This post is based on a meeting I had with Eric Duchemin, Associate Professor of Science and the Environment at UQAM, who has taught students working in urban agriculture for several years now. (I participated in the École d’été sur agriculture urbaine in 2010.) A grad student giving a talk about the urban agricultural history of Montreal, so I took the opportunity to ask Eric some questions about remediating landscapes and urban soil and returning it back to primary use – that is, forestry and agriculture.
He did not say “it’s impossible,” but that is what it comes down to. There are two reasons why. When it comes to agriculture, the Province immediately declassifies built land into a class that you cannot farm on. The processes of
- developing land,
- things that happen on that land while it is built on,
- while it is occupied, and
- the process of demolition of structures,
all poison and destroy the soil. The legal process and cost of remediating that soil is prohibitively expensive. The gist of it: having to excavate the soil, install a certain kind of liner, and then replace the soil with new soil (from where?) or else ship out that soil, remediate it for metals (hydrocarbons being rather easy to biodegrade), and then put it back in place. These would be the requirements before you farm the land.
This boggles my mind: why are we so careless that we allow anything to happen to such an extent that in each case, we must compartmentalize soil away from the underlying geology, in order to protect what remains? When it comes to highway – and highrise – construction and demolition, I can see the extent of the problem. But in lower developments, I don’t understand.
You might have animal agriculture, provided you bring in the food from somewhere else, because the animals will not be getting enough healthy forage from plants growing in compacted and potentially contaminated (testing will help) city soil – and the tracts of land will not be big enough to support medium- and large-scale livestock farming.
On that note, to keep in mind while gardening: don’t amend vegetable gardens with cow manure. It contains a lot of trace metals, as a consequence of biomagnification.
Restoration of landscapes from urban features
My take: while I’m a pessimist in some things, I do think that Environment, Health & Safety (workplace EHS) can be a legalistic cult at times. Here I err not with them but on the side of optimism, science, and heritage values. I believe we can find a practical mix of crops, livestock, and supplies that would allow farming on former city land.
In addition: if trees will grow, who is to disallow silviculture? Why?
I have some reason to be optimistic. This following image shows you the relative availability of metallic nutrients, depending on the pH of the soil solution (water in soil):
From the graph: the general availability of metals for uptake by plants is strongest as the soil gets either more acidic or more basic. If you keep testing the soil and keep it within range, you should be able to keep the metals in the ground and not in the foliage you eat. Or, if you do decide to do something about chelating the metals, or change the pH and put an acid-loving plant in place, you may be able to impact (i.e. remediate), in a small way, the metallic content of the soil.
- The state of Victoria in Australia has a good guide to soil health here.
The only alternative to redeveloping a brownfield in Quebec is restoring it to parkland and forests. And Eric told me, apparently, city people don’t like forests. I don’t believe this. This is seriously vexing. If so, this is a problem with democracy, because why should we allow people in a majority to continue to prefer what is obviously bad, and came from misinformation, or zeroing out, in the first place? (Show people only cityscapes, they will think cityscapes are standard and good. Show them a forest, and they think exceptional and vacation.)
But knowing the pressures of public ownership, that forest would have to be privately owned by a wealthy person, or put under a conservation easement, or managed by the city as a woodlot, with the understanding that it is for the benefit of the environment and people.
When you consider how long it takes the geologic processes of this world to form soil, it is no surprise to me that we have to treat it gently. Outlaw building on “greenfield:” farmland, wetland, and forest; and improve the way we handle brownfield.