Could 1 Trillion Trees Fix Climate Change?

Earth has about 3 trillion trees, and since people started farming and building cities we've cut down almost half of them. In 2019 a team at ETH Zurich found room for about a trillion more on 900 million hectares outside cities and farms, an area about the size of the United States, and said those forests could one day store about 205 billion tonnes of carbon. That sounded like our best climate solution, at about 30 cents a tree. Then several teams of scientists pushed back: the number was about five times too big, much of the "empty" land is grassland and savanna, dark forests in the snowy north can warm the planet, and trees take 50 to 100 years to do their job. So what's the real plan? Protect the forests we have, let cleared land grow back, plant the right trees in the right places, and cut fossil fuel emissions, because no forest can keep up with about 38 billion tonnes of carbon dioxide a year. Chapters: 0:00 What if we planted 1 trillion trees? 0:21 The trees we have 1:03 How a tree eats air 1:47 Where would they go 2:45 What it would do 3:38 The catch 5:01 The best plan The visuals are illustrations: the valley, the town, the leaf, the cell, the globe's tree cover, the crews, the drones and the fire are cartoons, not to scale. Kajal and Rana are our own drawn characters. Country shapes are from Natural Earth; the globe's land cover is from the Solar System Scope texture map (CC BY 4.0). Music and sound effects are original, synthesized for this video. Sources: Crowther, T. W. et al. (2015), "Mapping tree density at a global scale", Nature 525, 201-205: https://doi.org/10.1038/nature14967 Yale News (2 Sept 2015), "Seeing the forest and the trees, all 3 trillion of them": https://news.yale.edu/2015/09/02/seei... Bastin, J.-F. et al. (2019), "The global tree restoration potential", Science 365, 76-79: https://doi.org/10.1126/science.aax0848 ETH Zurich release via Technology Networks, "How Trees Could Save the Climate": https://www.technologynetworks.com/ap... swissinfo.ch (4 July 2019): https://www.swissinfo.ch/eng/sci-tech... The Guardian (4 July 2019), "Tree planting 'has mind-blowing potential' to tackle climate crisis" (30 cents a tree; 50 to 100 years), reprint: https://portside.org/node/20546. Our calc: 1 trillion x $0.30 = $300 billion. Veldman, J. W. et al. (2019), Comment on "The global tree restoration potential", Science 366, eaay7976; summaries: https://www.gembloux.uliege.be/cms/c_... and https://agencia.fapesp.br/reforesting... Erratum to Bastin et al., Science 368 (2020): https://carbondioxide-removal.eu/2020... Global Carbon Budget 2025 (fossil CO2 about 38.1 billion tonnes in 2025): https://globalcarbonbudget.org/fossil.... Our calc: 205 Gt C x 44/12 = 752 Gt CO2, about 20 years at 38.1 Gt a year; a fifth of that is about 4 years. Lewis, S. L. et al. (2019), "Restoring natural forests is the best way to remove atmospheric carbon", Nature 568, 25-28; UCL News: https://www.ucl.ac.uk/news/2019/apr/r... CarbonPlan on the 2021 Bootleg Fire and the Klamath East offset project: https://carbonplan.org/blog/bootleg-f... and https://carbonplan.org/blog/klamath-e... FAO and UNEP (2020), The State of the World's Forests 2020: https://library.sprep.org/content/sta... Cook-Patton, S. C. et al. (2020), Nature 585, 545-550; WRI: https://www.wri.org/insights/young-fo... Mo, L. et al. (2023), "Integrated global assessment of the natural forest carbon potential", Nature 624, 92-101: https://doi.org/10.1038/s41586-023-06... World Economic Forum (22 Jan 2020), 1t.org launch: https://weforum.org/agenda/2020/01/on... IPCC 2006 Guidelines, Vol. 4, Ch. 4, Table 4.3 (carbon fraction of dry wood 0.47) Tree planting rates (1,500 to 3,000 a day by hand) and AirSeed's own claim of 40,000 pods a day per drone. Our calc: 1 trillion / 1,600 a day = 625 million planter days, so a million planters need 625 days. UN World Population Prospects 2024 (about 8.3 billion people in 2026): https://population.un.org/wpp/. Our calc: 1 trillion / 8.3 billion = 120.5. Natural Earth (country shapes): https://www.naturalearthdata.com Solar System Scope textures (CC BY 4.0): https://www.solarsystemscope.com/text...