Saturday, January 22

Florida to abandon palm trees to combat climate crisis

(CNN) — When you think of Florida, beaches and palm trees come to mind. But what if those palm trees were slowly replaced by other trees? That could happen over time due to climate change, and South Florida communities are trying to save the world from the climate crisis, one tree at a time.

“Palm trees do not sequester carbon at the same rate as our native tree canopy and they do not provide shade, they do not cool streets and sidewalks to help counteract the urban heat island effect offered by the tree canopy,” said Penni Redford, manager of Climate Change and Resilience of the City of West Palm Beach.

With atmospheric carbon dioxide levels higher than at any time in at least the last 800,000 yearsAccording to the National Office for Oceanic and Atmospheric Administration (NOAA), Earth must remove it or humans must stop adding it. In fact, the last time the concentration of carbon dioxide was this high was more than 3 million years ago.

Scientists are working on solutions to safely capture and contain atmospheric carbon. One approach is called “terrestrial carbon sequestration”, which basically consists of planting trees. A tree absorbs carbon during photosynthesis and stores it for the life of the tree.

But Florida’s beloved palms are the least effective at sequestering carbon. The average palm in South Florida only absorbs 2.2 kilograms of CO2 per year.

Compared to other trees – oaks, mahogany, pines and cedars – which can sequester more than 1,360 kilograms of CO2 during their lifetime, it may be better to exclude palm trees in favor of broadleaf or coniferous trees.

Despite restrictions, they warn of carbon emissions 0:54

Kristine Crous, a senior lecturer at the University of Western Sydney, explains that palm trees do not produce wood, so they are less effective at storing carbon.

This is why some do not believe that palm trees are trees at all. Botanists, ecologists and foresters have a variety of definitions of what a tree really is. (Palm trees are sometimes defined as large grasses, shrubs, and even trees, depending on who you ask.)

Regardless, the concern is that a standard passenger vehicle emits about 4.6 metric tons of CO2 per year, which means that we need a lot of trees to combat the amount of vehicles on the roads.

Although palm trees may not be good at sequestering carbon, cutting them is not the answer. Instead, programs in both West Palm Beach and Miami Beach, Florida, take the initiative to plant more capable trees to handle changing weather conditions.

“Palm trees, while an iconic part of the Miami Beach landscape, have gone from being an accent plant to an important component of the city’s urban forest,” it read. in the program outline de Miami Beach.

Having so many palm trees will not allow these cities to manage carbon sequestration as well as they would with other varieties of trees. By 2050, Miami Beach palm trees should represent no more than 25% of the public tree population, according to el plan Rising Above de Miami Beach.

“The living oak of the south, Quercus Virginiana: Big-crowned trees, can withstand occasional floods and hurricanes and are resistant to salt spray, provide habitat for birds and a variety of mosses and bromeliads in South Florida, “said Redford.

Even without considering logging and deforestation, Mother Nature fells many trees. As the Earth continues to warm rapidly, the loss of trees to hurricanes and floods will become an even greater concern in the future.

One in three tree species could become extinct 0:46

However, in the case of palm trees, the best solution may not be to simply replace them with more palm trees. Instead, they should be replaced by trees that are better at mitigating the climate crisis.

But we can’t just blame the palm trees, as the type of tree is just one piece of the puzzle.

Crous told CNN that the age of the tree is also an important factor: Younger trees absorb less carbon dioxide than older trees.

“Yes, tree species are important, some grow faster than others, so their response to elevated CO2 may also differ,” Crous said. “But it is important to distinguish between the responses of younger trees compared to older trees.”

The scientists set out to study whether old trees can really be taught new tricks to help them adapt to a changing climate.

Age is not just a number

Young trees and mature trees do not adapt to changes equally. So “planting more trees” in an effort to combat climate change is not a universal remedy.

Climate change is making hurricanes stronger, knocking down mature trees and even entire forests, which are most needed to slow climate change.

The canopy of a mature forest during the BIFoR fieldwork investigation.

“Planting trees is great, but valuing primary forests is just as important,” Crous said.

Is being done a joint research study from the University of Birmingham, the University of Western Sydney, Australian EucFACE and BIFoR FACE around the world to study how trees adapt to increased carbon dioxide in the atmosphere.

Research shows that mature oak trees can increase their rate of photosynthesis by up to a third in response to higher levels of CO2. In just the first three years of the 10-year project, the 175-year-old oaks clearly responded to increased CO2 by increasing their rate of photosynthesis.

“Our specific goal was to quantify the photosynthetic response (carbon uptake) of these trees to future levels of atmospheric CO2,” said Anna Gardner.

This is great news from a carbon mitigation point of view. We have yet to reduce human greenhouse gas emissions, but it is encouraging to learn that some tree species can adapt to higher levels of CO2.

“Planting trees will certainly help reduce CO2 levels,” Crous said. “But since trees take a long time to mature, it will be a slow effect, and we really need to reduce emissions now by including other measures.”

The study looked at a variety of things, such as the age and type of trees, and the amount of sunlight available.

“Tree type certainly matters in this regard. But more so, our climate models are using data from seedlings and young trees to diagnose how old forests will absorb future increases in CO2 in the air,” said David Ellsworth, professor of physiology. of the tree at the University of Western Sydney.

That is why it is so important that we save landscapes and forests with dense older and more mature trees.

Research groups at the University of Birmingham in a forest of trees.

“Our CO2 in the atmosphere and its impacts on the climate would be much worse if we didn’t have these old forests, and these old forests can adjust and increase CO2 uptake in the future,” Ellsworth said.

The study notes that the amount of forest carbon uptake in the future, and subsequent carbon sequestration, “will be crucial determinants of future atmospheric CO2 concentrations. Therefore, quantifying the photosynthetic response under elevated CO2 levels, especially for mature trees, it is essential to understand the carbon uptake of forests under a changing atmospheric composition. “

Planting new trees in Florida

Trees alone will not solve the climate crisis, but they can help if we know how to use them correctly.

Redford says West Palm Beach gives away 1,000 native trees a year for residents and businesses to plant.

“We have an active tree planting program,” Redford explains of the program they are using in West Palm Beach. The goal is to help Floridians not only beautify their environment, but also better prepare them for future global warming. To do that, Redford said, you have to be selective.

“We don’t use our canopy tree fund to plant palm trees,” Redford said.

West Palm Beach is planting trees as part of its Tree Canopy Improvement program.

Miami is also joining the initiative to change the planting priority to a variety of trees, but not palm trees. The programa Rising Above Miami Beach’s plan to combat the climate crisis includes an urban forestry master plan detailing the environmental benefits of planting shade trees, including species such as oak, ash, elm and sycamore, rather than palm trees.

“It may seem simple to select trees, but it takes thought and planning to have the right tree in the right place, one that can deliver the maximum benefits with minimal maintenance and does not contribute to other concerns such as fertilizer runoff and higher costs of water and maintenance, “Redford said.

There is also a plan for when construction leads to logging. Redford said that if a developer needs to remove trees and cannot replace them, they can pay a fund to have the trees planted elsewhere.

“Of course we try to save the trees or replant there first,” Redford said. “But if it is not possible, we seek to plant trees where they are most needed.”

Planting trees to remove carbon dioxide from the atmosphere is a critical component of climate change mitigation, experts say. But it is important to be smart about which trees we plant and pay more attention to saving the older trees we already have.

One in three tree species could become extinct 0:46

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