Urban Agricultural Systems Inspired By Nature Can Mitigate Climate Change
Urban Ecology is a way of looking at and studying the interactions between our built and natural environments. Far from being separate, nature and cities can benefit and benefit from each other is a complex web of interrelations. In a sense, Urban Ecology represents the maturation and combination of two science; urban planning and design, and ecology.
Almost by definition, cities are active, busy, bustling, ever-changing places where short-lived beings go about their busy days. Fast fashion, quick commerce, short election cycles – the world around us takes on various pace layers.
What better way to slow to slow things down than to seed cities with beings capable of living centuries or millennia? In what ways might a walk beneath ancient giants and twisted ancestors place us in a bigger here? A longer now?
Artist and musician Brian Eno once said that he wants to live in a “big here” and a “long now”. How long is your now? That is to say – what’s the timeframe in which you view our day to day? What timescale informs your decisions? Days? Months? Centuries?
In 01996, the LongNow Foundation (named by Eno) formed to “provide a counterpoint to today’s accelerating culture and [to] help make long-term thinking more common”. They define they now – the longnow – as the last 10 000 years and the next 10 000 years.
How differently would we act if we lived in a longer now? In what ways would our decisions change and in what ways might out priorities shift?
The point of slow landscaping is to provide continuity in a fast paced environment – to provide pause and contemplation – to remind us that we are the result of circumstances that extends way before (and after) us – that we’re living in the LongNow. Slow landscaping asks us to act in ways – and is an act in and of itself – that leaves future generations with more options than we inherited.
One strategy may be to plant long-lived trees on sites unlikely to be disturbed. A second more devious strategy might be to plant long-lived trees to protect existing and vulnerable sites from future disturbances or development.
Living longer than most buildings, slow landscapes would dictate the shape of the built environment – as opposed to the other way around. Cities and buildings would bend and shift to fit slow landscapes like geological features. Each tree would shape the fabric of the spaces it occupies. Poor architects and planners will hate them, but good ones will incorporate them into their designs.
There are many long-living species to choose from – a quick google search yields a list of the world’s oldest individual trees – many of which are slow growing conifers living in high alpine environments. I’ve selected a handful suitable for growing in my local (Edmonton) environment. I encourage you to see what will grow where you live.
One of three bristlecone pine species, P. aristata, can be found at local nurseries here in Edmonton and is a small to medium sized tree (20 feet tall and 25 feet wide) native to the Blackhills of Colorado.
Koren Pinenut is a slow-growing giant that produces edible nuts. Reportedly hardy to USDA zone 3, the Korean Pinenut is native to parts of Korea, Manchuria, Eastern Russia, and Japan. The tree can reportedly reach 100 feet, though, 30 to 50 feet is more typical for trees under cultivation. Plant one now and you’ll be harvesting pine nuts in 15 to 45 years – expect a yield of 10 to 20 pounds per tree. Bring a ladder.
Native to the high elevations of Alberta’s mountains, the whitebark pine is a long living Alberta tree with significant ecological value for wildlife (having coevolved with the local Clark’s nutcracker (Nucifraga columbiana) who bury and inadvertently propagate seeds. Like the Korean Pinenut, the seeds are edible, though, smaller.
The Whitebark pine is slow growing and can take on various forms depending on the harshness of its location. At high elevations, it sometimes grows as a multi-stemmed shrub but has the potential to get as large as 70 feet tall and 45 feet wide in more favourable conditions. The oldest recorded tree is 1200 years old.
The Whitebark Pine is currently a species under threat due to white pine blister rust, mountain pine beetle, and the ill effect of fire suppression. The most comprehensive sources of information on Whitebark pine that I could find is an Alberta Conservation Association report from 2007 and a profile on conifers.org.
A native Alberta tree found at high altitudes in the Rocky Mountains. Alpine Larch can grow anywhere from 30 to 80 feet tall depending on elevation – growing shorter at higher elevations. Soft green needles turn golden and fall off each year.
The oldest Alpine Larch is in Kananaskis and reported to be over 1900 years old. More information at conifers.org.
The trembling or quaking aspen grows locally in Alberta is has the potential to live for tens of thousands of years due to its massive underground root system that perpetually sends up new trunks. Though individual trunks – that present as individual trees – are short-lived, the plant as a whole can grow to be ancient.
The oldest know trembling aspen is named Pando growing in Utah’s Fishlake National Forest. Pando is a single male aspen tree estimated to be over 80 000 years old. Pando covers a staggering 106 acres, has over 4000 trunks, and has a mass around 6 600 metric tonnes.
Edmonton has embraced year-round decorative tree lighting, and it’s hard not to love it! An Edmonton Journal article from 2015 (Tiny white lights to adorn city tree year-round) states that the City’s forestry department “installed lights on 1000 city-owned trees in six business revitalization zones: Alberta Avenue, Beverly, Downtown, North Edge (107th Avenue), Old Strathcona, and 124th Street).” Walking Whyte, Churchill, or Giovanni Caboto amongst twinkling giant elms is magical, but it also has a potential dark side. If left unchecked, decorative tree lighting can cut into and even kill growing trees.
Beneath the bark of a tree lies a network of tissues that channel sugars, minerals, and water throughout the plant. When this flow of nutrients is interrupted by a cut or object wrapped tightly around the truck – a process called girdling – the tree can weaken or die. The danger of decorative lighting is that it can’t expand as the tree grows.
The same Edmonton Journal article goes on to state the “the lights are secured to the trees with zip-ties, and as the tree grows the zip ties will be loosened.” Unfortunately, this isn’t the case. Though I’ve seen zip ties used to secure extension cords running vertically up the trees, the decorative lights are secured by continuously wrapping the tree’s trunk and branches. As such, the only way to loosen the lights would be to remove and reinstall them.
But don’t trees grow super slow? Won’t it take years for decorative tree lighting to causes any damage? Let’s take a closer look – since most of Edmonton’s light wrapped trees are American elms, I thought I’d look into their rate of growth. Fair warning, the following segment contains math.
According to the City’s OpenTree data, (and some help from pi), the elms between 104th and 105th Street on Whyte have an average circumference of 51 inches. Though OpenTree doesn’t say their age, an Edmonton Journal article about the removal of diseased elms (between 99th street to 96th street) claims that they were planted sometime in the 40s. Let’s assume that the 104/105 elms are of a similar age.
Whyte Avenue Elms
Average Circumference = 4 feet 3 inches (51″)
Estimate of Age = 72 years
Growth rate of Circumference = 0.71″ per year
Since my Edmonton data is spotty, let’s turn to some old elms from our Southern neighbours. These trees may or may not be representative of an elm growing in Edmonton.
The Treaty Elm – Philadelphia, PE
Circumference = 24 feet (288″)
Age = 280 years
Growth rate of Circumference = 1.03″ per year
The Johnstown Elm – Johnstown, NY
Circumference = 16 feet (196″)
Age = 200 years
Growth rate of Circumference = 0.96″ per year
The math shows us that an elm can increase its circumference somewhere between 0.71 and 1.03-inches per year – which at first glance doesn’t seem like a lot. But consider that each strand of light wraps around the circumference of the tree 30 to 40 times! To prevent strangulation, a string of lights would have to increase its length by 30 to 40 times the annual growth of the tree’s circumference. That’s between 1.5 and 3.5 feet per year!
Though most trees can handle a few years covered in decorative lighting, lights can’t accommodate 1 to 4 feet of annual growth it’s a matter of time before they tighten, bite into the bark, and interfere with the flow of sap. The only way to prevent this is to remove and rewrap the tree at regular intervals or to run the lights vertically – a technique called tracing.
Don’t get me wrong, I love Edmonton’s decorative tree lighting – it seriously adds something to the city – especially during long, dark winters. But I also love trees, and the math doesn’t lie – a string of lights can go from loose to snug, to deadly in a few short years.
In the grand scheme of things, Edmonton’s elms are juveniles and could live for another two centuries. Considering that elms are already under threat from Dutch Elm disease and Elm Scale, it seems cruel to add strangulation into the mix. That being said, Edmonton’s not the fist municipality to use decorative lighting on trees. So in the interest of preserving our lights AND our urban forest, let’s see what other cities are doing.
The following decorative tree lighting guidelines are hand-picked from the City of Portland’s Department of Parks and Recreations and Cincinnati’s Department of Urban Forestry:
Non-seasonal lighting can not exceed three years.
If it sounds like I’m being tough on the City of Edmonton I must apologise – the work they do it beyond exceptional as demonstrated by the fact that they’re caring for and maintaining an inventory of over 267000+ urban trees, 7400 hectares of River Valley, city-wide naturalization, and running Roots for Trees and numerous other community beautification projects! When it comes to nature and urban forestry, you’d be hard-pressed to find a city as ambitious as Edmonton. They wrapped 1000 trees in stunning decorative lighting! 100 trees! How cool is that?! Seriously! But there are many more of us then there are of them and we can help! So if you see a tree that has outgrown its lights, contact the City by calling 311 and they’ll send someone to check it out.
Both tours will begin at the museum at 6 pm with stops in the river valley and Legislature grounds before heading towards Jasper Avenue. This walking tour will cover approximately 5km (2.5 hours) with a break at the halfway point.
You can register a spot on either tour by visiting the City of Edmonton’s Online eReg or by calling 311 with the respective course codes below:
When it comes to getting that perfect cut and keeping a healthy, natural lawn, you can’t beat one of these. Seriously, this is a grass powered lawn mower with a fertilizer attachment.
If you’re continually using the garden hose, there’s a chance that you’re doing it wrong. Actively and continuously needing to water your garden is a sign that you may have overlooked some simple but powerful water harvesting techniques. Here are [Read more…]
I know of no other Edmonton resident more controversial than Pica hudsonia; often referred to as the black-billed magpie or an annoying jerk. While many of us resent its 4 am wake-up calls, others find the Edmonton magpie fascinating. It’s the bird that [Read more…]
When ecologist Edward O Wilson coined the terms biodiversity and biophilia, he opened our eyes to new ways of viewing the world. Now, architects, designers, and academics such as Richard Register, Tim Beatley, and Geoffrey West are using lessons from ecology and network theory to design tomorrow’s resilient urban environment; biophilic cities.
What is a Biophilic City?
A biophilic city then embraces and incorporates natural systems into its design. They integrate the built and natural worlds in beneficial ways. The result? Biophilic cities are more attractive and less prone to floods, droughts, resource shortages, waste, and boredom. Biophilic cities have the potential to save money, resources, and spark the imagination.
Cities Are Natural – And Good For The Environment
We tend to view our built and natural environments as opposing forces. But I would argue that this perceived incompatibility has more to do with poor design than universal law. As it turns out, urban environments already play host to countless organisms. Let’s go a step further and argue that cities are natural. Far from being static, nature is the process of moving from few to many connections. In this successional process, each stage of builds upon the previous stage and creates the conditions necessary for the next. In this way, ecological systems diverge, diversify, and expand over time. What starts off as fragile becomes complex and resilient. As it turns out, cities behave in a similar way. What starts off as a small settlement expands to include many of the needs and services necessary to support the community. At each stage, the future is built on the present. As new connections grow, the system expands, and new possibilities emerge.
Biophilic Cities are Resilient
Resiliency is a property of systems and a measure of how connected its pieces are. As natural and built systems expand, their potential for connections increases rapidly.
Biophilic Cities Are Ecotones
Ecologists describe the intersection of two ecological systems as an ecotone. Ecotones bring together the biodiversity of each plus a few others (think otters at the edge of a lake). As a result, ecotones are rich in ecological relationships. They are among the most biologically diverse places on the planet. By design, Biophilic Cities are ecotones that connect economy, society and nutrients (money, food, and waste) with ecosystem services. Ex. Waste water runoff or the heat island effect become ecological solutions.
There’s something simultaneously very personal and completely public about having a favorite tree; it’s an interesting intersection between private, urban, and natural history. Trees are rooted in place and to love a tree is, in some small way, to love where you are – to become a part of it.
For anyone who’s walked around Edmonton, you’ll know that the City’s urban forest is pretty impressive. But trees aren’t just beautiful to look at; they cast shade, store carbon, provide habitat for animals, soak up millions of liters of water, and (yes) some even grow food. [Read more…]
Teacher, permaculture designer, master gardener, hobby beekeeper, consultant, and network nerd living in Edmonton, Alberta, Canada. Read More