Terroir is the foundation on which the great old world wineries are based upon. The word Terroir comes from the word terre "land". The heart of 'Terroir' is the assumption that the land from which the grapes are grown gives a unique quality that is specific to that region. Terroir is the essence of a wine that is captured by the geography, geology and climate of a certain place. Terroir can be explained as "a sense of place," which is given by the sum of the effects that a local, or specific environment has had on the wine made.
Terroir was first coined when french monks who were winemakers, developed the concept of terroir by observing the differences in wines from different regions, vineyards, or even different sections of the same vineyard. The French began to use the concept of terroir as a way of describing the unique aspects of a place that influence and shape the wine made from it. However, Terroir was prevalent before the French; the ancient Greeks believed in a similar concept. They would stamp amphorae with the seal of the region they came from and soon different regions of Greece established reputations based on the quality of their wines.
Terroir can be distilled into a few components, those include: climate, soil type, topography and other plants that grow in and around the vine plots. It is also believed that decisions made during the growing and winemaking process can either worsen or enhance the expression of terroir in the wine. These include decisions such as pruning, irrigation and selecting the time of harvest. In the winery the use of cultured or native yeast, oak, length of maceration and time in contact with lees, temperature during fermentation as well as processes like micro-oxygenation, chaptalization, clarification with fining agents, and reverse osmosis all have the potential to either worsen or improve the terroir.
Terroir is seen in France as the most important factor in determining the taste of a wine's small differences between sites, in terms of their climate, soil properties and microclimates. However, Terroir has been a controversial topic in the wine industry, especially throughout the New World wine producers of NZ, Australia, California etc.
It is often portrayed that new world countries do not have terroir in the same way the old world vineyards do. This is somewhat misleading. The vineyards in the new world differ just as they do in the old world countries, and so terroir is just as much present as it is in the old world. A lot of differences in terroir between the old and new world, is because of the temperature. Old world wines have predominantly cool climates, whereas new world countries like America and Australia are warm/hot climate. This warm climate imparts a more fruity, sweet and strong oaky taste that reduces the likelihood of capturing the terroir of the region. Compared with the old world, which has a delicate cool climate, thus have a better chance of expressing the terroir of its region.
Another misconceived idea is that young vines don't express terroir, and that real terroir expression only comes from deep-rooted vines. This is not proven or accepted by all in the wine industry, but many well-respected producers praise the quality of older vines.
It is interesting to note that the french word for winemaker, vigneron, is translated to "wine-grower" than to "winemaker", emphasizing their religion that the wine is made from the land and not by human intervention. Rather we are seen as the caretakers, and not the creators.
Below are a few good books on terroir which can be purchased online.
Terroir: The Role of Geology, Climate, and Culture in the Making of French Wines
Great wine terroirs