The global tree restoration potential

See allHide authors and affiliations

Science  05 Jul 2019:
Vol. 365, Issue 6448, pp. 76-79
DOI: 10.1126/science.aax0848

eLetters is an online forum for ongoing peer review. Submission of eLetters are open to all. eLetters are not edited, proofread, or indexed.  Please read our Terms of Service before submitting your own eLetter.

Compose eLetter

Plain text

  • Plain text
    No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
Author Information
First or given name, e.g. 'Peter'.
Your last, or family, name, e.g. 'MacMoody'.
Your email address, e.g.
Your role and/or occupation, e.g. 'Orthopedic Surgeon'.
Your organization or institution (if applicable), e.g. 'Royal Free Hospital'.
Statement of Competing Interests

This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Vertical Tabs

  • RE: No Bonn Challenge restoration commitment exceeds a country’s potential area
    • Matthew E. Fagan, Department of Geography and Environmental Systems, UMBC
    • Other Contributors:
      • Rakan A. Zahawi, Lyon Arboretum, University of Hawai’i at Manoa, Honolulu, Hawaii
      • J. Leighton Reid, School of Plant and Environmental Sciences, Virginia Tech, Blacksburg, Virginia

    Bastin et al. (2019) misrepresent the current status and potential achievability of commitments to restore vast areas of land under the Bonn Challenge. Their statement that “Approximately 10% of countries have committed to restoring an area of land that considerably exceeds the total area that is available for restoration” is incorrect, and arises from an oversimplified understanding of the restoration options available under Bonn Challenge commitments. We are concerned that these misunderstandings will further undermine the Bonn Challenge, rather than promote improved implementation of restoration pledges.

    Bastin et al. (2019) assume in their analysis that all Bonn Challenge area commitments are to restore non-forest, non-agricultural land to forest cover. However, a variety of potential restoration options are available to Bonn Challenge program participants that are not included in this assumption, including silviculture, agroforestry, and planting mangrove forests (Dave et al., 2017).

    These alternatives make up large proportions of the commitments from many countries. For example, silviculture (e.g., forest thinning and prescribed burning in the American West) constitutes 96% of the US restoration pledge of 17 Mha. Likewise, agroforestry (e.g., planting trees in agricultural fields) makes up >70% of El Salvador’s restoration pledge of 1 Mha (MARN, 2017).

    The potential restoration maps utilized in Bastin et al. (2019) deliberately exclude agricul...

    Show More
    Competing Interests: None declared.
  • RE: Planting shrubs is more sustainable in a drying world

    J. F. Bastin and colleagues (“The global tree restoration potential,” 05 July, p. 76) predict that there are currently 0.9 billion hectares (ha) of forest with restoration potential, but ~223 million ha may be lost by 2050, and ~174 million ha will be lost despite aggressive CO2 reduction. Although tree planting can significantly reduce CO2 and help reverse climate change, another crucial vegetation type should not be overlooked—shrubs.
    Global drylands will increase by 7% by the end of the 21st century (1) and planting trees in arid lands may be inopportune. The reasons: (i) trees are more susceptible to drought-induced embolism (2) and are more likely to die owing to hydraulic failure (3) than shrubs; (ii) large-scale tree planting can adversely affect local water resources due to the presence of denser canopies and higher transpiring water loss (4) and (iii) the maintenance costs are high (5). Therefore, tree planting in expanding arid and semi-arid regions is not sustainable. For example, the Three-North Shelter Forest Program that launched in 1978 in China resulted in indiscriminate tree planting without consideration for physiological limits and has led to 3 million ha of degraded plantations comprising young olded-trees (e.g., Populus simonii & Robinia pseudoacacia). In northern China, ~16% of coniferous forests and ~10% broadleaved and mixed conifer-broadleaved forests in plantations are not suitable for tree planting (6) and shrubs, such as Tamarix ramosi...

    Show More
    Competing Interests: None declared.
  • RE: Tree planting is not a silver bullet to address climate change
    • Karen D Holl, Professor, University of California, Santa Cruz

    Bastin et al. (2019) highlight the potential role that restoring forests can play in sequestering carbon and thereby help combat climate change, along with dramatic and rapid efforts to reduce greenhouse emissions. As somebody who has studied tropical forest restoration forest two decades, I concur that restoring forests, in areas previously covered by forests, provides important services beyond just carbon sequestration, such as conserving biodiversity and improving water quality, but I contend that they grossly overestimate the climate change mitigation potential of forest restoration.

    First, they base their assessments of carbon sequestration potential on relatively intact forests. Extensive research shows that the rate and extent of forest recovery is strongly affected by the intensity of past human disturbance, invasive species, increasing wildland fires, and numerous other factors. In other words, it is unlikely that much of the heavily disturbed lands that they propose for forest restoration will recover to the extent predicted by their model and certainly not over the time frame of a decade or two that will be needed to keep warming to below 2°C or even the short, 30-yr duration they use in their model.

    Second, they only briefly note that “much of the land that could potentially support trees across the globe is currently used for human development and agriculture, which are necessary for supporting an ever-growing human population” overlooking a ri...

    Show More
    Competing Interests: None declared.
  • RE: Soving Climate Crisis Today with Trees for Tomorrow

    from Greta Thunberg (July 5 at 11:30 AM):
    Yes, of course we need to plant as many trees as possible.
    Yes, of course we need to keep the existing trees standing and rewild and restore nature.
    But there’s absolutely no way around stopping our emissions of greenhouse gases and leaving the fossil fuels in the ground.
    “The only way we can keep below 1.5C or 2C, is to stop emitting fossil fuels.” says Glen Peters, research director at Norway’s Center for International Climate Research.
    “It could take hundreds of years to add enough mature forests to remove what we will emit in 20 years at the current rate of 40GtCO₂/yr”

    Competing Interests: None declared.
  • RE: Important Omission in This Article

    The calculations in this historic article omit the undeniable cooling effects of the shade cast by one trillion trees.

    As such, the projected benefits of planting one trillion trees is understated by a non-negligible amount in this work.

    Competing Interests: None declared.

Stay Connected to Science

Navigate This Article