“Agroforestry involves the intentional integration of trees with other aspects of agriculture,” Baker said.
“There’s not only a place for foresters in agroforestry, but also row crop, livestock and even horticultural producers.”
Agroforestry concentrates on five main practices: alley cropping, forest farming, silvopasture, riparian buffers and windbreaks.
“Alley cropping is the practice of planting crops in between rows of trees,” Baker said. “It may seem counterproductive for a farmer to plant trees in a field, and in most cases this is not what a farmer wants or needs. However, sometimes it makes sense.”
In the early years, crops are harvested between the rows of trees. Later, lumber and/or nuts and other crops may be harvested from the trees as they mature.
Common alley cropping plantings include wheat, corn, soybeans or hay planted between rows of black walnut or pecan trees, he said. Nontraditional or value-added crops might include sunflowers or medicinal herbs between rows of nut trees alternated with nursery-stock trees.
Fine hardwoods like walnut, oak, ash and pecan in alley cropping systems can potentially provide high-value lumber or veneer logs while the landowner derives income from a companion crop planted in the alleyways.
Forest farming is the practice of growing high-value specialty crops under the protection of a forest canopy.
“There are many shade-tolerant crops that can be grown within a forest. Some of these are quite valuable,” Baker said.
Forest crops like ginseng, mushrooms and decorative ferns are sold for medicinal, culinary and ornamental uses.
“Or your entire planting may be of woody species that produce food, such as nut crops or elderberries,” he said.
Silvopasture is the integration of livestock and pasture under trees.
“This is not simply turning the livestock out into the woods,” Baker said. “It is truly a well-designed rotational grazing system, benefiting both the trees and the livestock.”
In a typical silvopasture practice, perennial grasses and/or grass-legume mixes are planted between rows of trees for livestock pasture. The trees not only provide a long-term investment for nut crops or a timber harvest, but also provide the animals shade in the summer and a windbreak in the winter.
Riparian forest buffers deal with areas along stream banks and other waterways. Farmers losing cropland to streams might create a buffer with trees, shrubs, grasses and forbs to prevent erosion.
“In extreme cases, it may take some engineering practices to help stabilize the stream bank,” Baker said.
Windbreaks can protect livestock and crops, and control soil erosion. Windbreaks can help keep drifting snow away from roads or spread snow more evenly across a field, increasing spring soil moisture.
Of the 9GT carbon humans yearly emit extra, 5GT is extra absorbed by plant life.
The remaining 4GT is less than 0.5% of the total biomass, easy to compensate:
keep more trees standing, grow more trees
use wood/bamboo for sustainable constructions (from toys to airplanes)
returning C in the form of charcoal and biochar into the soil
Rainforest clearance in Brazil. Photograph: Getty
Deforestation, and especially the destruction of rainforests, is a hugely significant contributor to climate change. Scientists estimate that forest loss and other changes to the use of land account for around 23% of current man-made CO2 emissions – which equates to 17% of the 100-year warming impact of all current greenhouse-gas emissions.
As children are taught at school, trees and other plants absorb CO2 from the air as they grow. Using energy from the sun, they turn the carbon captured from the CO2 molecules into building blocks for their trunks, branches and foliage. This is all part of the carbon cycle.
A mature forest doesn’t necessarily absorb much more CO2 that it releases, however, because when each tree dies and either rots down or is burned, much of its stored carbon is released once again. In other words, in the context of climate change, the most important thing about mature forests is not that they reduce the amount of CO2 in the air but that they are huge reservoirs of stored carbon. If such a forest is burned or cleared then much of that carbon is released back into the atmosphere, adding to atmospheric CO2 levels.
Of course, the same process also works in reverse. If trees are planted where previously there weren’t any, they will on soak up CO2 as they grow, reducing the amount of greenhouse gas in the atmosphere. It is thought that trees, plants and other land-based “carbon sinks” currently soak up more than a quarter of all the CO2 that humans add to the air each year – though that figure could change as the planet warms.
Unsurprisingly, the relationship between trees and local and global temperature is more complicated than the simple question of the greenhouse gases they absorb and emit. Forests have a major impact on local weather systems and can also affect the amount of sunlight absorbed by the planet: a new area of trees in a snowy region may create more warming than cooling overall by darkening the land surface and reducing the amount of sunlight reflected back to space.
In an increasingly busy, complex world, we need time to reset our minds and create something that will benefit our health and the minds and health of those around us. Permaculture allows us to back away from that constant change. It reminds us of the basic rhythms of life. And it throws in good, home grown food as well!
Thirteen years ago I was searching the shelves of the BYU library for gardening books that would compliment the horticulture degree I was working on. I found a little-used book with an unusual word in the title: permaculture. I knew that horticulture meant garden growing and that agriculture meant farming, but I had never heard of permaculture.
The term permaculture was first coined when two Australians, Bill Mollison and David Holmgren, saw how farming was becoming industrialized and chemically intensive in the 1970s and created a farming system that was sustainable and environmentally friendly. Sustainable enough that a farm didn’t need to rely on expensive products from far away like fertilizers and pesticides. They designed a type of farm that could feed people without destroying the earth. Mollison and Holmgren combined the words permanent and agriculture to come up with the new name for their system: permaculture.
I took the book home and read it. I had never seen organization and design used to produce food, cut down on labor and to reduce negative environmental impact. I never thought of using perennials and fruit and nut trees as the heart of the food garden. I never thought of how simple weed control could be. And I never thought of how to best use the water from rain and snow to help my garden.
As I finished my degree, I used permaculture to help me in landscape design classes. After graduating, I used permaculture to make my work projects better and easier to maintain. I looked for opportunities to use waste for better plant production and nutrition. I even found myself sneaking around my bosses because they weren’t willing to try something new and “untested.”