Branham: Aspen trees are having heart attacks

This summer has been hot. Too hot. We are in a stage 2 drought in the Roaring Fork Valley, in a drought pattern that stretches back 20 years. When I started to research what the impact of the drought could be on our aspen trees, I discovered something shocking.  

Aspen trees under heat stress can succumb to a heart attack. Did you know that? 

Could we lose our beloved aspen trees to climate change? 

I’ve felt a pain in my chest the last few weeks as I walk the East Maroon Portal trail and find browned and shriveled thimbleberry bushes. Where is the fireweed and Indian paintbrush? Everything is brittle and crispy. And then the aspen leaves, turning yellow, brown, and even black in mid-August. As I walk, clouds of fine dust float up from the forest floor. The trees look bent over and weary, enduring a summer with so little rain. 

In the last few days, I could feel the Earth drink the rain with gratitude. What a relief. But this rain does not solve the drought.  

Droughts kill trees. And often, we don’t see the impact of the die-off for decades. But there is something else going on. 

A recent study from the University of Utah published in the New Phytologist found that under heat stress, trembling aspen trees can succumb to something like a heart attack (Fickle et al, 2025). It works like this: Trees have these little tiny straws that go down through their roots into the soil and up to their leaves. The water in these pipes is under a healthy tension that makes it flow. But, in drought, the aspens have to pull harder and harder on the water in the soil to try and get it up to their leaves. As they do, the tension reaches a breaking point, and little air bubbles start to shoot in and begin blocking the pipes that move the water through the tree. Basically, an embolism unfolds. The process is like a chronic arterial disease. And the trees as young as three years old are vulnerable. 

The aspen trees begin to die from within their hearts. And, horrifyingly, changing temperatures — due to human-driven climate change — is to blame. 

We heat the planet through emitting greenhouse gases and fossil fuels. The Earth’s natural and perfect symbiosis begins to tilt. More periods of drought. Less snow pack. Less rain. Extreme weather events unfold.  

And now, aspen trees are having heart attacks. 

I see this as an ecological and spiritual crisis. And we have a moral responsibility to act. How can we return to right relationship with the trees?  

If we do not curb rising global temperatures, drought patterns will increase, and we may permanently loose our aspen forests in this valley. Yes, nature will adapt and replace them with hardier species who can survive the climate.  

But what is Aspen without our aspens?  

Since it can take years to see the full impact of a drought on the trees, it’s easy to look outside and think things are fine. Today, it rains. The aspens stand. 

But the climate is bending and warping under global heating. It’s hard to see this. It’s harder to feel it. But we must. Because by the time a massive die-off of Aspens in this valley happens, it will be too late.  

Can the threat of aspen heart attacks help us take reducing carbon emissions seriously?  

There is still time. And already, the aspen trees are growing their buds for next year. They will store them until spring. Even now, you can see them on the twigs. 

The aspen trees live out their promise to us. What is our promise to them? 

Dr. Lindsay Branham is an environmental psychologist, scholar, author, and Emmy-nominated filmmaker whose work explores embodied kinship between humans and the Earth. Subscribe to her Substack at lindsaybranham.substack.com.