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Are Cork Trees Endangered? Things May Not Be What They Seem

Cork bark has been keeping wine fresh for thousands of years but is facing its greatest threat ever: a decrease in demand. The myth of endangered cork trees may be lining the pockets of some while harming fragile ecosystems. So how did the rumor start and is harvesting cork actually beneficial to the environment? Here’s everything you need to know about the culture, preservation, and tumultuous history of cork.

Cork On the Mediterranean

A type of resilient oak tree known for it’s unique bark, the cork oak (Quercus suber) has been sustainably stripped and harvested along regions of the Mediterranean since the time of the ancient Egyptians, Greeks and Romans.

A Non-Linear History

Cork oak bark is known for it’s permeability, buoyancy, insulation and anti-microbial properties along with many other characteristics.

These qualities prompted ancient civilizations to use cork bark material in their shoes, fishing nets, roofs and, most famously, as bottle stoppers. Some cork stoppers have even been found in shipwrecks from 500 BC and in the ruins of Pompeii.

However, the history of cork is not entirely linear. While ancient cultures utilized cork trees extensively, the use of cork bark actually diminished in the Dark Ages. There is not a lot of conclusive evidence as to why cork lost its popularity during this time but it is widely accepted that a decline in trade was most likely at fault.

Making a Comeback

In the 1600s cork became popular once again with the help of a monk named Dom Pierre Pérignon.

Coming out of the Dark Ages, glass makers developed a new method for making bottles that narrowed the necks of the containers and made it easier for them to be sealed with glass or other materials common at the time.

Pérignon had recently been successful in combining black and red grapes into a clear, bubbly wine and needed to find a way to seal his bottles that kept the fizz inside.

One day he observed Spanish travelers sealing their water containers with cork oak bark and adopted this method to fit the narrow necks of the new style of glass bottle. It was a perfect match and the rest is history!

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So What Makes Cork Oak Bark So Special?

The uniqueness of cork bark is determined by two specific factors: suberin and the bark’s cell structure.

Suberin is a waxy substance found in most plants that aids in the regeneration process if a plant has been wounded. However, the levels of suberin found in cork oak trees are extremely high and give the bark its characteristic qualities.

Suberin is permeable which helps the tree prevent water loss and, in turn, makes cork oak bark waterproof, fire-resistant and insulating.

The cells of cork oak bark are distinctive in that they are 14-sided polyhedrons and completely filled with air. When you add suberin to the cork cell structure you get a versatile cell full of air that is permeable (which keeps the air in and the water out), making it a light-weight, waterproof and buoyant material.

Cork Cell Structure
The Cell Structure of Cork Oak Bark. Source: ResearchGate

Fun Fact: The discovery of cells, the building blocks of life, were first observed through cork! A scientist named Robert Hooke noticed the visual airiness of a cork wine stopper and decided to look at it under a microscope. Noticing the open, block-like structures, Hooke named them after Pérignon’s living quarters in the monastery: cells.

The Only Way To Harvest Cork: Sustainably

Rows of Cork Trees in Portugal

The only way to harvest cork bark is through sustainable methods.

Cork trees can grow to be anywhere from 250-300 years old on average, with some cork oaks know to have been over 500 years old. The largest cork oak today is the Whistler Tree.

Standing over 45 feet tall, the Whistler is 236 years old.

To harvest cork, only the bark is taken, leaving the tree to continue growing and regenerating its bark for the next harvest. The trees are never cut down for their cork.

Like a sheep’s wool, a cork stripper, or tirador, uses a special axe to remove the top layer of the bark. The outer bark is skillfully cut by hand and gingerly removed so as not to harm the tree’s cambium layer beneath it.

Tiradores train anywhere from 4 to 8 years before they are fully qualified to strip cork oak trees.

Cork Stripping
Cork Stripping. Source: The Portuguese Cork Association

After a cork tree is stripped, it isn’t touched for another 9 to 10 years until the bark regenerates. Interestingly, this stripping process and the sustainable management of cork oak forests actually contribute to the oak’s longevity.

An initial harvest doesn’t begin until a cork oak is at least 25 years old. Even then, the first 2 harvests are not viable for use in viticulture and are instead sent to be used in other cork products.

Finally, after the initial growth period of 25 years and the first 2 harvests, a cork tree can be labeled as mature and useful for bottling wine at about 45 years old.

See Related: Wildlife Conservation Society

The Heart of Local Economies

Cork harvesting is a long-term investment and cork forests are often passed down through family operations.

The majority of cork oak forests are located in Portugal and Spain. Portugal alone accounts for over 50% of the cork industry and over 70% of cork harvested worldwide is used in the wine industry.

In some Portuguese towns, over 80% of the local population relies on cork for income. Whether they’re directly harvesting cork, using the groves as a grazing ground for herds of sheep, or collecting the oak’s acorns to grind into animal feed, the forests touch almost every facet of life in these regions.

Cork tree farmers must employ sustainable and safe forestry practices to ensure the viability and longevity of their operation. Regular plantings and manual harvesting ensure that cork forests continue to thrive. Caring for the oaks is the top priority of the cork industry.

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The Cork Tree Myth

Today’s wine shelves display several different ways to stopper bottles. From screw caps and crown caps to synthetic or natural corks, the options are endless.

So why is the world of wine moving away from only using traditional, natural cork and how did the rumor of endangered cork trees begin?

The answer is built on compounding misinformation leading to a modern-day Dark Age.

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Introducing the Screw Cap

In 1964, an Australian winery director named Peter Wall wanted to reduce the risk of cork taint and commissioned a company to invent the current aluminum screw cap.

Wine Screw Cap

Cork taint can give wine an unpleasant or moldy flavor. It is the combined result of a bacteria or microbial infection of the cork that produces a compound called Trichloroanisole (TCA) and sub-standard quality control practices during processing. TCA is what gives tainted wine its unwanted flavor.

While cork taint in the 1960s affected less than 2% of all bottles from Europe, it was more common in Australia, affecting almost 5% of bottles there.

Experiencing higher rates of cork taint, Peter Wall’s desire to find a way to negate its impact on his operations led to cork stopper alternatives that not only reduced the risk of taint but were also extremely cheap.

Today, the cost of a natural cork stopper can be up to $1.50 whereas a metal screw cap is less than $0.20.

It should be noted that since the 1960s a lot of research has gone into cork taint and it has been discovered that TCA can not only be found in cork but in wooden barrels and other containers as well.

This means that if TCA is present anywhere in the wine-making process, cork taint can still affect bottles that have non-cork closures. With this knowledge, today’s current cork taint numbers affect less than 1% of all bottles worldwide.

See Related: Australasian Organizations

The Misinformation Campaign Begins

When sampling wine in a restaurant, it is tradition to smell the cork.

Wine Stoppers

This action stood at the beginning of Peter Wall’s difficulties as there was no cork to smell from a screw-top bottle. Consumers needed to be encouraged to look past the screw cap’s cheap and untraditional function.

The profitability of bottling wine by cheaper methods gave birth to two pieces of misinformation: that screw caps were better for wine and that cork trees were endangered.

Wineries in the late 20th century began to tout the supposed benefits of screw caps as a way of validating the cheaper closures. Today, the debate still rages whether corked or screw tops are better for the taste of wine. Personally, I can’t tell the difference in taste and there is proven science on both sides of the argument.

But the perceived differences in taste of the screw cap over cork weren’t enough to convince everyone. This led to manipulation of information geared toward the growing conservationist movement.

By claiming that cork oak was an endangered tree species (it’s not), western wineries utilizing screw caps actually garnered false sympathy for cork oaks in the Mediterranean. This led to a decline in demand for cork.

However, wineries were not necessarily lying to consumers, adding to the confusion surrounding the myth of the endangered cork oak tree.

As mentioned previously, the bulk of the cork industry is located in Portugal. Cork has been essential to the Portuguese economy, culture and environment for hundreds of years. Some forms of protection for cork oaks have existed in Portugal since 1259.

During the industrial revolution, Portugal, along with the rest of the world, underwent extreme changes that affected society, led to a population boom, and repurposed swaths of land.

Worried that cork forests would be chopped down and replaced for a faster-growing cash crop, affecting the livelihoods of its citizens and the economy, the Portuguese government implemented stricter laws on cork conservation. These protections are still evolving today and it is currently a crime to cut down or remove cork oaks in Portugal without permission.

The extensive laws and protections surrounding Portuguese cork oak have been interpreted by some to signify that the tree species is endangered. Again, this is false, the IUCN Red List states that cork oak lies in the “least concern” category for endangerment as management for the species is currently in place.

The management the IUCN refers to is actually the manual harvesting process of cork oak groves maintained by humans.

A Convoluted Narrative Continues

As consumer demand for cork began to suffer among wine enthusiasts in the 1990s due to misinformation, some key events helped to solidify the myth.

In 1993, some sensationalist articles like this one from the LA Times, drew attention to a disease that started affecting cork oak trees in Portugal. It claimed that the spreading disease would spell the end for corked wine once and for all.

In reality, while the disease did some considerable damage in the early ’90s, several case studies helped to stem the worst of the predictions. Today, with better forest management for the cork oak tree, that crisis has been averted.

Additionally, as the climate crisis and environmentalism theories gain more traction today, it seems counterintuitive to think that consumer demand for a tree-product would actually help the tree. In reality, this is exactly what cork oak forests need.

The Environmental Benefits of Cork Oak Forests

The majority of cork trees grow on the Iberian peninsula and have been managed since Portugal introduced the first laws protecting them in the 1200s. This puts cork oaks at the very beginning of modern environmentalism.

Portugal Cork Oaks
Cork Oak Forest. Source: Britannica, Josef Muench

Cork Oak Trees: The Last Stand

Cork forests are also found along desert regions of the Mediterranean in Northern Africa and Southern Europe. Cork trees are resilient, requiring little nutritional soil and are able to survive droughts by lowering their metabolism.

Due to the effects of global warming the Sahara Desert has been growing each year, consuming the viable land around it. Able to survive in arid conditions, the roots of a cork forest maintain water and help to keep sandy soils from eroding or sending areas into a state of desertification.

Cork trees growing in these regions act as a last line of defense against the encroaching desert.

Wildfire Prevention

Climate change is not only affecting arid regions of the world but is increasing the risk of wildfires everywhere. For people on the Iberian peninsula, cork production actually helps prevent the devastating effects of wildfire.

Part of the cork grove management process includes removing shrubbery and excessive amounts of biomass that could be used as wildfire fuel.

While the cork oaks are fire-resistant, hardly any other plant in the area is and when combined with an arid landscape and global warming, areas left unmanaged could spell disaster for communities in the region.

Protecting a Rich and Diverse Ecosystem

It’s hard to find anything on our planet today that hasn’t been touched by humans. We’re polluting our oceans, chopping down forests for development, and giving back less than we take. But human-shaped landscapes like cork oak forests can maintain large areas critical to biodiversity.

Mimicking a natural ecosystem, cork oak forests are biodiversity hot spots along the Mediterranean.

They help to protect endangered species such as the Iberian lynx, Barbary deer and the Spanish imperial eagle as well as several threatened plant species.

See Related: How Do Animals Adapt To Their Environment?

The Carbon Question

One of humanity’s greatest challenges today is to slash the amount of pollutants and CO2 we release into the air each year. So what is the carbon difference between cork and alternative plastic or metal wine caps?

Besides being completely free of pesticides and chemicals, cork trees and forests are estimated to retain 14 million tons of CO2 annually.

Living hundreds of years, cork oak trees are big contributors to the fight against climate change. On top of that, a single wine cork can retain about 112 grams of CO2—a net positive.

Aluminum screw tops, on the other hand, are produced with the highest carbon footprint out of all wine bottle stoppers. The processing of all aluminum products is estimated to produce over 70 millions tons of waste and pollutants every year.

Screw caps are even worse because they’re usually lined with Polyvinylidene chloride (PVDC), a type of toxic plastic that’s been banned in many Western European countries.

Cork Consumption Supports Environmentalism

The uniqueness of cork is not only found in its characteristics, but in its approach to environmentalism as well. It is, perhaps, the only species that benefits from consumer demand and it’s not just the cork trees that benefit but the entire ecosystem they blanket.

As the endangered cork myth dissipates, a growing number of creative cork products are entering the market and replacing plastic and metal products.

These range from cork yoga mats to shoes to fishing rod handles and even flooring. Vegan fashion is introducing cork handbags, wallets, and home products. Cork is even being used as insulation in spacecraft!

Most importantly, there’s a resurgence in cork wine stoppers. The wine tasting debate will continue to rage but the environmental debate has a solid outcome: buy cork.

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Are cork trees endangered species?

Cork trees are not currently considered endangered species. They are, however, threatened by a number of factors, including climate change and the increasing use of alternative materials. Cork is a sustainable and eco-friendly material, and efforts are being made to ensure the continued health and survival of cork forests.

Is cork really sustainable?

Cork is a sustainable material that is harvested from the bark of cork oak trees. The harvesting process does not harm the tree, as the bark grows back and can be harvested again in the future. Additionally, cork forests provide important habitats for a variety of plant and animal species, making the use of cork a sustainable choice for consumers and industries alike.

Do cork trees grow in the United States?

Cork trees do not grow naturally in the United States. They are primarily found in Mediterranean countries such as Portugal, Spain, and Italy. The bark of the cork tree is harvested every 9-12 years and used to produce cork products such as wine stoppers and flooring.

Can you harvest cork without killing the tree?

Yes, it is possible to harvest cork without killing the tree. The process involves carefully removing the outer bark of the cork oak tree, which regenerates over time and can be harvested again in the future. This sustainable method of harvesting cork ensures the longevity of the tree and the surrounding ecosystem.

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