Megafire smoke has long-lasting impacts on orchard trees

Our world is becoming increasingly familiar with massive wildfires, aptly termed “megafires,” which ravage landscapes and ecosystems with unprecedented force.

These destructive forces of nature are known for their immediate devastation, but recent studies reveal that their impacts stretch far beyond the scorched earth, ash-filled air, and charred forests they leave in their wake.

Smoke drains the energy reserves of trees

One of the less-observable effects of megafires is the long-lasting damage they impose on orchard trees. According to researchers, these effects can significantly disrupt future yields and agricultural stability.

In a game-changing study conducted at the University of California, Davis, scientists discovered that the thick smoke produced by megafires can adversely affect the energy reserves of trees and result in a staggering 50% reduction of their nut harvest.

This startling fact places new importance on understanding the role of wildfires and their smoke in both agricultural and natural ecosystems.

Megafire smoke and orchard trees

The team at UC Davis had initially embarked on an assessment of how trees, specifically almond, pistachio and walnut varieties, handle heat and drought by storing energy in the form of carbohydrates.

While their research was ongoing between 2018 to 2022, megafires in 2020 swept over 4.2 million acres across California. The fires produced a dense cover of smoke, ash, and particulate matter that lingered for weeks.

Effects of prolonged smoke

This unexpected development presented a unique opportunity to observe how the prolonged and pervasive smoky conditions might influence carbohydrate levels in trees and ultimately affect their growth and productivity.

Study lead author Jessica Orozco from the UC Davis Department of Plant Sciences elaborated on the potential impacts of megafire smoke on orchard trees.

“Photosynthesis produces carbohydrates, which are critical elements for tree survival,” Orozco explained. “Trees need carbohydrates not just to grow but to store energy for when they’re under stress or when photosynthesis isn’t happening.”

Lingering impacts of megafire smoke

The thick smoke altered light conditions, occluding some direct sunlight and casting a shadow over the orchards, while simultaneously creating a diffuse light effect that filtered through the smoke.

This diffusion could potentially aid trees in generating more carbohydrates. However, Orozco explained that the smoke was so dense that its increase probably didn’t offset the loss of direct sunlight.

The researchers observed that megafire smoke didn’t just diminish the carbohydrate reserves in trees but instigated lasting losses, which pressed on even after the fires had been extinguished.

Notably, the most severe wildfire activity often aligns with the period when trees begin to store carbohydrates to get through winter dormancy and fuel spring growth. The impact of smoke was far greater than anticipated.

“We were expecting to see some impact especially in the months when the smoke was really dense, but we weren’t expecting the smoke to have such a lingering effect and result in a significant drop in yield,” said Orozco.

Complexity of megafire smoke

The scientists are not yet sure which components of megafire smoke caused this drastic drop in tree carbohydrate levels, but the complexity of the smoke’s composition presents several possibilities.

It’s plausible that one or a combination of factors, such as reduced light availability, elevated ozone concentrations, and increased particulate matter levels – all known to interfere with photosynthesis – are to blame for the significant decline in energy storage within the trees.

The findings underline one thing very clearly; the risks posed by wildfires are not just immediate and visible – they have far-reaching and enduring consequences.

Growing threat to agriculture

The impact of megafires extends beyond the immediate damage to crops and soil. As climate change accelerates, scientists warn that the frequency and intensity of megafires will continue to rise, posing a growing threat to agricultural production.

Hotter temperatures and prolonged drought conditions create the perfect environment for these large-scale fires to ignite and spread.

The increasing prevalence of megafires highlights the urgent need for solutions that can mitigate the long-term impacts of smoke on crops.

Early-warning systems, innovative farming techniques, and fire-resistant plant varieties could become essential tools in preserving agriculture in fire-prone regions.

As megafires become more frequent, understanding their effects will be crucial for developing effective adaptation strategies.

The study is published in the journal Nature Plants.

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