Climate change, plant adaption and guilds
Diversity rules
One of the questions going around my mind for a while is: will plants be able to adapt fast enough in the light or rapid and erratic climate change? How can we help that process? Should we help that process? And what about our growing systems, how should we adapt and design them for the times we live in? And what about wild/rewilded systems?
Where are we now
One of the ART’s original patrons was James Lovelock, originator of Gaia Theory: that life on earth interacts with their surroundings to form a self-regulating system that helps maintain conditions for life on the planet.
To show that this theory was not contradictory to the principles of natural selection, Jim developed the Daisyworld model as an example of a simple self-regulating system that regulates temperature (for a fuller explanation and interactive visual see https://www.islandsoforder.com/daisyworld.html)
A typical Daisyworld graph is below. You can see that the world with daisies has its temperature regulated over a wide range, whilst the world without has no such response. The point where the stresses of increased inputs cause the regulation system to fail (between 1.5 and 1.6 luminosity below) is called a tipping point.
The Daisyworld model was made more complex – showing, for example, that a more diverse collection of life forms leads to more stable climate regulation – but of course is nothing as complex as the earth itself.
What you can’t see in the graph above is that just before the tipping point, there is usually a big increase in variability – wobbles up and down from the smooth line.
For the earth there are numerous tipping elements in the climate system which also interact and may trigger each other in unknown ways. The unknowns are still huge, but it is becoming clearer that we are shockingly close to some of the tipping points and might already have crossed some of them.
One of the indications that we could be very near tipping points is the increasing variability of our weather. As climate change continues there are more weather extremes, and it is these that have a more significant effect on plants than gradually increasing global temperatures.
The future for plants
Plants in our growing systems and in the wild are going to experience increased instability, more weather extremes and more variability in year-to-year conditions, which is going to be very challenging.
In Britain and much of the world, climate zones are shifting Northwards at about 5Km per year. This is hundreds of times faster than after the last ice age. Some plants can move that quickly – think dandelion or willow seeds that can move tens of km on the wind. But many cannot – lots of trees take a few decades to flower and then have seeds that can only travel small distances.
If there were large contiguous areas of wild land then some species in the wild could move north with the shifting climate but many could not. And in Britain we don’t have that much wild land at all. This means that for a lot of our ‘native’ species they can’t move and therefore will have to try and adapt where they are. This too will be easier for some than others. Those that can’t move could die out – this is already starting to happen to English oaks in the Southeast of the country.
In addition, beneficial and pest insect/animal species are all adapting at different rates, some able to keep up with the shifting climate but many not.
For plants that we cultivate the challenges are just as great. Annuals and fast-flowering plants have the potential for fast seed adaption to new conditions, but if the variability in weather is inconsistent from year to year then what will they be trying to adapt to? For a lot of other perennial and woody plants, they could have greater problems in adapting.
What should we do / what can we do
For our wild/’native’ systems there are more questions than firm answers that people agree on. Should we introduce new species to take over as some – eg. English oak as above – die out? We can allow some species to naturally move north and colonise but only a few can move fast enough to do this. Do we accept degraded ecosystems or do we intervene? This relates to deeper questions about the role of Humans on this planet – I am not comfortable with the ‘humans as stewards’ attitude which has not worked well so far!
As for growing systems to feed the human population, this is what we are trying to show in the most ecologically sound way. In many ways it is based on giving to the land rather than taking from it.
One of the legacies of ten thousand years of agriculture and plant selection is the monoculture mindset, which is closely related to the commercialisation of agriculture. Modern economics – not so much a science as a materialistic scheme for wrecking the earth – has devalued agriculture to the extent that many feel forced down the monoculture route. In a shifting and erratic climate, monocultures are the very last thing we need.
The only way our growing systems might be able to cope in the future is by embracing diversity. Almost all the work on crop science has been on single crops, yet there is clear evidence that mixtures of plants, especially perennials, can be more productive, be better for soil, store more carbon, and be more resilient to climate and other stresses.
So how do we implement greater diversity in our growing systems to get resilience?
Diversity of plant species
Diversity of plant families (eg. apples, pears and plums are all in the Rosaceae so do not make a very resilient collection)
Diversity of life spans reflecting nature - not too many annuals
Diversity within species – more use of seedling plants, less use of cloned plants
Embracing and allowing death of species to enable new opportunities
Polycultures – intimate mixing of plants within systems
Designing using ecological guilds (see below)
Basically, we want to try and recreate functioning ecosystems using plants more useful to Humans than found in most wild systems. In resilient agroecosystems we try and maximise the connections between the elements (plants, animals, insects, fungi etc) and using ecological guilds is one the best ways to do this.
Designing with ecological guilds
There is a lot of confusion over the use of the word ‘Guild’.
Originally used for groups of artisans engaged in a similar trade, ecologists have defined it in several ways, and Bill Mollison defined it in a different way for Permaculture systems.
Many people confuse guilds and polycultures. Polycultures are groups of species growing in the same patch. Sometimes polycultures are guilds but not always! Likewise, not all guilds are polycultures. Guilds often contain support species or system species.
Here I am using the guild definitions refined by Dave Jacke (forest garden designer and lead author of Edible Forest Gardens). These are clearer, more useful and more based on scientific ecology than Mollison’s definition.
Do I have to consciously use guilds?
You don’t. Plants can mixed more randomly, and if you use a large enough diversity then various guilds will emerge. And some of your normal planning will include guilds. But your system will not be as resilient compared with the one that will emerge through conscious use of guilds to some degree.
Defining guilds
Guilds are assemblages of species (which can include plants, animals/humans, insects, amphibians and others) that have a specific function or share a specific resource, and which generate a desired emergent property or outcome. There are three types, which are not mutually exclusive and can often overlap with species in both.
Resource Partitioning Guild (or Resource Sharing Guild) – RPG
The species in this guild partition or share a resource to avoid competition. The species in it are usually in the same ecological niche. Using a RPG will lead to reduced competition, increased biodiversity and increased productivity for individual guild members and the ecosystem as a whole.
Examples
A canopy layer forest garden design is an RPG sharing light
Mutual Support Guild - MSG
Here the yields of one species meet the needs of another in the guild. The species are not necessarily in the same ecological niche, nor in the same patch, in fact they can sometimes be a long way away (several miles). “Support plants” or “System plants” often dominate MSGs. Apart from plants – birds, frogs, reptiles, insects, bacteria and fungi all offer functions that can support each other. Using a MSG reduces stress and work to maintain the system, increases stability of the system and reduces waste.
Examples
Comfrey (Symphytum officinale) with the nearby fruiting shrubs is an MSG with the comfrey providing potassium in particular.
Community Function Guild – CFG
This guild is based on species which share a community niche or function. The species can be of wide diversity and types from different niches but all basically doing the same job. A CFG provides redundancy and therefore stability of ecosystem function; increases diversity and ecosystem resilience. If species niches overlap too much, may cause competition. Ideally CFGs will also function as RPGs.
Examples
Good king henry (Chenopodium bonus-henricus) and wild strawberry (Fragaria vesca) form a Ground covering CFG
How to use guilds in food forests and forest gardens
Even if you do not consciously design using guilds, you will get some in your forest garden plantings. Some parts of forest garden design, for example designing the canopy layer or designing the ground cover layer, are basically designing a guild.
Polycultures are more effective if they are guilds.
However, the more guilds there are in your system, the more resilient and long-lived the system will be, and the less you will need to work to maintain it. So ideally try to design some of these guilds or add in plants over time to construct them. There is an almost infinite amount of time you could spend on designing guilds so you have to balance that against the time available and benefits gained (many of which are difficult or impossible to measure).
Some main outcomes for guild design
Outcome: Pest population balance
Outcome: Soil fertility maintainance/improvement
Outcome: Weed control
Outcome: Maximise productivity
