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Geoengineering by Growing Urban Rainforests  RSS feed

 
pollinator
Posts: 1831
Location: Toronto, Ontario
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I have been looking for mention of this idea elsewhere on this site, but I haven't found a thread addressing it yet, so I will start one of my own.

Urban centres are plagued by an overabundance of a number of things besides people. Concrete-generated heat-islands often result in a higher plant hardiness zone, carbon dioxide levels, as well as other emissions, are more concentrated, and the nutrient levels in untreated sewage and runoff are markedly higher.

Why don't we take all these "waste" products and put them to use growing a solution?

Taking Toronto and other urban areas around the Great Lakes, why not grow a rainforest analogous to temperate rainforests from similar plant hardiness zones around the world?

What we lack here in the east are the giant trees of out west, the Western Redcedar, for instance, that will grow a metre a year for the first 75 years of its life. What we also lack is a forest system whose individuals can live for many hundreds of years. I think these two things would be of great benefit.

I, of course, would want to curate a forest system, not only a single species. But I think it would be beneficial to get a whole guild surrounding giant, quick-growing, long-lived tree species as shelter belts for any applicable cities.

Such a shelter belt could easily be incorporated to benefit from integration with waste water and sewage treatment. In addition, the heat island effect offers some buffering from more sudden temperature swings.

The new rainforests would absorb carbon dioxide and clean the air. They would also eventually end up moderating the climate with regards to sudden changes in humidity. Properly situated, they could eventually provide shade for overheated waterways and concrete infrastructure, minimising the heat island effect, lowering groundwater and surface water temperatures and increasing oxygen levels for natural systems. And the fact that the forests would be fertilised with nutrients that would have otherwise found themselves eutrophying waterways downstream means yet more for the health of aquatic ecosystems.

Any thoughts?

-CK
 
gardener
Posts: 4895
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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That is a novel idea Chris, but I think there would be issues with root growth and all the concrete and asphalt destruction that comes with that root growth.

The Western Red Cedar is a shallow root system tree, no real tap root, the primary roots can get to be 36 inches in diameter and be 80 to 90 feet long, these roots usually are at the surface for a 60 inch distance from the trunk edge.
As these trees grow in a fire disturbance ecosystem, they like to drop Leg sized limbs in windy conditions, this keeps them from being killed by a crown fire.
Those dropping limbs can kill, I doubt that any government would want them in an urban environment.
Another problem is trying to take west coast trees and grow them on the east coast, it doesn't seem to work, it was tried back in the Late 1050's to early 1960's and the trees died because of the cold coming in winter along with lake effect snows and winds.
Even NY City gets snow along with high winds and I don't know of any city that functions more like a heat sink than NYC.

Another idea, why not plant and grow the lost giants that were indigenous to the area?
A look back in time, say to the early 1700's or early 1800's should give the natural species that were logged out during the building up of the north east coast.
While it is true you most likely can't re-establish the Chestnut giants there are other species that were logged out and just never replanted.

Redhawk

 
Chris Kott
pollinator
Posts: 1831
Location: Toronto, Ontario
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Interesting. Thanks for the input, Redhawk.

Do you think it's possible to build a Great Lakes Rainforest guild, for instance, from native trees? Do you think it possible to have a similar kind of climactic effect as is seen in the West?

Also, are there any trees that you would want to import from a temperate rainforest that doesn't have an analogue here?

I think the limb-dropping is a valid reason why you wouldn't want such trees over roadways and such, but what of park areas designated for, well, not strictly speaking conservation, as I am suggesting augmentation with non-native species, but for greenspace, not really designed for foot access except by foot path?

There are, for instance, urban parks around riparian areas that can't be built up because of the seasonal flooding. Ravine areas are also great people-free zones, and they can, depending on orientation, easily have a warmer, more humid microclimate due to being sheltered by increased land texture.

I just think developing, as a specific example of a larger idea, a Great Lakes Rainforest complex would regulate humidity and rainfall patterns, and decrease the severity of the dry season at the end of the summer. More water and an evening out of temperature extremes would probably ameliorate food production for the whole of the effected area.

-CK
 
Bryant RedHawk
gardener
Posts: 4895
Location: Vilonia, Arkansas - Zone 7B/8A stoney, sandy loam soil pH 6.5
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Yes it is very possible to reforest with the native trees, after all they were cut because they were easy to get to and huge.
White pine was one tree that used to be there in huge sizes.
There are old growth white pine boards used as flooring in some of the really old houses that are 24" across and these are quarter sawn boards, which means the tree these boards came from was at least 48 inches in diameter and probably more like 60+ inches in diameter.

Let's think about your idea of putting large limb dropping trees in a park. Where do people like to sit when they go to a park? where do they usually put the bike/walking paths in parks? What happens when a 300 lb. limb falls 100 feet and hits a walker or their dog or child that ran away for a game of come catch me mommy?

seasonal flooding might be a great spot to see if cypress trees could survive there.

The other issue with the west coast giants is that high winds can and will blow them down, Nor-easter winds can get to around 100 mph.
I've seen a giant redwood fall over from high winds, the tree was 300 feet tall and it took out two other giant redwoods on its way to the ground.
It felt like a small earth quake when it hit and the pit at the roots was only 4 feet deep, but it was over 20 feet in diameter.

I love the idea, I just think the research needs to be directed towards a re-establishment of the trees that grew in that area and are adapted to that area.

Redhawk
 
Posts: 332
Location: SW PA USA zone 6a altitude 1188ft
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You might look to Pittsburgh as a sample of what you might do. Pittsburgh has so many steep hillsides that can't be built on, too steep for roads. So they are forests within the city. No one maintains these areas, they just grow wild. You could use the species that grow well there as a guide to what'd grow well in an urban area. Myself I can't remember what species. As a kid we played in the woods right there in the city. I seem to remember articles saying that locust was what started out growing there. But I don't remember thorns? I also don't remember fruit trees. Wait, I do remember a giant pie cherry tree, next to a pair of "city steps".

There was a park called West Park which spanned much of the North Side. Retired folks sat there on park benches under huge shade trees. The only species I remember was the Ginkgo that we called what the berries smell like. That's maintained, lot of leaves to clean up.'Now the drug dealers sit under the huge shade trees on the benches. The city has a lot of huge shade trees growing out of the devil strip between the street and the sidewalk. The attorneys love the condition of the sidewalks. If I picked the trees planted I'd choose a lot of Sugar Maples. If I still lived there I'd scatter Sugar seed on those hillsides.
 
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