Sami Grover

DCL

Last week our exploration of permaculture design principles looked at using one element to achieve multiple functions - for example chickens providing not just eggs, but also poop, bug control and even tilling in the form of a chicken tractor. The idea being that diversity breeds resilience - with the sum of multiple yields outweighing the single (albeit optimized) yield of a factory farmed bird.

But there's another aspect to the diversity story - and it's almost the reverse of last week's lesson - namely also ensuring that one function is supplied by multiple elements. It's plain old common sense - grow nothing but one variety of apples and you'll be screwed when it succumbs to disease. Similarly, rely solely on well water, and you'll have problems when the aquifers run dry - but not so if you also collect rainwater and practice good dry farming techniques.

So wherever a need is particularly important - and I'd say food, energy and water are among the most important - then it's only sensible to meet those needs from as diverse a range of sources as possible. Even as simple an act as planting different varieties of tomatoes (pictured) means you have a wider range of flavors, a greater resistance to disease, and a longer harvest period.

Salivating over sustainable eats? Learn how to make your own with help from Emeril Lagasse in Planet Green TV's organic cooking show, Emeril Green.