Just How Much Hotter are Treeless Streets?

Urban heat island effects are caused by building materials like pavement and concrete absorbing more heat than natural surfaces like plants, making cities much warmer than their surroundings.

In Medellín, Colombia, Weathered's Maiya May found out how much of a difference trees can make to mitigate this effect.

Weathered: Earth's Extremes is now streaming on the PBS App

[foxgloved]

I’ve looked into the studies on this. Turns out the areas with less trees/more heat/more pollution are poor formerly redlined neighborhoods. See for example “Disproportionate exposure to urban heat island intensity across major US cities” Hsu et al 2021 in Nature.

[suzannepottsshorts]

After losing so many trees to the emerald ash borer, we lost almost 3/4 of our tree canopy to a derecho. We've been planting trees, but they need time to grow.

[martinbaker]

It's so true. I lived in Singapore, where much of the nation is covered with trees, and was much more comfortable than Thailand where I now live, where they actively seem to demolish trees 😢

[Rutabega_NG]

In the US it seems to vary by city.

I remember at some point in the '80s there was a massive push to put trees all over the city here (Cincinnati), where they could. They focused on the urban areas; the less urban areas already have trees.

We also have green space in every neighborhood. Some bigger than others, but every neighborhood has at least one grassy public area. Didn't appreciate that until I visited NYC.

It does make a significant difference.

[EZUS]

I was surprised to see Memphis doing pretty good job on keeping the trees up. 🌳🌴🌲

[Entre]

Been watching you for a while now. Keep up the great work! It’s rare that I pass on a video from you or your colleagues.

[lonevoice]

We’ve known this for years. What happens is a bunch of trees are planted, silver shovels, photo ops, politicians posing. But, when it comes to taking care of these trees, having experts on staff to treat sicks trees, to replacing dead or hazardous trees, suddenly there’s no money and the people end up hating them for the mess they cause. Great to plant trees in urban areas, critical for human health, but without a maintenance infrastructure, they’re a problem.

[LS-xyzt]

I had to run my AC way less this summer because I moved to an apartment surrounded by trees. They kept things cool indoors up to 90°.

[nmatheis]

What's up, my alma mater PSU giving serious lessons on the importance of trees! Woot woot!!!

[Julian_Wang-pai]

The old centre of Ho Chi Minh City (Saigon) is avenued by trees - roughly 30m (100ft) tall forest giants. Remarkable.

[estherstephens]

I just watched this episode of Weathered. It’s crazy that even Medellin, Columbia is handling this better than the U.S. At least making a better effort.

[_maxgray]

Curious which US cities aren't part of the tree loss trend - what are they doing differently and how can we replicate it?

[WakandaleezaRazz]

It’s important to note you said 80 degree day. We in Houston have trees all over the place, but when it’s 95-105 it doesn’t help as much. Temps are getting hotter period

[jannetteberends]

That it differs so much! Trees alongside the road are also better for Road safety. It slows cars down.

[piratapan]

Pls also do Celcius when Fahrenheiting

[MoonThuli]

They're actively growing other things in Medellin too...

[ttopero]

I’ll blame our car culture for killing existing urban trees & preventing new trees from growing to a full canopy to shade pavement. Not directly, but by the demand for parking space especially, even more than travel lanes. The areas without sidewalks should have a healthier tree canopy since they can be planted with less pavement over their root zone but the space between the sidewalk & street actually encourages trees so the absence of sidewalks perversely doesn’t encourage street tree lines.

[LaSpastica]

The majority of urban trees I’ve seen planted in the U.S. are planted improperly, with the roots covered over by pavement, and over mulching around the base of the trees. Those are at least some contributing factors to why trees are dying in our cities.

[JRussellDay]

So streets without trees are hot, but if it wants to be cool it needs trees, this is the sort of mixed messages that give our streets such low confidence they just let people walk all over them..

[Obzurv]

We also need reflective nano particulate on asphalt roads/Streets