The theory behind biodiversity in vineyards

In conventional agriculture, soil is considered a reservoir of minerals and water for plants. Farmers add synthetic fertilizer into the system to increase crop yield, and pesticides to prevent crop loss. This methodology has a lot of advantages, not the least being economies of scale and the ability to consistently produce large amounts of food.

However, conventionally farmed land can develop specific kinds of problems. Natural resources are used up faster than they are replenished and pest/disease outbreaks can be larger in a single crop environment where the natural ecosystem has been displaced and insects lack natural enemies. Groundwater quantity and quality declines, topsoil is often washed away, animal or insect species disappear, and pest outbreaks can gradually become more resistant to chemical control.

Organic farming developed in the 1970s as a response to these problems. And in 2000s there has been more discussion of sustainable farming methods. The basic idea behind sustainable farming is to conserve natural resources instead of depleting them (eg. preventing topsoil erosion and protecting water quality by reducing the amount of pesticides, nitrate and other contaminants.) Other ideas include compost instead of synthetic fertilizer to keep soil fertility high, crop rotation and pairing botanically unrelated crops so disease outbreaks are contained.

Biodiversity
Conserving biodiversity, or the number and mix of species in the property from the soil bacteria, to plants and animals is considered an aspect of sustainable farming. A benefit to conserving diversity of plant life is that pest outbreaks are less prevalent when there are diverse set of plants that provide SNAP functions. SNAP stands for the elements of “ecological engineering” needed to stimulate beneficial insect populations: Shelter, Nectar, Pollen and Alternative Prey.

Vineyard regions that can be modified to increase species:

  • hedgerows (high or low growing plants) to harbor benefiical insects
  • cover crops in row middles for beneficial insects
  • water features near tasting room for frogs and other sensitive species
  • maintaining any riparian habitat on property

A key thing to remember is that adding plant species can present their own particular problems if chosen or managed poorly. For example, insects that reside in the cover crop can migrate to the grapevine if the cover crop is disced at the wrong time in the insects’ lifecycle. Or non-beneficial insect populations can increase when the cover crop is left un-disced. Another potential problem is that some cover crops distract insects from feeding on the mealybug (a grape pest). And some high-growing hedgerows can develop lateral roots that compete with grapevines for water and nitrogen. Grass cover crops can be too competitive with the vines as well.

It’s unclear whether increasing the number of species on vineyard property has other direct benefits, but some organic growers believe in indirect benefits and some biodynamic growers believe in spiritual benefits, eg. “life-force of the vineyard”.

Further reading:
see Natural Enemies, Hedgerows, and other books in the reading list.
see Cover Crops, Hedgerows, Ecosystem Health in Vineyard Landscapes

credit: RL Bugg lecture 101C

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