Human Ancestors Evolved in a Low-Carbon World
By Tim Radford
For the entire 2.5 million years of the Ice Age epoch called the Pleistocene, it was a low-carbon world. Atmospheric carbon dioxide hovered around 230 parts per million. Not only did Homo sapiens evolve on a low-carbon planet, so did Homo erectus and most other human species now known only from fossil evidence in Europe and Asia.
And this long history of a planet kept cool and stable by low levels of greenhouse gas in the atmosphere continued long after the discovery of fire, the Stone Age, the Bronze Age, the Iron Age, the fall and rise of empires and the Industrial Revolution.
Only in 1965 did carbon dioxide levels pass 320 ppm, after a century of exploitation of fossil fuels that released ancient carbon back into atmospheric circulation.
By 2019, the carbon dioxide concentration in the atmosphere had tipped 410 ppm and is still rising. In less than a century, human action had raised planetary average temperatures by around 1°C. At present rates, this average could reach 3°C by the end of this century.
Researchers have known for a century that humans emerged in a cooler world, but much of the story of the distant past was based on the evidence of fossils and sedimentary rocks. The latest research pushes the detailed atmospheric carbon dioxide accounting back to at least 2.5 million years.
Researchers report in the journal Nature Communications that they studied the pattern of carbon isotope readings preserved in the deep yellow soils of China's Loess Plateau. What they found confirmed 800,000 years of annual evidence from the ice cores of Antarctica and Greenland – and far beyond that limit.
The wind-blown Loess of China dates back to at least 22 million years and each successive layer carries isotope evidence that can be read as testimony to the atmospheric conditions in which the soils were laid down.
The latest find confirms that the normal state of the planet during human evolution was cool, with low levels of atmospheric carbon. Homo erectus was the first known human predecessor to exploit fire, systematically fashion stone hand axes, and to leave Africa for Asia and Europe.
"According to this research, from the first Homo erectus, which is currently dated to 2.1 to 1.8 million years ago, we have lived in a low-carbon environment – concentrations were less than 320 parts per million," said Yige Zhang, a geoscientist at Texas A&M University in the U.S., who worked with colleagues in Nanjing, China and the California Institute of Technology.
"So this current high carbon dioxide experiment is not only an experiment for the climate and the environment – it's an experiment for us, for ourselves."
"This is definitely further evidence that fossil fuels and anthropogenic activity actually has fundamentally changed the climate." In my 1st @EcoWatch post today, studies show the speed and scope of the #ClimateCrisis is unique in the last 2,000 years: https://t.co/SdL04YZStu— Olivia Rosane (@orosane) July 25, 2019
Reposted with permission from our media associate Climate News Network.
- Redwoods are the world's tallest trees.
- Now scientists have discovered they are even bigger than we thought.
- Using laser technology they map the 80-meter giants.
- Trees are a key plank in the fight against climate change.
They are among the largest trees in the world, descendants of forests where dinosaurs roamed.
Pixabay / Simi Luft<p><span>Until recently, measuring these trees meant scaling their 80 meter high trunks with a tape measure. Now, a team of scientists from University College London and the University of Maryland uses advanced laser scanning, to create 3D maps and calculate the total mass.</span></p><p>The results are striking: suggesting the trees <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">may be as much as 30% larger than earlier measurements suggested.</a> Part of that could be due to the additional trunks the Redwoods can grow as they age, <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">a process known as reiteration</a>.</p>
New 3D measurements of large redwood trees for biomass and structure. Nature / UCL<p>Measuring the trees more accurately is important because carbon capture will probably play a key role in the battle against climate change. Forest <a href="https://www.wri.org/blog/2020/09/carbon-sequestration-natural-forest-regrowth" target="_blank">growth could absorb billions of tons</a> of carbon dioxide from the atmosphere each year.</p><p>"The importance of big trees is widely-recognised in terms of carbon storage, demographics and impact on their surrounding ecosystems," the authors wrote<a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank"> in the journal Nature</a>. "Unfortunately the importance of big trees is in direct proportion to the difficulty of measuring them."</p><p>Redwoods are so long lived because of their ability to <a href="https://www.nature.com/articles/s41598-020-73733-6" target="_blank" rel="noopener noreferrer">cope with climate change, resist disease and even survive fire damage</a>, the scientists say. Almost a fifth of their volume may be bark, which helps protect them.</p>
Carbon Capture Champions<p><span>Earlier research by scientists at Humboldt University and the University of Washington found that </span><a href="https://www.sciencedirect.com/science/article/pii/S0378112716302584" target="_blank" rel="noopener noreferrer">Redwood forests store almost 2,600 tonnes of carbon per hectare</a><span>, their bark alone containing more carbon than any other neighboring species.</span></p><p>While the importance of trees in fighting climate change is widely accepted, not all species enjoy the same protection as California's coastal Redwoods. In 2019 the world lost the equivalent of <a href="https://www.worldwildlife.org/threats/deforestation-and-forest-degradation" target="_blank" rel="noopener noreferrer">30 soccer fields of forest cover every minute</a>, due to agricultural expansion, logging and fires, according to The Worldwide Fund for Nature (WWF).</p>
Pixabay<p>Although <a href="https://c402277.ssl.cf1.rackcdn.com/publications/1420/files/original/Deforestation_fronts_-_drivers_and_responses_in_a_changing_world_-_full_report_%281%29.pdf?1610810475" target="_blank" rel="noopener noreferrer">the rate of loss is reported to have slowed in recent years</a>, reforesting the world to help stem climate change is a massive task.</p><p><span>That's why the World Economic Forum launched the Trillion Trees Challenge (</span><a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a><span>) and is engaging organizations and individuals across the globe through its </span><a href="https://uplink.weforum.org/uplink/s/uplink-issue/a002o00000vOf09AAC/trillion-trees" target="_blank" rel="noopener noreferrer">Uplink innovation crowdsourcing platform</a><span> to support the project.</span></p><p>That's backed up by research led by ETH Zurich/Crowther Lab showing there's potential to restore tree coverage across 2.2 billion acres of degraded land.</p><p>"Forests are critical to the health of the planet," according to <a href="https://www.1t.org/" target="_blank" rel="noopener noreferrer">1t.org</a>. "They sequester carbon, regulate global temperatures and freshwater flows, recharge groundwater, anchor fertile soil and act as flood barriers."</p><p><em data-redactor-tag="em" data-verified="redactor">Reposted with permission from the </em><span><em data-redactor-tag="em" data-verified="redactor"><a href="https://www.weforum.org/agenda/2021/03/redwoods-store-more-co2-and-are-more-enormous-than-we-thought/" target="_blank">World Economic Forum</a>.</em></span></p>
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