In modern times, air pollution is increasing as the population increases. People in metro cities as well as cities and towns have to live in extremely polluted environments.
However, British researchers found serious effects on their physical and mental health. Researchers conducted a study of 3.6 million people in England. Neurological, respiratory, and cardiovascular diseases, as well as mental health problems, such as depression and anxiety, have been found to be among the most common exposures to air pollution.
According to a recent research of more than 20,000 trees across five continents, older trees in the forest canopy are more tolerant of drought than younger ones and may be better suited to weather future climatic extremes.
The findings, in the opinion of University of Michigan forest ecologist Tsun Fung (Tom) Au, a postdoctoral fellow at the Institute for Global Change Biology, emphasise the significance of protecting the world’s last old-growth forests, which are biodiversity hotspots and store significant amounts of climate-warming carbon.
According to Au, main author of the study that was published online on December 1 in the journal Nature Climate Change, “the number of old-growth forests on the world is diminishing, while drought is anticipated to be more frequent and more extreme in the future.”
“From a climate mitigation standpoint, preservation of older trees in the upper canopy should be the top priority given their strong tolerance to drought and their excellent ability for carbon storage.”
Younger trees in the higher canopy were also shown to have increased resilience, which is the capacity to resume pre-drought growth rates, provided they are able to survive drought.
While selective logging, deforestation, and other hazards have contributed to the global reduction of old-growth forests, subsequent regeneration has resulted in forests that are increasingly dominated by younger trees, either naturally or by tree planting.
For instance, in the highest canopy layer of temperate forests across the world, the area occupied by trees less than 140 years old already significantly outnumbers that of older trees. Younger trees are anticipated to become more crucial to ecosystem health and carbon sequestration as forest demographics continue to change.
It has crucial implications for future carbon storage in forests, according to Au, as older trees in the top canopy are more drought tolerant and younger trees in the upper canopy are more drought resilient.
These findings show that due to the abundance of younger trees and their higher vulnerability to drought, the short-term effects of drought on forests may be severe. On the other hand, those younger trees have a better capacity to recover from drought in the long term, which may be advantageous to the carbon stock.
Given that reforestation has been highlighted by the Intergovernmental Panel on Climate Change as a potential nature-based option to help reduce climate change, Au and colleagues claim that such implications will need additional research.
The importance of preserving an intact forest cover and the carbon storage it provides as a social and environmental protection was also reinforced in the Sharm el-Sheikh Implementation Plan, which was released during the COP27 United Nations Climate Change Conference in Egypt in 2022.
“These discoveries affect how we manage our forests, so take note. According to Justin Maxwell, a senior author of the study and professor at Indiana University, “Historically, we have managed forests to encourage tree species that have the finest wood quality.”
“Our results indicate that managing forests for their capacity to store carbon and to be drought-resistant might be a key tactic in combating climate change, and that taking into account the age of the forest is a key factor in how the forest will adapt to drought.”
The growth response of 21,964 trees from 119 drought-sensitive species was examined using long-term tree-ring data from the International Tree-Ring Data Bank, both during and after the century’s droughts.
They concentrated on the tallest canopy of trees. The forest canopy is a zone made up of mature, overlapping tree crowns that is multilayered, physically complex, and biologically significant.
The researchers divided the upper canopy trees into three age groups—young, middle, and old—and looked at how age affected drought response for various types of hardwoods and conifers.
They discovered that under drought, young hardwoods in the top canopy exhibited a 28% growth loss as opposed to an old hardwood’s 21% growth drop. During a severe drought, the 17% disparity between young and old hardwoods increased from 7%.
Although the age-related variations might seem relatively insignificant, the study’s authors claim that when taken into account globally, they might have “massive consequences” on regional carbon storage and the world’s carbon budget. This is especially true for temperate forests, which are among of the biggest global carbon sinks.
Conifers in the study had fewer age-related drought-response variations than hardwoods, which the researchers attribute to the fact that needle-bearing trees often live in more drier climates.
The present study was a component of Au’s dissertation for his doctorate at Indiana University, and he kept working on it after joining the University of Michigan’s Institute for Global Change Biology, which is housed in the School for Environment and Sustainability.
Instead than concentrating on a particular forest type, the new research is a synthesis that depicts the overall impacts of thousands of trees in varied forests spanning five continents. According to the authors, another distinctive feature of the current study is its emphasis on trees in the high forest canopy, which lessens the confusing effects of tree height and size.
