Permaculture is a design science for sustainable agricultural environments. Through the observation of natural function, it seeks to integrate and arrange  various elements within a farm enterprise (e.g. plants, animals, buildings and infrastructures) in such a way that they support and benefit each other while  performing multiple functions (e.g. harvesting water, providing shelter, feeding farm stock).

It was developed in Tasmania during the 1970s by two Australians, David Holmgren and Bill Mollison. They took the view that modern industrial agriculture  was too highly dependent on the use of non-renewable resources and that this was leading to reduced biodiversity and increasing pollution of soils and  water. In response, they developed a design process for agricultural systems that would sustain the needs of both nature and human habitation. They  coined this process of sustainable agriculture 'permaculture'.

Core ethics
Permaculture has 3 core ethics at its foundation:

• care of the earth
• care of people
• a fair share of resources.

The last core value implies limits on the consumption of resources are needed and that humanity must find ways to live within these limits.

The overriding intention of the design process is to provide sustainable human habitation within agriculture. Due to its focus on natural ecosystems, it  borrows heavily on other nature-orientated approaches to agriculture such as organics, biodynamics and biological farming. However, what distinguishes it  from others are 12 design principles, which are structured and scientific in their approach. They look for positive outcomes and opportunities and use  feedback mechanisms to evaluate and self regulate.

This results in systems for sustainable agriculture that are responsive to change and will evolve over time. The approach allows ideas to be adopted from  any source, even from conventional chemical farming systems. This allows systems to be developed that are based on sound reasoning and not blind  dogma. All too often, 'nature-friendly' systems of agriculture turn into exercises of what you 'can't do' rather than 'what's possible'. 

The principles themselves are broad in their description and flexible in their interpretation. This has resulted in many different implementations which can  now be found throughout the world. These include urban as well as rural situations. 

Tools used in implementing the permaculture design process

 1. Zones
Zones are a way of grouping design elements according to their demand for use, for example different areas on a farm can be considered different zones. Z  zones can be designated from 1 to 4. Zone 1 might typically be an area closest to the farm house; zone 2 would be the next area further out; zone 3 the  next again and 4 the furthest out. The idea is that zones associated with home activities, and are frequently used and require the most attention and input,  are situated close to the house for convenience and efficiency. A zone 1 area might typically include the vegetable and herb garden. In contrast, a zone 4  area might require little attention or is infrequently used. It might typically include long lived perennials such as found in agroforestry or a firewood coppice. 

2. Layers
Layers are functional units used in forest design.  A 'number 1 layer' might include the tallest of trees; a number 2 layer smaller trees such as fruit trees; a  number 3 layer shrubs; a number 4 layer herbaceous plants and small perennials and so on. Thoughtful placement of these varying layers can be used to  build functioning agricultural ecosystems.

3. Edges
This concept exploits an observation in nature that where very contrasting habitats meet, such as where a forest meets an ocean, ecosystems are rich in  activity and productivity. A design might emulate this phenomenon, for example on a farm pond by having the shoreline formed into several fingers that  spiral out into the surrounding land. This enhances the pond edge effect resulting in greater productivity within the shoreline ecosystem. Likewise, crops  can planted out in similar patterns to achieve similar productivity outcomes.

4. Guilds
A guild is a group of different plants that happily share similar environments and can be planted together. Plant guilds can provide mutual benefits. For e  example, one plant species in a guild might be good at attracting beneficial insects from which all species within the guild benefit. 

Example of an innovative sustainable agriculture solution by Joel Salatin
Where there is a good understanding of ecosystem interactions, bringing various design elements together using this process can result in some innovative solutions for sustainable agriculture, such as in the following example of a method used by small farming guru Joel Salatin.On his farm Polyface, Joel Salatin uses free range poultry housed in moveable 'tractor coops'. Typically, these coops are moved daily onto pastures that have been recently grazed by stock. As the poultry forage amongst the pastures, their eating and scratching activities provide valuable weed and insect control. Their scratching activities improve soil aeration while their droppings contribute to soil nutrient cycling and organic matter levels. While supplementary feed is still required using this system, feed costs are lower while their droppings, instead of being a potential liability, become a valuable asset. The bonus is having access to great tasting free-range eggs and meat.

The author, Roger Martyn has spent 20 plus years working in agriculture and horticulture since graduating from Massey University with an Agricultural Science degree. He has helped many farmers improve their farm productivity and profitability as well as often increasing the enjoyment they got out of farming.