#Tropical Trees

[colorsoutofearth]

Close up of Palm leaves (Thrinax radiata)

Photo by Will Burrard-Lucas

[rjzimmerman]

Excerpt from this story from Smithsonian Magazine:

Last October on the island, Gora, Esquivel-Muelbert and their research team embarked on the first expeditions of the Gigante Project, an ambitious effort to find out what’s killing giant tropical trees around the world. And the island was a great place to start. The largest trees in the research forest are about 1,000 times bigger than the median tree size, Gora says.

Some of the dead or dying giants look like towering skeletons—sunlight streams through the gaping hole in the canopy where their crowns once flourished. Now, they’re leafless and snarled in lianas. At ground level, beetles have moved in, eating away at the trunks and leaving behind sawdust-like piles of frass.

Learning what kills giant trees is a question of increasing urgency. In 2022, a Nature study conducted in Australia suggested that the death rates of tropical trees there have doubled since the 1980s.

The research gives tropical forest ecologists reason to believe that the giant trees are also being affected by this trend. But they don’t know for sure. Existing mortality data is not based on giant tree deaths. In fact, research on tropical trees has historically overlooked giants because their enormous size, long life spans and rarity make it difficult to study them. Therefore, scientists don’t have enough data to understand giant tropical tree mortality, or how it’s shifting due to climate change.

“We have no confidence about what’s going on for these big trees,” Esquivel-Muelbert says.

The Gigante Project seeks to fill that knowledge gap. Esquivel-Muelbert, Gora and their colleagues have launched an international effort to investigate drivers of giant tropical tree mortality, including lightning, wind, drought and disease. But their deaths aren’t the only mystery Gigante hopes to solve.

“If you had to guess, how old do you think the oldest trees in tropical forests are?” Gora asks.

“We don’t know,” he says. “The number of trees that are dated are in the dozens. We have no concept. We don’t even have a ballpark.”

How long does it take for a sapling to become a giant? How long can they live after they reach full size? Which giant tree species appear where? These are just a few of the seemingly endless questions that remain unanswered about giant tropical trees. The Gigante Project will inform the answers to these queries as well. But studying mortality is especially important at this time in Earth’s history, at the precipice of catastrophic warming and biodiversity loss.

Research suggests human-driven climate change is playing an outsized role in increasing the mortality of tropical trees. The 2022 Nature study that showed a doubling of tropical tree mortality since the 1980s identified atmospheric drying triggered by global warming as a likely cause. Growing frequency and intensity of storms, drought and heat are just some of the other mechanisms by which climate change stresses and kills tropical trees.

Because the giant trees have survived for so long through many different pressures, one may assume that they would be more resilient than smaller trees. But while they are more tolerant to stress, their exposure to stress is greater. For example, giant trees are morevulnerable to wind and lightning due to their height, and some evidence suggests their high demand for water may mean they’re more vulnerable to drought, too.

Climate change is likely altering the mortality rates of tropical trees, and this added complexity makes understanding how and why giant ones die more pressing than ever before.

“We know that these temperature increases are occurring everywhere,” says David Bauman, a tropical forest ecologist not involved in the Gigante Project, and lead author on the Nature study.

[crudlynaturephotos]

[tothemettle]

A white Gustava superba, I'd not seen before, usually pale pink. Shrubby tropical tree to maybe 20 feet, dense foliage, Singapore > Thailand flowering Oct > Nov. Flowers > 6" dia, pleasantly perfumed.

[floralfantasy]

Gulmohar season has officially begun. The Delonix Regia tree is native to Madagascar and is found across tropical regions around the world. It is the national flower of St. Kitts and Nevis. 🧡