With the sun rising fast as we approach midmorning, our car moves cautiously up a dusty track surrounded on all sides by an abundant spread of thousands of Cork Oak trees.

These are noble forests where the Cork Oak itself is the keystone species that support a whole web of life both above and below ground. Amazingly, the largest store of subterranean water in the Iberian Peninsula is in the cork forests.

Although nearly all Cork Oak forests are in southern Europe and North Africa, the majority, around 34%, grow in Portugal. In Morocco, Algeria and Tunisia, the cork forests literally face down the Sahara that, to date, has pushed further north as the temperatures around the midlatitudes rise as a response to climate change. 

Drought and fire

The long roots of the Cork Oak stretch outwards in the topsoil and several metres downwards to drink as the heat rises in the summer months. However, it is the bark of the tree, the cork bark, that acts as a thermal barrier to heat stress and protects the trunk. 

Even with the succession of forest fires that have become more frequent and extreme in recent years, the Cork Oak can withstand partial burning and even protect buds that stay pocketed within the bark.

Much of the really extreme fires we see in the news are not Cork Oak but rather Pine and Eucalyptus trees that ignite when densely planted forests catch fire and whip up into blazing infernos. 

This is put into perspective by Amorim Director of Marketing, Carlos de Jesus, when he explains that many people who inherit land often have other careers and are less able or interested in maintaining large tracts of forest. Planting Pine or Eucalyptus can offer quick and often easier returns with less hassle. 

Harvest cycle

There are 732,000 hectares of cork forest in Portugal. These forests have been protected by decrees dating back to the 12th century. Respect for the forests is immense and the workers who harvest the trees are well rewarded for their expertise, being among the most highly paid agricultural workers in the world.

We join a team of contract workers who are moving through the forest performing the delicate ritual of stripping bark. Sun-drenched but focussed, the workman approaches the tree with his axe raised, swinging it with an essential force to pierce the cork exterior without causing any damage to the tree. 

He then proceeds to carefully pull back the bark to reveal a blushingly almost iron-red trunk that will be marked with the number 9 denoting this year. It will then be left for 9 years to regenerate itself for another harvest. This process is as healthy for the Cork Oak tree as it is bountiful for those who make use of the cork itself.

Building materials

We are taken by Carlos de Jesus high up to a restaurant with a sweeping view overlooking the city of Lisbon. The vast River Tagus sweeps down from the East to meet the Atlantic, while the rest of Lisbon undulates in and out of sight. On the way up here, we pass the Lisbon Cruise Terminal, designed by esteemed architect João Luís Carrilho da Graça. 

Carlos explains that during the construction of the Cruise Terminal it transpired that the original designs would have to be modified to incorporate a lighter material. That material turned out to be granulated recycled cork mixed with concrete. This composite formed a creamier textured material, that lost none of its former attributes of strength but reduced the weight load by 40 percent.

With cement used for construction being a major source of global greenhouse gas emissions, finding new more eco-friendly construction materials is one of the challenges for an industry that is must expand in order to meet the demands of our species.

The cork solution greatly impressed architect Carrilho da Graça, who noticed not only that the weight saving was huge, there is “also great insulating capacity and structural capacity of resistance.” 

He also noticed that concrete mixed with cork had the potential to be softer in texture than normal paint or plaster, meaning it meets the aesthetic needs of internal spaces, including those designed for living.

Wine

Retreating a short way from the balcony over the city to the inside dining area, Carlos picks up the cork that has been set aside from the wine we are drinking, holding it up pinched between his fingers. He explains how ten years of R&D at Amorim have developed processes that eradicate trichloroanisole (TCA), also often referred to as cork taint, using a process called NDTech. It was the high rate of TCA that drove so many wine producers to switch to aluminium screw-caps and plastic stoppers instead. 

Globally, this switch has embedded a hugely unnecessary environmental cost onto recycling a bottle of wine.

In the UK alone we consume around 33million bottles of wine per week. Many of those bottles will use screw-cap or plastic closures. There has been a misconception that screw-caps are better for the environment than corks because no trees are harmed in the production process. 

Having witnessed the careful cork harvesting process and visited the Amorim factories, where last year 5.4 billion cork closures were produced, the idea that a non-recyclable aluminium and plastic-lined screw-cap can be better for the environment is laughable. In addition, plastic closures (often called plastic corks) are also the worst kind of solution for closing wine as they are both ineffectual and environmentally unfriendly.

It is estimated that a glass bottle of wine has a carbon footprint of around 300-400 grammes of CO2. When I spoke to Amorim CEO, Antonio Amorim he said, “We can identify that one single cork that has a weight of 5 or 6 grammes can retain 392 grammes of CO2.”

In seeking to quantify the real environmental differences between the plastic, screw cap and cork closures, Amorim commissioned PriceWaterhouseCoopers to conduct a verified audit of all three. Taking greenhouse gases alone, natural cork displayed a massive twenty-four fold advantage over aluminium and a nine-fold one over plastic.

Antonio Amorim puts it this way, “It is not comparable because we have done a product life assessment in between, cork, plastic and screw caps and it is like 25-nil in soccer terms because we are carbon negative and plastics and screw-caps are clearly carbon positive.”

Unrecycled

While digesting the experience of visiting the cork forests and listening to what are the various applications of natural cork, whether newly harvested or recycled, it seemed that chucking our cork closures away is a horrible waste of a valuable resource.

Natural cork may well prove to be one of many ingredients in the future of architecture in the west. It has already been labelled by NASA as Nature’s own polymer and has been used in countless launches into space due to its extraordinary thermal properties. 

Could a willing public conspire with retailers to upcycle corks for increased utility after the wine has long since been recycled? Is there room for this ingredient to be reprocessed to help improve the UK’s building standards of affordable homes in a more circular economy approach we so badly need?

Strengthening defences

Antonio Amorim expressed a growing concern in Portugal that desertification is spreading from Africa into the Iberian Peninsula: “In a country like Tunisia the desert stops where the cork forest starts. Portugal has a programme to replant a bunch of cork trees in the south part of the country because we are afraid that this desertification movement can ramp up from North Africa to the south of the Iberian Peninsula.” 

The life expectancy of the Cork Oak is 150 years but the harvest cycles produce ongoing retention of carbon. Antonio points out that “one tonne of cork produced retains 73 more times of weight in CO2 in retention.”

One of the drawbacks that has slowed cork planting is the period of 25 years before a cork tree reaches maturation and can be harvested. Amorim has started to plant their own forests in the south conducting tests with drip irrigation techniques that demonstrate that the 25-year gap can be closed to 10 years. Another side effect of this is the increase in the survival rate of young plantations. After the first harvest, the irrigation must then be stopped so that the integrity of the cork is not compromised.

Earth stewardship

In recent months we have witnessed from both satellite and land-based footage, the Amazon Rainforest ablaze in what has been rightly categorised a catastrophe for all life on Earth. The task of locking up greenhouse gases from the atmosphere is moving too rapidly in the wrong direction. 

The Cork Oak forests that line the Mediterranean shores, holding back the Sahara desert, offer a glimpse of how the natural world has developed its own materials for withstanding higher temperatures. 

It is speculated that the Cork Oak trees developed their thermal protecting bark at a time when fires were much more prevalent than they have been for hundreds of thousands of years. But we know that temperatures are going up and that fires and deserts are spreading. If we are to take a more custodial approach in respect of our planet, then embracing nature’s gifts is likely the safest route to the future.

This Author

Nick Breeze writes about wine and climate change.  He posts regularly on Secret Sommelier  is an organiser of the Cambridge Climate Lecture Series. He is on Twitter at @NickGBreeze.