This is an air conditioner. Here’s a group of them. It’s also a water filter, an air purifier, a bike rack, a stimulus package, a therapist, a shamwow, crime stopper, noise reducer, traffic calmer, and oh right, a tree! Let me explain. There are a lot of trees in the Halifax region. How many? Maybe a thousand? Maybe a hundred thousand? Well, try 52 million. Put together, all those trees are part of what we call the Urban Forest. In fact, the municipality has a 442 page long document about this, called the Urban Forest Master Plan and if you’re wondering why we need 442 pages for, um, trees? You’ve come to the right place. Because, as it turns out, trees aren’t just pretty things to look at. They actually provide many important benefits. For example, air purification. In a city, the air can easily become polluted, whether that’s from industrial activity, or even just traffic from the streets. Now, one way to make sure our air is clean and breathable is to purify it with cool things like the smog free tower. It sucks in pollutants from the air, turns it into rings, and costs just $54,000 each. Or, you could plant a tree because trees are experts at cleaning the air. They trap airborne pollutants with their leaves and take in carbon dioxide through photosynthesis. In total, we estimate trees in Halifax trap 1478 metric tons of pollutants every year. So next time you’re, I don’t know, breathing? You can thank a tree for that. Here’s another benefit. Trees are cool to be around. Literally. Yea, they provide shade for people and nearby buildings but they also cool through a process called evapotranspiration. On a hot sunny day, trees are releasing water into the atmosphere, cooling the air around them and that is crucial for a city. You see, urban areas have a lot of surfaces that either create heat or reflect heat and that usually means that cities are hotter than their surroundings. A phenomenon know as the Urban Heat Island effect. So is the solution to set up a bunch of air conditioners on our streets? Heck no. Plant a tree instead. Here’s one more. When it rains in Halifax, which is quite often, that water has to go somewhere and, if not handled properly, it can lead to flooding and erosion. Well, trees play an essential role in handling that stormwater. They slow it down with their foliage while their roots absorb water and stabilize the soil around them. They’re kind of like a living shamwow. Remember those? Anyways, trees come with a lot of benefits and it turns out you can do the math on how valuable they are. With that, many smart people have calculated that trees in Halifax provide $9,600,000 worth of air purifying services, $12,400,000 worth of cooling, and $2,100,000 in savings for stormwater management. In fact, it’s estimated that for every dollar we spend on a tree in Halifax, we get $8 dollars back in benefits. But money isn’t even half the story here. Studies have linked trees to lowering stress, reducing crime, reducing noise, slowing down traffic, lowering road rage, reducing the number of accidents, increasing property values and, yea it’s a lot. So if there’s one thing you need to take away from all this, it’s that trees are really really useful and important. But if you can spare a bit more time, I want to leave you with two more things Size isn’t always everything in life but when it comes to trees, it makes all the difference. Larger trees means more air purification, more cooling, and more water absorption. And it’s not just that bigger trees are better, the relationship between a tree’s size and its benefits is exponential. That means, as a tree grows, it’s benefits grow faster? I’m not a mathmatician but I think all that really goes to say, it’s important to keep trees around for their whole lives because their benefits are greatest when they have a chance to fully mature. Look at this photo taken of the Halifax Hydrostone houses just after they were built in 1921. Those little saplings weren’t doing much back then but today, those trees are giving back all kinds of benefits to this neighbourhood. Where a tree is located is key. As a general rule of thumb, the closer trees are to people, the more good they can do for people. A really effective spot is the space between the sidewalk and the road. That’s where a tree can provide shade and cooling for nearby buildings while absorbing pollutants from road traffic and, yea, all that stuff I mentioned earlier. And that can be tricky. In many cities, this part of the road is also used for powerlines and having trees growing near these lines can be a hazard. That being said, the city’s position is that it’s still very much worth the effort to plant trees here and share the space because the benefits are that valuable. On top of that, they’ll soon be rolling out a program to prune street trees regularly every seven years to help manage those risks and that’s just great. So to recap, trees are valuable, bigger trees are even more valuable and the closer trees are to us, the more they benefit us. Now, I have to be honest with you. Deep down, I don’t think we like trees because of their ability to sequester carbon, provide shade, or absorb stormwater. There’s something more about trees that draws us to them. Something that’s hard to put into words or numbers. But the thing is, a lot of the time, that intagilble feeling we have about trees makes it difficult to defend keeping them. On paper, they become a pretty thing to look at, a nice to have, but ultimately, a second priority. But the reality is trees are an essential part of our cities and if doing a bit of math helps us appreciate them a bit more, well I’m all for it. Money may not literally grow on trees, but it most definitely pays to have trees around. To learn more about the role of trees in Halifax, visit the city’s urban forestry page at their website.