Cold Climate Syntropic Agroforestry
This is a follow-up to our first article about Cold Climate Syntropic Farming. Read the first article here.
Syntropic agroforestry makes use of fast-growing trees and grass to produce mulch and fertility, most often for fruit trees and vegetables that grow alongside. The vibrant multi-story tree systems are often eye catching, and well-managed syntropic farms show that diligent human labor can regenerate ecosystems.
In 2016, I was enthralled with syntropy, and visited a large-scale syntropic farm, Fazenda da Toca, in the state of São Paulo, Brazil. My goal was to understand how the practices I saw in Brazil could work in cold climates like my own: New York State, in the Northeast United States. The month after I returned from South America, I wrote a long article on temperature climate syntropy. Here I’ll be more concise.
Eucalyptus and banana, Fazenda da Toca, State of São Paulo, Brazil
7 Takeaways:
Understand on the concepts, and adjust the practices.
Watch out for rodents, at least in North America.
Below-ground biomass isn’t as sexy, but it might be your end goal.
Plant according to your goals, and your budget (time and money).
Unless you are a trained arborist, do not use a chainsaw without two feet on the ground.
Biomass is a very low bar. What else can we achieve?
The higher your latitude, the more space you’ll need between trees.
Understand on the concepts, and adjust the practices.
Syntropic farming takes advantage of rapid tree and grass growth, using tree branches and raked hay as mulch. This biomass decomposes, increasing organic matter and moisture retention in the soil. When trees and grass are pruned and cut, they also release hormones that stimulate growth in neighboring trees. When a tree’s branches are pruned, some of its roots will die off as a result – and the soil fungi and bacteria will then decompose those roots into fertility. “As above, so below.”
In cold climates, using grass as mulch (herbaceous biomass) seems to make more sense than throwing tree branches on the ground. It can be easily mechanized with common equipment, which is important given labor rates in New York State are 4-10x higher than we might see in Latin America. Grass also decomposes faster than wood does, and though we always want 100% soil cover, we don’t want rough branches at the foot of our fruit trees. It might seem neurotic, but in North America, rodents such as voles will nest in this pile of sticks, and will strip the bark off the trees, killing them to the ground.
Watch out for rodents, at least in North America.
Rodents such as voles wreak havoc on orchards. Rough mulch at the base of fruit trees can serve as nesting habitat, and should be used with caution.
Rodents are one of the biggest challenges when establishing living orchards. The tradeoff between mulch and rodent habitat is potent, independent of syntropic practices. Even in the enterprise budgets for California avocado orchards, there are specific line items for gopher management and eradication. Where snowpack is significant, voles will tunnel underneath the snow, find and eat tree bark and roots, and delete years of work. Some orchard managers will walk or drive around the orchard to compress the snow, such that it freezes into more solid ice. Thick branches used as mulch further complicate this dynamic.
Animals such as dogs with a strong prey drive (terriers etc.), along with birds of prey can alleviate rodent pressure. On my farm, I have hawk perches. The hawks sit on the branch, 24 feet up, and wait to swoop down for a meal. A 50:50 mix of peanut butter and baking soda will also dehydrate voles to death, without poisoning dogs, foxes, or birds of prey. Domestic cats are the foremost cause of bird death globally, and their anti-rodent benefit should be weighed against their systemic assault on biodiversity.
Below-ground biomass isn’t as sexy, but it might be your end goal.
In cold climates, focus more directly on feeding the soil. Below-ground biomass in the tropics is profoundly important, but it is often seen as a co-benefit of aboveground biomass complexity. Cold temperate forests generally hold 10% more of their biomass below-ground, compared to tropical forests, and maintain roughly double the percentage soil organic matter. Therefore in cold climates, interplanted trees can certainly be pruned for biomass, but more of our attention should likely be on root sloughing (dieback), along with soil bacteria and fungi – as opposed to canopy management itself. Linking what is biologically relevant with the economics of syntropic farming, below-ground biomass and soil fertility may best be achieved with warm-season cover crops, compost, biological and mineral amendments, and decomposing fine wood chips imported to the farm. If you’re starting with dead, compacted soil: till in decomposed woodchips and seed 1-2 rounds of cover crops before thinking about accumulating biomass with trees and shrubs.
Plant according to your goals, and your budget.
Those interested in syntropic farming are usually pursuing a combination of reforestation and food production. Syntropic farming inherently involves human management and thus requires that we plan for the specific people that will be working in the system. At Propagate, we plan agroforestry systems for a wide variety of contexts, and the syntro crux often boils down to whether we are prioritizing:
A. Reforestation, with some food production, or
B. Growing food, with some ecological flair.
There is no wrong answer. But our species selection and planting orientation is going to change drastically depending on a manager’s qualitative goals. And on how much time and money they want to spend on their trees.
How do you value your labor? A few years ago, we ran a financial analysis for a syntropic cacao farm in The Dominican Republic. Additional crops included cassava, bananas, breadfruit, citrus, and avocados, with a variety of common biomass species. At a $2/hr labor rate, common for Haitian migrants in the DR, the farm yielded above-market-rate returns. At a $4/hr labor rate, common to rural Chile or Argentina at the time, IRR dropped to 0-2%. Returns of course vary by region and access to markets, but this is to say that labor is the highest-weight variable when seeking to forecast returns in a syntropic system.
Overyield, Propagate’s planning software, enables rapid prototyping of agroforestry, complete with multi-species patterning and budgets that auto-update with design changes.
Syntropic agroforestry yields a lot more than money: from biodiversity and time in nature, to relationships, experiences, an understanding of how trees work, building materials or firewood, great food, and a sense of purpose. Those interested in syntropy are often motivated by non-financial capital, but that does not absolve us of the time commitment that syntropic agroforestry requires of us. Hence: we must plant a system that aligns with not only our expected yields, but also how we want to spend our time and money. Installing a syntropic system is by no means free – it is often expensive. So stay sober and plan thoroughly.
We often see high-pruned eucalypts in the tropics. This practice is dangerous, and given that cold climate systems are likely to only have one strata, it is even less optimal at higher latitudes. Coppicing or pollarding biomass trees at ground level or waist height generally makes much more sense.
Unless you are a trained arborist, do not use a chainsaw without two feet on the ground.
I once split my face open whitewater kayaking, my teeth slicing my upper lip open against the bow of another boater. I waited for four hours to get stitches, in a rural Canadian emergency room, behind a young man with a large chainsaw cut across his arm. Lots of blood. Not recommended. Years before, my friend Alistair cut into his knee with a chainsaw. The recovery was long, but his friend Melissa helped him along. They are now married with three amazing children. A silver lining! Let’s hope for romance without chainsaw accidents. This is all to say: syntropic farming attracts adventurous young people that are low in risk aversion (myself included), and what could be more fulfilling than climbing a tree with a chainsaw in the name of ecological regeneration? Climbing arborists have the most dangerous job, and if we want to be able to walk through our agroforestry systems for years to come, we’d best think long and hard before making our farm dependent on high-pruned trees.
Biomass is a very low bar. What else can we achieve?
If I order woodchips by the truckload, I can get them delievered to my farm for $12-20 per cubic yard. It makes more sense for me to prune my biomass trees, throw the sticks on the ground to be mowed over, and then mulch with imported woodchips, than it does to throw tree branches on the ground. Roughly 4x more expensive in France, the woodchip calculus changes, but many cold humid climates are not wood-scarce to the extent that it makes economic sense to grow our own woodchips. As a result, we can plan around more diverse benefits and yields of our non-market species. Examples include woody florals, pollinator support, nitrogen fixation, fungal affiliations and of course: below-ground biomass.
The higher the latitude, the more space you’ll need between your trees.
Fast-growing trees are usually “pioneer” species, which grow well in disturbed areas, but have short lifespans. By pruning these species, syntropic land managers aim to keep these trees in a state of vigorous juvenile growth, in order to create the conditions for production trees and “climax” species to thrive. In the tropics, eucalypts and acacias fill this niche, casting partial shade on the fruit trees below. In cold climates, trees compete much more intensely for light. In cold temperate climates, a hybrid poplar is not an overstory tree for an apple the same way an acacia is for cacao or coffee. Instead: coppiced and low-pollarded willows, poplars and alders can be interspersed with fruit trees, and managed for below-ground biomass and ectomycorrhizae. Nitrogen-fixing shrubs such as Amorpha fruticosa, Siberian pea shrub, speckled alder, and guomi can fertilize adjacent trees. Black locust can be harvested for fence posts in successional reforestation, perhaps inclusive of blackcurrants, which are deer-resistant and one of the few shade-tolerant fruits for my home biome.
What can syntropic agroforestry actually look like in cold-climate North America?
The Food Forest at Ramble On, in Trumansburg, New York, uses adapted syntropic principles to grow 20 types of fruit, with an additional 20+ species for biomass and biodiversity.
If our goal is an ecologically vibrant food forest, or a biodiverse orchard, we can look to fruit trees and shrubs, with interspersed biomass shrubs and coppiced trees. Fruit species that generally thrive in cold, humid climates without hyper-intensive integrated pest management include Saskatoon serviceberries, blackcurrants, mulberries, seaberry, elderberry, asian pear, and persimmons. Shrubs I personally like for pollinator and biomass benefit include all types of shrub willow, red osier dogwood, false indigo (Amorpha), winterberry, witch hazel, and buttonbush. Winter rye is a phenomenal option for herbaceous biomass, planted right alongside a row of trees. It can be cut toward the end of May, or early June, which is a perfect time to be mulching, given the late spring dryness that now seems all too common.
If our objective is reforestation with some fruit and wood products, black locust grown for fenceposts and willows grown for pole wood can serve as our early-successional species. Long-term hardwoods such as chestnuts and hickory can provide a long-term food crop, with blackcurrants to be harvested for snacks and sorbet.
This text is not exhaustive, nor is it completely applicable to all cold, humid climates. New Zealand and Patagonia have lower rodent pressure than North America, England, and Hokkaido do. Planting trees is rewarding. Let’s make it count.