Is Cork Sustainable or Is It Bad For The Environment?

is cork eco friendly and good for the environment

I always prefer to buy wine (red wine if you’re asking) that is sealed with a cork rather than a screw top. It’s always seemed more natural to me and the wine always seems to taste nicer inside!  

Around my house, I also have a few cork coasters, place mats and have been thinking about getting a segment of cork flooring. It got me thinking about the material and I soon realised I know next to nothing about cork, where it comes from, how sustainable it is and whether it’s environmentally friendly or not.

After an afternoon researching, I was amazed at what I found out about cork and wondered how I didn’t know this before!? Don’t worry, everything I found out is also here in this blog.

If you’re short of time and are looking for a quick answer…

Cork is a fantastic, environmentally friendly and sustainable material. The cork oak tree is also a really important species within the ecosystem in which is grows, supporting an abundance of biodiversity and physical ecological processes, as well as the people and economies where it’s found.

If you’ve got a little more time and want to find out why cork is so eco-friendly, brilliant. Let’s take a slow scroll through the wonderful world of cork.  

Where does cork come from?

large cork oak tree
Large cork oak tree. Source: Pixabay

Let’s start off with the basics.

The cork that we use for wine stoppers, noticeboards, as coasters for our drinks and for flooring all comes from the same place – the cork oak tree.

Cork primarily comes from one tree, the Quercus suber, otherwise known as the cork oak. This species of cork tree is native to southwest Europe and north Africa and is a member of the same family in which the chestnut oak (Quercus montana) and common oak tree (Quercus robur) are a part of.

The majority of cork that we use in and around our homes is grown from cork oak forests in Portugal and Spain, plus smaller percentages from Morocco, Algeria, Tunisia, Italy and France.

The cork oak tree has evolved to grow a thick layer of bark to protect itself from the harsh conditions (lots of sun, little rainfall, bush fires) of the Mediterranean regions where it grows.

Are cork oak trees grow native to these regions?

Yes, cork oaks are native to the Mediterranean region and have been here for many, many thousands of years. In fact, fossil remnants of the cork oak have been found in the Mediterranean basin dating over 25 million years old and fossils found in Portugal over 10 million years old, demonstrating the trees ancient history in this region.

Naturally, cork oaks grow in mixed forests alongside other oaks, pines species and olive trees, who produce olives and olive oil. Check out my article on the most sustainable cooking oil.

On the Iberian Peninsula, cork oak landscapes are known as a ‘montado’ in Portugal or a ‘dehesa’ in Spain. These habitats combine cork trees with high quality pastures and rotation crops and have been ranked as one of the most valuable habitats in Europe.

The cork oak is an important keystone species in these areas and is thus treated accordingly by people and communities.

Cork trees are so important to the communities where they are grown in Portugal (where it is also their national tree) that they are protected by law and each one is identified and regulated individually. It is a crime to cut down a cork oak tree here and they’ve been protected in Portuguese law since the year 1209!

Cork oak landscape in Portugal with young cork and olive trees, a large chestnut to the left and cherry tree to the right
Cork oak landscape in Portugal with young cork and olive trees, a large chestnut to the left and cherry tree to the right. Source:

Why is cork environmentally friendly?

Growing cork oak trees has been both stable and sustainable for the environment and workers for hundreds of years.

They are considered environmentally friendly for a number of great reasons:

Cork has a positive impact on local biodiversity

Cork oak landscapes have a major positive impact on other plants and animals and can sustain a rich mix of biodiversity.

In such landscapes plant diversity levels can reach 135 species per square metre. The polar opposite of a monoculture. The cork oak woodlands are also home to a high diversity of animals, including a number of threatened species such as the Iberian lynx, Iberian imperial eagle, barbary deer, black vulture and black stork. They also temporarily support millions of migratory and wintering birds.

Cork oak forests are a big carbon dioxide store

All plants absorb CO2 from the atmosphere in order to live and grow. This captured carbon is then stored inside the plant. This is why deforestation is such a problem. In the Andalusian forests, it’s estimated that cork trees store over 15 million tonnes of CO2 alone.

– Cork trees helps protect important ecological processes

The cork oak landscapes also play a vital role in protecting the physical environment and sustaining crucial ecological processes. If you haven’t been before, the Mediterranean is a hot, dry region, particularly in the summer. The cork trees help protect against soil erosion through wind and lowers the water erosion and run off rate.

The environmental services don’t stop there.

The tree tops create a microclimate which prolongs the growing session by creating less extreme environments. The trees also produce a large amount of organic material which rots and enriches the soil, as well as bringing nutrients up from the lower to upper soil levels, which the local vegetation can also access.

All these facts are backed up by scientific reports cited in a 2006 published by the World Wildlife Fund looking at the importance of cork oak trees to the environment and local economies. Have a look at my blog which discusses if WWF are a good charity to donate to.

– Cork trees support local people

Another incredible important aspect about cork oak forests is that they support and benefit local people and livelihoods. The trees and their product have a high economic value, and because of their sustainable nature create plenty of jobs in rural locations over the long term. The cork oak woodlands almost single-handedly guarantee the survival of local communities. This is sustainability in a nutshell – true harmony of nature and people.

How is cork harvested and is cork production sustainable?

skilled worker stripping away bark from cork oak tree
Skilled worker stripping cork from the Cork Oak between May-August. Source: Apcor

Cork trees are grown naturally in their native environment and are left untouched and without interference for their thing for the first 25-30 years of life.

Once the cork on the outside of the tree reaches a certain thickness, the bark is harvested by stripping away layers in late Spring or early summer. It’s done at this time of year as the tree is physiologically active, meaning the cork can be stripped off without damaging the underlying tissue layer.

Once harvested the trees are marked with a date and left to regrow and regenerate over many years. On average the tree won’t be harvested again for another 9-12 years whilst the bark grows back. This is a completely renewable, sustainable cycle.

Producing and harvest cork requires no trees to be cut down. Zero. Once the layer of cork is taken, the tree continues to live and grow. This is similar in the way that latex from rubber trees is harvested, without the need to chop the tree down. You can read if rubber is bad for the environment here and all about biodegradable balloons.

“The harvesting of the bark of the cork oak offers one of the finest examples of traditional, sustainable land use”

World Wildlife Fund

As the cork oak lives between 100 and 300 years, this cycle can be repeated many times and the benefits can be continually reaped. The average cork tree usually yields 40-60kg of cork when harvested but older, larger trees can yield 100s of kilograms.

farmer marking the year of harvest on cork oak tree for 9 years time
Farmer writing the date on the Cork Oak so the date is known for the next harvest in 9 years time. Source: Cork Quality Council

Another plus point for local workers is that cork harvesting from the tree is done entirely by hand. The expert tiradors use a very sharp axe to make cuts on the outer layer of the tree (being extremely careful not to damage the underlying living cells) before wedging their axe underneath the strip and peeling the layer of cork off.

Like all careful crafts, this is a skilled job. Thanks to this, cork harvesting is one of the best paid agricultural jobs in the world!

During the regrowth period, the forest persists in all its glory as the cork oak helps to keep the local landscapes and ecosystems stable, as well as absorbing a large amount of carbon dioxide from the atmosphere.

A study in 2005 by Luis Gil et al found that a harvested cork oak tree absorbs 3 to 5 times more CO2 than one which is not harvested. How good is that?

That’s not all when it comes to wine stoppers and carbon footprints. Let’s consider the alternatives of plastic and aluminium screw tops for a second. A study developed by PWC found that the production of a plastic stopper releases around 10 times more CO2, and even worse was the aluminium stopper that releases 26 times more carbon dioxide that a cork stopper.

Why do some people think cork is bad for the environment?

Let’s start with the elephant in the room (blog). As you’re googling ‘is cork eco-friendly’, you’re bound to find answers telling you that cork is bad for the environment and not eco-friendly.

How can you have two contrasting answers to a fairly simple question?

The problem seems to stem from the harvesting. Many people believe that cork is bad for the environment because the trees need to be cut down to be harvested. This is not true.

Cork trees are harvested by stripping the bark from the lower section of the main trunk, then left to regenerate and grow its unique cork bark again, during which it is constantly absorbing carbon dioxide from the environment.  

Some people also believe that a cork oak forest is a planted monoculture that destroys the local habitat in favour of a economic crop. This also isn’t true. Cork grows naturally and is a native of where it is mainly produced around the Mediterranean basin. As we discovered above, cork oak landscapes have a vast number of positive impacts and benefits to the local environment and ecosystem.

This differs to other common household materials, such as plastic and even silicone, which is often deemed environmentally friendly but is still heavily manufactured. Have a more in-depth read here on whether silicone is better than plastic for the environment.

Why is using cork eco-friendly?

As we’ve seen so far, the growing, harvesting and regeneration of the cork tree is an incredibly sustainable process.

Even better, because the tree is native to the south and west corners of the Mediterranean where the vast majority of the world’s supply comes from, it’s not causing harm to the local environment. In fact, as we’ve seen in the section above, the cork oak landscapes actively benefit all local biodiversity, including both plants and animals.

This contrasts to palm oil trees for example, which are actually native to Africa and were only brought to South-East Asia around 100 years ago and decimate landscapes with their over-powering, carefully managed monocultures.

If we want to get a little bit more technical, cork has a very low embodied energy. This is a value that takes into account all the energy needed for production, extraction and transportation. Compared to a material like concrete or silicone, cork has an extremely low embodied energy.

cork oak landscape in south portugal
Cork oak landscape in Serra do Marvao in Portugal. Source:

Let’s tick off a few frequency asked questions that people often have on whether cork is eco-friendly.  

Is cork biodegradable?

Yes, natural cork is an eco-friendly material that is completely biodegradable. Cork will biodegrade without producing any toxic residues.

Is cork recyclable?

Yes, cork is very much recyclable. When a product, such as a wine stopper, is no longer in use, it can be recycled into other products. I’m planning on recycling my own cork collection at some point into something useful, such as a noticeboard, for the house.

Is cork compostable?

Yes, cork is a 100% natural product so can be composted along with your other organic waste. To compost quicker, cut your cork up into smaller chunks and make sure there is some greenery into your compost mix too. Remember a good compost pile is a mix between ‘brown’ waste i.e. materials that contain a lot of carbon like cork, and green waste such as grass or veg that contains more nitrogen and protein. The composting microorganisms will be happy.

Is cork renewable?

Yes, cork is a highly renewable material. The bark of a cork oak is harvested for the first time when it is around 25 years old, then after that is left for at least 9 years. During this time, the cork naturally regrows and regenerates on the tree.

The average cork oak can be harvested around 15 times over its lifetime over between 100 and 300 years.

The largest and most productive cork oak tree in the world is the Whistler Tree in the Alentejo region of Portugal. Planted in 1783, this exceptional tree is home to numerous birds and has been harvested every 9 years since 1820. In 1991, around 1,200kg of cork was harvested from the Whistler, enough to produce 100,000 cork stoppers!

The tree is still in excellent condition, which goes to show how renewable and astounding the cork tree is. If you’re wondering, the next harvest will be in 2027.

Other benefits of using cork

As if all that wasn’t enough, this exceptional natural material has even more benefits. I’ve listed some of the top benefits below that would all be great on their own, but with cork you get them all!

  • Lightweight – as cork is around 50% air, it is very lightweight. This contrasts to solid timbers which are extremely heavy due to the densely packed fibres leaving little space for anything else. This means any cork product is easy to move around and takes less energy to do so.
  • Flexible – cork is also highly flexible and can be used for a variety of products
  • Soft to the touch – great for household products
  • Hypoallergenic
  • Fire resistant – cork can withstand high temperatures and when it does burn it doesn’t go up in flames as other flammable materials do thanks to the natural materials in contains. This is why it’s been used by NASA in space-bound rockets.
  • Thermal insulator – fantastic insulating properties that keep heat in or out depending on your perspective. Another reason for NASA’s use. Also why it’s a great eco-friendly insulation for your home.
  • Acoustic insulator – in a similar way that it isn’t good at conducting heat, it’s not very good at letting sound through either.
  • Waterproof – of course it’s waterproof, this is why it makes such a good wine stopper! This is thanks to the natural structure of cork, which is not very permeable to liquid or gases.

Even cork that doesn’t pass the quality tests for a wine stopper has another use. There is little to no waste from cork production. Lower grade cork gets collected, ground up and recycled into other cork products or at the very worst, burned for heat.

cork oak wine stoppers in a pile
70% of all cork oak goes into making wine stoppers

With all that in mind, I think you’ll agree that cork is an amazing, natural material. In fact it has so many benefits to both the environment, local ecosystem over 100 of years whilst the tree is kept fully functioning and healthy, it’s one of the greenest, environmentally friendliest materials on earth!

So, at the minimum, make sure your next bottle of wine comes with a cork stopper rather than a screw cap. You’ll not only be drinking a better quality wine (in my opinion), you’ll be helping to preserve the ancient Mediterranean cork oak forests plus all the other biodiversity and ecological benefits that come with this, as well as the local montados, dehesas and skilled workers in business.  

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