It’s hot here in the Sonoran Desert. It’s not unseasonably hot and unbearably humid, like it is in so much of the US these days. Triple-digit summer weather is standard here in Southern Arizona, and—at least right now—we’re not hitting the record temperatures that we did last summer. That said, overexposure to the sun is a real risk.
For that reason, I take my morning walks as soon as it’s light enough to see safely. And on a recent morning walk, I came across this sunburned palo verde tree. Yes, sunburned. Though still alive, something caused it to fall on its side, and its bark has gotten sunburned from overexposure.
Did you know that some trees photosynthesize through their bark? We think of aspen trees as having white bark, but many aspen trunks have a green tinge, at least at some points during the year. It turns out that’s chlorophyll, the same chemical that allows leaves to photosynthesize. Aspen trees photosynthesize through their bark in winter and early spring, helping sustain the plants in mountainous regions with long winters where typically only evergreens thrive.
Palo verde trees also photosynthesize. In fact, their leaves are so small that nearly 75% of photosynthesis comes through the bark. Based on the sunburn I saw, I would bet those leaves are more important to the tree in providing shade. Just a few hours of summer sunlight in the Sonoran Desert is evidently enough for any creature!
We don’t photosynthesize, but we do need sunlight. Time in the sun can increase vitamin D levels, which helps the body absorb calcium. Sunlight also helps us maintain a positive mood and avoid depression (hence the development of specialized lamps and “daylight” lightbulbs). But overexposure is a danger. It’s much more efficient (and much less dangerous than risking skin cancer) to get our vitamin D from food and supplements.
Earth would be dry and dead without the sun, yet overexposure to sunlight causes dehydration, nausea, sunburn, cancer, and more. It’s definitely possible to have too much of a good thing. (The one exception I can think of is genuine, strings-free expressions of love.)
As summer continues to provide us with plenty of heat, I invite you to pay attention to the role of the sun in your life. Regardless of how hot it is in your part of the world, spend at least a moment in the sun this week. Give thanks for all it does for us…then finish your dash between car and house and give thanks for a cool place to shelter!
