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No, autumn leaves are not changing color later because of climate change

“Have scientists observed any changes in the timing or intensity of leaf color changes?”

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Credit: James Byard/Washington University
Fall foliage on the Danforth Campus of Washington University in St. Louis.

It’s that time of year again. The days are getting shorter, and the nights are cooling down. But when will the natural fireworks display of autumn leaves actually begin this year?

Many people believe that climate change is pushing back the start of fall leaf color to later in the year. The general thinking is that the warmer conditions anticipated under climate change will mean that trees can “hang on” to their green, energy-producing leaves longer. But scientists do not actually see this happening across North American forests, according to an expert at Washington University in St. Louis.

“Warmer temperatures in September and October reduce anthocyanin production in leaves, which could mean that fall colors would become less brilliantly red or purple,” said Susanne S. Renner, honorary professor of biology in Arts & Sciences. “This effect is well documented in certain species, such as sugar maple, where experimental cooling of branches increases anthocyanin concentration and color brilliance. If the first frost comes later than it used to, the brilliant foliage will appear later than it used to.

“However, other factors counteract this. Most important is that trees drop their leaves earlier if they have had a very productive spring and summer. This overrides any delaying effects of a warm fall.

“The end result is that leaves still start to die after about the same amount of time on the tree as they have in years and even decades past,” she said.

In fact, under some scenarios we might even see leaves turning red and yellow earlier. Renner co-authored a 2020 study in the journal Science that showed that increased growing-season productivity drives earlier autumn leaf senescence — the process through which plants break down and reabsorb key nutrients that had been deployed in leaves — in temperate trees.

“If climate warming continues unabated, the situation is likely to change after about 2040, with senescence then starting earlier than it does now,” Renner said.

Here, Renner answers a few additional questions related to autumn leaf color change.

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How do temperature and moisture conditions affect leaf color?

Yellow color in fall leaves is due to the retention of carotenoid pigments (xanthophylls) in senescing chloroplasts. Red and purplish color is due to the accumulation of anthocyanins in vacuoles, starting around September.

Rain does not affect these basic processes. Cold temperatures, however, enhance anthocyanin production, as shown experimentally in sugar maple. One can observe this in the sugar maple trees along St. Louis streets, which start turning colors at the very top, where the microclimate is coldest.

How might climate change alter color dynamics?

Because climate warming has resulted in warmer falls, in Canada and North America we are seeing less brilliant fall colors. Color brilliance is hard to quantify, but the effect has been experimentally demonstrated in sugar maple trees.

An interesting confounding factor is cleaner air. Thus, in Europe, atmospheric brightening due to cleaner air since 1983 has led to higher plant photosynthesis in the spring and summer — and earlier leaf senescence (compared with 1950-1982). These data, however, concern the breakdown of chlorophyll, not the production of red or yellow colors.

Will all kinds of trees respond in the same ways?

Absolutely not. Experimental work is revealing great species-specific differences. For example, trees that have nitrogen-fixing symbionts never turn red or yellow. Both pigments help protect leaves against damage from sunlight that is no longer usable for photosynthesis because of the massive degradation of chloroplast proteins in aging leaves. Trees with steady access to nitrogen may not bother with costly anthocyanin, but instead simply drop their leaves while still relatively green.

Are scientists already seeing changes to the timing or intensity of leaf color changes?

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Warmer falls reduce the brilliance of red and yellow leaf colors, but brilliance is hard to quantify in long time series for many species. Also, many species simply do not turn red or yellow.

We have a paper under review that analyzes satellite data on “greenness” in Northern Hemisphere forests. We found that across a large majority of forest areas, higher spring and summer temperatures have led to an earlier (!!!) senescence by, on average, about 1.5 days per degree Celsius. Senescence here refers to degradation of chlorophyll or greenness.

Where in the world are autumn leaves most likely to be affected by climate change?

Species that change leaf color to red or yellow are much more frequent in North America than in Europe. With continued climate warming and lack of frost nights in October, colors will be less brilliant, but the onset or dates of color change will not change much because of the counteracting factors that I mentioned earlier. In the more distant future (after about 2040), and with unmitigated climate change, leaf senescence in Northern Hemisphere trees and shrubs will occur ever earlier.

Source: Washington University in St. Louis

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Water is the other US-Mexico border crisis, and the supply crunch is getting worse

The U.S.-Mexico border is facing a severe water crisis exacerbated by climate change, increased demand, and pollution. Collaborative governance is essential to address these growing challenges effectively.

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View of the Rio Grande flowing through Ciudad Juarez, Mexico, photographed from the Paso Del Norte International Bridge. Paul Rarje/AFP via Getty Images

Gabriel Eckstein, Texas A&M University and Rosario Sanchez, Texas A&M University

Immigration and border security will be the likely focus of U.S.-Mexico relations under the new Trump administration. But there also is a growing water crisis along the U.S.–Mexico border that affects tens of millions of people on both sides, and it can only be managed if the two governments work together.

Climate change is shrinking surface and groundwater supplies in the southwestern U.S. Higher air temperatures are increasing evaporation rates from rivers and streams and intensifying drought. Mexico is also experiencing multiyear droughts and heat waves.

Growing water use is already overtaxing limited supplies from nearly all of the region’s cross-border rivers, streams and aquifers. Many of these sources are contaminated with agricultural pollutants, untreated waste and other substances, further reducing the usability of available water.

As Texas-based scholars who study the legal and scientific aspects of water policy, we know that communities, farms and businesses in both countries rely on these scarce water supplies. In our view, water conditions on the border have changed so much that the current legal framework for managing them is inadequate.

Unless both nations recognize this fact, we believe that water problems in the region are likely to worsen, and supplies may never recover to levels seen as recently as the 1950s. Although the U.S. and Mexico have moved to address these concerns by updating the 1944 water treaty, these steps are not long-term solutions.

Map of the Rio Grande and its drainage area through Colorado, New Mexico, Texas and Mexico.
The Rio Grande flows south from Colorado and forms the 1,250-mile (2,000-kilometer) Texas-Mexico border. Kmusser/Wikimedia, CC BY-SA

Growing demand, shrinking supply

The U.S.-Mexico border region is mostly arid, with water coming from a few rivers and an unknown amount of groundwater. The main rivers that cross the border are the Colorado and the Rio Grande – two of the most water-stressed systems in the world.

The Colorado River provides water to more than 44 million people, including seven U.S. and two Mexican states, 29 Indian tribes and 5.5 million acres of farmland. Only about 10% of its total flow reaches Mexico. The river once emptied into the Gulf of California, but now so much water is withdrawn along its course that since the 1960s it typically peters out in the desert.

The Rio Grande supplies water to roughly 15 million people, including 22 Indian tribes, three U.S. and four Mexican states and 2.8 million irrigated acres. It forms the 1,250-mile (2,000-kilometer) Texas-Mexico border, winding from El Paso in the west to the Gulf of Mexico in the east.

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Map of Colorado river and its drainage basin.
The Colorado River flows through seven U.S. states and crosses into Mexico at the Arizona-California border. USGS

Other rivers that cross the border include the Tijuana, San Pedro, Santa Cruz, New and Gila. These are all significantly smaller and have less economic impact than the Colorado and the Rio Grande.

At least 28 aquifers – underground rock formations that contain water – also traverse the border. With a few exceptions, very little information on these shared resources exists. One thing that is known is that many of them are severely overtapped and contaminated.

Nonetheless, reliance on aquifers is growing as surface water supplies dwindle. Some 80% of groundwater used in the border region goes to agriculture. The rest is used by farmers and industries, such as automotive and appliance manufacturers.

Over 10 million people in 30 cities and communities throughout the border region rely on groundwater for domestic use. Many communities, including Ciudad Juarez; the sister cities of Nogales in both Arizona and Sonora; and the sister cities of Columbus in New Mexico and Puerto Palomas in Chihuahua, get all or most of their fresh water from these aquifers.

A booming region

About 30 million people live within 100 miles (160 kilometers) of the border on both sides. Over the next 30 years, that figure is expected to double.

Municipal and industrial water use throughout the region is also expected to increase. In Texas’ lower Rio Grande Valley, municipal use alone could more than double by 2040.

At the same time, as climate change continues to worsen, scientists project that snowmelt will decrease and evaporation rates will increase. The Colorado River’s baseflow – the portion of its volume that comes from groundwater, rather than from rain and snow – may decline by nearly 30% in the next 30 years.

Precipitation patterns across the region are projected to be uncertain and erratic for the foreseeable future. This trend will fuel more extreme weather events, such as droughts and floods, which could cause widespread harm to crops, industrial activity, human health and the environment.

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Further stress comes from growth and development. Both the Colorado River and Rio Grande are tainted by pollutants from agricultural, municipal and industrial sources. Cities on both sides of the border, especially on the Mexican side, have a long history of dumping untreated sewage into the Rio Grande. Of the 55 water treatment plants located along the border, 80% reported ongoing maintenance, capacity and operating problems as of 2019.

Drought across the border region is already stoking domestic and bilateral tensions. Competing water users are struggling to meet their needs, and the U.S. and Mexico are straining to comply with treaty obligations for sharing water.

Cross-border water politics

Mexico and the United States manage water allocations in the border region mainly under two treaties: a 1906 agreement focused on the Upper Rio Grande Basin and a 1944 treaty covering the Colorado River and Lower Rio Grande.

Under the 1906 treaty, the U.S. is obligated to deliver 60,000 acre-feet of water to Mexico where the Rio Grande reaches the border. This target may be reduced during droughts, which have occurred frequently in recent decades. An acre-foot is enough water to flood an acre of land 1 foot deep – about 325,000 gallons (1.2 million liters).

Allocations under the 1944 treaty are more complicated. The U.S. is required to deliver 1.5 million acre-feet of Colorado River water to Mexico at the border – but as with the 1906 treaty, reductions are allowed in cases of extraordinary drought.

Until the mid-2010s, the U.S. met its full obligation each year. Since then, however, regional drought and climate change have severely reduced the Colorado River’s flow, requiring substantial allocation reductions for both the U.S. and Mexico.

In 2025, states in the U.S. section of the lower Colorado River basin will see a reduction of over 1 million acre-feet from prior years. Mexico’s allocation will decline by approximately 280,500 acre-feet under the 1944 treaty.

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This agreement provides each nation with designated fractions of flows from the Lower Rio Grande and specific tributaries. Regardless of water availability or climatic conditions, Mexico also is required to deliver to the U.S. a minimum of 1,750,000 acre-feet of water from six named tributaries, averaged over five-year cycles. If Mexico falls short in one cycle, it can make up the deficit in the next five-year cycle, but cannot delay repayment further. https://www.youtube.com/embed/IgWSMgg9TmE?wmode=transparent&start=0 The U.S. and Mexico are struggling to share a shrinking water supply in the border region.

Since the 1990s, extraordinary droughts have caused Mexico to miss its delivery obligations three times. Although Mexico repaid its water debts in subsequent cycles, these shortfalls raised diplomatic tensions that led to last-minute negotiations and large-scale water transfers from Mexico to the U.S.

Mexican farmers in Lower Rio Grande irrigation districts who had to shoulder these cuts felt betrayed. In 2020, they protested, confronting federal soldiers and temporarily seizing control of a dam.

U.S. President Donald Trump and Mexican President Claudia Scheinbaum clearly appreciate the political and economic importance of the border region. But if water scarcity worsens, it could supplant other border priorities.

In our view, the best way to prevent this would be for the two countries to recognize that conditions are deteriorating and update the existing cross-border governance regime so that it reflects today’s new water realities.

Gabriel Eckstein, Professor of Law, Texas A&M University and Rosario Sanchez, Senior Research Scientist, Texas Water Resources Institute, Texas A&M University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Nature

“Dolphins: The Ocean’s Overachievers”

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Dolphins are Smartypants

Ah, dolphins. The ocean’s golden retrievers. If the sea had a valedictorian, it would be a dolphin—wearing a tiny graduation cap, flipping its tail, and probably showing off by solving a Rubik’s Cube underwater. These marine marvels are the ultimate overachievers of the aquatic world, and frankly, they make the rest of us look bad.

“Dolphins: The Ocean’s Overachievers”

Dolphins

First off, dolphins are ridiculously smart. Scientists say they’re second only to humans in intelligence, which is both impressive and mildly insulting. I mean, have you ever seen a dolphin try to assemble IKEA furniture? No, because they’re too busy inventing underwater sonar and teaching each other how to use sponges as tools. Meanwhile, I’m over here struggling to open a bag of chips without ripping it in half.

And let’s talk about their social lives. Dolphins are the ultimate extroverts. They travel in pods, which is basically the ocean’s version of a group chat that never stops buzzing. They’re always playing, gossiping, and probably roasting each other about who’s the slowest swimmer. They even have names for each other! Can you imagine? “Hey, Flipper, pass the seaweed!” “Nice one, Bubbles, but I’m busy teaching this octopus how to high-five.”

But here’s the kicker: dolphins are also pranksters. They’ve been known to blow bubbles and then swim through them like it’s some kind of underwater TikTok trend. They’ll also play catch with pufferfish, not because they’re hungry, but because the pufferfish release toxins that give them a little “buzz.” That’s right—dolphins are out here getting high on pufferfish while the rest of us are debating whether pineapple belongs on pizza.

And don’t even get me started on their acrobatics. Dolphins can leap 20 feet out of the water, spin in midair, and land gracefully like they’re auditioning for Dancing with the Stars: Ocean Edition. Meanwhile, I trip over my own feet walking to the fridge.

So, what’s the takeaway here? Dolphins are smarter, cooler, and more fun than most of us will ever be. They’re the ocean’s MVP, and honestly, they know it. But hey, at least we have thumbs, right? …Oh wait, they’ve probably figured out how to use those too by now.

Stay salty, my friends. And if you see a dolphin, just bow. They deserve it. 🐬

For further reading on dolphin research, check out these related links:

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https://royalsocietypublishing.org/doi/10.1098/rspb.2018.0948

https://www.wilddolphinproject.org/the-evolution-of-dolphin-research-embracing-new-technology/

https://manoa.hawaii.edu/news/article.php?aId=13420

The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/

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The Earth

The US natural gas industry is leaking way more methane than previously thought. Here’s why that matters

Research reveals that methane emissions from U.S. natural gas operations are significantly underestimated, with a leak rate of 2.3 percent, which poses serious climate concerns and challenges in accurate measurement.

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The authors conferring at a natural gas facility in Colorado. Colorado State University, CC BY-SA

Anthony J. Marchese, Colorado State University and Dan Zimmerle, Colorado State University

Natural gas is displacing coal, which could help fight climate change because burning it produces fewer carbon emissions. But producing and transporting natural gas releases methane, a greenhouse gas that also contributes to climate change. How big is the methane problem?

For the past five years, our research teams at Colorado State University have made thousands of methane emissions measurements at more than 700 separate facilities in the production, gathering, processing, transmission and storage segments of the natural gas supply chain.

This experience has given us a unique perspective regarding the major sources of methane emissions from natural gas and the challenges the industry faces in terms of detecting and reducing, if not eliminating, them.

Our work, along with numerous other research projects, was recently folded into a new study published in the journal Science. This comprehensive snapshot suggests that methane emissions from oil and gas operations are much higher than current EPA estimates.

What’s wrong with methane

One way to quantify the magnitude of the methane leakage is to divide the amount of methane emitted each year by the total amount of methane pumped out of the ground each year from natural gas and oil wells. The EPA currently estimates this methane leak rate to be 1.4 percent. That is, for every cubic foot of natural gas drawn from underground reservoirs, 1.4 percent of it is lost into the atmosphere.

This study synthesized the results from a five-year series of 16 studies coordinated by environmental advocacy group Environmental Defense Fund (EDF), which involved more than 140 researchers from over 40 institutions and 50 natural gas companies.

The effort brought together scholars based at universities, think tanks and the industry itself to make the most accurate estimate possible of the total amount of methane emitted from all U.S. oil and gas operations. It integrated data from a multitude of recent studies with measurements made on the ground and from the air.

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All told, based on the results of the new study, the U.S. oil and gas industry is leaking 13 million metric tons of methane each year, which means the methane leak rate is 2.3 percent. This 60 percent difference between our new estimate and the EPA’s current one can have profound climate consequences.

Methane is a highly potent greenhouse gas, with more than 80 times the climate warming impact of carbon dioxide over the first 20 years after it is released.

An earlier EDF study showed that a methane leak rate of greater than 3 percent would result in no immediate climate benefits from retiring coal-fired power plants in favor of natural gas power plants.

That means even with a 2.3 percent leakage rate, the growing share of U.S. electricity powered by natural gas is doing something to slow the pace of climate change. However, these climate benefits could be far greater.

Also, at a methane leakage rate of 2.3 percent, many other uses of natural gas besides generating electricity are conclusively detrimental for the climate. For example, EDF found that replacing the diesel used in most trucks or the gasoline consumed by most cars with natural gas would require a leakage rate of less than 1.4 percent before there would be any immediate climate benefit.

What’s more, some scientists believe that the leakage rate could be even higher than this new estimate.

What causes these leaks

Perhaps you’ve never contemplated the long journey that natural gas travels before you can ignite the burners on the gas stove in your kitchen.

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But on top of the 500,000 natural gas wells operating in the U.S. today, there are 2 million miles of pipes and millions of valves, fittings, tanks, compressors and other components operating 24 hours per day, seven days a week to deliver natural gas to your home.

That natural gas that you burn when you whip up a batch of pancakes may have traveled 1,000 miles or more as it wended through this complicated network. Along the way, there were ample opportunities for some of it to leak out into the atmosphere.

Natural gas leaks can be accidental, caused by malfunctioning equipment, but a lot of natural gas is also released intentionally to perform process operations such as opening and closing valves. In addition, the tens of thousands of compressors that increase the pressure and pump the gas along through the network are powered by engines that burn natural gas and their exhaust contains some unburned natural gas.

Since the natural gas delivered to your home is 85 to 95 percent methane, natural gas leaks are predominantly methane. While methane poses the greatest threat to the climate because of its greenhouse gas potency, natural gas contains other hydrocarbons that can degrade regional air quality and are bad for human health.

Inventory tallies vs. aircraft surveillance

The EPA Greenhouse Gas Inventory is done in a way experts like us call a “bottom-up” approach. It entails tallying up all of the nation’s natural gas equipment – from household gas meters to wellpads – and estimating an annualized average emission rate for every category and adding it all up.

There are two challenges to this approach. First, there are no accurate equipment records for many of these categories. Second, when components operate improperly or fail, emissions balloon, making it hard to develop an accurate and meaningful annualized emission rate for each source.

“Top-down” approaches, typically requiring aircraft, are the alternative. They measure methane concentrations upwind and downwind of large geographic areas. But this approach has its own shortcomings.

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First, it captures all methane emissions, rather than just the emissions tied to natural gas operations – including the methane from landfills, cows and even the leaves rotting in your backyard. Second, these one-time snapshots may get distorted depending on what’s going on while planes fly around capturing methane data.

Historically, top-down approaches estimate emissions that are about twice bottom-up estimates. Some regional top-down methane leak rate estimates have been as high as 8 percent while some bottom-up estimates have been as low as 1 percent.

More recent work, including the Science study, have performed coordinated campaigns in which the on-the-ground and aircraft measurements are made concurrently, while carefully modeling emission events.

Helpful gadgets and sound policy

On a sunny morning in October 2013, our research team pulled up to a natural gas gathering compressor station in Texas. Using an US$80,000 infrared camera, we immediately located an extraordinarily large leak of colorless, odorless methane that was invisible to the operator who quickly isolated and fixed the problem.

We then witnessed the methane emissions decline tenfold – the facility leak rate fell from 9.8 percent to 0.7 percent before our eyes.

It is not economically feasible, of course, to equip all natural gas workers with $80,000 cameras, or to hire the drivers required to monitor every wellpad on a daily basis when there are 40,000 oil and gas wells in Weld County, Colorado, alone.

But new technologies can make a difference. Our team at Colorado State University is working with the Department of Energy to evaluate gadgetry that will rapidly detect methane emissions. Some of these devices can be deployed today, including inexpensive sensors that can be monitored remotely.

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Technology alone won’t solve the problem, however. We believe that slashing the nation’s methane leak rate will require a collaborative effort between industry and government. And based on our experience in Colorado, which has developed some of the nation’s strictest methane emissions regulations, we find that best practices become standard practices with strong regulations.

We believe that the Trump administration’s efforts to roll back regulations, without regard to whether they are working or not, will not only have profound climate impacts. They will also jeopardize the health and safety of all Americans while undercutting efforts by the natural gas industry to cut back on the pollution it produces.

Anthony J. Marchese, Associate Dean for Academic and Student Affairs, Walter Scott, Jr. College of Engineering; Director, Engines and Energy Conversion Laboratory; Professor, Department of Mechanical Engineering, Colorado State University and Dan Zimmerle, Senior Research Associate and Director of METEC, Colorado State University

This article is republished from The Conversation under a Creative Commons license. Read the original article.


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