Guy R. McPherson was part of a panel that gathered remotely on 17 September 2024.…
Science Update: Overheated Forests Becoming Net Carbon Sources?
Inside Climate News: Many Overheated Forest May Soon Release More Carbon Than They Absorb
Science Advances: How close are you to the temperature tipping point of the terrestrial biosphere?
Excerpt from Nature Bats Last, “Climate-Change Summary and Update,” Self-Reinforcing Feedback Loop Number 22:
Drought-induced mortality of trees contributes to increased decomposition of carbon dioxide into the atmosphere and decreased sequestration of atmospheric carbon dioxide. Such mortality has been documented throughout the world since at least November 2000 in Nature, with recent summaries in the February 2013 issue of Nature for the tropics, the August 2013 issue of Frontiers in Plant Science for temperate North America, and the 21 August 2015 issue of Science for boreal forests. The situation is exacerbated by pests and disease, as trees stressed by altered environmental conditions become increasingly susceptible to agents such as bark beetles and mistletoe (additional examples abound).
One extremely important example of this phenomenon is occurring in the Amazon, where drought in 2010 led to the release of more carbon than the United States that year (Science, February 2011). The calculation badly underestimates the carbon release. In addition, ongoing deforestation in the region is driving declines in precipitation at a rate much faster than long thought, as reported in the 19 July 2013 issue of Geophysical Research Letters. An overview of the phenomenon, focused on the Amazon, was provided by Climate News Network on 5 March 2014~. “The observed decline of the Amazon sink diverges markedly from the recent increase in terrestrial carbon uptake at the global scale, and is contrary to expectations based on models,” according to a paper in the 19 March 2015 issue of Nature. Finally, according to a paper in the 1 July 2016 issue of Global Biogeochemical Cycles, the 2010 drought completely shut down the Amazon Basin’s carbon sink, by killing trees and slowing their growth.
Tropical rain forests, long believed to represent the primary driver of atmospheric carbon dioxide, are on the verge of giving up that role. According to a 21 May 2014 paper published in Nature, “the higher turnover rates of carbon pools in semi-arid biomes are an increasingly important driver of global carbon cycle inter-annual variability,” indicating the emerging role of drylands in controlling environmental conditions. “Because of the deforestation of tropical rainforests in Brazil, significantly more carbon has been lost than was previously assumed.” In fact, “forest fragmentation results in up to a fifth more carbon dioxide being emitted by the vegetation.” These results come from the 7 October 2014 issue of Nature Communications. A paper in the 28 December 2015 online issue of the Proceedings of the National Academy of Sciences indicates Amazon forest could transition to savanna-like states in response to climate change. Savannas are simply described as grasslands with scattered trees or shrubs. The abstract of the paper suggests that, “in contrast to existing predictions of either stability or catastrophic biomass loss, the Amazon forest’s response to a drying regional climate is likely to be an immediate, graded, heterogeneous transition from high-biomass moist forests to transitional dry forests and woody savannah-like states.”
The boreal forest wraps around the globe at the top of the Northern Hemisphere. It is the planet’s single largest biome and makes up 30 percent of the globe’s forest cover. Moose are the largest ungulate in the boreal forest and their numbers have plummeted. The reason is unknown.
Increasing drought threatens almost all forests in the United States, according to a paper in the 21 February 2016 online issue of Global Change Biology. According to the paper’s abstract, “diebacks, changes in composition and structure, and shifting range limits are widely observed.”
For the first time scientists have investigated the net balance of the three major greenhouse gases — carbon dioxide, methane, and nitrous oxide — for every region of Earth’s land masses. The results were published in the 10 March 2016 issue of Nature. The surprising result: Human-induced emissions of methane and nitrous oxide from ecosystems overwhelmingly surpass the ability of the land to soak up carbon dioxide emissions, which makes the terrestrial biosphere a contributor to climate change.
An abstract of a paper to be published in the April 2016 issue of Biogeochemistry includes these sentences: “Rising temperatures and nitrogen (N) deposition, both aspects of global environmental change, are proposed to alter soil organic matter (SOM) biogeochemistry. … Overall, this study shows that the decomposition and accumulation of molecularly distinct SOM components occurs with soil warming and N amendment and may subsequently alter soil biogeochemical cycling.” In other words, as global temperatures rise, the organic matter in forests appears to break down more quickly, thereby accelerating the release of carbon into the atmosphere.
Published Recently:
McPherson, Guy R. 2020. Academic Pursuits. Woodthrush Productions, New York.
Latest peer-reviewed journal articles:
McPherson, Guy R. 2020. Near-Term Loss of Habitat for Homo sapiens. Earth & Environmental Science Research & Reviews 3(4):216-218.
McPherson, Guy R. 2020. The Means by Which COVID-19 Could Cause Extinction of All Life on Earth (pdf). Environmental Analysis & Ecology Studies 7(2):711-713.
McPherson, Guy R. 2020. The Role of Conservation Biology in Understanding the Importance of Arctic Sea Ice (pdf). Earth & Environmental Science Research & Reviews 3(3):147-149.
McPherson, Guy R. 2020. The Myth of Sustainability (pdf). Earth & Environmental Science Research & Reviews 3(3):117-122.
McPherson, Guy R. 2020. Trees Cannot Sequester Enough Carbon to Slow Abrupt Climate Change. Modern Concepts & Developments in Agronomy (pdf) 6(4). DOI: 10.31031/MCDA.2020.06.000641
McPherson, Guy R. 2020. Earth is in the Midst of Abrupt, Irreversible Climate Change. Journal of Earth and Environmental Sciences Research 2(2).
McPherson, Guy R. 2020. Will COVID-19 Trigger Extinction of All Life on Earth? (pdf). Earth & Environmental Science Research & Reviews 3(2)2:73-74. doi.org/10.33140/EESRR.03.02.04
McPherson, Guy R. 2019. Going Halfway: Climate Reports Ignore the Full Evidence, and Therapists Ignore Grief Recovery. Clinical Psychology Forum 321:28-31.
McPherson, Guy R. 2019. Becoming Hope-Free: Parallels Between Death of Individuals and Extinction of Homo sapiens. Clinical Psychology Forum 317:8-11. The full paper is linked here.
Books Published Recently:
McPherson, Guy R. 2020. Another Voice Crying in the Wilderness: My Homage to Edward Abbey, in three formats:
Signed, inscribed edition (includes postage and handling within the United States). These copies will be signed by the author and inscribed to whom you wish (e.g., “To Bill and Jane …”).
McPherson, Guy R. 2019. Only Love Remains: Dancing at the Edge of Extinction. Woodthrush Productions, New York.
McPherson, Guy R. 2019. Revised Second edition of Going Dark. Woodthrush Productions, New York.
Pauline Panagiotou Schneider and Guy R. McPherson. 2018. Revised Second Edition of Ms. Ladybug and Mr. Honeybee: A Love Story at the End of Time. Woodthrush Productions, New York.
McPherson, Guy R. 2019. Revised Second edition of Walking Away from Empire: A Personal Journey. Woodthrush Productions, New York.
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