Photo credit: Representative Cover Image Source: The frigid water of Niagara Falls empties into the frozen Niagara River on the Canadian side of Niagara Falls, Ontario, Canada. (Photo By Raymond Boyd/Getty Images) – Array
For centuries, Niagara Falls has witnessed some strange incidents. In 1827, a hotel owner sent a flock of wild animals down the falls in a cargo ship, and only a goose survived. But on June 12, 1969, something even stranger happened when the US Army Corps of Engineers stopped the waterfall’s flow. Scientists drained Niagara Falls to conduct research, reported Business Insider.
Representative Image Source: General View of Niagara Falls Park Before the total solar eclipse on April 8, 2024, in Niagara Falls, New York. (Photo by Joan Amengual/VIEWpress)
Niagara Falls is an impressive waterfall connecting three waterfalls at the southern end of Niagara Gorge, bordering Ontario in Canada and New York in the United States. The three water bodies are named Horseshoe Falls, American Falls, and Bridal Veil Falls, in order of their size. While the Horseshoe Falls is at the border of two countries, the other two are within the United States. Bridal Veil Falls is separated from Horseshoe Falls by Goat Island and from American Falls by Luna Island, with both islands situated in New York.
According to the Bright Side, Niagara Falls was first formed around 12,000 years ago, after the last Ice Age. The falls appeared after the ice sheets covered the area of Southern Ontario, and they started moving southward, creating basins of the Great Lakes on the way. They melted and released enormous quantities of water into the basins. As the ice melted, the resulting waters started to flow down through what is known as the Niagara River, Lake Erie, and Lake Ontario.
Representative Image Source: Frozen snow and ice cover the Niagara River on the Canadian side of Niagara Falls on February 28, 2015, in Niagara Falls, Ontario, Canada. (Photo By Raymond Boyd/Getty Images)
By the 17th century, Niagara Falls started gaining popularity as a tourist attraction. In 1842, author Charles Dickens visited the site, and describing the beautiful vista, he wrote “When I felt how near to my Creator I was standing, the first effect, and the enduring one — instant lasting — of the tremendous spectacle, was Peace.” The falls were not just a natural wonder, but also a bounty of natural resources.
A few years after King C. Gillette predicted Niagara Falls could become part of a city called Metropolis, Nikola Tesla designed one of the first hydroelectric plants near the falls. He considered it a significant achievement in human history, per Smithsonian magazine. Over the years, piles of boulders had been building up at the base of the falls. In 1931, almost 76,000 tons of rock slid downwards to the base, and in 1954, 185,000 tons fell, as per Business Insider. So, boulders were not only causing an unsightly appearance but also posed the risk that the falls would soon turn into rapids.
Representative Image Source: Sightseers take pictures of a nearly frozen Niagara Falls on February 20 2015 in Niagara Falls, Ontario, Canada. (Photo by Aaron Vincent Elkaim/Getty Images)
So, in the summer of 1969, some scientists were tasked with removing and examining these boulders. Their goal was to analyze how they could save the falls from erosion. To do this, the US Army Corps of Engineers brought 27,000 tons of rock loaded into thousands of trucks and used these to create a dam, blocking the waters. These waters were diverted to the Horseshoe Falls that absorbed the gushing stream diligently, according to the Bright Side.
When the waterfall was drained, researchers were surprised by what they found on its dried bottom. Plenty of coins sprawled on the waterless bed that people might have thrown in the waterfall to make a wish. Apart from coins, they found the bodies of two humans. In the following few weeks, more than 100,000 people visited the spot to witness the waterless falls from a bare cliff. Most of them were curious about why the water was stopped, and how long it would remain blocked. Meanwhile, for the next five months, engineers worked relentlessly to examine the bed of boulders, and in 1974, concluded that the boulders were necessary to maintain the posture of the waterfall. The American Falls International Board declared in a report that it was against their removal.
Representative Image Source: Pexels | Chaifaastic
So, on November 25, 1969, a crane arrived at the Niagara site and drilled a hole in the dam. Through the hole, water began to surge in torrential streams. The American Falls was freely gushing once again. However, scientists have estimated that the falls might need to be blocked again at some point, to repair the surrounding bridges.
When these plots are planned — as opposed to letting vacant lots grow wild, which is valuable in its own right — they become extra powerful. You may have even enjoyed one without knowing it: the “pocket garden.” Tucked into spaces accessible to pedestrians, like sidewalks, hospital grounds, and campuses, they can be engineered to turn heat-absorbing concrete into air-cooling oases packed with vegetation and seating for people to escape the metropolitan bustle.
“This increasing prioritization of creating green spaces in unexpected spots and underutilized spaces in communities is not only going to be making our communities more resilient, it’s going to be making people healthier,” said Dan Lambe, chief executive of the nonprofit Arbor Day Foundation, which promotes urban forestry. “A little bit of green goes a long way.”
Pocket gardens aren’t gardens in the agriculturally productive sense, but ornamental grounds, Grist reports. (Though there’s nothing stopping a designer from adding a fruit tree or two.) Ideally, they’re host to native plant species, which bring several benefits. For one, they attract native pollinators like insects and birds, which get a source of food that powers them to go on and fertilize plants elsewhere, like crops in urban farms. And two, if the vegetation is adapted to a particular region or condition, it’s already used to the local climate — drought-tolerant varieties, for instance, won’t require as much water to survive. Furthermore, choosing native grasses that don’t need mowing can cut down on maintenance costs. And picking trees with big canopies will increase the amount of shade for people to use as refuge from the heat. (Sorry, palm trees, that means you’re disqualified.)
Biodiversity — mixing tree species as opposed to planting 10 of the same kind — is key here. That attracts a broader range of pollinating animals, and builds resiliency into the system: If you only plant one variety of tree and a disease shows up, it can spread rapidly.
And speaking of disease, trees have an additional superpower in their ability to scrub urban air of the pollutants that contribute to respiratory problems. In addition, the vegetation of a pocket park releases water vapor, bringing down air temperatures. This mitigates what’s called the urban heat island effect, in which cities absorb the sun’s energy all day and slowly release it into the night. Combined, reduced air pollution and temperatures improve public health.
There’s also the harder-to-quantify bonus of people getting out of their cars and gathering in public spaces, no matter how diminutive. “It’s actually a transition toward the pedestrian — toward the person — and away from the vehicle,” said Eric Galipo, director of campus planning and urban design at the architecture firm FCA, which has integrated pocket gardens in its projects. “We may not spend as much time together as a society as we used to, and so these are great opportunities for that sort of connection to happen.”
When the rains come, these verdant plots take on another role as an infrastructural asset. As the planet heats up, rainfall increases because a warmer atmosphere can hold more moisture. In response, cities like Los Angeles and Pittsburgh are getting rid of concrete to open up more green spaces, which absorb rainfall, allowing it to seep underground. This reduces pressure on sewer systems that are struggling to handle increasingly heavy deluges. These systems, after all, were designed long ago for a different climate than we’re dealing with today.
When a city prioritizes green spaces, you can actually hear the difference. Barcelona, for instance, has been developing superblocks, which aim to improve city life by transforming car infrastructure into walkable spaces. That includes the development of “green axes” (the plural of “axis,” not the tool for chopping), full of vegetation and paths for strolling. A recent study found that after these spaces were pedestrianized and vehicles disappeared, average noise levels fell by 3.1 decibels. (For context, hearing a car traveling at 65 mph from 25 feet away would be 77 decibels.)
While 3.1 may not seem like much, each increase of 10 decibels means a tenfold rise in loudness. And we have to consider not just the decibels but how the kind of noise changed as Barcelona developed green axes: Revving engines, honking horns, and even the occasional cacophony of a car accident were replaced with voices. As the built environment dramatically changed, so too did the way that folks on foot experienced their surroundings. “If people see green in general, the noise perception tends to change,” said Samuel Nello-Deakin, a postdoctoral researcher at the Autonomous University of Barcelona and lead author of the study. “You think that things are not as noisy as they actually are. So there’s also this interesting interaction, right, between sort of what you hear and what you see.” In addition, green spaces absorb city racket, keeping it from bouncing off of and between buildings and pavement, insulating residents from the din.
With less commotion comes still more gains to public health. Noise pollution is an invisible crisis worldwide, as studies link the stress it causes not just to struggles with mental health, but physical problems like hypertension and heart disease. By contrast, pocket parks and other green spaces encourage people to ditch their cars and move their bodies. “There are also physical health benefits from walking, biking, and being outside that over a lifetime tend to have a cumulative positive effect on what our society spends in health care,” Galipo said.
So as cities increasingly realize and utilize the power of greenery, the environmental, auditory, and social fabric of the urban landscape transforms. “There’s a gravity to this green space that brings people out,” Lambe said. “And all of a sudden, neighbors are connecting, generations are connecting, cultures are connecting. Trees are about the one thing that everybody can agree on.”
Across Appalachia, rust-colored water seeps from abandoned coal mines, staining rocks orange and coating stream beds with metals. These acidic discharges, known as acid mine drainage, are among the region’s most persistent environmental problems. They disrupt aquatic life, corrode pipes and can contaminate drinking water for decades.
However, hidden in that orange drainage are valuable metals known as rare earth elements that are vital for many technologies the U.S. relies on, including smartphones, wind turbines and military jets. In fact, studies have found that the concentrations of rare earths in acid mine waste can be comparable to the amount in ores mined to extract rare earths.
Scientists estimate that more than 13,700 miles (22,000 kilometers) of U.S. streams, predominantly in Pennsylvania and West Virginia, are contaminated with acid mine discharge.
We and our colleagues at West Virginia University have been working on ways to turn the acid waste in those bright orange creeks into a reliable domestic source for rare earths while also cleaning the water.
Experiments show extraction can work. If states can also sort out who owns that mine waste, the environmental cost of mining might help power a clean energy future.
Rare earths face a supply chain risk
Rare earth elements are a group of 17 metals, also classified as critical minerals, that are considered vital to the nation’s economy or security.
MP Materials’ Mountain Pass Rare Earth Mine and Processing Facility, in California near the Nevada border, is one of the few rare earth mines in the U.S. Tmy350/Wikimedia Commons, CC BY-SA
China controls about 70% of global rare earth production and nearly all refining capacity. This near monopoly gives the Chinese government the power to influence prices, export policies and access to rare earth elements. China has used that power in trade disputes as recently as 2025.
The United States, which currently imports about 80% of the rare earth elements it uses, sees China’s control over these critical minerals as a risk and has made locating domestic sources a national priority.
The U.S. Geological Survey has been mapping locations for potential rare earth mining, shown in pink. But it takes years to explore a locations and then get a mine up and running. USGS
Although the U.S. Geological Survey has been mapping potential locations for extracting rare earth elements, getting from exploration to production takes years. That’s why unconventional sources, like extracting rare earth elements from acid mine waste, are drawing interest.
Turning a mine waste problem into a solution
Acid mine drainage forms when sulfide minerals, such as pyrite, are exposed to air during mining. This creates sulfuric acid, which then dissolves heavy metals such as copper, lead and mercury from surrounding rock. The metals end up in groundwater and creeks, where iron in the mix gives the water an orange color.
Expensive treatment systems can neutralize the acid, with the dissolved metals settling into an orange sludge in treatment ponds.
For decades, that sludge was treated as hazardous waste and hauled to landfills. But scientists at West Virginia University and the National Energy Technology Laboratory have found that it contains concentrations of rare earth elements comparable to those found in mined ores. These elements are also easier to extract from acid mine waste because the acidic water has already released them from the surrounding rock.
Acid mine drainage flowing into Decker’s Creek in Morgantown, West Virginia, in 2024. Helene Nguemgaing
Experiments have shown how the metals can be extracted: Researchers collected sludge, separated out rare earth elements using water-safe chemistry, and then returned the cleaner water to nearby streams.
It is like mining without digging, turning something harmful into a useful resource. If scaled up, this process could lower cleanup costs, create local jobs and strengthen America’s supply of materials needed for renewable energy and high-tech manufacturing.
But there’s a problem: Who owns the recovered minerals?
The ownership question
Traditional mining law covers minerals underground, not those extracted from water naturally running off abandoned mine sites.
Nonprofit watershed groups that treat mine waste to clean up the water often receive public funding meant solely for environmental cleanup. If these groups start selling recovered rare earth elements, they could generate revenue for more stream cleanup projects, but they might also risk violating grant terms or nonprofit rules.
To better understand the policy challenges, we surveyed mine water treatment operators across Pennsylvania and West Virginia. The majority of treatment systems were under landowner agreements in which the operators had no permanent property rights. Most operators said “ownership uncertainty” was one of the biggest barriers to investment in the recovery of rare earth elements, projects that can cost millions of dollars.
Not surprisingly, water treatment operators who owned the land where treatment was taking place were much more likely to be interested in rare earth element extraction.
Map of acid mine drainage sites in West Virginia. Created by Helene Nguemgaing, based on data from West Virginia Department of Environmental Protection, West Virginia Office of GIS Coordination, and U.S. Geological Survey
West Virginia took steps in 2022 to boost rare earth recovery, innovation and cleanup of acid mine drainage. A new law gives ownership of recovered rare earth elements to whoever extracts them. So far, the law has not been applied to large-scale projects.
Across the border, Pennsylvania’s Environmental Good Samaritan Act protects volunteers who treat mine water from liability but says nothing about ownership.
Map of acid mine drainage sites in Pennsylvania. Created by Helene Nguemgaing, based on data from Pennsylvania Spatial Data Access
This difference matters. Clear rules like West Virginia’s provide greater certainty, while the lack of guidance in Pennsylvania can leave companies and nonprofits hesitant about undertaking expensive recovery projects. Among the treatment operators we surveyed, interest in rare earth element extraction was twice as high in West Virginia than in Pennsylvania.
The economics of waste to value
Recovering rare earth elements from mine water won’t replace conventional mining. The quantities available at drainage sites are far smaller than those produced by large mines, even though the concentration can be just as high, and the technology to extract them from mine waste is still developing.
Still, the use of mine waste offers a promising way to supplement the supply of rare earth elements with a domestic source and help offset environmental costs while cleaning up polluted streams.
Early studies suggest that recovering rare earth elements using technologies being developed today could be profitable, particularly when the projects also recover additional critical materials, such as cobalt and manganese, which are used in industrial processes and batteries. Extraction methods are improving, too, making the process safer, cleaner and cheaper.
Treating acid mine drainage and extracting its valuable rare earth elements offers a way to transform pollution into prosperity. Creating policies that clarify ownership, investing in research and supporting responsible recovery could ensure that Appalachian communities benefit from this new chapter, one in which cleanup and clean energy advance together.
Photo credit: Mickey Pullen/Smithsonian Environmental Research Center –
A long-running experiment is testing tree mixes to develop the healthiest forests.
Around the world, people plan to plant more than 1 trillion trees this decade in an ambitious effort to slow climate change and reduce biodiversity loss. But if the past is prologue, many of those planted trees won’t survive. And if they do, they could end up as biological deserts that lack the richness and resilience of healthy forests.
However, many tree-planting commitments have a critical flaw: They rely too heavily on monoculture plantations – vast areas planted with just a single tree species.
A grove of commercially grown poplar trees, planted in lines with not much active beneath them. Mint Images via Getty Images
Rather than gambling on a single species and hoping for the best, science now points to a smarter path that captures both ecological and economic benefits while minimizing risk: mixed-species plantings that mirror the biodiversity of a natural forest, ultimately creating forests that grow faster and are more resilient in the face of constant threats.
The long-running BiodiversiTREE study compares forest plots containing several tree species with single-species monocultures. The results, illustrated here, show that mixed-species plots, right, produce 80% larger trees compared with monocultures, left, resulting in denser canopy growth that creates cooler understory microclimates, leading to more abundant and species-rich communities of insects, spiders and birds. Sergio Ibarra/Smithsonian Environmental Research Center
We are community and landscape ecologists at the Smithsonian Environmental Research Center. Since 2013, we and our colleagues have been rigorously testing this idea in a large, ecosystem-scale experiment called BiodiversiTREE. The verdict is striking: Trees in mixed forests don’t just survive – they outgrow their monoculture counterparts and support dramatically more biodiversity.
Trees with diverse neighbors grow larger
Thirteen years ago, we teamed up with volunteers to plant nearly 18,000 tree seedlings on 60 acres of fallow fields on the Smithsonian Environmental Research Center campus near the Chesapeake Bay.
We didn’t plant just a single species. We planted 16 different native species from all walks of tree-life. Some species were fast-growing timber species, some were mid-story species, and some were slow-growing species that might not reach full size for a century or more.
Some plots we planted with just a single species – homogenous rows of the same species over and over again. But others were planted with random allotments of four and 12 species, reflecting the middle and upper ends of tree diversity in similar-sized areas of our local forests.
We asked a simple question: What would happen if we tried to mirror nature and plant a mixture of species instead of a monoculture?
A drone image shows some of the BiodiversiTREE plots, including monocultures, outlined in white, and mixture plantings, outlined in green. Mickey Pullen/Smithsonian Environmental Research Center
The monoculture plots – those that survived – resemble traditional plantation forestry that historically has dominated rural lands in the Southeast and Pacific Northwest in the U.S. They contain rows of tall, narrow trees with sparse canopies and little life below.
The mixed-species plots, by contrast, are layered, complex and dynamic, with foliage filling the canopy and a diversity of plants and animals thriving underneath.
These visual contrasts reflect real ecological gains. Trees grown in mixtures, including important timber species like poplar and red oak, are up to 80% larger than the same species when grown alone. Mixed plots supported fewer leaf pathogens, more abundant caterpillar communities that provide food for birds, and increased phytochemical diversity in their leaves. We hypothesize that these leaf chemicals, some of which deter animals from eating them, reduced browsing damage from hungry deer, ultimately leading to higher tree growth in the mixed plots.
Plots with several tree species also had much fuller, denser leaf canopies, leading to cooler, shadier conditions that help understory plants flourish and support up to 50% more insects, spiders and birds.
The fuller canopy of 12-species forest plots like the one above supports more insects and birds than the monoculture plots. John Parker/Smithsonian Environmental Research CenterA sycamore monoculture plot at the BiodiversiTREE project provides little canopy cover. John Parker/Smithsonian Environmental Research Center
This pattern isn’t unique to our site. The BiodiversiTREE project is part of TreeDivNet, a global network of large-scale experiments spanning more than 1.2 million trees and hundreds of species. Across continents and climates, the results are consistent: Forests with a mix of species tend to grow larger, store more carbon and better withstand stress from drought, pests and disease.
So why are monocultures still common?
Despite decades of evidence, mixed-species plantings remain relatively rare in practice. Most commercial forestry operations still rely on monocultures, and these plantations are counted toward international planting campaigns aimed at slowing climate change and reversing biodiversity loss.
Technician Shelley Bennett uses high-resolution GPS to lay out plots for an experiment at the Smithsonian Environmental Research Center in Maryland. Regan Todd/Smithsonian Environmental Research Center
A new experiment at the Smithsonian Environmental Research Center called “Functional Forests” aims to bridge some of the gaps between science and practice. We’re developing intentionally designed combinations of trees to test whether specific mixtures of species can contribute ecological benefits while also providing timber and other services that humans need to support a thriving, sustainable economy.
Each of the 20 tree species in the Functional Forests project was chosen to provide one or more benefits, including timber, wildlife habitat, food for people, resistance to deer and climate resilience. But no single species provides all of these benefits.
Some of the nearly 200 plots will contain a single species, while others include carefully selected combinations of five species assembled based on the functions they provide. Some plots are protected from deer browsing, while others are left exposed.
The Functional Forests project includes trees with edible fruits like the pawpaw (Asimina triloba), one of 20 different tree species being planted there. Jamie Pullen/Smithsonian Environmental Research Center
By comparing these approaches, we can test how different planting strategies perform across a range of goals, from timber production to food production and from biodiversity to climate resilience.
Landowners and communities have different priorities, whether that’s producing wood, supporting wildlife or creating forests that can withstand a changing climate. The idea behind Functional Forests is to design plantings that can deliver these multiple benefits all at once, rather than optimizing for just one, essentially leveraging the positive effects of biodiversity to achieve real-world goals.
Planting 1 trillion trees wisely
The stakes are high. Restoration has become a major global investment, with hundreds of billions of dollars already being spent annually. Getting it wrong means wasted resources and missed opportunities to address some of the most pressing environmental challenges of our time.
If the world is going to plant a trillion trees, we believe it needs to do more than just put seedlings in the ground. It needs to rethink what a forest should be.
The goal isn’t just to grow trees. It’s to grow forests that last.
