Geoengineering by Growing Urban Rainforests

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

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

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

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

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.

There isn't enough urban room for a urban rain forest that would have much of an impact. Just to counter the co2 of the humans in a large city would take hundreds of acres, probably thousands of acres. The best way is to keep the forests and farm land we have. Require and enforce replanting after logging. Go to a longer cycle between loggings. Bigger trees convert more co2. Stop urban sprawl.

The initial draw for me to Western Redcedar was that they grow about a metre a year for their first 75 years in adequate to optimal conditions. If there are any eastern species that will do this, I would love to know about them.

I think the ravines that we have all around Toronto are a great place for this type of project to get a toehold. Our ravine ecosystems are collapsing due to invasives that originated from ornamental plantings, so rather than bemoan that, I think it would be a great time to reengineer those ecosystems. If they were just revamped versions of what was here earlier, maybe with all the trophic niches filled where perhaps they weren't before, that would still be amazing.

I would prioritise thriving ecosystems resilient to human damage and change over the novelty of giant trees that grow fast and fall on you.

But I would still like the giant trees. I know that the Eastern White Pine, for instance, will grow about a metre a year between the ages of 15 and 45, but it takes them 15 years to get to that point. That will do, I suppose, but from the perspective of geoengineering through carbon sequestration, more biomass means more sequestration. By the time the pine is ready to start really taking off, the redcedar is already 15 metres tall, and by the time the pine tops out, the redcedar will be 45 metres tall, with another thirty to go before it slows.

I know that a straight-up transplantation wouldn't work, and might be a bad ecological idea, besides. But in the case of ecosystem collapse, and as a measure to turn the excess nutrient and carbon resources of urban areas into systems that buffer against and ultimately work to combat anthropogenic climate change, it is a compelling thought to me.

So if we were going to redesign a temperate hardwood/boreal transitional eastern analogue of a western rainforest, what could it look like? White pines, red mulberries, red and/or black oak, poplar and birch? Sugar maples? What food forest elements would we work in?

If we were designing a complete forest system to supplant a collapsed one, not only in and around cities, but in cases of forestry industry-aligned monocultures that are now failing due to climate and insect issues, what would the pieces look like, what would their functions be, and what would be examples of them that we could use?

-CK

There are other trees that will do what you are looking for Chris.
Ponderosa Pine, Sitka Spruce, Douglas Fir, Port Orford Cedar, Alaska Yellow Cedar, all are faster growing, longer living and these have deeper root systems as a bonus.

If these can be established either as a mix or in groves (the way nature plants them is small to large groves mixing another species around the fringes).
I think you would have a very good base for a new ecosystem that was quite similar to the ancient ecosystem.

Redhawk