Washington DC: A new analysis of U.S. Forest Service data shows that climate change is changing forests differently across the country. With increasing temperatures, intensifying droughts, wildfires, and disease outbreaks wreaking havoc on trees, researchers warn that forests in the American West are facing the brunt of the repercussions. The study, led by UF Biology researchers J. Aaron Hogan and Jeremy W. Lichstein was published in the Proceedings of the National Academy of Sciences. The study reveals a pronounced regional imbalance in forest productivity, a key barometer of forest health that gauges tree growth and biomass accumulation. Over the past two decades, the Western U.S., grappling with more severe climate change impacts, has exhibited a notable slowdown in productivity, while the Eastern U.S., experiencing milder climate effects, has seen slightly accelerated growth.
Forests play a critical role in regulating the Earth’s climate, acting as carbon sinks that sequester approximately 25% of human carbon emissions annually. However, their ability to store carbon hinges on the delicate balance between the positive and negative effects of climate change. The study, using national-scale forest inventory data, models trends from 1999 to 2020, analyzing 113,806 measurements in non-plantation forests.
“We are witnessing changes in forest functioning as forest ecosystems respond to global change drivers, such as carbon-dioxide-fertilization and climate change,” said Mr Hogan.
It is the future balance of these drivers which will determine the functioning of forests in the coming years to decades.
Some drivers, such as droughts and forest pathogens, have negative effects on productivity, but other drivers, such as carbon-dioxide fertilization, are predicted to have positive effects. This phenomenon suggests that increased carbon-dioxide levels enhance plant growth by increasing photosynthesis, which inspired the researchers to take a deeper look at its impact.
“The U.S. Forest Service has been monitoring the growth and survival of over a million trees across the U.S. for multiple decades,” said Mr Lichstein.
We were interested to see if their data provided evidence for increased rates of tree growth, as predicted by the carbon-dioxide fertilization hypothesis.
While tree growth in the Eastern U.S. aligns with expectations, the Western region shows extreme climate effects overshadowing any positive growth trends, challenging the prevailing assumption that forests’ carbon-storing ability will continue to increase.
Mr Lichstein said,
Our study suggests that future projections of climate and sea-level rise may be too optimistic because, in reality, ecosystems are likely to store less carbon in the future. Less ecosystem carbon storage means more carbon in the atmosphere and therefore more warming and accelerating climate change.
The findings also illuminate the fact that climate change is not a uniform force but rather a dynamic agent with region-specific influences. The study illustrates how the degree of climate change can push forests past a tipping point. Some forests are already approaching or surpassing climate thresholds which shift them to become sources of carbon, rather than sinks that remove carbon from the atmosphere.
Mr Lichstein said,
Ecosystem carbon sequestration is not guaranteed to be permanent, and it can be reversed by climate change. This reversal is already happening in the Western U.S., and there are signs that it may also be happening in other drought-impacted regions of the world, such as the Amazon.
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It might be tempting to chalk the losses up to extreme events. But, according to the researchers, the decline in productivity in the Western U.S. cannot be attributed to increased rates of tree mortality.
Mr Lichstein said,
We hear a lot about wildfires in the Western U.S., which kill a lot of trees and release carbon to the atmosphere. But our study shows that additional ecosystem carbon loss in Western forests is occurring due to declining tree growth rates.
With trees growing slower due to adverse climate change effects, including decreased precipitation, the study implies that, even without the intensifying wildfires, the carbon sink in Western forests will continue to weaken without urgent action to reduce human greenhouse gas emissions.
Mr Hogan said,
We must have healthy forests in connection with emissions reduction to restore the global carbon balance and limit climate change.
The transformations observed in U.S. forests raise concerns about their future resilience and sustainability. The researchers hope their findings highlight the urgent need for governments and industry to work together to reduce greenhouse gas emissions and achieve net-zero emissions as soon as possible.
Mr Lichstein said,
Our results highlight the need for reduced global greenhouse gas emissions. Without the emissions reductions that scientists have been urging for decades, forest carbon sinks will likely weaken, which will accelerate the pace of climate change.
Also Read: Climate Change Declined Snowpack In Northern Hemisphere Between 1981, 2020: Study
(This story has not been edited by NDTV staff and is published from a syndicated feed.)
NDTV – Dettol have been working towards a clean and healthy India since 2014 via the Banega Swachh India initiative, which in its Season 10 is helmed by Campaign Ambassador Ayushmann Khurrana. The campaign aims to highlight the inter-dependency of humans and the environment, and of humans on one another with the focus on One Health, One Planet, One Future – Leaving No One Behind. It stresses on the need to take care of, and consider, everyone’s health in India – especially vulnerable communities – the LGBTQ population, indigenous people, India’s different tribes, ethnic and linguistic minorities, people with disabilities, migrants, geographically remote populations, gender and sexual minorities. In a world post COVID-19 pandemic, the need for WASH (Water, Sanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign will continue to raise awareness on the same along with focussing on the importance of nutrition and healthcare for women and children, fight malnutrition, mental well-being, self-care, science and health, adolescent health & gender awareness. Along with the health of people, the campaign has realised the need to also take care of the health of the eco-system. Our environment is fragile due to human activity, which is not only over-exploiting available resources, but also generating immense pollution as a result of using and extracting those resources. The imbalance has also led to immense biodiversity loss that has caused one of the biggest threats to human survival – climate change. It has now been described as a “code red for humanity.” The campaign will continue to cover issues like air pollution, waste management, plastic ban, manual scavenging and sanitation workers and menstrual hygiene. Banega Swasth India will also be taking forward the dream of Swasth Bharat, the campaign feels that only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and the country can become a Swasth or healthy India.
