmental change and living things on Earth is necessary to identify conditions that could host such life elsewhere. One major finding is that the evolution of complex organisms (i.e. animals) occurred at a time when the availability of oxygen on Earth rose dramatically. The oldest animal fossils, more than 550 million years old, indicate that the arrival of complex animals followed changes in the amount of oxygen present in these ancient oceans. Thus, identifying exoplanets with well-oxygenated atmospheres may be critical in the search for complex ‘alien’ life. —Scott Evans, fellow, paleobiology, National Museum of Natural History

Humans, From a Genetic Perspective, Aren’t All That Different From Each Other

Today, our species, Homo sapiens, stands more than 7.7 billion strong. Yet genetic evidence from modern humans strongly indicates that despite our outward differences, we have less genetic diversity in the entire human species than among chimpanzees of the same troop. We are even less genetically diverse than wheat. How is this possible? Sometime between around 60,000 to 100,000 years ago, a small population of modern humans migrated out of Africa, and all living humans in Eurasia, Australia and the Americas are descendants of these intrepid travelers. Outside of sub-Saharan Africa, where populations remained stable, prehistoric human populations during this time were so small that we would likely have been on the endangered species list. All living modern humans are descendants of the survivors of this tenuous time for our species, and most of our species’ genetic diversity is African. Does our low genetic diversity mean we are more susceptible to diseases and less able to adapt to environmental changes? We might learn the answers to these questions sooner rather than later. —Briana Pobiner, paleoanthropologist, Human Origins Program, National Museum of Natural History

“Space Weather” Can Impact Life on Earth

By the first Earth Day in 1970, scientists using space satellites knew that magnetic fields—called belts—surrounded our planet. These belts protect the Earth’s atmosphere from the Sun’s solar wind. This interaction produces the well-known phenomenon of “northern lights” or aurora borealis. But only in 1972, when Apollo 16 carried a specially designed telescope to the Moon, did we begin to learn crucial new details about the Earth’s outermost layer of atmosphere, called the geocorona. It is a cloud of hydrogen atoms, which plays a vital role in regulating the impacts of the Sun on Earth, particularly during periods when a strong and energetic solar wind hits Earth. Such events—called geomagnetic storms—have the potential to disable spacecraft orbiting the earth, as well as overwhelm basic infrastructures of our daily life, such as electrical grids and communications systems. Through Apollo 16, and subsequent space missions, we have come to appreciate that “space weather,” as much as everyday weather, can profoundly affect our human world. —David DeVorkin, curator space sciences, National Air and Space Museum

Making a Difference

Dune grass in Chesapeake Bay
Through advanced chemistry and mapping land use with satellites, researchers are reducing polluted runoff in the Chesapeake Bay. onathan Newton / The Washington Post via Getty Images

The Air Has Gotten Better

A 1970 special issue of Mad magazine on air pollution featured an ominous full-color image of Earth wearing a World War I-era gas mask. Inside, a New York City butcher is seen cutting solid blocks of air and wrapping them in paper. Fifty years later, the air is significantly cleaner that it was back then. The exception is carbon dioxide, which is up 25 percent. Since 1970 smoking (at least of tobacco) is way down, sick building syndrome is far less common, acid deposition from sulfur dioxide is lower, lead additives have been removed from gasoline, and stratospheric ozone levels are on the mend. Let’s work to see these trends continue and accelerate in years to come. —Jim Fleming, research associate, National Museum of American History

A Successful Campaign to Stop Littering Proved That Change Can Happen

Many Americans are familiar with that icon of forest safety, Smokey Bear. Less well-known today is a character born out of the same ecological impetus: Johnny Horizon. Horizon was created in 1968 by the Bureau of Land Management to front an anti-littering campaign. He was a handsome combination of cowboy and park ranger, appearing like an eco-warrior version of the Marlboro man. His message was patriotic: “This land is your land. Keep it clean!” His popularity peaked in the mid-1970s, when he fronted a campaign to “Clean Up America by Our 200th Birthday.” Citizens signed a pledge to do their part, and celebrities of the time like Burl Ives and Johnny Cash joined the campaign. Thanks to Horizon’s pledges and similar campaigns, littering has dropped by about 60 percent since 1969. After his success in 1976, the BLM retired Horizon, according to some reports due to the expense of his campaign. Horizon lives on in Twin Falls County, Idaho, which every year hosts a “Johnny Horizon Day” litter-pick up.”—Bethanee Bemis, political history, National Museum of American History

A Problem as Big as the Ozone Hole Could be Solved

One of the amazing environmental success stories of the past half century was the discovery and reversal of the ozone hole. Developed in the 1920s, chlorofluorocarbons (CFCs) served initially as refrigerants but were eventually used in hair sprays, deodorants and many more everyday products. In 1974, the journal Nature published an article by Mario Molina and Sherry Rowland declaring that large amounts of CFCs may be reaching the stratosphere and leading to the “destruction of atmospheric ozone.” This destruction allowed harmful ultraviolet radiation to reach earth’s surface, leading to increased instances of skin cancer, disruptions in agriculture, and global climate modification, they argued. Their laboratory discovery was confirmed when

NOAA atmospheric chemist Susan Solomon led an expedition to show that the hole in the ozone over Antarctica came from its chemical reaction with CFCs. Her discovery was a major step toward the 1987 Montreal Protocol, the international agreement to phase out CFCs. Representatives from 49 countries agreed to freeze the production and consumption of certain ozone-depleting CFCs at 1986 levels by the year 1990. This treaty was an early instance of global environmental cooperation on the basis of the precautionary principle. More than two decades later Molina and Rowland would go on to receive the Nobel Prize in Chemistry for their work in bringing the ozone crisis to the attention of the world. In 2019, NASA and NOAA confirmed the ozone hole was the smallest on record. This rescue from planetary catastrophe shows the power of international cooperation we so desperately need today. —Arthur Molella, emeritus, Lemelson Center; Abeer Saha, curator of engineering, work and industry division, National Museum of American History

Some Ideas Arrive Before the Public Is Ready to Embrace Them

President Jimmy Carter famously encouraged Americans to set their home thermostats to 65 degrees to help combat the energy crisis of 1977. In an address delivered just two weeks into his term, the president wore a beige cardigan sweater and stressed the need for conservation, a strategic energy policy, a new Department of Energy, and an increase in the use of solar power. Two years later, Carter installed 32 solar panels on the roof of the West Wing to heat water for the White House. The executive mansion’s experiment in solar energy only lasted seven years. During the Reagan administration the panels were removed for roof repairs and not reinstalled. Carter may have been ahead of his time. In 1979, most Americans did not follow his examples of solar panels, or pile on sweaters instead of turning up the heat. Today, tax credits are available to homeowners who take advantage of solar energy and, since 2013, solar panels are back on the White House roof. —Lisa Kathleen Graddy, political history, National Museum of American History

Even the Smallest Wetlands Have Big Impacts

Wetland protection became an important issue in the 1970s and legislative efforts to protect wetlands generated political battles that continue to rage today. Should isolated wetlands, sites that are physically separated but periodically linked hydrologically be protected because they are or are not ‘waters of the U.S’ based on the Clean Water Act? The scientific evidence is clear: these unique ecosystems provide important benefits and should be protected. The wetland story has not ended but from small beginnings, wetlands are now part of our social fabric and wetland science highlights the recognition that natural ecosystems provide beneficial work for humans at no cost. —Dennis Whigham, senior botanist, Smithsonian Environmental Research Center

Powerful Images Can Send a Valuable Message

The first Earth Day coincided with the ascendency of television news, as Americans turned to the visual medium for reports on the space race, the Vietnam War, and urban protests. The year prior, an oil spill off the coast of Santa Barbara, California, coated 800 square miles of ocean and blackened more than 35 miles of the state’s scenic coastline. For decades to come, television producers and documentary filmmakers would use images of oil-soaked birds and marine mammals and despoiled beaches from the spill as historical or comparative perspectives for subsequent environmental disasters, such as 1989’s 11-million-gallon Exxon Valdez spill and 2010’s 210-million-gallon Deepwater Horizon spill. The Santa Barbara oil spill demonstrated the power of visual imagery in motivating and sustaining political action on behalf of the environment. Now, in an era of social media and ubiquitous cell-phone cameras, citizens continue to share visual testimonies about the most immediate and dire consequences of global climate change, helping to amplify science-based warnings and to nourish an escalating, worldwide environmental movement. —Jeffrey K. Stine, curator for environmental history, National Museum of American History

The Chesapeake Bay Is on the Mend

The Chesapeake Bay, the nation’s largest estuary, is home to interconnected ecosystems. In 1970, we didn’t consider climate change. Now our long-term experiments on the Bay’s wetlands and forests clearly show the impacts of humans on the Earth and its climate. Through advanced chemistry and mapping land use with satellites, we’re reducing polluted runoff from the 64,000 square mile watershed. Scientists at the Smithsonian’s Environmental Research Center use genomics to measure the Bay’s biodiversity, identify invasive species and detect recovering numbers of fishes in our rivers. Innovative telemetry tracks the migrations of blue crabs, sharks and waterfowl to protect their life cycles. Computers allow us to synthesize vast amounts of environmental data to drive improved management and wise business practices. —Anson “Tuck” Hines, marine ecologist and director, Smithsonian Environmental Research Center

American Ginseng Is a National Treasure Worth Protecting. We Just Can’t Agree How

Wild American ginseng (Panax quinquefolius) is a valuable forest botanical that has been harvested from the Appalachian region for hundreds of years, and traded with China where its roots are widely used in traditional medicine. In 1975, it was listed as endangered by the international regulatory group known as the Convention of International Trade in Endangered Species of Wild Fauna and Flora (CITES). This placed restrictions on the plant’s gathering, even though some of the “new” rules were already being practiced by traditional harvesters. Others ran counter to their ecological knowledge. Opinions vary widely as to whether adding wild American ginseng on the CITES list was helpful or harmful to its conservation, and changes over the years have caused many to question the current CITES rules on wild American ginseng. Still, ginseng’s recognition as an endangered plant since the mid-1970s has put a spotlight on this historically and culturally important plant and its uncertain future. —Betty Belanus, Center for Folklife and Cultural Heritage

Human Ingenuity

A field of wind turbines in Germany
A major milestone was achieved over the past decade when the cost of renewables such as wind and solar became competitive with fossil fuels at both residential- and industrial-scale production. Photo by Jan Woitas/picture alliance via Getty Images

Angkor in Southeast Asia Was Far More Advanced in Shaping Its Environment Than We Had Known

In the 1970s, scholars characterized Angkor—a tightly woven complex of temples in Cambodia—as an isolated place reserved for the dynasty’s kings. Recent research has revealed instead that Angkor was the largest pre-industrial city in the world during the 9th to13th centuries A.D. Vast irrigation systems were built to divert rivers and create monumental reservoirs. However, at the end of the medieval climatic anomaly—a period of unusually warm, wet weather—the reservoirs dried and this urban center returned to jungle, while surrounding cities emerged. Overgrown as it became, Angkor’s impact can still be seen. Recent LIDAR scans peeled away the layers of time to show significant changes to the earth’s surface. A seemingly natural cliff is a thousand-year-old dam. A series of low-lying hills is a village. We now know that Angkor was a sprawling, highly populated city that permanently transformed the environment. —Emma Natalya Stein, assistant curator of South and Southeast Asian Art, National Museum of Asian Art

GPS Revolutionized The Way We Saw the World

A behind-the-scenes utility in everyday life, the Global Positioning System (GPS) is also an indispensable tool for learning about Earth. Originally a satellite-based navigation technology developed in the 1970s for the U.S. military, GPS is fundamentally an information system that lets us know a spot on the globe with a latitude-longitude accuracy of within 10 meters and time within nanoseconds. Applications for that kind of knowledge have revolutionized mapping and furnished a new dynamism to earth and environmental sciences. GPS is especially useful for studying phenomena in motion—like tracking shifts in tectonic plates, monitoring ice sheet behaviors, observing active volcanoes, measuring atmospheric changes, following the path of oil spills, or counting acres of diminishing forests. In all these ways and more, GPS helps us understand the modern world. —Carlene Stephens, curator Division of Work and Industry, National Museum of American History

Global Communication Brings Us Closer Together

Since the inaugural Earth Day, the creation of a global satellite communications network has proven crucial. Three years before the first Earth Day, the first global broadcast was the 1967 television program “Our World,” which instantaneously joined together “points dotted around the circumference of [our] home planet, Earth.” The program reached upwards of 700 million viewers (nearly a fifth of the world’s population) promoting cross-cultural awareness and environmental action. Each segment began with a live broadcast of a baby being born, then posing the question “...but into what kind of world?” That question still is very much with us today. As we deepen our understanding of climate change, satellite communications have been a crucial means to make vivid the world over our collective responsibility to shape a future for ourselves and our children. —Martin Collins, curator, National Air and Space Museum

An Ancient Labrador Figurine Could Give Us a Visual From the Past

In 1978, at a 1,500-year-old site in Saglek Bay on the northeastern end of Canada, the mysterious predecessors of the Thule and modern Inuit of arctic Canada and Greenland, suddenly came to life. A small gray soapstone carving, only three centimeters high and entombed in frozen soil, was one of the first three-dimensional visuals of a person from the Dorset culture, which existed for three millennia and died out in the 15th century. After living successfully in the North American Arctic for 4,000 years, they disappeared without a trace, unable to compete with the more powerful Thule Inuit arriving from Alaska as whale hunters in a time of climate change. The Saglek Dorset Lady reminds us that the cultural isolation they enjoyed for thousands of years did not protect them in the long run. This woman wears a parka with an unusual high, open collar rather than the hood known from Inuit dress. Gouge holes in her back suggest the carving served some ritual purpose. Since then, other high-collared Dorset carvings have been found, but the Dorset Lady from Labrador was our first glimpse showing the vanished Dorsets as ‘real’ people. —Bill Fitzhugh, curator and anthropologist, Arctic Studies Center, National Museum of Natural History

Cross-Cultural Solutions Can Offer Concrete Benefits

Cement manufacturing is an incredibly energy-intensive process, and a major source of carbon dioxide (CO2) emissions. Ferrock, a carbon-negative cement alternative developed by inventor David Stone, changes the game by incorporating recycled and waste materials, and absorbing CO2 in its production. Stone, whose work has been supported by grants from the EPA and Tohono O’odham Community College, collaborated with Richard Pablo, a member of the Tohono O’odham nation. Together, they mobilized Pablo’s community, collecting discarded bottles from drinking sites on the reservation; the crushed glass goes into Ferrock. “These bottles are teachers! They teach a bad life,” says Pablo. Stone agrees: “Through the ritual of picking up bottles, of cleaning the desert, we build a space for a new and strong spirit. . . . This is a good path and will bind us and the land together.” —Joyce Bedi, senior historian, Lemelson Center

Everyone Can Do Science

Over the past 50 years, we have witnessed the dramatic rise of citizen science. The most popular of these programs have been in the fields of ecology, conservation and astronomy with millions of citizens contributing billions of data points every year by exploring gut microbiomes, counting birds, and searching for new planets. With this force of on-the-ground science nerds, experts are capturing data at extremely fine spatial and temporal scales. All this information is making scientific findings more accurate, and scientific predictions more robust. Citizen science is helping folks identify plants in their backyard using iNaturalist, find rare birds in their county using Ebird, and precisely predict local weather in remote areas using the Citizen Weather Observer Program. —Sahas Barve, fellow, Division of Birds, National Museum of Natural History

Renewable Energy Can Be Cheaper Than Fossil Fuels

A major milestone was achieved over the past decade when the cost of renewables such as wind and solar became competitive with fossil fuels at both residential- and industrial-scale production. Decarbonizing the energy sector is the most important action to take to avoid the worst socio-environmental scenarios predicted by climate change models and chart a healthier future for life on Earth. As the efficiency of renewables continues to improve and costs continue to drop many investors, governments and homeowners have been making the economically and socially wise decision to switch to green energy. In terms of direct comparisons, the recent International Renewable Energy Agency (IRENA) report details how renewable generation is becoming more of an obvious economic decision. More than 75 percent of onshore wind power and 80 percent of utility scale solar expected to be built by 2020 will provide electricity at a lower price than the cheapest generation from new coal, oil or natural gas. Renewable generation could already replace 74 percent of U.S. coal generation with an immediate cost savings to electricity customers—a figure projected to rise to 86 percent by 2025. —Brian Coyle, conservation producer, Conservation Commons

Consumer Electronics Repair Is Critical to Sustainability

Many 21st-century consumer products (particularly electronics) have been designed to be replaced. But not all products; in the U.S., the practice of repair is resurging, a promising trend that sees companies responding to consumer pressures. Sustainable design is an essential element of making the world more equitable. As a cultural anthropologist, I have studied third-party repair of cellphones and examined the circular economy of these devices as they are bought and sold around the globe. Repair helps demystify our electronics, makes us better stewards of our indispensable devices, and helps us advocate for policies that counteract built-in obsolescence, which needlessly impacts our planet. Humans are part of a wider ecology and so are our devices, which are built with precious and diminishing materials. Repair as an ethos and practice helps us all live more sustainably. —Joshua Bell, curator of globalization, National Museum of Natural History

Big Industry Sees the Benefits of Alternative Energy

Environmentalist Fisk Johnson proudly pushed the button in 2012 putting two giant wind turbines online. The mighty leviathans standing 415 feet tall and producing nearly 8 million kilowatt hours of electricity per year provide 15 percent of the power for the sprawling SC Johnson manufacturing plant in Waxdale, Wisconsin. It was a giant step in reducing the company’s reliance on fossil fuels. Has there ever been a downside to wind power? More than 100 years earlier, midwestern farmers and ranchers moving into the arid Great Plains turned to wind as a power source pumping water from underground to nourish their operations. Between 1870 and 1900, American farmers put about 230 million acres into agricultural production, much of it in the Great Plains. Were windmills environmentally sound? They did not contribute to air pollution, but they promoted new settlement, the plowing of prairie lands, and the draining of ancient aquifers. —Peter Liebhold, curator of work and industry, National Museum of American History

There’s a Downside, Sometimes, to Human Ingenuity

Humans have bottled water for centuries—especially mineral waters believed to have healing properties. But almost all water bottles were made of glass until May 15, 1973, when the U.S. Patent Office granted patent 3,733,309 for the biaxially oriented polyethylene terephthalate (PET) bottle to Nathaniel C. Wyeth and Ronald N. Roseveare, both working for the DuPont corporation. To call these bottles “ubiquitous” today seems an understatement. More than 480 billion of them are sold each year, or one million every minute. PET is nonbiodegradable but recyclable—though only 31 percent of PET bottles are recycled in the United States; the remainder goes to landfills, or even worse, into lakes and oceans. Nathaniel Wyeth’s brother, artist Andrew Wyeth, and his father, illustrator N.C. Wyeth are perhaps better known than the inventor of the PET bottle, but the damaging impact of Nathaniel’s invention on the environment is one that calls for remedy. —James Deutsch, folklorist, Smithsonian Center for Folklife and Cultural Heritage

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