— from the blog of Guy McPherson, Nature Bats Last
…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 andmistletoe (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.
Dennis Murray, a professor of ecology at Trent University in Peterborough, Ontario, thinks the dying moose of Minnesota and New Hampshire and elsewhere are one symptom of something far bigger – a giant forest ecosystem that is rapidly shrinking, dying, and otherwise changing. “The boreal forest is breaking apart,” he says. “The question is what will replace it?”
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.
23. Ocean acidification leads to release of less dimethyl sulphide (DMS) by plankton. DMS shields Earth from radiation. (Nature Climate Change, online 25 August 2013). Plankton form the base of the marine food web, some populations have declined 40% since 1950 (e.g., article in the 29 July 2010 issue of Nature), and they are on the verge of disappearing completely, according to a paperin the 18 October 2013 issue of Global Change Biology. As with carbon dioxide, ocean acidification is occurring rapidly, according to a paper in the 26 March 2014 issue of Global Biogeochemical Cycles. Acidification is proceeding at a pace unparalleled during the last 300 million years, according to research published in the 2 March 2012 issue of Science. Over the past 10 years, the Atlantic Ocean has soaked up 50 percent more carbon dioxide than it did the decade before, measurably speeding up the acidification of the ocean, according to a paper published in the 30 January 2016 issue of Global Biogeochemical Cycles. Not surprisingly, the degradation of the base of the marine food web is reducing the ability of fish populations to reproduce and replenish themselves across the globe, as reported in the 14 December 2015 online edition of theProceedings of the National Academy of Sciences.
Diatoms, one of the major groups of plankton, is declining globally at the rate of about one percent per year, according to a paper in the 23 September 2015 issue of Global Biogeochemical Cycles.
The Southern Ocean is acidifying at such a rate because of rising carbon dioxide emissions that large regions may be inhospitable for key organisms in the food chain to survive as soon as 2030,according to a paper in the 2 November 2015 online issue of Nature Climate Change.
A paper in the 26 November 2015 issue of Science Express indicates millennial-scale shifts in plankton in the subtropical North Pacific Ocean that are “unprecedented in the last millennium.” The ongoing shift “began in the industrial era and is supported by increasing N2-fixing cyanobacterial production. This picoplankton community shift may provide a negative feedback to rising atmospheric CO2.” One of the authors of the papers is quoted during an interview: “This picoplankton community shift may have provided a negative feedback to rising atmospheric carbon dioxide, during the last 100 years. However, we cannot expect this to be the case in the future.”
Further research on primary productivity in the ocean was published in paper in the 19 January 2016 issue of Geophysical Research Letters. Referring to the Indian Ocean, the abstract concludes, “future climate projections suggest that the Indian Ocean will continue to warm, driving this productive region into an ecological desert.”
For the first time, researchers have documented algae-related toxins in Arctic sea mammals. Specifically, toxins produced by harmful algal blooms are showing up in Alaska marine mammals as far north as the Arctic Ocean — much farther north than ever reported previously, according to apaper in the 11 February 2016 issue of Harmful Algae. The abstract indicates, “In this study, 905 marine mammals from 13 species were sampled including; humpback whales, bowhead whales, beluga whales, harbor porpoises, northern fur seals, Steller sea lions, harbor seals, ringed seals, bearded seals, spotted seals, ribbon seals, Pacific walruses, and northern sea otters. Domoic acid was detected in all 13 species examined and had the greatest prevalence in bowhead whales (68%) and harbor seals (67%). Saxitoxin was detected in 10 of the 13 species … These results provide evidence that … toxins are present throughout Alaska waters at levels high enough to be detected in marine mammals and have the potential to impact marine mammal health in the Arctic marine environment.”
24. Jellyfish have assumed a primary role in the oceans of the world (26 September 2013 issue of the New York Times Review of Books, in a review of Lisa-ann Gershwin’s book, Stung! On Jellyfish Blooms and the Future of the Ocean): “We are creating a world more like the late Precambrian than the late 1800s — a world where jellyfish ruled the seas and organisms with shells didn’t exist. We are creating a world where we humans may soon be unable to survive, or want to.” Jellyfish contribute to climate change via (1) release of carbon-rich feces and mucus used by bacteria for respiration, thereby converting bacteria into carbon dioxide factories and (2) consumption of vast numbers of copepods and other plankton.
25. Sea-level rise causes slope collapse, tsunamis, and release of methane, as reported in the September 2013 issue of Geology. In eastern Siberia, the speed of coastal erosion has nearly doubled during the last four decades as the permafrost melts. And it appears sea-level rise has gone exponential, judging from Scribbler’s 4 May 2015 analysis. Considering only data through 2005, according to a paper published 28 September 2015 in the Proceedings of the National Academy of Sciences, the 500-year return time of floods in New York City has been reduced to 24.4 years.
26. Rising ocean temperatures will upset natural cycles of carbon dioxide, nitrogen and phosphorus, hence reducing plankton (Nature Climate Change, September 2013). Ocean warming has been profoundly underestimated since the 1970s according to a paper published in the online version ofNature Climate Change on 5 October 2014. Specifically, the upper 2,300 feet of the Southern Hemisphere’s oceans may have warmed twice as quickly after 1970 than had previously been thought. According to a 22 January 2015 article in The Guardian, “the oceans are warming so fast, they keep breaking scientists’ charts.”
Another indication of a warming ocean is coral bleaching. The third global coral bleaching event since 1998, and also the third in evidence, ever, is underway on Australia’s Great Barrier Reef. According to Australia National News on 28 March 2016, a survey of the Great Barrier Reef reports 95% of the northern reefs were rated as severely bleached, and only 4 of 520 reefs surveyed were found to be unaffected by bleaching.
27. Earthquakes trigger methane release, and consequent warming of the planet triggers earthquakes, as reported by Sam Carana at the Arctic Methane Emergency Group (October 2013)…