Steward's Notes – Sharing Stories of Nature in the Land Between
Is Your Neighborhood The Hottest In Peterborough?
On August 15th 2021 it was 23.9°C at the Peterborough Municipal Airport. By all respects, an average summer temperature. If you looked at a thermometer outside your house though, it might paint a much different picture. In the downtown core and areas along Lansdowne St. temperatures reached as high as 40°C. This represents over 15°C temperature difference! What is happening and how can it be stopped?
The urban heat island is a phenomenon we’ve long known about. It occurs when natural land cover such as forest or meadows are replaced with surfaces that retain heat such as asphalt, concrete or pavement. These surfaces then radiate the heat back out into the local environment, warming the surrounding area. The effect can increase the cost of heating, and put elderly or other vulnerable citizens at risk of heat stroke, and even death.
The urban heat island effect often puts the most vulnerable populations at risk. Some of Peterborough’s lowest income census areas have the highest recorded temperatures. You’ll notice on the map that areas directly south and north of the downtown which are characteristic as lower income neighborhoods, have some of the highest recorded temperatures, while some of Peterborough’s more affluent neighborhoods have much lower recorded temperatures.
Image #1: Downtown South Peterborough. 35% to 43% low income households. On average +15°C
Image #2: Monaghan Ward 1% to 5% low income households. On average, +5°C
Image #1 characterizes a neighborhood south of downtown. Census Canada considers between 35% and 43% of the population to be low income. This neighborhood is one of the hottest in Peterborough, coming in at a 15°C temperature deviation. Meanwhile Monaghan Ward represented in image #2 only recorded a 5°C temperature deviation. It is clear that land cover and tree canopy have a huge impact on temperature deviation. With the additional pressure of climate change, these deviations are likely to become more pronounced over time.
What can be done about urban heat though? Luckily we have some solutions! Planting trees is once again, a major winner in this regard. Not only does tree planting decrease average temperatures, it can lower heating and cooling bills year round for residents, overall a huge win for the climate. Removing asphalt and other “high heat” surfaces can also benefit neighborhoods, replacing asphalt with grass is even a viable solution for combating urban heat. Depave projects around the country have made major inroads in this regard, and perhaps focusing on lower income neighborhoods could have an additional impact.
In all, reducing the urban heat island effect gives us one more incentive to restore ecosystems, plant trees, and protect our natural areas. Perhaps years from now, when you look at the thermometer outside your house, it may more accurately reflect the temperature across our city.
Data provided by USGS through LANDSAT 8.
Calculating π Using Lakes from the Land Between
Hey folks! I know I’m late to the party, but hey I post on the last week of the month, so happy π day! In addition to environmental shenanigans, I also enjoy some good olde mathematics goofiness, especially when there is some great geometry involved. So in celebration of this year’s π day, I thought I’d try and find some lakes in the Land Between that will give us as close an approximation of π as possible working backwards from their surface area.
For those of you unaware, π day happens every year on March 14th (3/14) due to the numerical date’s similarity to the value of π (3.14….)
The first problem to overcome when calculating pi from a lake’s geometry is the shoreline fractal problem ie. the coastal paradox. Essentially, depending on the length of the ruler you use, you can get wildly different results. A shoreline is a curved fractal that looks very different depending on the scale at which you view it. From an airplaine, details on the shore you could see at ground level totally vanish, while details under a microscope reveal even more intricate patterns within the shoreline. All of this means that it is actually quite difficult to measure the actual length of a shoreline, take this exaggerated example:
Here is Little Lake in Peterborough. Using 2 different length rulers I get different results for the shoreline length. As I increase the detail, the length of the shoreline increases by 0.23km! Thankfully for us, the Ministry of Natural Resources produces standardized map layers we can use to calculate the area of different lakes. We’ll use the map layer meant to be viewed at 1:100,000 scale.
For those of you who need a refresher, the formula for calculating the area of a circle can be done with the following formula:
In order to calculate π we need to do some rearranging. For this problem the two givens we have are the lake’s “circumference” and it’s area. Unfortunately, this is where we need to fudge things a little bit. In order to calculate π we will need to have a radius in addition to the lake’s area. In order to calculate the radius we will take the average of 3 measurements of the lake’s diameter and divide by 2. So now are formula looks like this:
Now that we know what our formula is, lets go find some lakes to measure. For starters, lets try the obvious, Round Lake near Havelock. Its in the name so it must be pretty close to a circle!
Is Round Lake the roundest? Stay tuned to find out!
Plugging all of that into a calculator gives us a value of pi that is equal to 3.91! Pretty good for a natural object, but can we do better? Is Round Lake the roundest of the lakes?
I’ll spare you the math on this one. Longford Lake is in the middle of nowhere, I’ve never visited, but it sure looks nice from space! Maybe I’ll check it out someday if its pi enough.
Is North Longford Round Enough?
With an average radius of 524m and an area of 1,140,948m2 North Longford clocks in at a pi value of 4.15. So sorry Longford, may you rest peacefully in continued obscurity.
Next up we’ll try Halls Lake north of Minden off Highway 35. Its a deep lake that is quite round with some nice trails nearby. Lets give it a shot!
Halls Lake: Pretty round don’t ya think?
All righty! We did the math (the monster math?) here at Stewards Notes and determined that Halls Lake is more round than Round Lake! Clocking in at a value of 3.02 for π! Congratulations Halls Lake! Be sure to visit Halls Lake some day and give a toast to how π it is.