Terroir
“No other major civilization in Europe or elsewhere has ever valued the soil more than the French or associated it more intimately with the good.”
– Armand Fremont
Terroir
No less authoritative a wine writer than Jancis Robinson has called terroir an untranslatable French term. I beg to differ. It is one of the metaconcepts of fine wine. And, like so many of the most interesting ideas in wine it resists a simple definition. While it is a subtle and illusive quarry, it is no less real because of that. It is certainly not exclusively within the provenance of French winegrowers or thinkers. The best scientific work on terroir to date was done by a group of German researchers studying Riesling[1]. There remain many misconceptions of what constitutes terroir, and there is even less consensus on what a simple definition would consist of.
Terroir has from the beginning been a concern of producers, critics and academics more than of consumers. For terroir to be perceived wines must be relatively free of flaws and consistent bottle to bottle. Terroir is a characteristic of a group of wines. It is a regional characteristic and individual bottles contribute to it without having it per se. A bottle of wine reflects terroir without containing it. Not all wines are capable of expressing terroir. It appears to be most closely associated with wine’s aromas, and it has been demonstrated scientifically more often in whites than reds. The modern concept and system of appellation is underlain and supported by terroir, and a brief history of the development of appellation will help to show how terroir arose as a theory in fine wine. Part and parcel of this is also a discussion of how critical writing on wine arose historically.
A Brief History of the Concept
Terroir is a relatively recent word even in France - its country of origin. In English speaking countries the understanding of the word is even younger. The general concept that different regions made wines of variable type and quality stretches back 4,000 years to the pre-classical world of ancient Egypt where wine was recorded to come from various locations and to be classified into at least two quality categories. By the time of the Roman Empire it is known that fortunes were being squandered on food and wine, but little discussion of their relative quality survives. Given the nature of winemakers we can assume that from the beginnings they observed that some sites produced better wines than others. Wine as we understand it today was an ephemeral thing to the ancients. It is likely that it was only available shortly after the harvest given what we know about the storage and preservation techniques of the time. The well documented practice in ancient times of adding flavorings and water to wine indicates a drink that was not all that attractive in and of itself.
By following developments in several areas we can roughly outline how terroir became important as a concept in the 20th Century. Wine laws and wine criticism are the two main areas that support the existence of and aided the development of the idea. Some technical developments were needed before quality was consistent enough for terroir to be observed. Most of the changes that allowed terroir to emerge originated in the 19th Century.
It is extremely difficult to find any specific comparative writing about wine prior to 1800. That does not mean that comparisons were not made only that they were not crucial enough to have been recorded. In 1816 this begins to change when Andre Julien a Burgundian topographer published his encyclopedia which examined wine regions, varieties and relative quality[2]. In this work he not only described regions and their wines, but most importantly utilized a ranking of five quality levels within regions. His categorization of Bordeaux properties had a large effect on the later seminal 1855 classification which has survived in modified form to this day. Julien worked in the wine trade, which from the beginning has been the breeding ground of some of the best thinking and writing about wine.
It is not coincidental that in the 1820’s the first machine capable of molding glass bottles was developed in England. For a subtle aspect such as terroir to be discovered and accepted wine needed a vessel in which its quality could be protected and preserved while it negotiated the normal channels of commerce. The cork stoppered bottle was just that container.
Shortly after Julien’s work in France Cyrus Redding, a journalist, published A History and Description of Modern Wines in London in 1833. This was the first important wine book published in English. While Redding fancied himself a poet his contemporaries preferred his writing on wine and it is this which has carved out his niche in history. He includes details on the production of wine as well as on the quality of the wines themselves.
The 19th Century also saw the publication of many books on specific wine regions such as Jules Lavelle’s landmark Histoire des Vins de la Cote d’Or in 1855 the same year as the Bordeaux classification. In some ways Lavelle’s book though not as well-known was more important from the perspective of terroir. In it he observes the connection between the soil and the expression of flavor, which is one of the central tenants of terroir. Lavelle was a professor of medicine at Dijon and also published works on Botany[3]. The majority of these early wine publications that dealt with specific regions were largely statistical in nature, and rarely judged relative or comparative quality of the wines. Travel guides to wine regions were the most popular wine publications through the 19th Century. The appetite for this class of wine books has not diminished with time.
Beginning with the legal designation of certain sub regions of the Douro in Portugal in 1750 governments began the demarcation of appellations. Over the next 150 years the wine trade routinely paid more for wine from certain sub regions than others – up to three times the price paid for ordinary wine of the region. It was also during this period that the average citizen first had access to good wine. Naturally the wealthy and aristocratic who wished for better quality wine supported the classification and demarcation of the best sites[4]. Wine was largely categorized by price, and this in turn led to widespread fraud. In response to this producers in both Chablis and the Medoc formed syndicates in 1900 to protect their reputations for quality and price[5]. Champagne which was frequently the victim of fraud was an early adopter of a trade syndicate as well. The French government followed the lead of the producers and began enacting laws to protect the quality of agricultural products in 1905. This lead to the AOC regulation of appellations in the late 1930’s which codified the vineyards of France.
In the early 20th Century wine writing also evolved. In England writers such as H. Warner Allen emerged from the wine trade and began reporting in depth on the quality of individual producers and wines. Andre Simon served a similar role in the United States. In many ways this period of wine writing from the turn of the century until the 1970’s was a golden age characterized by highly literate and urbane writers with deep knowledge and connoisseurship based on their experiences in the wine trade. Even a hundred years along it remains worthwhile spending time with their books.
In the 1960’s and 70’s both Germany and Italy enacted appellation control systems or significantly reformed their wine regulations. Their systems were primarily focused on assurances of origin and authenticity and less on the grading of wines within regions as was applied to the most prestigious French appellations. It is no coincidence that the concept of terroir arose in France where gradations of quality within regions also had its origin. Appellation systems offer support to the concept of terroir that sites have specific unique flavor effects, and that a hierarchy can be established between similar sites. These systems show association, but are not a direct proof of terroir in the scientific sense. This would have to wait until the very end of the 20th and the beginnings of the 21st Century to be proven under the rigorous standards of modern science.
Terroir in France
From as early as the 17th Century the concept of terroir has existed in France. An agriculturist of the time Olivier de Serres stated, “The fundamental task in agriculture is the understanding of the nature of their terroir.” The idea was further elaborated during the 19th Century, a period in which there was great interest in all aspects of geography. The geographer Vidal de la Blanche was instrumental in the elaboration of many of these concepts linking soil with the culture of cuisine. The creation of the Cru in Bordeaux for the 1855 Paris Exhibition was a natural outgrowth of this interest in categorizing sites by quality.
The battles to establish and protect the commercial values of specific regions through the appellation system further strengthened the idea that wine is more than a product with certain characteristics, but rather an expression of a unique soil and region. While this has undoubted economic value to the producers and landowners, it would be cynical to attribute the development of the ideas solely to their commercial advantages[6]. It was no coincidence that wine was the product the created the appellation system, though other products such as cheeses and olive oil would follow. Wine shows the character of its origin when carefully crafted, and it is stable and slowly developing enough to allow the time to compare and consider that character.
Terroir in English
While the word itself has been used since the 1400’s to refer to the soil of an area, the use of the word terroir in English to express a sense of the ecology of flavor or the typicity of site is quite recent. If you look at wine publications in English from the 1960’s and 70’s such as Hugh Johnson’s or any of the other important writers there is no mention of terroir whatsoever. The only mention in English that I am aware of through the 70’s was Michael Broadbent’s mistaken use of it as a term for dirty or unpleasantly earthy wine. By the 1980’s a more correct use of the term was starting to emerge especially in books about Burgundy. In these one found references to terroir as the influence of the soil. With time the concept expanded to encompass not just the soil but all the specifics of the site as influences. Some of this confusion is of course semantic as we refer to terroir as both the flavors resulting from the site, and as the unique characteristics of the site itself. Terroir can be used correctly to describe both the physical characteristics of the site and the flavor expression in the wine that is a result of the site.
Matt Kramer defined terroir as “somewhereness” in his important book Making Sense of Burgundy. Andrew Jefford calls it “placeness”. While these are both succinct and essentially the same, they don’t say enough. Peter Sichel says it better when he states, “Character is determined by terroir - quality is determined largely by man.” By the early 1990’s John Gladstone’s definition in Viticulture and Environment correctly defined it from a viticulturist’s point of view as “the total natural environment of the vine”. It was a short step from here to expand the definition to the suite of flavors produced by a unique environment at which point the English speaking world and the French were in agreement as to what terroir is.
Proving Terroir
“Terroir as a concept is well established, but still ambiguous.”
For quite a long time terroir, somewhat like belief in God or biodynamics, had to be taken on faith. When I began making wine in the late 1970’s most new world winemakers were more convinced that climate and technique were the predominant factors underpinning quality in fine wine. The French’s obsession with soil seemed quaint at the time, and their generally antiquated winemaking was part and parcel of the distain that was felt for their concepts. Fortunately winemaking forces one to constantly question basic precepts, and it is now rare to find a good winemaker worldwide who does not believe to some degree or another that terroir exists.
It is important to state what terroir is not as well. It is certainly not expressed by all types of wine. It is not the universal armature that supports fine wine. Certain technical and stylistic decisions can obscure it even in wines where the expression of terroir is possible.
Anecdotal Evidence of Terroir
“Wine inarguable displays the strongest geographic signature of all agricultural products.”
– Matthew Goddard
The concept of terroir would not have arisen without some basis in fact. I am sure that from the beginnings of winemaking there have been associations in the minds of the producers between certain sites and certain trends in flavor. One of the strongest supporting arguments is the economic one. Using Burgundy, one of the world’s oldest winegrowing areas as an example. In Burgundy there are tenfold price differences in wine produced from nearby plots of land which have similar if not identical viticultural and enological treatments. It seems unlikely that this would have happened without some real differences between the wines based on their location. And what differs between the locations is primarily soil. This pattern exists in many other winegrowing regions as well.
It is worth examining some specific tastings and producer based trials before moving on to look at the scientific studies supporting terroir. I personally recall some tastings in the early 1990’s that were illuminating to me about the nature of terroir. The Carneros Quality Alliance had been asked by the California Wine Institute to host a group from the Japan Sommelier Society. We were asked to present California Pinot Noirs to this group of professional tasters. Acacia, where I worked at that time, was the hosting winery. Several local winemakers besides me joined in the tasting. We presented three flights of six wines each. The wines were grouped by region, six each from Carneros, Russian River and Central Coast. All were from the same vintage and selected from the top producers of the region. When the wines were tasted as groups it was apparent to all tasters that there was a regional flavor or terroir that distinguished or identified each group. Yet, the next day when the same wines were re-tasted in a random blind array by the winemakers who had participated in the first tasting, none of the winemakers could with certainty identify which wine was from where. The regional terroir that had been obvious when the wines were poured in groups was too subtle an effect to allow the winemakers to identify the individual wines when they were not grouped. If we had only tasted these wines in random blind flights we would have concluded that there was no regional terroir that you could group them under. Yet, we all recognized that terroir when tasting the wines as regional groups. I concluded from this that the regional terroir did exist, but that it was a property of a group of wines and not of a single wine. Also, that the expression of terroir was subtle, and difficult to discern in any one wine with any certainty.
I had a similar experience when tasting in Burgundy. A day spent tasting in Volnay followed by tastings in Pommard and Beaune left me feeling like I knew and recognized what the terroir of these villages was yet I also knew that if I was given a random wine from any one of them blind that my chances of correctly identifying it would be slim. I began to be much more circumspect in my use of the word terroir, while still believing it to be real.
There have been several instances that I am aware of where winegrowers traded grapes in order to informally test whether it was the source of the fruit or the hand of the winemaker that was dominant. In Burgundy it was observed that Volnay made in Gevrey ended up tasting more like where it was made than where it was from. This effect could be termed the sociology of terroir. There is an old saying that we learn how to farm by looking over the fences of our neighbors. The same can be said of winemaking. A local community of winemakers will over time come to an informal consensus of the best way to make wine, and what the local wine is supposed to taste like. This consensus is never absolute, but does have an influence on the general style. We are social creatures by nature and this aspect of terroir must be kept in mind.
Similar casual tests of terroir were made over the years in California as well with mixed results at best. The most comprehensive of these was certainly The Cube Project. This was undertaken beginning in 2010 by three wineries; Bouchaine in the Carneros region of Napa, Anne Amie in Oregon, and Lincourt in the Central Coast of California. Each year for three vintages each of the wineries would harvest a selected block of Pinot Noir and send portions to the other two wineries and keep a portion for themselves. The choice of picking date was determined by the winemaker on site so that aspect of winemaking was constant for each site each year. All three winemakers made wines from all three locations each year. There were no constraints on the winemaking style imposed on the individual winemakers. So, each vintage nine wines were made which could then be compared. This was continued over three harvests so that vintage variations could be taken into account for a total of twenty seven wines. This project was conceived at the Steamboat Pinot Noir Conference, which has been held at the Steamboat Inn in Oregon for three decades. The resulting wines were shown as they appeared and at other winemaker technical conferences and assorted consumer and trade tastings.
It is difficult to summarize a project this complex in a few sentences, but some of the observations support other work on terroir being done under scientifically controlled conditions. In 2010, the initial year, winemaking seemed to trump the effects of location. The following year saw the opposite with the vineyard sites overwhelming the effects of the winemaking. It was observed throughout that seemingly slight differences in winemaking led to profound effects on the expression of terroir. The flavors of the wine were dynamic especially in their youth and with bottle age the terroir seemed to show more clearly. The specific conditions of the fruit in each vintage informed the winemaking decisions and the winemaking changed the wine’s expression of the vineyard flavor so vintage effects on terroir were amplified as a result.
When these wines were presented to professional tasters in blind random order the vast majority of tasters could not “solve” the matrix of which wines were from a given terroir or winemaker’s hand. This was similar to the more general tasting by the Japanese sommeliers cited above.
Scientific Evidence
Qualitative studies first demonstrated terroir’s reality. These studies employed descriptive sensory analysis to investigate the existence of terroir. They asked if certain words would reliably be used for wines from one region over another. Several studies found this to be true - which is a qualitative proof of terroir. In 1995 another level of proof emerged when a cooperative research project between the Carneros Quality Alliance and Enologix, a private wine consulting company, demonstrated the first quantitative proof of terroir[7]. A group of winemakers were used as the expert tasters. Ten terms for aroma of the wines were developed and then analysis of the volatile chemistry of the wine was carried out. After statistical analysis it was found that the concentrations of the chemical compounds correlated with the descriptive sensory analysis and showed that that there was regional distinctness and uniqueness between wines from different areas. Research such as this where both sensory analysis and chemical analysis of flavor correlate with region are the gold standard proof of terroir. This was the first such study to accomplish this, and in essence was the first robust scientific proof for a concept that had been fermenting for many years.
Scientific work has continued on terroir. If we look at only those studies where both qualitative and quantitative data agree, almost all of the proofs have been accomplished when white wines were studied. One of the few such studies finding terroir in reds was conducted using French Grenache. Grenache is known to be a lighter aroma driven red wine. It appears that terroir is expressed by aroma, and that it is a characteristic expressed more lucidly in lighter bodied wines. Most of the studies examining the phenomena in red wines failed to find evidence of terroir. This conclusion from a French study examining terroir utilizing Cabernet is typical, “Terroir is not a permanent combination. Rather it is an effect overridden by vintage and climatic effects.”[8] Another French study has one of my favorite titles of all time; “Typicality Related to Terroir from a Conceptual Perceptual Representation – Study of Links with Enological Practices”. Their conclusions were threefold and quite enlightening.
Different conceptions of the ideal wine by winemakers makes consensus of style impossible.
At the same time all appellations within France are supposed to be based on a supposed consensus of ideal regional flavor.
When tested with red wine in this instance winemaking influences overwhelmed the geographical influences (terroir).
Conclusions such as this appear to call into question the entire French AOC system. But not so fast[9]. There are other aspects to consider. Modern winemaking has made for far tastier wine in general. There are fewer flawed wines certainly. This should make terroir more visible as there are fewer off notes to obscure it. But counteracting this trend is the ability of the average winemaker to make fuller riper red wines. Because terroir seems to be expressed best by aroma in wines with low extract the trends of modern red winemaking towards fuller, riper and more extracted wines is reducing the likelihood of terroir being expressed[10]. Perhaps for many red wines the concept of terroir may be becoming antiquated. The French AOC system and the concepts of terroir and cru[11] that are at their foundations were developed during a time when red wines were lighter and far less ripe than current wines. Advances in winegrowing have made for a different landscape where terroir is not evident in many red wines. This does not preclude its persistence in more elegant classically structured wines.
There have been and continue to be attempts to quantify terroir through the development of mechanistic models and terroir units. The multivariate and subtle nature of terroir has so far hobbled these efforts, and seems destined to continue to defy them into the foreseeable future.
Soil Versus Other Influences
The word terroir originates from the word for soil. In the traditional winegrowing areas of France there has long been an association made between soil and flavor. In many parts of the New World there was the contrary belief that climate and winemaking techniques were the dominant factors in the creation of specific flavor styles, and that soil’s influence was far less important. As we have seen in the preceding discussions both points of view have validity. New World winemakers realized that technique can be the dominant force in a wine’s flavor. Certain European winemakers knew that it didn’t have to be, and when it wasn’t the more subtle effects of soil could be showcased.
For many decades the study of soils, pedology, did not yield specific connections or proofs of terroir yet the belief in the primacy of soils as the basis of terroir continued. Part of this conflict or confusion was the misplaced conception that mineral elements of the soil could be selectively taken up and directly influence the flavor of the wine. The idea for example that a slate soil would somehow create a slate aroma in the wine. This is patently impossible from the perspective of both plant physiology and human physiology of flavor perception. All effects of soil on flavor are secondary as are the effects of other aspects of the site. The only primary flavor effects of a site would be in the case of contamination such as a grove of Eucalyptus trees that permeated the vines with their aromatic oil and directly influenced the flavor of the wine.
Recent work in Germany utilizing Riesling seems to indicate that soil may very well be the most important influence in the expression of terroir. This work was done under the direction of Ulrich Fischer and performed primarily by Andrea Bauer. Numerous scientific publications resulted from it as well as articles about it in the wine media. Riesling was chosen for its known ability to express location. The fact that the wines are not normally influenced by oak or malolactic was also considered positive. The work began in 2004 in the Pfalz and was expanded to other winegrowing areas in 2005. Sites were chosen in diverse regions but which shared similar specific soil types. Wines that were made under controlled conditions by the researchers and wines made under undirected winery conditions were both studied. Tastings were performed by groups of professional tasters. The sensory protocols used were first rate. What they discovered supported the idea that soil type is one of the most dominant influences on aroma and flavor.
In essence they found that the flavors of wines made from similar soils but far apart geographically had more in common that wines made from different soil types that were located close together. This effect was found over multiple vintages and was found in the wine made under normal commercial conditions as well as in the wines made under controlled laboratory conditions. This demonstrated that there are aspects of the site namely the soil type that are not obscured by individual winemaker’s vinification techniques or by vintage variation.
They also analyzed forty-six volatile compounds and found clear grouping of these compounds by soil type not withstanding significant variations caused by vintage and vinification. This quantitative chemical analysis confirms and supports the sensory analysis. This to my knowledge is the first work of its kind to find direct flavor correlations and corresponding chemical compounds with soil type. It was common even a few years ago to hear it said with certainly that the effects of soil are secondary on flavor. This research found that soil similarity is equal to aroma similarity, and that this trumps the location of the soil. That is a soil in the Mosel will give the same aroma as the same soil in the Rhinepfalz. This was true when the winemaking was controlled under laboratory conditions, but also held true when there were differences in winemaking.
Another study conducted in 1998 by the same principal author found that when wines from two vintages, five producers and six vineyard designations were compared in a sensory study of Rheingau Riesling that only in some of the vineyards was terroir the dominant element. In other vineyards the terroir effect was overwhelmed by vintage and winemaking technique. This supports the idea that terroir is both subtle and specific, and does not exist in all locations even in wines such as German Rieslings that are known to be capable of expressing terroir.
Chloe Roullier-Gall working in Burgundy has been investigating analytical differences between Pinot Noir wines produced by the same winery from specific climats that are close together geographically and are on similar soil types. This is searching for the existence of the most subtle aspect of terroir. While the research is in its early stages they have found that the terroir effect is small in comparison to the vintage effect. This is confirmation of what other researchers have found. Another intriguing aspect of their research has been that the terroir effect in these wines is less evident in young wines and that it takes a few years of bottle age before the terroir effects can be demonstrated chemically. This echoes the observations made during The Cube project discussed under practical investigations of terroir.
Work done by Victoria Carey and her group in Stellenbosch South Africa utilizing both Cabernet Sauvignon and Sauvignon Blanc point to the primary role of environmental versus management practices when thinking about terroir. They studied more than twenty sites over seven vintages and analyzed the effect of all environmental and management practices on the expression of terroir. With the exception of clone in Sauvignon Blanc and crop yield in Cabernet all significant factors relating to wine character were found to be environmental, that is terroir based. Gonzalez-Centeno investigating regional character in Spain over four distinct regions using Merlot and Cabernet and multiple vintages found that the regional grouping was agro climatic more than varietal. So in this case the regional character overcame even the variety itself.
Besides work done with the flavor and chemistry of finished wines there has been research aimed at finding terroir in grapes and must. In this work huge numbers of compounds are analyzed and patterns of correlations searched for. Most of this work has been done with red wine varieties. When single vintages have been looked at the correlations have been found mainly by producer and vintage and not by region. This supports much of the work done on wine. However, when multiple vintages have been investigated patterns begin to emerge. A study based on a single clone of Corvina grown in the Verona area of Italy followed seven vineyards over three years and the pattern of correlations supported distinct terroirs. It is interesting to me that no single strong link could be found to any one aspect such as soil or viticultural practices, but rather the linkage was to the general conditions of the vineyard.
Other research on levels of stilbenes such as resveratrol found in red grapes have shown over multiple studies that terroir effects were greater than enological or varietal effects. In general these studies of grapes have found that flavonoids, anthocyanins and sesquiterpenes are the classes of compounds that tend to cluster around geographical loci.
Sarah Knight and Matthew Goddard working with New Zealand Sauvignon Blanc have proposed that populations of Saccharomyces that are regionally specific may be playing a role in the terroir expression of uninoculated wines. They hypothesize and have published results showing that this may be possible. They have published data from only one vintage at this point and used only chemical analysis of micro fermentations without any sensory work or commercial scale wines. Given what is known about the variation in strains of Saccharomyces from vintage to vintage and from ferment to ferment within the same vintage in the same wineries this idea will obviously need further study as a terroir effect must be one that persists over vintages.
In white wines in general and in Sauvignon Blanc in particular yeast plays an inordinately large role in the flavors of the wine, and this argues for a role for yeast in the definition of terroir. Many definitions of terroir already include the influence of the vintner as part of them. Perhaps understanding the role of yeast is best left as an aspect of the vintner’s contribution to terroir.
[1] Andrea Bauer and Ulrich Fischer decades long research into the subject will be dealt with at length subsequently.
[2] Topographie de tous les vignobles connus
[3] When considering the accomplishments of 19th Century polymaths such as Lavelle it makes one wonder if the today’s world is filled with too many distracting pleasures.
[4] Prior to the political and social upheavals of the 18th Century the ownership of the best sites was largely in the hands of the aristocracy and the church and not available to the middle class or the ordinary citizen.
[5] It is interesting to contemplate that the producers themselves were the first to mobilize to protect the quality of their wines, and their actions mobilized the government. While consumers in modern times are often suspicious of producers in terms of purity and quality, such suspicion may be misplaced in the case of wine.
[6] Joseph Capus an agronomy professor from the Gironde who was instrumental in the development of the AOC system in the 1930’s believed that the main flaw of the AOC was that it only addressed provenance. He felt that an assessment of quality and authenticity were equally necessary. Authenticity is here used in the sense of typicity or trueness to type, which is one of the pillars that supports terroir.
[7] S.P. Arrhenius, L.P. McCloskey and M. Sylvan – Chemical Markers for Aroma of Vitis vinifera Var. Chardonnay Regional Wines J. Agric. Food Chem. 1996 44(4) pp 1085-90 It’s publication in this highly regarded peer reviewed scientific journal is a measure of its validity. Not everyone took kindly to having terroir be demonstrated to be a verifiable fact for these wine regions. Matt Kramer whose writings on terroir had intrigued me seemed particularly miffed that it was proven. For him terroir was a quasi-mystical aspect of Burgundy. I think he felt that its scientific proof somehow diminished it. I was surprised. I thought he would have been as delighted as a Jesuit who had been informed that God’s existence had been scientifically proven. Perhaps it was the fact that it was proven utilizing California Chardonnay instead of Burgundy that was disappointing to him.
[8] It is interesting to note that even when it was not found, the author presumes its existence and states that it (terroir) was overridden. Rather than simply stating that it did not exist.
[9] It is not as if there are no studies in red wine demonstrating terroir. As just one example in 2012 A.L. Robinson et al in the American Journal of Enology and Viticulture found that ten Cabernet regions in Australia could be distinguished from each other based on sensory descriptors. What is true is that studies where both sensory and chemical markers have been discovered have been almost exclusively in white wines.
[10] Very ripe wines tend towards a more generic flavor profile and away from the specific and distinctive. An exceedingly ripe Pinot Noir for example may be easily mistaken for Syrah or Zinfandel. It is impossible for a Pinot to express the terroir if it doesn’t even taste like Pinot Noir. This dulling of the varietal specific flavor may also be one of the reasons that modern red wines do not seem to express terroir. There have also been increases in the average level of tannin in red wines over the last few decades. This is concomitant with the increase in color density. It is well understood that wines with higher levels of tannin are less aromatic due to the reductive strength of the tannins. This too is blocking the expression of terroir as aroma is the primary grammar of terroir.
[11] Cru is a concept very similar to terroir which developed in Bordeaux. Vedel describes it as; “A zone in which all the products share unique characteristics, or are different from those of neighboring soil.” Unlike terroir it also considers the reputation and marketing of the wines as part of the cru. There have been regional interpretations of these concepts from the beginning. Emile Peynaud another product of Bordeaux associated terroir strictly with the soil not with all the influences of the site.