The other principles that I've reviewed have been:
Catch and Store Energy
Obtain a Yield
Apply Self-Regulation and Accept Feedback
Use and Value Renewable Resources
Produce no Waste
Design from Patterns to Details
Integrate, Rather than Segregate
Use Small and Slow Solutions
I was also very excited this month to find another blogger who is currently reviewing the permaculture principles from their own perspective, see more here. If you know of any other good permaculture blogs, please do let me know :)
Diversity is a really important principle to consider from a farming perspective because so much of agriculture is anti-diversity. The ideal conventional agriculture concept is to use herbicide to kill everything in a paddock and then plant one crop, the plants will all grow to similar height and ripen at the same time, so that they can be easily harvesting mechnically. Then paddock is sprayed again. With livestock, again the ideal is to produce animals that all look the same, and most farmers stick to one type of animal only.
Last summer we planted cow pea with our forage sorghum and the guys at the produce store thought we were mad, I would have liked to plant even more diversity, but we are experimenting gradually. What it comes down to is recognising that we can obtain a better yield overall by encouraging diversity. Sure we might not have grown quite as much sorghum or as much cow pea as we would have done if we planted them separately, but together they both seemed to thrive and the cattle ate the whole lot. Generally if you have a diverse range of plants growing, any pest or diseases can't get established and wipe out the whole lot, the way they can in a monoculture crop. For that reason, we don't worry to much if we end up with some weeds or other grasses in the paddock, its all part of the diversity, as long as they don't take over.
There is of course a fine line between competition and synergy, as discussed in Integrate, Rather than Segregate, you can have too much of a good thing and end up choking out a weaker species that does need its own space, or some extra nutrients.
I found it interesting also that David discussed diversity within a breed and damage done by stud and show breeding. Where animals have been breed for particular physical attributes and not for practicality, for example show chickens that no longer lay well, we have lost an entire breed and virtually have to start again to create a breed that has the atributes that we as permaculture farmers need (this was also discussed in my favourite chicken book). The ideal chicken lays well, has a large body suitable for eating, is able to forage, avoid predators, and survive in our climate, I don't care what it looks like! Braford cattle were originally bred for their hardiness, but after our bull got eye cancer recently we realised that some studs seem to be breeding for aesthetics and using too much Hereford, so that the animals are not as resistent to eye cancer as the original Braford breed. We need to value the diversity in animals so that we can establish breeds with desirable attributes in our own climate.
In my garden, I like to use diversity by planting both edible plants and few flower plants and by also letting most plants go to seed. This encourages beneficial insects, both pollinators and predatory insects that feed on nectar, and reduces pest problems in the garden.
How do you use and value diversity at your place?