Agroforestry is the growing of trees or shrubs with other agricultural crops. It can range from lines of trees intercropped with a cereal like wheat, to fully integrated forest garden systems incorporating trees, shrubs and perennial crops in a self-sustaining system.
Over the last few hundred years almost all the research and agricultural effort has been focussed on annual plants, to the extent that most of the world population depends on them. This wasn’t always the case, though, and many people have forgotten that the mass growing of annuals on a field scale is never going to be sustainable because they take a huge amount of energy to grow. As long as energy is cheap and available they can continue their dominance – but it is clear now that energy is not going to remain cheap for much longer.
We need to move much more towards perennial crops – whether it be tree-based crops (for example, nuts to take the place of some of the cereals) or smaller plants – for example perennial vegetables like perennial onions. In other words a move towards agroforestry.
Perennial plants, once established, take much less work to maintain than annuals – you only have to plant once (in a long while anyway), and most plants look after themselves with far less susceptibility to pests, diseases or the vagaries of the weather than annuals. Perennial plant products are often more nutritious than their annual counterparts too, because their roots systems are larger and can get more nutrients out of the soil.
Sustainable growing requires a change in attitudes too. Agriculture has been misled into thinking that every bit of ground needs to be productive – in other words needs to have a crop coming from it. This is never going to be sustainable. Truly sustainable growing systems must devote a proportion of the land to plants with ‘system’ functions – in other words, plants which increase the health and resilience of the whole growing system (whether or not they produce a crop). Such plants would usually include nitrogen-fixing species (to make the use of nitrogen fertilisers unnecessary), and also plants to deter pests and diseases by, for example, attracting predators of likely pests or by confusing pests with aromatic emissions.
The most sustainable systems will be closed-loop systems, where no extra nutrients are brought in and the growing system sustains itself. Forest gardens are an example of this.
Agroforestry systems are less suited to very large scale production than monocultures, so by their nature they will smaller scale – which also means that they are much more likely to be integrated far better with their local economy: crops are likely to be sold and used locally, so the mass transport of food should decrease significantly as these systems become more popular.
Agroforestry systems have many other benefits – for example wildlife value is very high, they can provide shelter and thus reduce energy usage for heating or cooling, and so on. Once understood we’ll wonder how we ever did without them!
Martin Crawford, 2015
Martin is Director of the Agroforestry Research Trust (and his books include Creating a Forest Garden (Green Books, 2010) and How to Grow Perennial Vegetables (Green Books, 2012).