Thursday, April 11, 2024

Why Wild Bird Lovers Should Choose Top-of-the-Crop Natural Feed: If you can't read it, don't feed it

(Joan Casanova) Have you ever wondered what’s in your favorite packaged foods, grabbed a box from your pantry, read the ingredients and realized you still didn’t know what you’re eating? The ingredients in some processed foods can read like a chemist’s shopping list. Now imagine if backyard birds could read. What would they say about the ingredients in the food you feed them?

A growing number of Americans are choosing natural foods for their pets; nearly one-third say they prefer natural products, according to People who feed wild birds also want to know they’re feeding the most natural and nutritious options. It’s hard to be confident when reading the mystifying ingredient list on feed bags makes you feel like a bird brain.

With an abundance of options, ranging from commercial bird feeds to small-batch varieties, understanding the differences can help bird lovers make informed choices to meet wild birds’ nutritional needs while considering factors like sustainability and quality.

The wild bird experts at Cole’s Wild Bird Products, Co. offer these tips to ensure you’re feeding your feathered friends a healthy, natural diet.

While commercial bird feeds aim to provide basic nutrition for birds, the quality and nutritional content can vary. Some mixes contain a high proportion of less desirable seeds and fillers, offering limited nutritional value.

Small batch bird feeds prioritize nutritional content, using premium ingredients rich in essential nutrients, fats and proteins. This can provide birds with a more balanced diet, promoting overall health and vitality.

Avoid commercial bird feeds that are full of cheap fillers, such as red milo, millet, cracked corn, oats and wheat. Fillers lack nutritional value and birds will kick them right out of the feeder.

Instead, select small batch, natural feed comprised of top-of-the-crop seeds which contain no chemicals or mineral oil like Cole’s and bypass seed coated with them. Some commercial bird feeds are coated with mineral oil and mixed with crushed rock to add “vitamins.” Current regulations allow manufacturers to list nutritional components of mineral oil (iron, zinc) and crushed rock (vitamin A, calcium carbonate) separately, which can make the ingredients look more impressive. Mineral oil makes birdseed shiny and helps hide dirt and dust, and crushed rock adds weight to the product.

Take note of ingredients you can’t read; often it’s an indication the ingredient is synthetic or lab engineered. Ingredients like menadione sodium bisulfite complex and thiamine mononitrate aren’t found in natural foods; they’re man-made versions of vitamins. The rule of thumb for buying all-natural is “If you can't read it, don't feed it.”  

Focus on serving feed with an ingredient list you can read and understand. For instance, Cole’s Sunflower Meats contains nothing but shelled sunflower seeds and White Millet contains 100% white millet. Super simple, right?

Study birds visiting your feeders and research feed they prefer or buy feed from a reputable company that’s done that work for you. For example, Cole’s offers select natural seed choices developed and based on research about what birds actually eat. Feed is specifically formulated to attract certain species of birds as well as the largest number of birds. No cheap filler seeds are used and seed is cleaned to ensure quality – no sticks and dirt. When you know and serve what backyard birds prefer, they’ll keep coming back for more.

Supplement seed with natural foods you have at home. For example, woodpeckers love raw peanuts, mockingbirds love fruit and chickadees savor suet. Soak raisins and currants in water overnight then serve or purchase blends with a dried fruit and nut mixture, like Nutberry suet. To attract orioles, skewer halved oranges on a spike near feeders.

Buy feed from companies specializing in wild bird food. Some offer bird feed as a side product of pet products or grass seed producers. Conversely, Cole’s exclusively produces and sells products for feeding backyard birds. Seeds are packaged like human food in “Harvest Fresh Lock” packaging so seeds don’t lose nutritional content or dry out and spoil.

To learn more about all-natural feed options with ingredients even birds could understand, visit

Photos courtesy of Cole’s Wild Bird Products

Cole’s Wild Bird Seed

Tuesday, March 26, 2024

Excessively high rents are a major burden for immigrants in US cities

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Nashville is one of the fastest-growing U.S. cities and increasingly a destination for immigrants. Joe Sohm/Visions of America/Universal Images Group via Getty Images
Madhuri Sharma, University of Tennessee and Mikhail Samarin, University of Tennessee

Rents across the U.S. have climbed to staggering levels in recent years. Millions of renters spend more than 30% of their income on rent and utilities, a situation that housing experts call being cost burdened.

High rents affect almost all segments of the population but are an especially heavy burden for immigrants, particularly those who have not yet become U.S. citizens. Immigrants, both documented and undocumented, play important roles in the U.S. economy. They often provide the cheapest labor in the riskiest of industries. Yet they are still not broadly accepted or supported in many U.S. cities.

We are geographers who study housing market issues, including racial-ethnic diversity and housing affordability. Our research on Nashville, which has emerged as an immigrant metropolis in the Southern U.S., suggests that foreign-born residents who are not yet citizens are far more burdened by high rents than other groups.

Many immigrant workers in Nashville spend more than 50% of their incomes on rent. This makes it hard for them to afford education and job training, healthy food, health care and other necessities that can help them participate as productive residents. Heavy rent burdens undermine their ability to have a higher standard of living and to be included in mainstream society.

As immigrants increasingly fan out across the U.S., we believe cities receiving new foreign-born residents should anticipate a growing need for affordable housing.

A 2022 study found that immigrant families in San Diego faced some of the highest rent burdens in the surrounding county.

Hard times for renters

The past 15 years have been challenging for renters across the country. In the 2008-09 recession, which was triggered by a collapse in the housing market, millions lost their homes to foreclosure and became renters. Tighter financing made it harder for others to buy homes. By 2015, almost 43 million households had been pushed into renting.

Today about 37% of U.S. homes are occupied by renters. By 2020, almost 46% of U.S. renters paid more than 30% of their household income toward rent. As of June 2021, the median monthly rent in the 50 largest U.S. cities was $1,575 – an 8.1% increase from June 2020.

The heaviest rent burdens fall disproportionately on minorities. Almost 46% of African American-led renter households are rent burdened, compared with 34% of white households.

The COVID-19 pandemic worsened housing insecurity for people of color because of longstanding racially targeted policies and widespread health and economic disparities. Renters of color faced higher cost burdens and eviction rates. In Nashville, this was especially true in Latino and Somali communities.

Why immigrant housing matters

Immigration is the main driver of population growth in the U.S., which is important for filling jobs and boosting tax revenues. After dipping because of pandemic-era restrictions in 2020-22, immigration to the U.S. started growing again, adding 1.1 million new residents in 2023.

Foreign-born residents make up 7.15% of the U.S. population today. Most of these immigrants are not citizens, although more than 878,000 people became citizens in 2023. The median length of time these new citizens spent in the U.S. before becoming naturalized was seven years.

Nashville is the largest metropolis in Tennessee and one of the fastest-growing immigrant gateways in the South. It is home to over 37% of Tennessee’s Latino population and has been a major destination for Latinos and other foreign-born residents since the early 2000s.

For our research, we used census data estimates for 2015-19 from the National Historical Geographic Information System covering metro Nashville’s 13 counties, which contain 372 census tracts. We found that Nashville’s most racially and ethnically diverse neighborhoods had the highest levels of rent burden.

This includes census tracts with high shares of foreign-born residents who are not yet citizens, especially if those residents are Black or Latino. Our analysis of the 37 census tracts (10% of the region’s total) with the largest shares of foreign-born residents who are not yet citizens shows that the average monthly rent paid by a household in these tracts was $1,306.20, compared with $1,288.70 metrowide.

In the 37 tracts with the largest shares of Latino residents and Black residents, we found that about 21% of households spent more than 50% of their household income on rent.

Our findings corroborate other scholarly analyses of Nashville’s Somali refugees, who tend to be clustered in communities that also house other diverse groups, including Egyptians and other African immigrants. In these areas, gentrification and urban renewal have forced several Black and Somali communities from ownership into renting.

We believe specific groups of foreign-born residents may either have been ineligible or didn’t know how to apply for government-funded housing and rental assistance programs and may have had to rent from predatory landlords as a result. Some Muslim immigrants also avoid applying for bank loans because of a concept in Islamic banking called ribā, which views charging interest on loans as unjust and exploitative.

More encouragingly, we found that tracts with newer housing stock, built since 2000, have relatively lower rent burdens even though those tracts are home to many Black and non-Asian minority residents. This suggests that newer development has an important role to play in mitigating rent, especially in suburban, relatively affordable locations. In the 37 census tracts with the most foreign-born residents who are not yet citizens, about 28% of the total housing stock was built in 2000 or later, compared with 23% across Nashville.

A row of men in hard hats, shoveling dirt.
Federal, state and city officials break ground in 2022 on a mixed-income residential development at Cayce Place, Nashville’s largest subsidized housing property. The city is replacing aging structures on the site, built between 1941 and 1954. Metropolitan Development and Housing Agency, CC BY-ND

Easing rent burdens

One of the best ways to mitigate rent burdens is to build more housing and create affordable housing. However, communities sometimes oppose affordable housing projects and pro-development zoning because of fears of crime, traffic congestion or populations viewed as undesirable. Nashville is not immune to this syndrome.

The cost of housing has been a heated topic in the Nashville region since the mid-2010s. A 2023 Urban Institute report recommended creating more affordable housing in Nashville by promoting partnerships among academic, faith-based and health care institutions that own land that could be developed for housing. And the Metropolitan Council for the Nashville region plans to substantially revamp building codes to promote new housing construction.

However, critics argue that the council gives too much weight to anti-development arguments. And there is little discussion of specific ways to help groups that are ineligible for benefits and assistance that are available to U.S. citizens.

A crowded meeting room with speakers clustered at a podium.
Members of the Tennessee Immigrant & Refugee Rights Coalition celebrate on March 26, 2019, after the defeat of a state bill that would have barred most landlords from renting housing to people in the U.S. illegally. AP Photo/Jonathan Mattise

A priority for cities

Our research shows that creating more rental opportunities can help reduce rent burdens for all. We see great potential to take this research further through community-based investigations of local nuances that may add to rent burdens, especially factors and processes that can’t be adequately captured in quantitative data analysis. Many local actors have important roles to play, including elected officials and local nonprofits and community organizations that work to promote rights for immigrants and refugees.

Given the important role that immigrants play in filling jobs and contributing to local economies, we believe that helping them afford housing is a smart strategy, especially for growth-oriented cities.

Madhuri Sharma, Associate Professor of Geography, University of Tennessee and Mikhail Samarin, Lecturer in Geography and Sustainability, University of Tennessee

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

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Saturday, March 23, 2024

Nuclear’s role in a net-zero world

Is nuclear power a necessary part of the energy transition away from fossil fuels? As the debate rages on, new technologies and smaller reactors may be shifting the balance.

In an online video from Ultra Safe Nuclear Corporation, a cartoon simulation shows a tsunami wiping out one of their future nuclear power stations and cutting off power. What happens next? Not much: The reactor quietly shuts itself down. “It cools off just by sitting there, no moving parts or fluids, no operator actions,” says the reassuring video. “We’ve designed a reactor that is inherently safe no matter the events.”

The Seattle-based Ultra Safe and dozens of other companies like it are at the forefront of a global nuclear energy revival. As the world urgently needs to wean itself off fossil fuels, reduce greenhouse gas emissions and get the planet’s temperature under control, policymakers, companies and researchers are reexamining nuclear energy as a green alternative that can help bolster the power produced by renewables like wind and solar. Today the industry is emerging from a period of stagnation, with a promise to double or triple its capacity by 2050.

That revival is undergirded by two hot technology trends. Companies like Ultra Safe are aiming to build small modular reactors (SMRs) designed to be just a fraction of the size of former plants, to reduce both building costs and the scope of possible disasters. And many are aiming to utilize new technologies designed to make meltdown accidents impossible and to create less long-lived waste.

This video (from Ultra Safe Nuclear Corporation, a nuclear power company) shows the safety features built into a design for a small modular reactor.


But the surge in interest is not without controversy. As with everything in the nuclear landscape, debate rages about whether society actually needs nuclear to tackle climate change, and whether the new systems are as shiny as they seem — with reasonable arguments for and against every promise and risk. Some say the new technologies could offer a fantastic solution to our energy woes; others say nuclear is beset with so many environmental, social and economic problems that it is best abandoned in favor of other ways to meet the globe’s energy demands.

The next few years will decide what course nuclear power takes in the world’s energy future. “This is a moment of truth,” says Francesca Giovannini, a nuclear policy expert at the Harvard Kennedy School. Over the next few decades, nuclear power is “either going to make it, or that industry is fundamentally done for. ... It’s 50/50 how this goes.”

Ups and downs in nuclear power output

Nuclear power poses some obvious risks — meltdown accidents, nuclear fuel being diverted to weapons programs, environmental issues posed by mining for uranium, the problems of storing nuclear waste. Against a backdrop of such concerns, alongside shifting economics of energy production, nuclear power production started to level off in the early 2000s and even dipped briefly after the Fukushima power plant accident of 2011. Some nations, most notably Germany, decided to shutter their nuclear programs entirely. But global nuclear power production is now starting to inch upward again.

Today, nuclear plants produce about 10 percent of global electricity, making nuclear the second largest source of non-fossil-fuel energy after hydropower. There are about 440 nuclear power plants in operation globally; another 60 or so are now being built, and around 100 are on order or planned.

Most Intergovernmental Panel on Climate Change scenarios for keeping the world below 1.5 degrees Celsius of warming include some kind of increase in nuclear power capacity. In the International Energy Agency’s (IEA) pathway to net zero, global nuclear power production doubles over 2022 levels by 2050. A key reason for this is that nuclear is seen as a good way to provide consistent baseload power to prop up more variable renewable sources of energy like wind or solar. Without nuclear, advocates say, we would need to build far more wind and solar power plants to ensure reliable supplies, doubling or tripling costs over power networks that include nuclear.

Nuclear has plenty of advantages: It produces no carbon emissions (and, counterintuitively, releases less radioactive uranium and other elements into the environment than burning coal does). It takes up a lot less land than renewables, a not insignificant consideration. If the goal is to decarbonize quickly and with as little social pain as possible, “nuclear is essential,” says Kai Vetter, a nuclear physicist at the University of California, Berkeley.

At the UN’s Convention on Climate Change meeting in Dubai in December 2023, more than 20 nations signed a declaration to triple nuclear capacity by 2050. And cash is flowing into this effort. In 2020, the US Department of Energy (DOE) notably gave $160 million for two demonstration plants to get up and running by 2027. And in 2022, the European Union declared that some nuclear projects could call themselves “green” in the same way as renewables, opening the door to environmental financing mechanisms.

But as with almost every issue relating to nuclear power, the arguments in favor of nuclear have their detractors. Public policy expert M.V. Ramana at the University of British Columbia is one of many, for example, who say that baseload power is an outdated concept. A smart, diverse and flexible electric grid, they argue, can assure a reliable power supply by shunting power among sources and storage facilities.

And with the cost of renewables falling fast, today’s economic estimates about the relative costs of power sources may not mean much in the future.

Then there’s the question of safety. The grand total of lives lost from all nuclear power generation to date, while hard to quantify, is certainly far lower than the number of people killed by air pollution related to the burning of fossil fuels; a recent paper by NASA scientists concluded that nuclear power saved roughly 1.8 million lives from 1971 to 2009 thanks to avoided air pollution. By some accounts nuclear power has also proved less deadly than wind power, which has been linked to drownings at offshore wind farm sites and helicopter collisions with turbines.

But fatality is arguably a blunt way to measure the impacts of the nuclear industry, which also include the risk of accidents contaminating large tracts of land, plus numerous other effects related to such things as mining and waste storage. Ramana has documented how the burden of these last issues falls disproportionately on Indigenous and disempowered communities, working against the goals of social justice. Nuclear power, he writes, “does not fit with any idea of a responsible and cleaner energy system.”

Small and shiny: New nuclear technologies

If we are to pursue nuclear power at the scale called for by the IEA, it will take a herculean effort. The IEA’s pathway requires the world to ramp up from building five big nuclear plants per year to 20 per year over the next decade. Big plants typically cost billions of dollars and come with big financial risks. Westinghouse Electric Company, for example, recently filed for bankruptcy in the face of billions of dollars of cost overruns during the construction of four nuclear plants in the United States.

One plan for reducing those epic and prohibitive costs is to build small modular reactors, ranging from reactors that can be shipped on a truck and produce a couple of hundred megawatts, to tiny single-megawatt sizes that are more akin to hefty diesel generators. The modules could be pre-built in a factory and shipped to a site for installation. All this should make these reactors less frightening prospects for investors (though the end price per unit of electricity might wind up higher than that from a larger nuclear power plant).

A handful of SMRs are already in operation in Russia, China and India. Dozens more are in development. Canada has a national SMR action plan, and as of 2021 there were 10 SMR proposals under review (including one from Ultra Safe).

But so far, the promise of enticingly low costs for SMR builds hasn’t materialized, says Granger Morgan, a physicist and codirector of the Center for Climate and Energy Decision Making at Carnegie Mellon. Morgan has crunched the numbers for nuclear in the US and was disappointed. “I thought SMRs were going to hold much more promise, but we can’t make the numbers wash,” he says.

That message was hammered home in November 2023 when the company NuScale scrapped its high-profile advanced plans to build an underground SMR in Idaho in the face of cost hikes. “Would it be nice to have nuclear? Yes absolutely,” says Morgan. “Will it be affordable? That’s very much an open question.”

Others argue that small isn’t always beautiful. While smaller plants present a smaller risk from smaller potential accidents, this strategy also means more plants overall, which means more facilities to protect against theft and terrorism. “You have way more fissile material dispersed; you will have to secure way more infrastructure,” says Giovannini. “I mean, that becomes a mess.”

Next generation nuclear

While some are focusing on making nuclear plants smaller, there’s a parallel movement to make them safer and more efficient. The next generation of reactor designs — Generation IV, in the industry’s lingo — includes a suite of six major reactor families, all very different from today’s standard, each with many possible variants under development. Much of the attention (particularly in the US) has been focused on three of these: high-temperature gas-cooled, molten salt and sodium-cooled.

The ideas behind these technologies, and even some early-stage power plants, have been around for decades. But the new variants of these old ideas combine novel fuels and designs, promising to be safer, more efficient and environmentally friendly. “They’re doing all kinds of whizz-bang, high-tech stuff,” says Morgan, who has no doubt that newer reactors can be made safer than old ones.

Most existing reactors are water-cooled uranium systems, which were chosen as the dominant technology largely as a quirk of history. Like all reactor types, they have their pros and cons. They need high pressures to stop their coolant waters from boiling off at typical operating temperatures around 300 degrees Celsius. And they are designed to work with relatively slow-moving neutrons — the subatomic particles that collide with nuclear fuel to initiate nuclear fission. Slow-moving neutrons are more likely to interact with fuel particles, but systems that use them are also limited in the kinds of fuels they can use. Catastrophe can strike if the fission reaction runs amok or the reactor gets too hot and the core “melts down,” as happened at Three Mile Island, Chernobyl and Fukushima, spewing radiation into the environment.

The latest models of water-cooled reactors (sometimes called Gen III Plus, including many SMRs) use new design tricks to reduce the number of safety systems that require human intervention, aiming to stop accidents in their tracks automatically. Gen IV reactors, though, use entirely different coolant materials, are usually designed to operate at higher, more efficient temperatures, and often use faster-speed neutrons that can convert the most prevalent natural isotopes of uranium into usable fuel, or even feed on nuclear waste.

High-temperature gas-cooled reactors, for example, run at temperatures up to 950°C, making them 20 to 33 percent more thermally efficient than water-cooled reactors. Since the core materials used in these reactors are typically stable up to 1,600°C, which is hotter than lava, there’s a large margin of safety. The reactor in Ultra Safe’s video is an SMR that falls into this category; its small size helps, too, with passive cooling. Ultra Safe also makes their own fuel pellets, encased in a bespoke material that they say retains radioactive materials even in extreme conditions. They’re hoping to build their first commercial micro-reactor in Canada.

In molten salt reactors, both fuel and coolant are already liquid. So meltdowns, in the traditional sense, are impossible. And liquid-sodium-cooled reactors have a built-in safety feature: If they heat up, the liquid sodium expands and allows more neutrons to escape through the gaps between atoms, so the reaction (which is driven by neutrons) naturally winds down. The US Department of Energy has funded the US company TerraPower (which has Bill Gates as a major investor) to build a demonstration plant of its sodium-cooled Natrium reactor in Wyoming by 2030.

Nuclear waste not, want not

Waste is one area where the new designs really see some significant improvements, says Giovannini. “None of the reactors have entirely solved the problem of nuclear waste, but they do provide some significant solutions in terms of quantity,” she says. The spent fuel from traditional light water reactors needs to be buried in special repositories for hundreds of thousands of years, because of the production of long-lived radioactive byproducts. Some Gen IV reactors, on the other hand, can transform spent fuel into more fissile isotopes and use it for further fission reactions. This can improve efficiency and produce waste that need only be stored for hundreds of years.

Not everyone, though, thinks all these systems are as shiny as they seem. In 2021, the Union of Concerned Scientists published a report entitled “‘Advanced’ Isn’t Always Better,” in which they highlighted issues with safety, sustainability and nuclear proliferation. They concluded that nearly all the Gen IV reactor types “fail to provide significant enough improvements over [light water reactors] to justify their considerable risks.”

The report was criticized by some for being ideologically antinuclear, says Giovannini. But, she says, “it was very fair” to point out that new tech comes with new worries. Liquid salt, the report pointed out, is corrosive; liquid sodium metal can burst into flame when in contact with water or air. High-temperature gas-cooled reactors, the report concluded, while tolerant of high temperatures, are “far from meltdown-proof, as some claim.”

Hot idea

Many of these Gen IV systems offer another key benefit: Their higher temperatures can provide not just electricity but also useful heat. This could be used in many industrial processes, such as the production of steel, cement and fertilizer, which currently burn a lot of fossil fuels in their furnaces.

“That heat is pretty much for free,” says Vetter, who sees a particular utility for nuclear heat in desalination, getting clean drinking water out of saltwater as is done at the Diablo Canyon nuclear power plant in California. Indeed, X-energy, a leading US Gen IV nuclear company funded by the DOE, has partnered with Dow chemical company to build its first high-temperature gas-cooled reactor at a Dow chemical production site by 2030. Morgan, though, thinks that most industries will balk at the set-up costs.

Even if Gen IV reactors turn out to be technically superior, though, it may be decades before they can be thoroughly tested, passed by regulators and built at commercial scale. With little time to spare in the fight against climate change, the world might be better off simply ramping up old reactor designs that are already proven, says Esam Hussein, a retired nuclear engineer from the University of Regina, Canada. “We have the operating experience, we have the regulatory framework,” he says. “If the goal is to fight climate change, why don’t you go with the devil you know?”

In response to why we need a devil at all, many are quick to point out that no energy solution is problem-free, including renewables. Giovannini says she agrees with the nuclear industry’s criticism that we have “jumped on renewables in a very uncritical way.” Wind and solar require electronics and battery banks to store their energy; these in turn need elements like lithium and cobalt that can come with environmental and social justice issues from mining. “Nothing is 100 percent safe,” says Vetter.

It is hard for many to swallow data, assurances and statistics about nuclear, given its history and the huge amounts of money at stake. “I think the nuclear industry is selling a bunch of bullshit most of the time,” says Giovannini, who has been critical of how the industry deals with public concerns. But her own main worry about nuclear is “they’re moving too slow.” If companies like Ultra Safe, X-Energy, TerraPower and others are going to help fight climate change with Gen IV technologies and fleets of small reactors, she and others say, they’re going to have to ramp up fast.

Editor’s note: This story was updated on March 20, 2024, to change a name: Granger Morgan was referred to as Granger instead of Morgan in one reference. It was updated on March 21, 2024, to correct the specialty of Esam Hussein. He is a retired nuclear engineer, not a retired nuclear physicist.

Knowable Magazine

Climate change is shifting the zones where plants grow – here’s what that could mean for your garden

Climate change complicates plant choices and care. Early flowering and late freezes can kill flowers like these magnolia blossoms. Matt Kasson, CC BY-ND
Matt Kasson, West Virginia University

With the arrival of spring in North America, many people are gravitating to the gardening and landscaping section of home improvement stores, where displays are overstocked with eye-catching seed packs and benches are filled with potted annuals and perennials.

But some plants that once thrived in your yard may not flourish there now. To understand why, look to the U.S. Department of Agriculture’s recent update of its plant hardiness zone map, which has long helped gardeners and growers figure out which plants are most likely to thrive in a given location.

A U.S. map divided into colored geographic zones with a numbered key.
The 2023 USDA plant hardiness zone map shows the areas where plants can be expected to grow, based on extreme winter temperatures. Darker shades (purple to blue) denote colder zones, phasing southward into temperate (green) and warm zones (yellow and orange). USDA

Comparing the 2023 map to the previous version from 2012 clearly shows that as climate change warms the Earth, plant hardiness zones are shifting northward. On average, the coldest days of winter in our current climate, based on temperature records from 1991 through 2020, are 5 degrees Fahrenheit (2.8 Celsius) warmer than they were between 1976 and 2005.

In some areas, including the central Appalachians, northern New England and north central Idaho, winter temperatures have warmed by 1.5 hardiness zones – 15 degrees F (8.3 C) – over the same 30-year window. This warming changes the zones in which plants, whether annual or perennial, will ultimately succeed in a climate on the move.

U.S. map showing large areas colored tan, denoting a 5-degree increase in average winter minimum temperatures.
This map shows how plant hardiness zones have shifted northward from the 2012 to the 2023 USDA maps. A half-zone change corresponds to a tan area. Areas in white indicate zones that experienced minimal change. Prism Climate Group, Oregon State University, CC BY-ND

As a plant pathologist, I have devoted my career to understanding and addressing plant health issues. Many stresses not only shorten the lives of plants, but also affect their growth and productivity.

I am also a gardener who has seen firsthand how warming temperatures, pests and disease affect my annual harvest. By understanding climate change impacts on plant communities, you can help your garden reach its full potential in a warming world.

Hotter summers, warmer winters

There’s no question that the temperature trend is upward. From 2014 through 2023, the world experienced the 10 hottest summers ever recorded in 174 years of climate data. Just a few months of sweltering, unrelenting heat can significantly affect plant health, especially cool-season garden crops like broccoli, carrots, radishes and kale.

Radishes sprouting in a garden bed.
Radishes are cool-season garden crops that cannot withstand the hottest days of summer. Matt Kasson, CC BY-ND

Winters are also warming, and this matters for plants. The USDA defines plant hardiness zones based on the coldest average annual temperature in winter at a given location. Each zone represents a 10-degree F range, with zones numbered from 1 (coldest) to 13 (warmest). Zones are divided into 5-degree F half zones, which are lettered “a” (northern) or “b” (southern).

For example, the coldest hardiness zone in the lower 48 states on the new map, 3a, covers small pockets in the northernmost parts of Minnesota and has winter extreme temperatures of -40 F to -35 F. The warmest zone, 11b, is in Key West, Florida, where the coldest annual lows range from 45 F to 50 F.

On the 2012 map, northern Minnesota had a much more extensive and continuous zone 3a. North Dakota also had areas designated in this same zone, but those regions now have shifted completely into Canada. Zone 10b once covered the southern tip of mainland Florida, including Miami and Fort Lauderdale, but has now been pushed northward by a rapidly encroaching zone 11a.

Many people buy seeds or seedlings without thinking about hardiness zones, planting dates or disease risks. But when plants have to contend with temperature shifts, heat stress and disease, they will eventually struggle to survive in areas where they once thrived.

Successful gardening is still possible, though. Here are some things to consider before you plant:

Annuals versus perennials

Hardiness zones matter far less for annual plants, which germinate, flower and die in a single growing season, than for perennial plants that last for several years. Annuals typically avoid the lethal winter temperatures that define plant hardiness zones.

In fact, most annual seed packs don’t even list the plants’ hardiness zones. Instead, they provide sowing date guidelines by geographic region. It’s still important to follow those dates, which help ensure that frost-tender crops are not planted too early and that cool-season crops are not harvested too late in the year.

Orange flowers blooming with other plants and grasses.
California poppies are typically grown as annuals in cool areas, but can survive for several years in hardiness zones 8-10. The Marmot/Flickr, CC BY

User-friendly perennials have broad hardiness zones

Many perennials can grow across wide temperature ranges. For example, hardy fig and hardy kiwifruit grow well in zones 4-8, an area that includes most of the Northeast, Midwest and Plains states. Raspberries are hardy in zones 3-9, and blackberries are hardy in zones 5-9. This eliminates a lot of guesswork for most gardeners, since a majority of U.S. states are dominated by two or more of these zones.

Nevertheless, it’s important to pay attention to plant tags to avoid selecting a variety or cultivar with a restricted hardiness zone over another with greater flexibility. Also, pay attention to instructions about proper sun exposure and planting dates after the last frost in your area.

Fruit trees are sensitive to temperature fluctuations

Fruit trees have two parts, the rootstock and the scion wood, that are grafted together to form a single tree. Rootstocks, which consist mainly of a root system, determine the tree’s size, timing of flowering and tolerance of soil-dwelling pests and pathogens. Scion wood, which supports the flowers and fruit, determines the fruit variety.

Most commercially available fruit trees can tolerate a wide range of hardiness zones. However, stone fruits like peaches, plums and cherries are more sensitive to temperature fluctuations within those zones – particularly abrupt swings in winter temperatures that create unpredictable freeze-thaw events.

Packages for hardy fig and kiwi seedlings.
Following planting instructions carefully can maximize plants’ chances of success. Matt Kasson, CC BY-ND

These seesaw weather episodes affect all types of fruit trees, but stone fruits appear to be more susceptible, possibly because they flower earlier in spring, have fewer hardy rootstock options, or have bark characteristics that make them more vulnerable to winter injury.

Perennial plants’ hardiness increases through the seasons in a process called hardening off, which conditions them for harsher temperatures, moisture loss in sun and wind, and full sun exposure. But a too-sudden autumn temperature drop can cause plants to die back in winter, an event known as winter kill. Similarly, a sudden spring temperature spike can lead to premature flowering and subsequent frost kill.

Pests are moving north too

Plants aren’t the only organisms constrained by temperature. With milder winters, southern insect pests and plant pathogens are expanding their ranges northward.

One example is Southern blight, a stem and root rot disease that affects 500 plant species and is caused by a fungus, Agroathelia rolfsii. It’s often thought of as affecting hot Southern gardens, but has become more commonplace recently in the Northeast U.S. on tomatoes, pumpkins and squash, and other crops, including apples in Pennsylvania.

A stem dotted with small round growths.
Southern blight (small round fungal structures) at the base of a tomato plant. Purdue University, CC BY-ND

Other plant pathogens may take advantage of milder winter temperatures, which leads to prolonged saturation of soils instead of freezing. Both plants and microbes are less active when soil is frozen, but in wet soil, microbes have an opportunity to colonize dormant perennial plant roots, leading to more disease.

It can be challenging to accept that climate change is stressing some of your garden favorites, but there are thousands of varieties of plants to suit both your interests and your hardiness zone. Growing plants is an opportunity to admire their flexibility and the features that enable many of them to thrive in a world of change.The Conversation

Matt Kasson, Associate Professor of Mycology and Plant Pathology, West Virginia University

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

Wednesday, March 13, 2024

Moving trees north to save the forests

As the world warms, trees in forests such as those in Minnesota will no longer be adapted to their local climates. That’s where assisted migration comes in.

On a brisk September morning, Brian Palik’s footfalls land quietly on a path in flickering light, beneath a red pine canopy in Minnesota’s iconic Northwoods. A mature red pine, also called Norway pine, is a tall, straight overstory tree that thrives in cold winters and cool summers. It’s the official Minnesota state tree and a valued target of its timber industry.

But red pine’s days of dominance here could fade. In coming decades, climate change will make red pine and other Northwoods trees increasingly vulnerable to destructive combinations of longer, warmer summers and less extremely cold winters, as well as droughts, windstorms, wildfires and insect infestations. Climate change is altering ecological conditions in cold regions faster than trees can adapt or migrate.

Palik, a forest ecologist with the US Department of Agriculture’s Forest Service Northern Research Station, stops and points to a newcomer under the red-pine canopy: a broadleaf deciduous tree, bitternut hickory, as high as an elephant’s eye at about 10 feet tall and eight years old. “It’s doing really well,” he says.

This bitternut hickory probably shouldn’t be thriving in the Cutfoot Experimental Forest in north-central Minnesota, near Grand Rapids. It likely began as a seedling in a nursery in Illinois, to the south, where deep freezes are less extreme. Normally, if a southern-adapted seedling is planted in an unsuitably cold climate like this one, it can risk frost damage and its survival is threatened. But the newcomer’s lush, green foliage exudes good health.

It is a promising sign in a project that aims to keep forests growing in a warming world.

In the Cutfoot Experimental Forest in 2016, the Forest Service planted seedlings of eight tree species from seeds, collected from woods up to several hundred miles farther south, as part of an experiment that Palik manages. Four species are native to this northern region: eastern white pine, northern red oak, bur oak and red maple. Four species are uncommon or nonnative: white oak, bitternut hickory, black cherry and ponderosa pine.

Two decades back, these southern seedlings likely would have struggled to flourish here. Today, Palik and his team can see the success of almost all the southern trees they planted. “They are going like gangbusters,” he says, “which is indicative that the climate is right for them,” although the researchers don’t know about the seedlings’ long-term health yet. In seven of the eight species, the survival rate has been 85 to 90 percent.

“The climate typical of southern Minnesota from 20 years ago is now in northern Minnesota,” Palik says. Climatic conditions have moved about 200 miles north in just two decades.

Palik’s project is an experiment in forest assisted migration, the relocation of trees to help woodlands adapt and flourish despite the heating of their habitats from climate change. Foresters advocating assisted migration are typically not aiming to save specific species — instead, by moving trees, they want to help sustain productive forests for multiple benefits such as carbon storage, water filtration, wildlife habitat, recreational beauty and timber.

Experimenting with assisted migration calls for a different way of thinking about nature. Whereas ecological restoration typically looks to the past for cues on repairing degraded places, foresters exploring assisted migration are planting warmer-climate trees that could have a better chance of thriving under warmer future conditions.

Forestry companies have long moved trees around to improve timber production on privately held land. But forest managers have so far been cautious about assisted migration projects for conservation aims on public land. Most of their projects have been experimental and small in scale, typically moving tree populations relatively short distances to the northern parts of their native ranges.

Now, though, assisted migration research for conservation is getting bolder with growing concerns about future forest disruption from climate change. And the movement is growing internationally, with research happening in Spain, Canada and Mexico. Today, Palik’s study is one of 14 research projects in a network named Adaptive Silviculture for Climate Change (ASCC). Most foresters who are experimenting with assisted migration are planting trees farther north or planting trees from lower elevations at higher elevations.

Sites across North America include western larch-mixed-conifer forests in the Flathead National Forest in Montana; diverse pine-hardwood woodlands at the Jones Center at Ichauway in Georgia; spruce-fir forests of the Colorado State Forest; and mixed-pine-hardwood forests of the Petawawa Research Forest in Ontario, Canada. Some Forest Service scientists, including Palik, expect that assisted migration will transition from a subject of research to a standard management strategy.

In line with the trend, the Forest Service and many other federal and state agencies are looking at revising their policies to accommodate this strategy. The US Fish and Wildlife Service, for instance, is considering allowing forestry managers to relocate species beyond their historical range.

Artificially moving a forest, some biologists say, has risks. Relocated species might become invasive or disrupt the ecological balance of the forest. But, says Palik, “the risk of not trying to move species for climate change is larger.”

Diversify or decline

Assisted migration was first proposed in the 1980s when some biologists anticipated that habitat conditions could change too fast for species to keep pace. Recent proposals have called for relocating endangered species to new habitats where they would have a better chance of thriving: Mexican gray wolves to northern Arizona or to New Mexico or Texas, for example, or Karner blue butterflies farther north from southern Michigan.

Palik and other forest scientists, though, are working on a different conservation solution. They want to save stressed forests from further decline or even disappearance by planting large numbers of more southern-climate-adapted trees, thereby diversifying woodlands so their canopies can survive.

“Forests die fast and grow slowly,” says Lee E. Frelich, a forest ecologist with the University of Minnesota Center for Forest Ecology. As climate change continues, he says, some forests could vanish, replaced by encroaching grasslands that do not provide the types of wildlife habitat and other benefits that healthy forests do. “Your only option in that case,” he says, “is to bring in new species or live with whatever nature does,” which — in cases of extreme climate change — “is likely to be brushy vegetation and not be a forest for quite some time.”

Climate change has already contributed to rapid forest losses. In recent decades, forests on every forested continent have suffered intense heat waves and drought exacerbated by climate change, says Henrik Hartmann, an ecophysiologist at the Julius Kühn-Institute for Forest Protection in Germany and lead author of an overview of forest die-offs in the 2022 Annual Review of Plant Biology.

Extremes are a natural part of a forest’s life history, and trees typically adapt to them — but this time is different. “These extremes were enough to bring trees to the edge or beyond the edge of functioning,” Hartmann says.

Cold-winter lands like the Minnesota Northwoods are disproportionately affected by climate change, which is causing shorter winters, drier summers and longer fire seasons.

Minnesota has one of the coldest climates in the Lower 48 United States because it is strongly influenced by the Arctic. But the Arctic has warmed four times faster than the rest of the Earth since 1979, and the state now has the Lower 48’s fastest-warming winters. Since 1970, average winter temperatures in Minnesota have increased by nearly 5 degrees Fahrenheit.

Minnesota is also unusual for having four major plant boundaries within its borders: mostly cold-climate conifers in the Northwoods; temperate deciduous trees such as oaks and maples in the state’s middle and southeast; and former prairie grasslands and aspen parklands, these days predominantly farmland, to the west and southwest.

Now these boundaries are blurring. Temperate deciduous trees have begun invading the understory of conifers in the Northwoods because the warming climate has begun favoring them. Many Northwoods tree species, including red pine, are likely to lose more and more of their livable southern range as warming continues. When Northwoods trees fade from the scene in the southern range, researchers worry that the migration of deciduous trees to replace them will happen far too slowly for healthy, continuous forest canopies to survive.

At the same time, the ecology of the Northwoods is becoming more tenuous. As climate change continues, giant swaths of northern conifers are increasingly likely to collapse suddenly — over just a few years — from combinations of climate-driven drought, insect infestations and other stresses. Many northern native tree species might not grow back there because they would no longer be suited to the region’s changed climate.

Recently, Frelich and his colleagues studied a range of possible impacts from rising temperatures — largely dependent on carbon dioxide emission scenarios — on Minnesota forests by 2070. A rise of 1 degree Celsius above 1979-to-2013 average temperatures would allow broadleaf forests to further invade the Northwoods. With a 6 degree C rise, prairie would cover most of Minnesota, with only broadleaf forests surviving in the northeast corner.

Speeding up nature’s pace

Worldwide, trees move north and south and up and down mountains in long-term response to changing climate, their seeds dispersed by winds and carried by animals.

It can take a millennium for many forests to reach equilibrium in a new location, according to Hartmann. That’s not really a problem for the forests, which eventually migrate; instead, it’s a problem for people. On weekends in Germany, people walk in the hills and mountains and through the forests, which is very popular as recreation, says Hartmann. But now, “They’re all shocked — it looks like the moon, and the forest is dead.”

Waiting for new trees could take a while: Some tree species reach an age of 25 years before making their first seeds. “If we want all of the services [of forests], similar to what we had only a decade ago, then we may want to think about getting a few more options,” Hartmann says. “We should think about conserving a forest and not the forest that we know.”

That’s what Julie Etterson, an evolutionary geneticist at the University of Minnesota Duluth, had in mind when she cofounded the Forest Assisted Migration Project with Meredith Cornett, then of the Nature Conservancy, and David Abazs of the University of Minnesota Extension. Etterson was worried that native tree decline would create openings for invasive plant species and sought a way to preserve forests by gradually moving in southern trees. The Forest Assisted Migration Project aims to build a regional market for climate-adapted tree seedlings grown by local farms and nurseries based on principles of Etterson’s and Cornett’s research.

For one study, Etterson and colleagues acquired seedlings of red oak and bur oak grown from seeds collected in two climatic zones: one in northern Minnesota and one nearer the center of the state. Workers planted the seedlings on 16 sites in two northern seed zones as part of a Nature Conservancy reforestation project, and the trees were measured for three years. Red oak sourced from southern seeds — adapted to a slightly warmer climate — had higher survival, faster growth and other advantages compared with the northern type. Results for the southern bur oak, while more mixed, were also generally better than the northern bur oak.

Etterson’s experiments in assisted migration, done in collaboration with the Nature Conservancy and public and tribal agencies, provide a scientific foundation for including climate-adapted trees in reforesting efforts underway in the state: In 2023, for example, the Nature Conservancy planted 1.4 million seedlings across northern Minnesota as part of a multi-partner goal to have 10 million seedlings planted on public lands by the end of 2024. As they plant, workers select about three-quarters of seedlings in the traditional way — seeds are collected from a climate zone, grown to seedlings in that zone, and planted in that zone, too. The rest of the seedlings come from parent seeds collected in forests farther south.

“We are using the ones that science tells us are in the best position to be climate adaptation winners,” says Chris Dunham, associate director of forest resilience with the Nature Conservancy in Duluth. But they are turning the dial slowly, he says, “because there’s also plenty of unknowns dealing with natural systems.”

The dial is turning slowly for another reason: Nurseries in the state can’t provide enough local seedlings to meet growing demand for “climate-smart” trees. And so Abasz started organizing a broader supply chain of seed collectors, seedling growers and buyers, and set a five-year goal of expanding the Farm & Forest Growers Cooperative to a network of 100 farmers and nurseries to each grow 10,000 southern-adapted, locally grown tree seedlings per year. The program would then expand the number of purchase agreements with restoration agencies such as county forestry departments.

Through all of this, the Forest Assisted Migration Project would recommend which young trees to plant where, designating them as green, yellow or red. The designations are based on Etterson’s research findings, input from experts and different kinds of assisted migration.

Seedlings designated as green are considered safe to plant in northern Minnesota because they already thrive there. Southern seedlings of native species would be planted farther north but within their historical range. This is called assisted population migration.

Trees designated as yellow require more caution. This is assisted range migration — moving species beyond their current historical range to keep up with climate change. This process also mimics what natural seed dispersal might do. “These are species that may be just creeping in our area or have very small populations in our area,” says Abazs, such as Eastern hemlock and American beech.

These southern seedlings are more likely to become resilient trees. Among other things, the climate-adapted trees may bloom earlier in the year and end growth later in the fall, capturing longer periods of photosynthesis.

Finally, trees designated as red by the Forest Assisted Migration Project would be ones that could not naturally disperse seeds to northern Minnesota because the distance is too great. Relocating that category of tree would be considered assisted species migration. Seedlings from southernmost Minnesota or northern Iowa, for example, would be designated as red. “Those are ones that we are not entertaining at this point,” says Abazs.

A lesson from the ponderosa

One of Palik’s relocated species over at the Cutfoot Experimental Forest would have gotten a red rating by those guidelines. But Palik is placing bets on the tree as a future invaluable conifer for northern Minnesota.

Palik took ponderosa pine seedlings from seeds collected in northwest Nebraska, hundreds of miles to the south and west, and planted them in experimental plots for research purposes. Though only a fifth of them lived, the ones that survived have flourished. His experiment suggests that ponderosa pine — a tall, long-needled tree used for timber but adapted to warmer, dryer summers and more moderate winters — could someday thrive in northern Minnesota if red pine falls away.

Temperate broadleaf trees will continue to edge into the Northwoods, but they can’t replace the characteristic pinelands that define how many Minnesotans experience the region, Palik says.

Many forest managers could eventually face a choice: Consider moving southern trees into northern areas, or eventually wind up with fewer productive woodlands for timber and other uses.

It’s imperative, Palik says, that we work to maintain useful woodlands. “The forests at the end of the century are not going to be your grandfather’s forests,” he says. “But they’re going to be the forest your grandchildren inherit.”

Sunday, March 10, 2024

Toward truly compostable plastic

Materials scientists are cooking up environmentally friendly polymers from natural sources like silk, plant fibers and whole algae. Economics and acceptance remain hurdles.

It was hailed as a wonderful thing: During the oil boom in the 1950s, chemists began to render the waste coming out of refineries into plastic — plastic packaging, plastic furniture, plastic fibers woven into synthetic cloth. These were miracle materials, moldable and pliable but strong and lasting. In the decades since, annual global plastic production has skyrocketed: Humans have created 8 billion metric tons of plastic.

That boom has, to put it lightly, brought problems. More than half the plastic ever produced —some 5 billion metric tons — lies smeared across the surface of the Earth. Every day, more than 10,000 metric tons of plastic wash into the oceans. Plastic’s durability, one of the properties that makes this material so miraculous, has rendered it a potent pollutant.

To be fair to the early boosters, plastics have changed the world. So many essential technologies — from motor vehicles to cell phones to computers — use plastic. Foam insulation has helped to make homes 200 times more energy efficient. Plastic films extend the shelf life of perishable foods.

“I don’t like how people demonize plastics as if it is the most evil thing we have ever made,” says Eleftheria Roumeli, a physicist at the University of Washington and coauthor of a 2023 examination of sustainable polymers in the Annual Review of Materials Research. “It is a product of brilliant engineering.”

Rather than abandon this material, she thinks, we need to find a better, kinder version — polymers with the tensile strength and flexibility of modern plastics that are derived from sustainable biological sources and can be effectively returned to the environment.

This means rethinking plastic production from the ground up.

From monomer to polymer

The current approach to plastic production consists of two big steps: first a breaking down, then a building back up.

The breaking down — “cracking,” as it’s known, conducted under high heat and pressure — turns refined petroleum materials into simple molecules known as monomers. These become the backbone of the product that’s built back up. The chains or lattices that result are known as polymers and serve as the basic structural component of any plastic.

But the plastic is not done yet. Next comes the incorporation of additives — colorants and flame retardants and fillers. Materials scientists consider a wide variety of variables, from “hardness” to “tear strength” to “tensile modulus,” that indicate how a plastic fares under different kinds of stresses. The most important additives tune these properties, generally by tweaking the bonds between polymer chains. Chemicals known as plasticizers, for instance, embed themselves between chains, helping to increase flexibility — but, as a tradeoff, making the plastic easier to tear apart.

By mixing and matching polymers and additives, chemists create the final composite materials that are used in food wrappers and soda bottles, as microbeads in cosmetics, even as the flexible hydrogels that, in the form of contact lenses, we affix to our corneas to sharpen our sight. Through chemistry, a single polymer like polyvinyl chloride — or PVC, as it’s often known — can be rendered into rigid stormwater piping or clothing.

Plastic production accounts for as much as 8 percent of global fossil fuel consumption — a figure that could rise, according to one estimate, to 20 percent by 2050. But chemists were creating “synthetic” plastics decades before the oil industry took off, from, among other materials, waste oat husks and vegetable oil. One of the tacks toward more sustainable plastics is to turn back to such biological sources.

In 2006, for example, the Brazilian petrochemical company Braskem launched experiments to see if they could economically render sugar into ethylene, the most important monomer in commodity plastic production. By 2010, Braskem was selling a “fully biological” polyethylene plastic, or bio-PE.

The big upside of this material is that sugarcane will sequester carbon from the atmosphere as it grows. And since, structurally speaking, bio-PE is indistinguishable from its synthetic twin, bio-PE has been easy to deploy in applications such as food packaging, cosmetics and toys.

But being chemically indistinguishable is also a problem. Since polyethylene does not appear in natural environments, few microbes have developed the ability to break its molecular bonds. Bio-PE therefore does nothing to solve the waste problem. Just because something is a “bioplastic,” in other words, does not mean it is inherently sustainable.

“None of these terms are sufficiently regulated or meaningfully defined, which causes a lot of confusion,” says Rachel Meidl, a fellow in energy and sustainability at Rice University's Baker Institute.

Meidl categorizes plastics and their potential substitutes as existing across four quadrants. One axis charts the source of the materials: Some are “biobased,” drawn from biological materials, while some are petroleum-based. The other axis maps the downstream fate: Some materials are biodegradable and some are not. But even a material that lands in the best of these quadrants — both bio-based and biodegradable — is not necessarily a panacea. Being biodegradable just means that a material can be broken apart by microbes, even if the result is small bits of microplastics. The ideal materials are not just biodegradable but also compostable — a narrower category that indicates the material can break down into organic components that are harmless to plants and animals.

Compostability, unfortunately, is not easily achieved. You’ve almost certainly encountered polylactic acid, or PLA, in the form of compostable cutlery and take-out containers. The most common biobased plastic, PLA is technically compostable, but under specific conditions obtained only in industrial facilities that do not yet exist in sufficient numbers. Since most of today’s PLA take-out containers wind up discarded alongside food scraps, composters must waste time sorting out the two.

One way to improve plastics might be to search for better bio-sourced monomers. In 2020, a team of scientists in California reported they had isolated a type of monomer called a polyol from algae-produced oils, then reassembled it into a foam-like plastic that could be used in commercial footwear. The material effectively degraded when placed in soils.

Some scientists, though, think a better choice is to leave behind the standard energy-intensive two-step process of breaking down to monomers and then building back up. The natural world already supplies promising polymers that are all compostable, says David Kaplan, a biomedical engineer at Tufts University. And since they degrade at different timescales, if you select the right polymer or tune it properly, you can create materials to suit varied applications.

Consider cellulose, the most common biological polymer, present in the cell walls of plants. It is essentially a chain of sugar molecules, but these chains are assembled into tiny threads called nanofibrils, which are bundled into microfibers and then into the large fibers that are visible, such as the stringy strands in celery, for example. Materials scientists call this a hierarchical structure.

Synthetic polymers, in contrast, typically are pressed into a hopper and extruded into a homogenous glob. The result is “strong, hard bonds” between molecules, Kaplan says. “Biology doesn’t do much of that.” Instead, biopolymers feature much weaker bonds — typically electrostatic interactions that link the hydrogen atoms in one polymeric molecule to those in another, but at very high densities.

But by better understanding these structures, engineers will be able to improve upon the biological materials. Research has shown, for example, that the thinner a cellulose fiber, the greater the tensile strength, which means the material resists breaking under tension. The increased surface area means hydrogen atoms are better positioned to dynamically create and break bonds between adjoining chains.

Going straight to cells

Once you’ve given up monomers — scratching out an entire step in the plastic production process — why not go further? Some materials scientists are pursuing what Kaplan calls “bottom-up design”: Rather than isolating and remaking individual biopolymers, they use what nature has provided — creating bioplastic materials from whole cells or other biological materials, no breaking open and extraction required.

Roumeli, for example, has mined the promise of algal cells. They’re small, and therefore easily manipulable; they contain large amounts of proteins, which are biological polymers, alongside other useful materials. She and her students took powdered algae and passed it through a hot presser. After several trials in which they varied the pressing time, temperature and the amount of pressure applied — all of which affect the way the molecules bond — they found they could produce a material that was stronger than many commodity plastics.

The material was also recyclable: It could be ground back to powder and pressed again. (The tests showed that the material lost some strength with each generation of recycling, which is also the case for synthetic plastics.) If it were to be carelessly tossed into the dirt, the material would break apart at the same rate as a banana peel.

Kaplan has conducted similar work with silk, long presumed too fragile to be thermally processed. The thought was that the hydrogen bonds would break down under heat and the silk would simply burn. But in a 2020 paper, Kaplan and colleagues demonstrated that pellets of silk could be molded, like plastic, into a tunable material. Since then, he’s found that entire cocoons can be processed this way.

Such materials are a win-win, Roumeli says. They’re renewable and free of fossil fuels and can even soak up atmospheric carbon as they grow. They could biodegrade completely. “The only thing that is not a win is our economics — and our scalability,” she says.

Here is perhaps the biggest problem with this new approach to plastics: Its radical nature means that it’s going to be expensive, at least for now. To make a product cheap, you want to be able to produce it in already existing facilities, since that helps a startup avoid substantial capital costs. But the owners of those facilities are liable to see biological composites as too impure — as “junk,” says Gadi Rothenberg, a chemist at the University of Amsterdam’s Van ‘t Hoff Institute for Molecular Sciences.

Rothenberg notes that in the feedstock used to produce polyethylene terephthalate, the plastic used in soda bottles, only one molecule out of every 100,000 is anything but the desired monomer. Biological materials are rarely so pure.

Manufacturers may also simply prefer to go with tried-and-true over the unexpected. Rothenberg developed his own, plant-based sustainable polymer, which he figured was close enough to standard materials to be an easy, “drop-in” choice for furniture production. But when he first took it to companies, “in the beginning, they didn’t even want to hear about it,” he says. Even bio-PE, the sugarcane-based product that is chemically identical to its synthetic relative, costs as much as 30 percent more to manufacture, according to some figures, and so companies concerned about the bottom line are going to stick with the incumbent.

Today, bio-based plastics make up less than 1 percent of the current market, according to the trade association Plastics Europe. The push for biobased polymers “is not going to go anywhere until it reaches par on economics,” Rothenberg says. Ultimately, he predicts, governments will have to recognize the true, full cost of traditional plastic — its carbon footprint and the expenses involved with cleaning up pollution — before more sustainable materials will take hold.

Scientists in the vanguard are hopeful, though. Roumeli notes that synthetic polyethylene — “the cheapest and most produced and most consumed plastic that we have today” — once was a novelty. Kaplan says he has no doubt that one day, “all these precursors and polymers will be made biologically, or with true circularity in mind.”

“But we’re not there yet,” he adds. The trouble is, with plastic waste accumulating and temperatures rising, we may not have much time to wait.  Knowable Magazine