Changing Planet

You Cannot Save the Climate Without Trees

Clearing tropical rainforests will not stop climate change. (credit: Dan Klotz)

The People’s Climate March that trumpeted its way through the streets of Manhattan yesterday was led by communities on the front lines of climate change—and Indigenous Peoples were at the forefront of this group.  The tropical forests where they live are not only getting hammered by changing weather patterns, drug traffickers, invasive pests, and massive fires, but these woodlands are also being cleared at an alarming rate, making way for cropland, pastureland, strip mines, and other ventures that extract natural resources from the Earth.

The United Nations Food and Agriculture Organization rang the alarm bell on the world’s forests in April of this year.  Working off of its own data as well as the most recent reports from the Intergovernmental Panel on Climate Change—a group of 2,000 scientists from around the world—the FAO declared that 13 million hectares of tropical forests are now cleared every year, an area larger than half the countries in the world.  The process of this “conversion” releases an estimated 4 billion tons of carbon dioxide annually, almost twice the amount produced by urban transportation (cars, trucks, buses, et. al.) throughout the world.

The reason deforestation releases so much carbon dioxide is that trees store an incredible amount of carbon in their trunks, roots, and limbs.  The FAO also estimated that the world’s forests remove approximately two billion tons of carbon dioxide from the atmosphere every year.

One of the questions often raised by those seeking to clear out the forests is whether chopping away the old growth and planting young trees helps the planet. In the past, the rapid growth of young trees was thought to absorb more carbon than the slower growth of stately larger trees, or even the oldest found in old growth forests.

But that question was laid to rest in a thorough literature review from scientists at the US Geological Survey. In looking at 403 tropical and temperate tree species, the researchers found that “…large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme, a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree.”

So forests are valuable to nature, storing billions of tons of carbon at a point in time where the amount of carbon that human beings produce is radically changing our planet’s atmosphere.  Forests are also valuable, obviously, to the people whose lives and livelihoods depend on the forests remaining upright and living. We should do more to conserve the forests that remain, right?

Wrong, according to a researcher from the Yale School of Forestry and Environmental Studies.

In a controversial opinion piece that ran in the New York Times, the Yale professor presented a new argument for chopping down trees. The massive amounts of forest loss since the mid nineteenth century have supposedly cooled the planet by reducing the biogenic volatile organic compounds (BVOCs) released by forests, compounds that exacerbate the climate impacts of ozone, methane, and other industrial pollutants. Trees are also darker colored, and thus absorb more sunlight than light colored cropland.

The op-ed and its theories, however, don’t hold up under scrutiny. According to forest ecologist Michael Wolosin, the piece’s underlying research establishes that the impact of forests on carbon is three times larger than the impact of forests on BVOCs. Many more variables need to be included, he argues, before calculating whether forests should be devalued in any climate equation.

Steve Schwartzmann, PhD, who directs Environmental Defense Fund’s Tropical Forestry Work, notes that the clouds produced by rainforests reflect more light and heat than the trees absorb.  These clouds are also vital to global weather patterns. Large scale deforestation causes massive disruptions of precipitation, and he points to research from Princeton last year that connected deforestation in the Amazon to weather patterns over California.

Whether the last stands of our planet’s once-vast forests should remain standing is not a question to be tossed about lightly, in print or in real life.  Just ask those from Brazil or Indonesia or elsewhere who led the climate march.  They came to lend their voices to the outcry and hear what solutions the world might offer. We can only hope that they and their forests can be considered part of the answer.

Dan Klotz is a veteran writer and advocate on conservation efforts and the health and sustainability of our food systems. Dan's career has spanned a wide range of policy issues, including protecting sharks around the world, securing the land rights of indigenous communities, addressing the sustainability and research needs of agriculture both domestically and internationally, advocating for smoke-free workplaces, cleaning up toxic waste sites, and preserving wild areas on land and in the ocean.
  • Erich J. Knight

    My two cents for the trees;
    Dr. Unger “In reality,” is just as guilty about complexity as she accuses others of being.
    “the cycling of carbon, energy and water between the land and the atmosphere is much more complex.” quit so,
    has her group at the Yale School of Forestry and Environmental Studies, considered the paleoclimate data for afforestation?

    Anthropogenic activities led to the stabilization of atmospheric CO2 concentrations at a level that made the world substantially warmer than it otherwise would be.
    The Kayopo Indian people with their Terra Preta soils were no carbon Saints, lake sediments show us a 5 Gt Carbon draw down with their demise. Genghis Khan’s Empire also very “green” with a 700,000,000 ton draw down. Now disrupting agriculture by rape and pillage may not be a politically correct form of afforestation, but it works.

    Dr. Jim Hansen’s 100 gigatons of Afforestation will work, as trees have worked time and time again.
    The Black Death increased afforestation in Europe by one third, the mass death of farmers is bench marked across the Paleoclimatic climate records. The Columbian exchange, that Grand reunification of life, was not quite so deliberate, in fact quite unintentional, however the chips of life fell where they may, Losers and winners abound.

    Hansen’s Afforestation accounting for CO2 soil & forest sequestration is understated. Not giving full account for new understandings of the ecological services rendered in light of what we are learning about the Pleistocene and the Aerosol chemistry elephant in the room, way understated.

    Physicist tend to focus on the carbon, oxygen, and nitrogen contents of the organic materials.
    Pöhlker et al were surprised finding very high soil fungal potassium levels, up to 20 percent, in the 77 Amazonian carbonaceous aerosol samples, in the form of salts, in all but three of them.
    The samples were on the scale of mere millionths or billionths of a meter. The smaller the aerosol, the greater the proportion of potassium – those collected early in the morning were the smallest and richest in potassium. Larger particles contained more organic material but not more potassium. These facts suggest that potassium salts generated during the night acted as seeds for gas-phase products to condense onto, forming aerosols of different kinds. [1]

    NPP increases CO2 draw-down, sugar exudates pumped deep into soils, if we manage biomass carbon in more recalcitrant compost/humus, and really recalcitrant pyrolitic C, biochar, we moderate the Keeling CO2 curve,. More CO2 inspired, less respired from the breathing biosphere.

    The late Pleistocene to Holocene boundary shows a prestigious pedogenesis, the loess–paleosol sequences of the central and northern Great Plains record a broad peak of high effective moisture, a pedogenesis we can emulate with the bio-remediation techniques we advocate on these lists as the only economic way to reverse climate change..

    The new research concerning the ecologically limiting effects of Phosphorous caused by the loss of the Mega-Fanua means we have never seen the true vigor that forest & grass lands could have. That what we now see as “pristine” systems are but a shadow of their primary production potential. The Pleistocene megafauna extinctions resulted in large and ongoing disruptions to terrestrial biogeochemical cycling at continental scales, switching off this natural nutrient pump by a massive 98%. The megafauna diffused sodium inland and also reduced concentrations in plants near the coast. [2]
    (There is a whole parallel literature developing in the marine literature, with deep diving megafauna playing a key role in nutrient dispersal in the oceans).

    “The science says that spending precious dollars for climate change mitigation on forestry is high-risk:”
    I disagree, and Spending on atmospheric & Biospheric research is imperative.

    “We don’t know that it would cool the planet,”,
    I say historically we do.

    “and we have good reason to fear it might have precisely the opposite effect.”
    We must scrutinize these “reasons” in the light of new biospheric & hydrological cycling data.


    Holocene carbon emissions as a result of anthropogenic land cover change

    The Columbian Encounter and the Little Ice Age: Abrupt Land Use Change, Fire, and Greenhouse Forcing

    Salt Seeds Clouds in the Amazon Rainforest

    How salt in the rainforest becomes clouds


    The legacy of the Pleistocene megafauna extinctions on nutrient availability in Amazonia

    Are Nutrient Limitations a Consquence of the Pleistocene Megafauna Extinctions?

    The Trees that Miss the Mammoths

About the Blog

Researchers, conservationists, and others share stories, insights and ideas about Our Changing Planet, Wildlife & Wild Spaces, and The Human Journey. More than 50,000 comments have been added to 10,000 posts. Explore the list alongside to dive deeper into some of the most popular categories of the National Geographic Society’s conversation platform Voices.

Opinions are those of the blogger and/or the blogger’s organization, and not necessarily those of the National Geographic Society. Posters of blogs and comments are required to observe National Geographic’s community rules and other terms of service.

Voices director: David Braun (

Social Media