New milestone for Stellenbosch terroir initiative deciphering regional identity

New milestone for Stellenbosch terroir initiative deciphering regional identity

Unique terroir is a feature of almost every wine, but what does this mean exactly? A new booklet on Stellenbosch terroir highlights work being done to get more clarity.

“We’ve been trying hard to tie together the typicity of Stellenbosch, and this is part of the process,” said wine routes manager Elmarie Rabe at the booklet’s second volume release in early August.

As with the previous iteration, the publication provides statistics including defining co-ordinates, total area, number of vines, temperatures, and rainfall. The meat of it, however, lies in contributions on an array of related topics, including:

  • geological and cultural history;
  • common soils of the region;
  • typical organoleptic properties of Stellenbosch wines;
  • variation in these properties as they apply to varieties in specific areas; and
  • star cultivars, vineyard age, socioeconomic sustainability and vintages.

Among the organisations contributing to effort are the UCT Graduate School of Business (GSB) and School of Management Studies, Vinpro, SAWIS, Elsenburg Agricultural Institute as well as the Chenin Blanc Association, Old Vine Project, Pinotage Association and Stellenbosch Cabernet.

“Around the world, terroir is important because it lends identity,” said Dr Jonathan Steyn of UCT GSB. “We’re seeking commonality with what makes Stellenbosch unique and what informs the taste profile and varieties, because no one identity should rule.”

The outcome should be a quick reference and consistent tool about Stellenbosch terroir, he said.

“Terroir is about shared beliefs and people recognising a place over time for what can be replicated. it’s about taste too and therein lies the difficulty: how to identify the essence, human intervention and savoir faire.”

Also speaking on the day, viticulturist Dr Etienne Terblanche declared: “It’s an exciting time to be in research. For the first time we have this massive interpretive data set at our disposal. “South Africa’s fine wine category is only some 25 years old, and it has been a very important period”. He added that new understanding makes it possible to change traditional views of South African wine. 

A history of perspective

The French concept of terroir rests on three pillars – the physical environment, the biological environment and know-how – and has been built over many generations,” Dr Terblanche said.

“When terroir research got underway in South Africa some 20 years ago, the focus was purely on the physical environment. We quickly realised that trying to fast-track know-how built over centuries in Europe is a really costly thing to do. It’s the reason this kind of research eventually came to a halt.”

Improved technologies however, soon led to fresh insight thanks to lower-cost and easily accessible spatial data via Geographic Information Systems (GIS) and great local specialists.

“The only missing link is data of the wines and cultural impact,” he says, adding an example. “Producers want to know about which varieties to plant where, with the general notion being to decipher terroir. But that completely excludes the cultural and human factor.

“It’s the trick we’ve been missing.”

Dr Terblanche says the void needs to be filled through interpretation of terroir, “because it’s not a scientifically clean-cut laboratory system where if you have this you get that”.  

“If you reduce wine to that it becomes like any other product.”

The formation of the Cape landscape

A cornerstone of terroir is geology, a complex field that understanding can help to challenge traditional beliefs. “For example, South Africa has a young typicity wine culture with ancient geology as opposed to Europe’s old culture and young geology,” says Dr Terblanche.

“In geology, the lines are blurred and there’s no clean cut because of the changes that happen over millennia.

“To understand the region, you have to start with Pangea – the supercontinent from which came Australia, South America and Africa.”

The sedimentary shale soils of today were formed in the massive Adamastor lake as particles settled over 560 million years ago, creating a layer of some six kilometres thick. The lake covered most of the area that is the Cape peninsula.

During that time, the region experienced the intrusion of granites – where granite welled up through the rock without breaking through the earth’s mantle. Massive erosion followed, with the softer shales eroding faster than the granite.

At a point some 200 million years ago, the Cape orogeny – or formation of mountains through upward forces – began to take place. Continental plates crashed into each other, creating the Cape Fold Belt.

This upwelling essentially placed granites and shales in one layer with sandstone deposits at the top.

“Sandstone forms the top players of our soils,” Dr Terblanche said.

The period was followed by glacial movement, thawing and increased erosion. “Now we are in an extremely eroded situation and it’s very interesting for places like Stellenbosch.”

The situation in Stellenbosch

In other parts of the world, Dr Terblanche said, valley soils are generally the richest soils. “In Burgundy, for example, no-one wants to plant there because growth is too vigorous. In our case, we’ve passed that point. Weathering and erosion have exposed the lovely koffieklip on the valley floor that makes very good wines.  

“Our mid-slopes are generally where the vigorous soils are, and our valley floors are lower vigour soils. Everything has changed since the mountain building and soil forming.”

The soil composition relates to textures, he says. Sandstone erodes to a sandy profile. Shales are predominantly clays and erode to clay soils. Granite is the balance. It has coarse fragments and clay, which means it can erode to a duplex soil.

The soil composition in turn, links to how plants get water and “this is the most important thing in terms of talking about terroir expression,” Dr Terblanche says.

“The interaction of the plant with the soil is how it accesses the terroir. It is how the plant sends signals from its roots to the above grown structure to initiative its various biological actions.

“That timing compared to the timing of the climate at your specific site is what gives you the foundation of terroir grapes. The winemakers now need to make magic in terms of culture – know-how – to match what they’re getting with what they can produce.”

He adds that every part of Stellenbosch has all three soil types, but that it’s the combination of elements such as hills, proximity to the ocean, solar radiation and rainfall that create a particular expression.

Blowin’ in the wind

In defining Stellenbosch terroir, producers have also drawn on research into amongst others, the effects of ocean breezes.

Dr Terblanche highlighted a study of the early 2000s by French researcher Valérie Bonnardot and her team that used a weather station in Stellenbosch. “The first thing she noticed is that our summers are much cooler than expected, given our location at 32° latitude,” he said.

The cause was the influence of the ocean. Extensive air movement from False and Table Bay that occurs mid-afternoon reduces temperatures by three to four degrees Celsius.

“The effect reduces the further you are from the sea, but the shape of the Stellenbosch valley allows penetration to be measured across the region.

“The advantage of cooler weather means the plant enters band of temperature that encourages dedicated development of secondary metabolytes – the flavour compounds and the colour. The more time it can spend in that band, the more concentration there is and the more interesting the wine.

“The team also discovered that the increased humidity associated with the breeze brought coastal haze that not only contributed to reducing temperatures, but also reduced solar radiation, which is very positive.”

  • The Stellenbosch Terroir booklet is available from the office of Stellenbosch Wine Routes, situated at 47 Church Street, Stellenbosch.