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GREGORY SAVILLE · MATEJA MIHINJAC · LARRY LEACH
GREGORY SAVILLE · MATEJA MIHINJAC · LARRY LEACH
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The Rio+20 environmental conference in Brazil is wrapping up this week. Community safety, CPTED and crime prevention folks rarely see themselves in the environment. They should. How else can we get people to engage on their streets, parks, and public areas unless they are safe?
Luckily plenty of work has been done to show how that can happen. A new publication released at Rio+20 has a chapter co-written by myself and my ICA friend and South African architect Tinus Kruger that shows how environment and crime fit together. The book is titled Sustainable Cities and authors include the Secretary-General for the Conference on Sustainable Development (Rio+20) Sha Zukang, Executive Director of UN Habitat Joan Clos, the Mayor of Rio de Janeiro, Eduardo Paes and Danish Minister of Transport, Henrik Dam Kristensen. More details can be found on the Rio+20 Sustainable Cities website.
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"If you demolish the whole city for the flow of traffic, what destination for that traffic would be left?" - Mark Wagenbuur, How The Dutch Got Their Cycle Paths Whenever I show crime prevention successes and examples of livable streets it doesn't take long before someone barks: That can never work here! We're too different! Nonsense! Everyplace is different. Everyplace has similarities. Transferring a good idea from one place to another depends on one factor: Imagination! Transferring ideas from one place to another is called scalability. No successful company says "that can't work here". They say, "how can we make it work here." With that in mind I found a fascinating Twitter this week from my livability consultant colleague Megan Carr. Megan highlighted a short video by Mark Wagenbuur called "How the Dutch Got Their Cycle Paths". Holland has more bicyclists per capita than anywhere. Yet it is the world's safest place to cycle due to a carefully designed bike infrastructure. It wasn't always this way. Following WW2 the Dutch copied the American auto orgy: bigger roadways, more cars, tearing up public transit. They destroyed their old bicycle paths. Eventually they realized their cities couldn't cope with expanding traffic and increasing traffic deaths. By 1971 the annual number of car child deaths on roadways climbed to 1,400. Then came the 1970s oil and economic crisis. Costs skyrocketed. Sound familiar? Today in the middle of the Great Recession the leading cause of US deaths for 4-14 year olds is car crashes! The Dutch changed direction. During the 1973 oil crisis they instituted Car free Sunday's. Their goal was to cut oil dependency, increase road safety and street livability. It worked. By 2010 the number of child car deaths plummeted to 14 and that's not a typo! Drop two "0"s from 1,400! Today Holland has among the most livable and walkable streets in Europe. My favorite line from the video is for the can-never-work-here crowd: "The Netherlands problems are not unique. Their solutions should not be either."  Beautiful patterns tell us how...not why "When imagination sleeps, words are emptied of their meaning." Albert Camus - 1960 Last blog discussed a study by US Forest Service researchers showing how tree canopy in Baltimore cut urban crime by 12%. I just read a 2010 study commissioned by the Center for Disease Control showing how business improvement districts cut violent crime by the same amount in Los Angeles. So we cut crime 24% by planting tree canopies in a business improvement district (BID)? Sounds silly. That's because both studies are correlational - studies that show a pattern between two things, not a cause. We don't know why canopies or BIDs work, only that they seem to have impact. Dozens of correlational studies appear each year. Like research showing underarm deodorant causes cancer. Or toothpaste. Or cell phones. Or smoking which, it turns out, is true. What to do? There is a mantra in science: correlation-is-not-causation. Because there is a relationship doesn't mean you can infer cause. Tree canopy and BIDs may coincide with crime declines. That doesn't mean they cause them. Unfortunately neither can we dismiss correlation studies. Doing so may result in dismissing a good cause assertion. The International Agency for Research on Cancer lists criteria for testing correlational studies - a plausible mechanism between cause and effect, a singular relationship between before/after effects, a reasonable time between the cause/effect, and so on. Satisfying these criteria helps mitigate the correlation-is-not-causation dilemma. CORRELATION IS NOT CAUSE I think what correlational studies need is simple - a plausible theory explaining why. That way we'll know if a study shows a correlational relationship we are seeing a shuffle not a full step. Sometimes I wonder if theory-building is a dead language. It shouldn't be! That's where research creativity and imagination really show up (not in clever data manipulation or new statistical methods). There are some great publications that provide imaginative theory, for example Gilligen's Preventing Violence and Kennedy's Don't Shoot". It would be wonderful to produce a 24% cut in crime by planting tall trees with great canopy in a business improvement district. It would be a shame if they don't and we have no idea why.  Tree canopy in the island city of Montreal What to do about trees? You know, the CO2-sucking kind. Do they influence crime opportunity? I doubt they cause or solve it. Do they matter at all? I've written about the crime and tree theory before. New research calls for a revisit. Yesterday my Safe Cascadia colleague Tod Schneider found the latest evidence. It was a study called "The relationship between tree canopy and crime rates across and urban-rural gradient in the greater Baltimore region". First, what does CPTED have to say? CPTED guidelines generally mention trees only in passing. A typical example is the Tempe, Arizona CPTED guidelines on the Florida DOCA website. Those guidelines, as others like them, practically ignore canopy. They do suggest pruning for better sight lines and street lighting. But mostly trees are invisible in guidelines, unlike in the real world where they are not. When urban planner Elisabeth Miller and I wrote Saskatoon's CPTED guidelines we spent a bit more time on trees. We drew on research showing the positive effects of trees, particularly a recent Portland, Oregon study. Our conclusion: "Tall trees, especially those older trees with large trunks, are often associated with beauty and should be retained." And what does this latest research say? In the June issue of the journal Landscape and Urban Planning, US Forest Service researchers concluded "a 10% increase in tree canopy was associated with a roughly 12% decrease in crime."  Canopy along Moscow street It's not the definitive word, of course. Yet their tree/crime relationship held statistically for public and private areas. It also held for different socioeconomic neighborhoods. It didn't matter if low crime rich areas had more tree canopies and poorer areas didn't. They controlled for other factors like public versus private land. Same result. One exception - a patch of industrial, abandoned areas where canopies made things worse. Yet they were the exception not the rule. Mostly the study results suggest tree canopies contribute to safety. What to do about trees? Plant, prune and leave them alone. |
