Many people subscribe to the idea that there is no way to successfully combine ecosystem function and production for human needs. The Economist, in its special report on feeding the world from early 2011, quickly dismisses concerns about the ecosystem impact of people’s land use. The solution the article proposes for feeding the world in the future is to continue developing the yields of our existing staple crops.The strange thing about this position is that the Economist notes that the growth of yields has been slowing down. But they are counting on human ingenuity and the promise of genetic engineering to push the pace of yield growth back up again.My question is: what if we applied human ingenuity to the problem of feeding the world together with the problem of sustaining the world’s ecosystems? I am not calling a halt to development of our traditional crops, I am recommending that we not invest all our energy into systems that seriously impair global ecological function.In order to inform the discussion of people designing systems to restore ecosystem function, it is worth getting our minds around the size of human impact on ecosystems at this point in history….
This is looking at one important species for order of magnitude purposes only.
A production planting whose selection and distribution of plants mimics the architecture and functions of a forest ecosystemPatchy state of cover, resembles a mid-successional woodland more than a mature forest (intermediate successional state has highest NPP)Because it is modeled after a forest, it is layeredPolyculture – different species togetherInter-species tolerance and mutualism Diversity of plants, both productive and those intended for system benefitSelf-renewing soil fertilityNatural pest control, stability
It’s not even too much of a stretch to say that soil IS the terrestrial ecosystem.Soil is the ecological capital accumulated over thousands of years by an ecosystem. In Eastern North America, there’s a range of environmental conditions, but on average, soil forms at a rate of about 1” per 250 years. Tilled soils are as barren below ground as above ground. Compare a forest with the bare soil of a tilled field – even more life and complexity was removed by tilling below ground as above. Ecosystem function is inhibited by tilling.
Resembles a mid-successional woodland more than a mature forest.
By ordering plants by mature height, all the plants will end up receiving close to full sun exposure.
In this photo, south (and sun exposure) lie to the left, so the taller orchard trees are to the right where they will not shade the shorter plants. Moving from right to left, plant height steps down: trees, shrubs, perennials and annual vegetables.
Resembles a mid-successional woodland more than a mature forest.
POLYCULTURE - growing multiple species togetherOne scarcely ever finds a monoculture in the wild, in a functional ecosystem.In a monoculture, each plant seeks the same resources as every other: same sunlight, same water, same nutrients.In a polyculture, resources are partitioned [pic from Edible Forest Gardens]. We are aware of competition between plants. But what we have overlooked is beneficial interactions between plants. There is evidence to show plants in the woods are doing more than just tolerating one another – indeed, they may benefit in many ways from one another’s presence. Forest gardeners seek to understand and make use of the beneficial interactions between plants. This image shows a fruit tree growing at the Central Rocky Mountain Permaculture Institute – underplanted with species known to have root systems more effective at retrieving hard-to-reach minerals than the fruit tree, which are made available to the fruit tree when the leaves fall.
MUTUALISMFrom The Nature and Properties of Soils, one of the most widely used soil science textbooks. Grass’s more extensive root system better at retrieving scarce minerals like Phosphorous (P). Legume’s symbiotic bacteria fix Nitrogen (N) from the atmosphere into plant-available form. Mycorrhizae are fungi that have symbiotic relationships with most plant species – they help the plants retrieve minerals in exchange for sugars. In this case the mycorrhizae are connected to both plants and actually transfer nutrients from places of abundance to places of need. Isotope tracer studies record this effect. [possibly a good topic to start with] [size of mycorrhizal hyphae compared to fine root hairs]“A large oak tree may be feeding not only its fungal partner, but also other plants nearby” Plant Biology page 366.1 cubic inch of soil may have more than 1,000’ length of fungal mycelium.A side point: this is awesome stuff, we haven’t known about forever. There is likely some other stuff going on in the ecosystem that we haven’t noticed yet. I’m just guessing. So we should include as many of the puzzle pieces as we can in the agroecosystems we design, to give a better chance that some of the processes will go on even without us specifically providing and planning for them.
Nitrogen is one important example of an element important to plant growth, but there are many others.This planting also illustrates layering:The pecan is a canopy species, and will eventually grow as tall as 100’ or more.The pawpaw is an understory species, which will top out around 30’The bayberry is a shrub that may reach 10’ or 15’You might be wondering how the nitrogen and other nutrients get from the plant with abundance to the plants with lack… [next slide]
CONCLUSIONA forest garden is a forest adapted to people’s needs, and people’s needs adapted to the forest.
“[This special report]looks at ways to boostyields of the maincrops……the reaction againstintensive farming is aluxury of the rich.Traditional and organicfarming…cannot feedthe world”The EconomistFebruary 2011
Swamp White OakQuercus bicolorphoto sourceNative Trees for North American Landscapesby Sternberg and Wilson
SOURCES1900 Wheat USDA Wheat Data Yearbook Tables1950 Wheat USDA Wheat Data Yearbook Tables2011 Wheat USDA Wheat Data Yearbook TablesAcorns UCR David A. Bainbridge Use of Acorns for Food in California: Past, Present, FutureAcorns FK Forrest Keeling Nursery - 200lbs averge yield 35 canopy Kimberley OakNote: Acorns assumed to contain 45% nut meatfrom Sean B. Dunham Nuts About Acorns: A Pilot Study on Acorn Use in Woodland Period Subsistence inthe Eastern Upper Peninsula of MI050010001500200025003000350040001900 Wheat 1950 Wheat 2011 Wheat Acorns UCR Acorns FKFlour Yield: Pounds/Acre/Year
What Is a Forest Garden?PERENNIALLAYEREDPATCHYPOLYCULTURALSELF-FERTILE
“soils…act as the principalmedium for plant growth, regulatewater supplies, modify theatmosphere, recycle raw materialsand waste products, providehabitat for many kinds oforganisms….soil is a majorecosystem in its own right”Quotation and graphic fromThe Nature and Properties of Soilsby Brady and WeilPERENNIAL
Photo source:National Agroforestry Center PERENNIALLAYEREDPATCHY
Central Rocky MountainPermaculture InstitutePhoto source: apios.orgPERENNIALLAYEREDPATCHYPOLYCULTURAL
Diagram source:The Nature and Propertiesof Soils by Brady and WeilImage source:Plant Biologyby Graham, Grahamand WilcoxNitrogen-FixingBacteriaRoot NodulesxImagesource:Plant BiologybyGraham, Graham andWilcoxMycorrhizaePERENNIALLAYEREDPATCHYPOLY-CULTURAL