Planting Billions of Trees Is the 'Best Climate Change Solution Available Today,' Study Finds
Planting more than 500 billion trees could remove around 25 percent of existing carbon from the atmosphere, a new study has found. What's more: there's enough space to do it.
The study, published in Science Friday, set out to assess how much new forest the earth could support without encroaching on farmland or urban areas and came up with a figure of 0.9 billion hectares, an area roughly the size of the U.S., BBC News reported. That makes reforestation "the most effective solution" for mitigating the climate crisis, the researchers concluded.
"Our study shows clearly that forest restoration is the best climate change solution available today and it provides hard evidence to justify investment," senior study author and ETH-Zürich Professor Tom Crowther said, as BBC News reported. "If we act now, this could cut carbon dioxide in the atmosphere by up to 25 percent, to levels last seen almost a century ago."
The new trees would remove around 200 gigatonnes of carbon, or two thirds of what humans have pumped into the atmosphere since the industrial revolution.
New report reveals #reforestation is one of the most effective strategies for #ClimateChange mitigation.— Crowther Lab (@CrowtherLab) July 4, 2019
We must plant more trees🌲🌳, support restoration organisations and invest wisely.
>> https://t.co/2cGVl73Tz1#TreePotential pic.twitter.com/JFNbDeE42v
However, the researchers emphasized that tree planting was not a replacement for reducing greenhouse gas emissions or phasing out the use of fossil fuels.
"None of this works without emissions cuts," Crowther told Time.
Even if tree planting began today, it would take 50 to 100 years for the new trees to soak up those 200 gigatonnes of carbon, he told The Guardian. And, as National Geographic pointed out, the researchers found that potential tree-planting land could shrink by one-fifth by 2050 even if global temperature rise is limited to 1.5 degrees Celsius above pre-industrial levels, as some tropical areas could grow too hot to support forests.
Even so, Crowther said tree planting was an important means of immediate climate action.
It's "a climate change solution that doesn't require President Trump to immediately start believing in climate change, or scientists to come up with technological solutions to draw carbon dioxide out of the atmosphere," Crowther told The Guardian. "It is available now, it is the cheapest one possible and every one of us can get involved."
Assistant-Director General at the UN Food and Agriculture Organization René Castro praised the study's utility.
"We now have definitive evidence of the potential land area for re-growing forests, where they could exist and how much carbon they could store," Castro said, as The Guardian reported.
To reach their conclusions, the researchers first looked at around 80,000 satellite photographs of protected forest areas around the world to assess the tree cover in each. They then used Google Earth Engine mapping software to develop a model for predicting where new trees could grow, National Geographic explained. They found that more than half of the world's reforestation potential was located in six countries: China, the U.S., Russia, Australia, Canada and Brazil.
However, trends are moving in the opposite direction in Brazil, where deforestation is on the rise under the right-wing government of President Jair Bolsonaro. Recent satellite images show that a football-field-sized swath of the Amazon is being lost every minute, according to National Geographic.
Bolsonaro has also been hostile to the rights of indigenous communities to the forest. But such rights are essential for conservation: deforestation rates are much lower in forests that recognize indigenous claims.
"We have served as guardians of these lands for generations ... We also understand how to restore them to health," Joan Carling, a member of the Kankanaey tribe in the Philippines and co-convener of the Indigenous Peoples Major Group for Sustainable Development, told National Geographic by email. "With the security of our lands and resources, we can prevent destructive logging, mining, agri-business, and other projects from occurring in our territories."
Political realities are why some scientists criticized the optimism of Crowther's findings.
"Planting trees to soak up two-thirds of the entire anthropogenic carbon burden to date sounds too good to be true. Probably because it is," University of Reading professor Martin Lukac told BBC News. "This far, humans have enhanced forest cover on a large scale only by shrinking their population size (Russia), increasing productivity of industrial agriculture (the West) or by direct order of an autocratic government (China). None of these activities look remotely feasible or sustainable at global scale."
University College London professor Simon Lewis, meanwhile, said that the amount of carbon the study said trees would absorb was too high. He said the study had not accounted for the carbon already in the soil before trees were planted or the hundreds of years it would take for the trees to achieve their full storage potential, The Guardian reported.
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Kevin T. Smiley
When hurricanes and other extreme storms unleash downpours like Tropical Storm Beta has been doing in the South, the floodwater doesn't always stay within the government's flood risk zones.
New research suggests that nearly twice as many properties are at risk from a 100-year flood today than the Federal Emergency Management Agency's flood maps indicate.
Flooding Outside the Zones<p>About <a href="https://furmancenter.org/files/Floodplain_PopulationBrief_12DEC2017.pdf" target="_blank">15 million</a> Americans live in FEMA's current 100-year flood zones. The designation warns them that their properties face a 1% risk of flooding in any given year. They must obtain flood insurance if they want a federally ensured loan – insurance that helps them recover from flooding.</p><p>In Greater Houston, however, <a href="https://doi.org/10.1111/j.1539-6924.2012.01840.x" target="_blank">47% of claims</a> made to FEMA across three decades before Hurricane Harvey were outside of the 100-year flood zones. Harris County, recognizing that FEMA flood maps don't capture the full risk, now <a href="https://www.hcfcd.org/floodinsurance" target="_blank" rel="noopener noreferrer">recommends that every household</a> in Houston and the rest of the county have flood insurance.</p><p>New risk models point to a similar conclusion: Flood risk in these areas outstrips expectations in the current FEMA flood maps.</p><p>One of those models, from the <a href="https://firststreet.org/flood-lab/research/2020-national-flood-risk-assessment-highlights/" target="_blank">First Street Foundation</a>, estimates that the number of properties at risk in a 100-year storm is 1.7 times higher than the FEMA maps suggest. Other <a href="https://doi.org/10.1088/1748-9326/aaac65" target="_blank" rel="noopener noreferrer">researchers</a> find an even higher margin, with 2.6 to 3.1 times more people exposed to serious flooding in a 100-year storm than FEMA estimates.</p>
What FEMA’s Flood Maps Miss<p>Understanding why areas outside the 100-year flood zones are flooding more often than the FEMA maps suggest involves larger social and environmental issues. Three reasons stand out.</p><p>First, some places rely on relatively old FEMA maps that don't account for recent urbanization.</p><p>Urbanization matters because impervious surfaces – think pavement and buildings – are not effective sponges like natural landscapes can be. Moreover, the process for updating floodplain maps is locally variable and can take years to complete. Famously, New York City was updating its maps when Hurricane Sandy hit in 2012 but hadn't finished, meaning flood maps in effect <a href="https://projects.propublica.org/nyc-flood/" target="_blank">were from 1983</a>. FEMA is required to assess whether updates are needed every five years, but the <a href="https://www.fema.gov/cis/nation.html" target="_blank" rel="noopener noreferrer">majority of maps</a> <a href="https://www.oig.dhs.gov/sites/default/files/assets/2017/OIG-17-110-Sep17.pdf" target="_blank" rel="noopener noreferrer">are older</a>.</p><p>Second, binary thinking can lead people to an underaccounting of risk, and that can mean communities fail to take steps that could protect a neighborhood from flooding. The logic goes: if I'm not in the 100-year floodplain, then I'm not at risk. Risk perception <a href="https://doi.org/10.1088/1748-9326/ab195a" target="_blank" rel="noopener noreferrer">research</a> backs this up. FEMA-delineated flood zones are the major factor shaping flood mitigation behaviors.</p><p>Third, the era of climate change scuttles conventional assumptions.</p><p>As the planet warms, extreme storms are becoming <a href="https://nca2018.globalchange.gov/" target="_blank">more common and severe</a>. If greenhouse gas emissions continue to increase at a high rate, computer models suggest that the chances of a severe storm dropping 20 inches of rain on Texas in any given year will increase from about 1% at the end of the last century to 18% at the end of this one, a chance of <a href="https://doi.org/10.1073/pnas.1716222114" target="_blank" rel="noopener noreferrer">once every 5.5 years</a>. So far, <a href="https://www.rstreet.org/wp-content/uploads/2020/02/195.pdf" target="_blank" rel="noopener noreferrer">FEMA hasn't taken into account the impact climate change is having</a> on extreme weather and sea level rise.</p>
Racial Disparities in Flooding Outside the Zones<p>So, who is at risk?</p><p>Years of research and evidence from storms have highlighted social inequalities in areas with a high risk of flooding. But most local governments have less understanding of the social and demographic composition of communities that experience flood impacts outside of flood zones.</p><p>In analyzing the damage from Hurricane Harvey in the Houston area, I found that <a href="https://doi.org/10.1088/1748-9326/aba0fe" target="_blank">Black and Hispanic residents disproportionately experienced flooding</a> in areas beyond FEMA's 100-year flood zones.</p><p>With the majority of flooding from Hurricane Harvey occurring outside of 100-year flood zones, this meant that the overall impact of Harvey was racially unequal too.</p><p>Research into where flooding occurs in Baltimore, Chicago and Phoenix points to some of the potential causes. <a href="https://www.nap.edu/read/25381/chapter/4#16" target="_blank" rel="noopener noreferrer">In Baltimore and Chicago</a>, for example, aging storm and sewer infrastructure, poor construction and insufficient efforts to mitigate flooding are part of the flooding problem in some predominantly Black neighborhoods.</p>
What Can Be Done About It<p>Better accounting for those three reasons could substantively improve risk assessments and help cities prioritize infrastructure improvements and flood mitigation projects in these at-risk neighborhoods.</p><p>For example, First Street Foundation's risk maps account for <a href="https://firststreet.org/flood-lab/research/flood-model-methodology_overview/" target="_blank">climate change</a> and present <a href="https://floodfactor.com/" target="_blank" rel="noopener noreferrer">ratings</a> on a scale from 1 to 10. FEMA, which works with communities to update flood maps, is <a href="https://www.fema.gov/media-library-data/1521054297905-ca85d066dddb84c975b165db653c9049/TMAC_2017_Annual_Report_Final508(v8)_03-12-2018.pdf" target="_blank" rel="noopener noreferrer">exploring rating systems</a>. And the National Academies of Sciences, Engineering and Medicine recently <a href="https://www.nationalacademies.org/news/2019/03/new-report-calls-for-different-approaches-to-predict-and-understand-urban-flooding" target="_blank" rel="noopener noreferrer">called for a new generation of flood maps</a> that takes climate change into account.</p><p>Including recent urbanization in those assessments will matter too, especially in fast-growing cities like Houston, where <a href="https://authors.elsevier.com/a/1boBRyDvMFW6W" target="_blank" rel="noopener noreferrer">386 new square miles</a> of impervious surfaces were created in the last 20 years. That's greater than the land area of New York City. New construction in one area can also <a href="https://scalawagmagazine.org/2018/01/city-in-a-swamp-as-houston-booms-its-flood-problems-are-only-getting-worse/" target="_blank" rel="noopener noreferrer">impact older neighborhoods downhill</a> during a flood, as some Houston communities discovered in Hurricane Harvey.</p><p>Improving risk assessments is needed not just to better prepare communities for major flood events, but also to prevent racial inequalities – in housing and beyond – from <a href="https://www.npr.org/2019/03/05/688786177/how-federal-disaster-money-favors-the-rich" target="_blank" rel="noopener noreferrer">growing</a> after the unequal impacts of disasters.</p>
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