What Is Terroir? What the Science Says

Terroir entered French in the 13th century. It comes from the Vulgar Latin terratorium, a change of the Latin territorium, from terra, land.^[4]

Burgundy is where the practice of naming wine after a single plot was worked out in most detail. The abbeys of Cluny, founded in 910, and Cîteaux, founded in 1098, played a central role in learning, farming and managing Burgundy's vineyard land, followed by the Valois dukes of Burgundy.^[6]

Wines were named after their plots only at the very end of the Middle Ages. The word climats, Burgundy's name for its named vineyard plots, first appears in writing in 1584. The first written classifications of the plots came from Morelot in 1831 and Lavalle in 1855.^[6]

In 2015, UNESCO added the 1,247 Climats of the Burgundy vineyard to its World Heritage List. They run along a fault line about 60 kilometers long.^{[6, 7]}

The wine writer Matt Kramer called terroir "that sense of 'somewhereness'" in Wine Spectator in 2000.^[5]

The OIV definition above lists what a terroir includes: "specific soil, topography, climate, landscape characteristics and biodiversity features." It is written "for descriptive purposes," and the OIV keeps it separate from the legal definition of a geographical indication, the protected place name on a label.^[1]

INAO, the French agency that runs the appellation system, defines a terroir as a bounded area where a human community has built up shared knowledge of production over its history, based on the interaction between a physical and biological environment and human factors. (Our translation.)^[2]

European Union law defines a protected designation of origin (PDO) as a wine whose quality or characteristics are "essentially or exclusively due to a particular geographical environment with its inherent natural and human factors." All of its grapes must come from the area. A protected geographical indication (PGI) needs at least 85% of its grapes from the area.^[57]

All three definitions include the people who farm the place and make the wine, alongside the land and the climate.

From 1996 to 2000, researchers in Bordeaux followed Merlot, Cabernet Franc and Cabernet Sauvignon on three soils: a gravel soil, a soil with a heavy clay subsoil and a sandy soil over a water table. They found that "the impacts of climate and soil were greater than that of cultivar." The authors concluded that climate and soil most likely act on the grapes through vine water status, the amount of water the vine has.^[8]

Terroir is hard to study because "many factors are involved, including climate, soil, cultivar and human practices, and these factors interact."^[9]

A 2018 review found that soil acts on the vine through three things: soil temperature, water supply and nitrogen supply. Soil temperature changes when the vine buds, flowers and ripens.^[10]

These factors can be measured. The ratio of carbon isotopes in grape sugar, written δ13C, records how much water stress the vine went through. Yeast assimilable nitrogen in the juice records its nitrogen supply. Together they let growers map terroir factors across a vineyard.^[10] A 2020 review concluded that "the terroir effect is mediated by measurable factors that can easily be monitored in the vineyard."^[12]

The grape variety has to fit the place. A site shows best when "the precocity of the grapevine variety is suited to the local climatic conditions," meaning the variety ripens fully near the end of the local growing season. Precocity is how early a variety ripens.^[9]

Wine grapes grow where the average growing-season temperature is between 12 and 22°C (54 to 72°F). Jones found that high-quality production is "more realistically limited to 13-21°C" (55 to 70°F).^[15]

Each variety has a narrower range. Pinot noir grows in regions averaging about 14 to 16°C (57 to 61°F), from Tasmania's Tamar Valley at the cool end to California's Russian River Valley at the warm end.^[15]

Temperature changes over short distances. In a study with 90 sensors across Saint-Émilion and Pomerol, minimum temperatures differed by up to 10°C (18°F) on the same day. The season's total heat, measured in degree-days (the sum of each day's average temperature above 10°C), varied by about 320 degree-days within one vintage.^[19]

Slope and aspect, the direction a slope faces, change how much sun and heat a vineyard gets. In a study of Nebbiolo vineyards, topography drove the differences in sunlight and heat, and the effect changed from year to year.^[20]

Cool nights are often credited with deeper color in red grapes. The evidence is mixed. In a 1972 experiment, grapes kept at 15°C (59°F) day and night colored much more than grapes given hot days and cool nights, and some varieties given hot days colored more when the nights were warm too.^[17] A 2007 study found that a daytime maximum of 35°C (95°F) cut anthocyanins, the red pigments, to less than half of what grapes made at 25°C (77°F).^[18]

Soil acts on wine mainly through water. Red wines of high quality come from vines of moderate vigor, held back by a mild water deficit or a low nitrogen supply. Those conditions are "most frequently met on shallow or stony soils, in moderately dry climates." White grapes need "regular but not excessive vine water and nitrogen supplies."^[9]

Soil also supplies the vine's bacteria. A 2015 study found that most of the bacteria living on the vine, from the roots to the grapes, "originated in the soil," and that soil pH, the soil's carbon-to-nitrogen ratio and vineyard management shaped them.^[30]

Soil does not give wine the taste of its rocks. The geologist Alex Maltman wrote: "Whatever minerality is, it cannot literally be the taste of minerals in the vineyard rocks and soils."^[27] Our soils guide covers nine soil types and what each does in a vineyard. Our minerality guide covers what tasters mean by a mineral wine.

Grapes carry yeasts and bacteria on their skins. A 2014 study of California vineyards found that "regional, site-specific, and grape-variety factors shape the fungal and bacterial consortia inhabiting wine-grape surfaces," and called the pattern a "nonrandom 'microbial terroir.'"^[31]

A 2016 follow-up ran more than 200 fermentations from Napa and Sonoma. Both the microbes and the wine chemistry told the growing areas and individual vineyards apart, and the microbes predicted which compounds the wines would contain.^[34]

In New Zealand, populations of the wine yeast Saccharomyces cerevisiae differed by region, and those regional populations "differentially affect wine phenotype," the chemistry of the finished wine.^[33]

In 2014, a commentary on the California study noted that the role of these microbes in "the flavor, color, and quality of the final product... still remains to be shown."^[32] The 2015 and 2016 studies above came after it.

A wild fermentation does not guarantee local yeast. In one vineyard study, 296 of 3,780 yeast isolates were commercial strains, 94% of them found within 10 to 200 meters of the winery, and they did not settle in the vineyard for good.^[35] At a Canadian winery, strains related to commercial yeast dominated the spontaneous fermentations.^[36]

Two Burgundy Climats were compared with ultrahigh-resolution mass spectrometry, a method that reads thousands of compounds at once. The two plots left different chemical fingerprints, clearest in the grapes, but "vintages have the most significant impact on fingerprints."^[37]

A 2023 study used raw gas chromatography data to name which of 7 Bordeaux estates each wine came from, and got every one right. It placed the vintage correctly up to 50% of the time. An estate combines its vineyards with its own winemaking, so the result does not separate the site from the cellar.^[38]

Strontium from the bedrock passes into the wine. The ratio of two strontium isotopes, 87Sr to 86Sr, stayed the same from rock and soil through the grape to the finished white wine, even after bentonite and yeast were added. Blends of two wines gave a value in between.^[39] Researchers study the ratio as a way to check where a wine comes from.^[40]

People can pick up origin too, within limits. Wine professionals told apart Pinot noirs from five Australian regions, and the authors concluded that "regionality is a strong driver of aroma typicity."^[42] In Corbières, blended reds from neighboring sub-regions could be told apart, but the strongest factor "seems to be linked to winemaking processes, including the type of blending."^[43]

In a study of blind tasting, training improved how often tasters named the grape variety correctly, and a group's combined guesses about where a wine came from beat chance.^[44]

Differences show up inside a single vineyard. In one Niagara vineyard, zones with different vine water status gave wines that differed in color and fruit, with similar differences in a hot vintage and a wet one.^[45]

The OIV definition includes "applied vitivinicultural practices" and "collective knowledge." INAO's includes human factors.^{[1, 2]}

Van Leeuwen and Seguin wrote that great terroir only emerges where economic and social conditions support quality wine production.^[9]

A 2018 review found that the expression of terroir "can be optimized by choosing appropriate plant material, and via vineyard floor management, fertilization and other management techniques."^[10]

The same choices are how growers adapt to a warming climate: rootstock, clone, trunk height, the ratio of leaves to fruit and the pruning date.^[22]

Terroir is the soil

The OIV lists soil next to topography, climate, landscape and biodiversity, and adds farming practice and knowledge.^[1] In the Bordeaux trials, climate mattered as much as soil, and both worked through the vine's water supply.^[8] Soil still matters: it sets the vine's water, soil temperature and nitrogen.^[10]

You can taste the rocks in a wine

Maltman concluded that minerality "cannot literally be the taste of minerals in the vineyard rocks and soils."^[27] Experts rating Burgundy Chardonnays disagreed strongly on which ones were mineral.^[29] A 2018 review found that perceived minerality tracks organic compounds and how reduced or oxidized a wine is.^[28] Rock does leave a trace: the strontium isotope ratio passes from bedrock into wine, but only a lab instrument can read it.^[39]

Old vines show more terroir

A study of Shiraz in the Barossa Valley found that, "contrary to popular belief," old vines yielded more than young ones.^[46] Wines from old vines tasted consistently lighter in fruit, and the grapes' composition sorted more by region than by vine age. The author concluded that the higher quality people attribute to old vines "is subject to environmental influence and is more complex than previously thought."^[47] This is one research program on one variety in one region.

Natural wine shows more terroir

Evidence for: regional yeast populations change a wine's chemistry, and the microbes on grapes predicted the compounds in Napa and Sonoma wines.^{[33, 34]} Evidence against: strains related to commercial yeast can live in a winery and dominate its spontaneous fermentations, and the winery's own microbes feed into the wine.^{[36, 34]} No published study compares how much terroir natural and conventional wines show.

Terroir is a marketing invention

Mark Matthews, a viticulture professor at UC Davis, asks in his book Terroir and Other Myths of Winegrowing whether terroir is "primarily a marketing ploy."^[49] The sociologist Marion Fourcade ties French terroir classification to "the protection of economic rents threatened by competition and fraud."^[50] Vaudour, writing on terroir at different scales, notes that it "has been related to... territory, name, strategies of advertising and marketing."^[52] On the other side, researchers have measured site effects in wine chemistry, strontium isotopes and professional tasting.^{[8, 37, 39, 42]} The two sides answer different questions: how the idea is used, and whether a place changes a wine.

Terroir only exists in France

Site signals have been measured in California, New Zealand, Australia and Ontario.^{[31, 33, 42, 45]} American cheesemakers have adopted the idea for their own landscapes.^[51]

Stressed vines make better wine

For red wine, the Bordeaux research found that "mild water deficit stress enhances grape quality," and grape sugar peaked at a mild deficit. Severe stress lowered quality.^[11] White grapes need "regular but not excessive vine water and nitrogen supplies."^[9]

In Beaune, the grape harvest started on September 28 on average from 1354 to 1987. From 1988 to 2018 it started 13 days earlier.^[21]

From 1950 to 1999, most of the world's top wine regions warmed during the growing season, and vintage ratings rose. The same study projected an average warming of 2°C over the next 50 years.^[14]

Researchers disagree on how much land will stop suiting wine grapes. A 2013 study projected that 25 to 73% of suitable area in major wine regions could be lost by 2050 under a high-emissions scenario.^[24] Van Leeuwen and colleagues published a reply titled "Why climate change will not dramatically decrease viticultural suitability in main wine-producing areas by 2050."^[25]

A 2024 review found that about 90% of traditional coastal and lowland wine regions in Spain, Italy, Greece and southern California "could be at risk of disappearing by the end of the century," while new regions such as southern England are emerging.^[23]

A study of 1,085 European geographical indications found that rules limiting which grape varieties growers may plant make regions more vulnerable to climate change.^[26]

INAO has run France's appellations since 1935, and Burgundy's appellations date from decrees in 1936.^{[3, 6]} European PDO rules require the wine's character to come from the place's "natural and human factors," with all grapes from the area.^[57]

The United States defines an American Viticultural Area (AVA) as "a delimited grape-growing region with specific geographic or climatic features that distinguish it from the surrounding regions and affect how grapes are grown."^[56] A petition for a new AVA must describe its climate, geology, soils, physical features and elevation, and evidence for the name "must come from sources independent of the petitioner."^[54] A wine labeled with an AVA needs at least 85% of its grapes from that area, and a vintage date needs 95% from that year.^[55]

What is terroir in simple terms?

Terroir is the way a place shapes a wine: its climate, soil, landscape and living things, and the knowledge the people there built up about farming it and making wine from it. This is close to the definition the OIV adopted in 2010.^[1]

Is terroir just the soil?

No. The OIV definition lists soil, topography, climate, landscape and biodiversity, plus farming practice. In Bordeaux trials, climate and soil both mattered more than grape variety, and both acted through the water the vine received.^{[1, 8]}

Can you taste terroir?

Within limits. Wine professionals told apart Pinot noirs from five Australian regions. In Burgundy, the vintage changed a wine's chemistry more than the plot did. No study supports tasting the rocks themselves.^{[42, 37, 27]}

Does terroir exist outside France?

Yes. Researchers have measured site effects in California, New Zealand, Australia and Ontario.^{[31, 33, 42, 45]}

How is climate change affecting terroir?

In Beaune, the harvest has started 13 days earlier on average since 1988 than it did from 1354 to 1987. Researchers disagree on how much land will stop suiting wine grapes.^{[21, 24, 25]}

What is the difference between terroir and an appellation?

Terroir describes how a place shapes a wine. An appellation is a legal area whose name goes on the label, with rules on where the grapes must come from. The OIV keeps the two definitions separate.^{[1, 57]}

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• [3] INAO, Histoire
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