How Can A Giant Saguaro Survive the Devastation of a Fire?

The devastation of a forest fire always makes me sad, especially when the forest consists of giant saguaros that take decades to grow.

I’ll make up for the years of the locust, the great locust devastation— Locusts savage, locusts deadly, fierce locusts, locusts of doom, That great locust invasion I sent your way. 

Joel 2:25 (MSG)

A Look at Devastation

As I entered the foothills east of Phoenix, I couldn’t help but gasp. Sometime between May and July, a fire had ravaged thousands of acres of desert. The devastation took my breath away. Giant saguaros stood sentinels over the scorched earth. Some had scorch marks all the way to their first arm.

How would the saguaros—a keystone species of desert health—survive the devastation of a fire?

Saguaros, a giant cactus species found only in the Sonoran Desert in southern Arizona, can grow from sea level to about 4000 feet. Numerous animal species depend on saguaros for food and shelter. Gila Woodpeckers and Gilded Flickers create cavities in the cacti for nests. Other bird species repurpose the nests for years.

Bats and insects help pollinate the flowers in the spring, and both animals and humans use the fruit saguaros produce.

Saguaros can live at least 200 years—much longer than the average human. In fact, the Tohono O’Odham people view saguaros as a different type of humanity. They call saguaros respected members of their tribe.

It may take a saguaro ten years to grow from seedling to one inch. The seeds flourish only in certain conditions—adequate moisture, heat, and protection. For this reason, saguaros do best under a nurse plant, such as a paloverde tree. The devastation of a fire wipes out the nurse plants, and scientists have noticed great gaps in saguaro ages.

Fires also blister and burn the skin of a saguaro, changing it from green skin capable of photosynthesis, to a tan-brown shell. Saguaros may starve to death or die from bacterial infections which enter through their scarred, cracked skin.

How Many Survive?

When scientists study areas devasted by fire in the past, they discover entire generations of cacti missing. The saguaros can’t grow until the nurse plants have an opportunity to grow back first. Saguaros well-established before the fire often survive, and once the nurse plants regrow, a new generation will spring up.

Fire devastation may outright kill a saguaro, or it may experience a slow death. Without the other plants present, the desert becomes susceptible to flooding and landslides. These events could topple saguaros with weakened root systems.

Scientists estimate the mortality rate for saguaros jumps from seven percent to over 40% in the decade after a fire. The mortality rate depends on the intensity of the devastation. The hotter the fire, the less chance the saguaro has of long-term survival.

A simple grass, brought over from Africa in the 1930s, causes the most damage to the giant saguaros. Buffelgrass, transplanted in and around the Sonoran Desert ecosystem as food for cattle and erosion control, burns hot enough to melt tin, zinc, and aluminum. The flames can reach 25 feet—high enough to severely damage a saguaro.

Now considered a noxious weed and highly invasive species, buffelgrass (Pennisetum ciliare, Cenchrus ciliaris) threatens the health of the Sonoran ecosystem. Local communities have started banding together to root it out safely (to keep it from releasing more seeds and spreading).

Invasive Species, Saguaros, and Me

Buffelgrass reminds me of sin. It seems like a good idea (the devil loves to dress sin up in fancy clothes), but the longer it sticks around, the more it invades our lives. When we least expect it, it can burst into flames—leaving devastation in its wake.

Like saguaros, we can live through the devastation. But a lot depends on our root system and how water-filled we are when the fire begins.

In fact, invasive sin can take out whole generations of Christians. I see this happening now with young people as they watch Christians bicker about preferences and self-preservation while justice and mercy burn to the ground.

What can we do to stop invasive species from taking out a generation?