Over at The Wine Feed, Laura Collier has written a three part post on why she drinks organic wine. From Part 1:

For a long time, well before I paid attention to the farming techniques of different wineries, I valued wines that have character. The common theme among most of my favorite wines is not a specific flavor or aroma or weight or grape or country or structure; rather it is personality and expression. Once I became interested in organic farming, and began looking into the farming methods of some of my favorite producers, I noticed that a large proportion of my favorite wines were crafted from organically farmed grapes. I don’t know why – perhaps it’s the complex soils and healthy vines undamaged by pesticides, perhaps it’s the extreme care and attention the wineries put into the wines, perhaps it’s the natural fertilizers that are used – but I have found that organic wines are more likely to have that vibrant expression, clarity of fruit, thought-provoking complexity, and unique personality than wines produced by conventional farming.

From Part 2:

Once the industrial chemicals have been released into the vineyard, they can have detrimental effects on the soils, grapevines, and overall ecosystem. Chemicals can damage plants by weakening the root systems of the plant, and can also damage the plant’s immune system. Grapevines are particularly sensitive to some herbicides, and herbicide injury to grapevines can last for several years after the application. The herbicides can reduce the vigor, yield, and fruit quality of the grapevine, weaken the vine’s immune system, and shorten the life of the vineyard. Industrial chemicals can also degrade the soils of vineyards, by reducing concentrations of essential plant nutrients. Furthermore, the overall ecosystem is damaged as beneficial insects, worms, and microorganisms are wiped out by industrial chemicals.

And Part 3:

Biological diversity, or biodiversity, is integral to the sustainability of balanced ecosystems. Pesticides, herbicides, and synthetic fertilizers have been proven to reduce biodiversity and thus endanger the stability of ecosystems. Several types of pesticides are toxic to beneficial insects, birds, mammals, amphibians, or fish. These pesticides accumulate in the food chain and can affect many more species than only those that were directly exposed to the pesticides. Also, pesticides and herbicides also can reduce the abundance of weeds, grass, and insects that are food sources for many species, and they can damage wildlife habitats by altering vegetation structure.