The Rio Grande is one of the longest rivers in North America, running some 1,900 miles (3,060 kilometers) from the Colorado Rockies southeast to the Gulf of Mexico. It provides fresh water for seven U.S. and Mexican states, and forms the border between Texas and Mexico, where it is known as the Río Bravo del Norte.

The river’s English and Spanish names mean, respectively, “large” and “rough.” But viewed from the Zaragoza International Bridge, which connects the cities of El Paso, Texas, and Ciudad Juárez, Mexico, what was once mighty is now a dry riverbed, lined ominously with barbed wire.

In the U.S., people often think of the Rio Grande mainly as a political border that features in negotiations over immigration, narcotics smuggling and trade. But there’s another crisis on the river that receives far less attention. The river is in decline, suffering from overuse, drought and contentious water rights negotiations.

Urban and rural border communities with poor infrastructure, known in Spanish as colonias, are particularly vulnerable to the water crisis. Farmers and cities in southern Texas and northern Mexico are also affected. As researchers who study hydrology and transboundary water management, we believe managing this important resource requires closer cooperation between the U.S. and Mexico.

A hidden water crisis

For nearly 80 years, the U.S. and Mexico have managed and distributed water from the Colorado River and the Lower Rio Grande – from Fort Quitman, Texas, to the Gulf of Mexico – under the 1944 Water Treaty, signed by presidents Franklin D. Roosevelt and Manuel Avila Camacho. The Colorado River was the central focus of treaty negotiations because officials believed the Colorado basin would have more economic activity and population growth, so it would need more water. In fact, however, the Rio Grande basin has also seen significant growth.

For the Rio Grande, the treaty allocates specific shares of water to the U.S. and Mexico from both the river’s main stem and its tributaries in Texas and Mexico. Delivery of water from six Mexican tributaries has become the source of contention. One-third of this flow is allocated to the U.S., and must total some 76 million cubic feet (2.2 million cubic meters) over each five-year period.

The treaty allows Mexico to roll any accrued deficits at the end of a five-year cycle over to the next cycle. Deficits can only be rolled over once, and they must be made up along with the required deliveries for the following five-year period.

These five-year periods, called cycles, are numbered. Cycles 25 (1992-1997) and 26 (1997-2002) were the first time that two consecutive cycles ended in deficit. Like the Colorado River, the Rio Grande has become over-allocated: The 1944 treaty promises users more water than there is in the river. The main causes are persistent drought and increased water demand on both sides of the border.

Much of this demand was generated by the 1992 North American Free Trade Agreement, which eliminated most border tariffs between Canada, the U.S. and Mexico. From 1993 through 2007, agricultural imports and exports between the U.S. and Mexico quadrupled, and there was extensive expansion of maquiladoras – assembly plants along the border. This growth increased water demand.

Ultimately, Mexico delivered more than the required amount for Cycle 27 (2002-2007), plus its incurred deficit from cycles 25 and 26, by transferring water from its reservoirs. This outcome appeased Texas users but left Mexico vulnerable. Since then, Mexico has continued to struggle to meet its treaty responsibilities and has experienced chronic water shortages.

In 2020, a confrontation erupted in the state of Chihuahua between the Mexican National Guard and farmers who believed delivery to Texas of water from the Rio Conchos – one of the six tributaries regulated under the 1944 treaty – threatened their survival. In 2022, people lined up at water distribution sites in the Mexican city of Monterrey, where the population had doubled since 1990. As of 2023, halfway through Cycle 36, Mexico has only delivered some 25% of its targeted amount.

Border politics overshadow water shortages

As climate change makes the Southwest hotter and drier, scientists predict that water shortages on the Rio Grande will intensify. In this context, the 1944 treaty pits humanitarian needs for water in the U.S. against those in Mexico.

It also pits the needs of different sectors against one another. Agriculture is the dominant water consumer in the region, followed by residential use. When there is a drought, however, the treaty prioritizes residential water use over agriculture.

The Rio Grande is affected by nearly the same hydroclimate conditions as the Colorado River, which flows mainly through the southwest U.S. but ends in Mexico. However, drought and water shortages in the Colorado River basin receive much more public attention than the same problems on the Rio Grande. U.S. media outlets cover the Rio Grande almost exclusively when it figures in stories about immigration and river crossings, such as Texas Gov. Greg Abbott’s 2023 decision to install floating barriers in the river at widely used crossing points.

The compact that governs use of Colorado River water has widely recognized flaws: The agreement is 100 years old, allocates more rights to water than the river holds, and completely excludes Native American tribes. However, negotiations over the Colorado between compact states and the U.S. and Mexico are much more focused than decision-making about Rio Grande water, which has to compete with many other bilateral issues.

Adapting to the future

As we see it, the 1944 water treaty is inadequate to solve the complex social, economic, hydrological and political challenges that exist today in the Rio Grande basin. We believe it needs revision to reflect modern conditions.

This can be done through the minute process, which permits Mexico and the U.S. to adopt legally binding amendments without having to renegotiate the entire agreement. The two countries have already used this process to update the treaty as it pertains to the Colorado River in 2012 and again in 2017.

These steps allowed the U.S. to adjust its deliveries of Colorado River water to Mexico based on water levels in Lake Mead, the Colorado’s largest reservoir, in ways that proportionally distributed drought impacts between the two countries. In the Rio Grande basin, Mexico does not have similar flexibility.

The U.S. also has the ability to proportionally reduce deliveries under a separate 1906 agreement that outlines water delivery from El Paso to Ciudad Juarez. In 2013, for example, Mexico received only 6% of the water it was due under the 1906 Convention.

Enabling Mexico to proportionally reduce Rio Grande deliveries according to drought conditions would distribute drought and climate change impacts more fairly between both countries. As we see it, this kind of cooperation would deliver human, ecological and political benefits in a complex and contentious region.

Vianey Rueda received funding through CUAHSI’s Instrumentation Discovery Travel Grant, which helps researchers learn about hydrologic instrumentation.

Drew Gronewold does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.

Strong winds blew across mountain slopes after a record-setting warm, dry summer. Small fires began to blow up into huge conflagrations. Towns in crisis scrambled to escape as fires bore down.

This could describe any number of recent events, in places as disparate as Colorado, California, Canada and Hawaii. But this fire disaster happened over 110 years ago in the Northern Rocky Mountains of Idaho and Montana.

The “Big Burn” of 1910 still holds the record for the largest fire season in the Northern Rockies. Hundreds of fires burned over 3 million acres – roughly the size of Connecticut – most in just two days. The fires destroyed towns, killed 86 people and galvanized public policies committed to putting out every fire.

Today, as the climate warms, fire seasons like in 1910 are becoming more likely. The 2020 fire season was an example. But are extreme fire seasons like these really that unusual in the context of history? And, when fire activity begins to surpass anything experienced in thousands of years – as research suggests is happening in the Southern Rockies – what will happen to the forests?

As paleoecologists, we study how and why ecosystems changed in the past. In a multiyear project, highlighted in two new publications, we tracked how often forest fires occurred in high-elevation forests in the Rocky Mountains over the past 2,500 years, how those fires varied with the climate and how they affected ecosystems. This long view provides both hopeful and concerning lessons for making sense of today’s extreme fire events and impacts on forests.

Lakes record history going back millennia

When a high-elevation forest burns, fires consume tree needles and small branches, killing most trees and lofting charcoal in the air. Some of that charcoal lands on lakes and sinks to the bottom, where it is preserved in layers as sediment accumulates.

After the fire, trees regrow and also leave evidence of their existence in the form of pollen grains that fall on the lake and sink to the bottom.

By extracting a tube of those lake sediments, like a straw pushed into a layer cake from above, we were able to measure the amounts of charcoal and pollen in each layer and reconstruct the history of fire and forest recovery around a dozen lakes across the footprint of the 1910 fires.

Lessons from Rockies’ long history with fire

The lake sediments revealed that high-elevation, or subalpine, forests in the Northern Rockies in Montana and Idaho have consistently bounced back after fires, even during periods of drier climate and more frequent burning than we saw in the 20th century.

High-elevation forests only burn about once every 100 to 250 or more years on average. We found that the amount of burning in subalpine forests of the Northern Rockies over the 20th and 21st centuries remained within the bounds of what those forests experienced over the previous 2,500 years. Even today, the Northern Rockies show resilience to wildfires, including early signs of recovery after extensive fires in 2017.

But similar research in high-elevation forests of the Southern Rockies in Colorado and Wyoming tells a different story.

The record-setting 2020 fire season, with three of Colorado’s largest fires, helped push the rate of burning in high-elevation forests in Colorado and Wyoming into uncharted territory relative to the past 2,000 years.

Climate change is also having bigger impacts on whether and how forests recover after wildfires in warmer, drier regions of the West, including the Southern Rockies, the Southwest and California. When fires are followed by especially warm, dry summers, seedlings can’t establish and forests struggle to regenerate. In some places, shrubby or grassy vegetation replace trees altogether.

Changes happening now in the Southern Rockies could serve as an early warning for what to expect further down the road in the Northern Rockies.

Warmer climate, greater fire activity, higher risks

Looking back thousands of years, it’s hard to ignore the consistent links between the climate and the prevalence of wildfires.

Warmer, drier springs and summers load the dice to make extensive fire seasons more likely. This was the case in 1910 in the Northern Rockies and in 2020 in the Southern Rockies.

When, where and how climate change will push the rate of burning in the rest of the Rockies into uncharted territory is harder to anticipate. The difference between 1910 and 2020 was that 1910 was followed by decades with low fire activity, whereas 2020 was part of an overall trend of increasing fire activity linked with global warming. Just one fire like 1910’s Big Burn in the coming decades, in the context of 21st-century fire activity, would push the Northern Rockies beyond any known records.

Lessons from the long view

The clock is ticking.

Extreme wildfires will become more and more likely as the climate warms, and it will be harder for forests to recover. Human activity is also raising the risk of fires starting.

The Big Burn of 1910 left a lasting impression because of the devastating impacts on lives and homes and, as in the 2020 fire season and many other recent fire disasters, because of the role humans played in igniting them.

Accidental ignitions – from downed power lines, escaped campfires, dragging chains, railroads – expand when and where fires occur, and they lead to the majority of homes lost to fires. The fire that destroyed Lahaina, Hawaii, is the most recent example.

So what can we do?

Curbing greenhouse gas emissions from vehicles, power plants and other sources can help slow warming and the impacts of climate change on wildfires, ecosystems and communities. Forest thinning and prescribed burns can alter how forests burn, protecting humans and minimizing the most severe ecological impacts.

Reframing the challenge of living with wildfire – building with fire-resistant materials, reducing accidental ignitions and increasing preparedness for extreme events – can help minimize damage while maintaining the critical role that fires have played in forests across the Rocky Mountains for millennia.

Kyra Clark-Wolf has received funding from the National Science Foundation and the Joint Fire Science Program

Philip Higuera receives funding from the National Science Foundation, United States Geological Survey, and Joint Fire Science Program.

Hundreds of millions of tons of single-use plastic ends up in landfills every year, and even the small percentage of plastic that gets recycled can’t last forever. But our group of materials scientists has developed a new method for creating and deconstructing polymers that could lead to more easily recycled plastics – ones that don’t require you to carefully sort out all your recycling on trash day.

In the century since their conception, people have come to understand the enormous impacts – beneficial as well as detrimental – plastics have on human lives and the environment. As a group of polymer scientists dedicated to inventing sustainable solutions for real-world problems, we set out to tackle this issue by rethinking the way polymers are designed and making plastics with recyclability built right in.

Why use plastics, anyway?

Everyday items including milk jugs, grocery bags, takeout containers and even ropes are made from a class of polymers called polyolefins. Polyolefins make up around half of the plastics produced and disposed of every year.

These polymers are used in plastics commonly labeled as HDPE, LLDPE or PP, or by their recycling codes #2, #4 and #5, respectively. These plastics are incredibly durable because the chemical bonds that make them up are extremely stable. But in a world set up for single-use consumption, this is no longer a design feature but rather a design flaw.

Imagine if half of the plastics used today were recyclable by twice as many processes as they are now. While that wouldn’t get the recycling rate to 100%, a jump from single digits – currently around 9% – to double digits would make a big dent in the plastics produced, the plastics accumulated in the environment and their capacity for recycling and reuse.

Recycling methods we already have

Even the plastics that make it to a recycling facility can’t be reused in exactly the same way they were used before – the recycling process degrades the material, so it loses utility and value. Instead of making a plastic cup that is downgraded each time it gets recycled, manufacturers could potentially make plastics once, collect them and reuse them on and on.

Conventional recycling requires careful sorting of all the collected materials, which can be hard with so many different plastics. Here in the U.S., collection happens mainly through single stream recycling – everything from metal cans, glass bottles, cardboard boxes and plastic cups end up in the same bin. Separating paper from metal doesn’t require complex technology, but sorting a polypropylene container from a polyethylene milk jug is hard to do without the occasional mistake.

When two different plastics are mixed together during recycling, their useful properties are hugely reduced – to the point of making them useless.

But say you can recycle one of these plastics by a different method, so it doesn’t end up contaminating the recycling stream. When we mixed samples of polypropylene with a polymer we made, we were still able to depolymerize – or break down the material – and regain our building blocks without chemically affecting the polypropylene. This indicated that a contaminated waste stream could still recover its value, and the material in it could go on to be recycled, either mechanically or chemically.

Plastics we need − but more recyclable

In a study published in October 2023, our team developed a series of polymers with only two simple building blocks – one soft polymer and one hard polymer – that mimicked polyolefins but could also be chemically recycled.

Connecting two different polymers together multiple times until they form a single, long molecule creates what’s called a multiblock polymer. Just by adjusting how much of each polymer type goes into the multiblock polymer, our team created a wide range of materials with properties that spanned across polyolefin types. But creating these multiblock polymers is easier said than done.

To link these hard and soft polymers, we adapted a technique that had previously been used only on very small molecules. This method is improved relative to traditional methods of making polymers in a step-by-step fashion, developed in the 1920s, where the reactive groups on the end of the molecules need to be exactly matched.

In our method, the reactive groups are now the same as each other, meaning we didn’t have to worry about pairing the ends of each building block to make polymers that can compete with the polyolefins we already use. Using the same strategy, applied in reverse by adding hydrogen, we could disconnect the polymers back into their building blocks and easily separate them to use again.

With an almost twofold increase in annual plastic use projected through 2050, the complexity and quantity of plastic recycling will only increase. It’s an important consideration when designing new materials and products.

Using just two building blocks to make plastics that have a huge variety of properties can go a long way toward reducing and streamlining the number of different plastics used to make the products we need. Instead of needing one plastic to make something pliable, another for something stiff, and a third, fourth and fifth for properties in between, we could control the behavior of plastics by just changing how much of each building block is there.

Although we’re still in the process of answering some big questions about these polymers, we believe this work is a step in the right direction toward more sustainable plastics.

We were able to create materials that mimic the properties of plastics the world relies on, and our sights are now set on creating plastic compositions that you couldn’t with existing methods.

Katherine Harry receives funding from RePLACE (Redesigning Polymers to Leverage a Circular Economy) funded by the Office of Science of the US Department of Energy.

Emma Rettner receives funding from RePLACE (Redesigning Polymers to Leverage a Circular Economy) funded by the Office of Science of the US Department of Energy.