Yes, there are Blue Zones.
Let’s talk about Green Zones.

Healthy Aging

Can we all be evergreens?

There has been a lot of talk about Blue Zones these days. You know, those wonderful places on Earth where people live the longest. With fall quickly approaching, however, we decided to dive into the science behind autumn leaves – and why some trees get to be forever green. That got us thinking – can we make our own Green Zones?

So, why do some trees shed their autumn leaves in the cold – while others keep them?

In a whopping 40-page review, T.J. Givnish covers a number of theories on why some trees shed their leaves every fall, and why others get to stay green all year long. Here are the top explanations:

• Autumn leaf-dropping (aka deciduous) trees use big leaves to gather a bunch of energy during the sunny months. The result: Burned out leaves by autumn, but stored energy for the winter months. Hello, East Coast.
• In contrast, evergreen trees use smaller leaves that more evenly extract the sun’s energy throughout the year, requiring less concentrated periods of energy and less nutrient-rich soil to keep that gorgeous green color. Hello, West Coast.

T.J. Givnish points out, however, a triple paradox to these theories. Trees drop leaves in the West. Evergreen trees thrive in the East. There are also evergreen trees that swap out their leaves… yet stay green.

Solving the triple paradox

So, what is really behind what drives leaves to drop, and are there any ties between aging leaves and aging humans? In their paper titled, ‘The ecology of leaf life spans,’ Chabot and Hicks unlocked the secret to leaf longevity. Ready for it?

Great. Here it is:

Net income = Σ PfiF + Σ PuiU – C – W – H – S

Simple, right? This equation basically shows that the more energy a tree spends on making baby leaves every year, the shorter the leaves live. This isn’t really a big surprise, because the same phenomenon is observed in mammals. The larger a mammal’s energy investment to make large litter sizes, the shorter its lifespan. Since humans already have pretty darn small litter sizes (aka, typically one baby at a time), we have already leveraged this longevity secret.

Being tough and unattractive extends longevity… if you’re a leaf.

In his paper, T.J. Givnish proposes a number of other ways trees extend the lifespan of their leaves. Are you a leaf and want to live longer? Here are two top tips:

1. Be tough. Leaves with tougher cell walls are less likely to freeze and die during a frost. They are also less likely to fall off from dehydration during drought. The thicker a leaf and the greater a leaf’s “mechanical tissue”, the more resilient it is to life’s challenges.
2. Look unappealing (to eat, that is). Leaves that are difficult to eat and digest are less likely to meet their demise being digested by herbivores. Clearly, this helps to extend a leaf’s longevity. Yes, we just made herbivores the enemy in this story.

There may be some Green Zone truths relevant to human longevity.

You’re an appealing person, so we’re not going to mess with that. Here’s a couple of plant longevity tricks that are relevant to us humans:

• Build up your mechanical tissue. While Givnish described toughness as the amount of “mechanical tissue” in plants, for us, this equates to muscle. Numerous studies, including many summarized in Izquirerdo & Singh’s recent paper, have shown that stronger muscles result in improved resilience and longevity in humans. While plants don’t have thumbs, we do. So, put those kettlebells to work.
• Strengthen your cell membranes. Just like plant cells, mammalian cell strength directly dictates longevity. We covered this topic a couple of weeks ago, and the same message remains: as described by A.J. Hulbert, the longer we can keep our cells strong and protected against aging-related breakdown, the lower the oxidative damage, and the longer and healthier we live.

So, to become an evergreen, build up your muscles… and your cellular strength.