Recent reversal in loss of global terrestrial biomass

Journal name:
Nature Climate Change
Volume:
5,
Pages:
470–474
Year published:
DOI:
doi:10.1038/nclimate2581
Received
Accepted
Published online

Vegetation change plays a critical role in the Earth’s carbon (C) budget and its associated radiative forcing in response to anthropogenic and natural climate change1, 2, 3, 4. Existing global estimates of aboveground biomass carbon (ABC) based on field survey data provide brief snapshots that are mainly limited to forest ecosystems5, 6, 7, 8. Here we use an entirely new remote sensing approach to derive global ABC estimates for both forest and non-forest biomes during the past two decades from satellite passive microwave observations. We estimate a global average ABC of 362 PgC over the period 1998–2002, of which 65% is in forests and 17% in savannahs. Over the period 1993–2012, an estimated −0.07 PgC yr−1 ABC was lost globally, mostly resulting from the loss of tropical forests (−0.26 PgC yr−1) and net gains in mixed forests over boreal and temperate regions (+0.13 PgC yr−1) and tropical savannahs and shrublands (+0.05 PgC yr−1). Interannual ABC patterns are greatly influenced by the strong response of water-limited ecosystems to rainfall variability, particularly savannahs. From 2003 onwards, forest in Russia and China expanded and tropical deforestation declined. Increased ABC associated with wetter conditions in the savannahs of northern Australia and southern Africa reversed global ABC loss, leading to an overall gain, consistent with trends in the global carbon sink reported in recent studies1, 3, 9.

At a glance

Figures

  1. Aboveground biomass carbon stores and density by biome.
    Figure 1: Aboveground biomass carbon stores and density by biome.

    a, Total ABC in eight biomes circa 2000 (mean estimate; error bars indicate the 90% confidence interval). ‘Tropical forests’ include those in Southeast Asia, Africa and the Americas (that is, South America, Caribbean countries and Mexico); remaining forests are considered as ‘boreal/temperate’. ‘Shrublands’ includes both open and closed shrublands; ‘Croplands’ includes both ‘croplands’ and ‘cropland/natural vegetation mosaic’ based on the MODIS IGBP land-cover map for 2001 (ref. 16). b, ABC density per unit area circa 2000. The bottom, middle and top band of the box represent the 25th, 50th (median) and 75th percentile, respectively, and the ends of the whiskers represent the 5th and 95th percentile for all corresponding grid cells. c, Annual trends in total biome ABC for 1993–2012 (mean estimate; error bars indicate the 90% confidence interval). The classification relates to year 2001 and grouping of different biomes to the same colour is mainly based on woody vegetation canopy cover, that is, 10–60% for shrublands, savannahs and woody savannahs and less than 10% for grasslands. Croplands with harvest and thus considerable variation in woody components are grouped with grasslands.

  2. Mean annual change in aboveground biomass carbon between 1993 and 2012.
    Figure 2: Mean annual change in aboveground biomass carbon between 1993 and 2012.
  3. Interannual variations in aboveground biomass carbon (ABC) storage.
    Figure 3: Interannual variations in aboveground biomass carbon (ABC) storage.

    a, Time series of annual total ABC for all ecosystems, expressed as the difference from 1993 values. b, Time series of annual total ABC in five biome groups (merged as per colour codes in Fig. 1), with a classification based on MODIS IGBP 2001 (ref. 16). c, Time series of annual tropical forest ABC over the Americas, Southeast Asia and Africa. Southeast Asia here includes Asian countries as well as Papua New Guinea (see Supplementary Fig. 3b). d, Time series of the annual total ABC and normalized rainfall for the savannahs and woody savannahs of southern Africa and northern Australia. Coefficients of determination (r2) between ABC and rainfall are 0.53 and 0.65 for southern Africa and northern Australia, respectively. The solid line represents the mean value and the shadow represents the CI90 range.

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Affiliations

  1. ARC Centre of Excellence for Climate Systems Science & Climate Change Research Centre, University of New South Wales, Sydney, New South Wales 2052, Australia

    • Yi Y. Liu &
    • Jason P. Evans
  2. Water Research Centre, School of Civil and Environmental Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia

    • Yi Y. Liu
  3. Fenner School of Environment & Society, Australian National University, Canberra, Australian Capital Territory 0200, Australia

    • Albert I. J. M. van Dijk
  4. CSIRO Land and Water Flagship, Canberra, Australian Capital Territory 2601, Australia

    • Albert I. J. M. van Dijk
  5. Earth and Climate Cluster, Department of Earth Sciences, Faculty of Earth and Life Sciences, VU University Amsterdam, Amsterdam 1081 HV, Netherlands

    • Richard A. M. de Jeu
  6. Global Carbon Project, CSIRO Oceans and Atmosphere Flagship, Canberra, Australian Capital Territory 2601, Australia

    • Josep G. Canadell
  7. Water Desalination and Reuse Center, Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, 23955-6900, Saudi Arabia

    • Matthew F. McCabe
  8. School of Geography and Remote Sensing, Nanjing University of Information Science and Technology, Nanjing 210044, China

    • Guojie Wang

Contributions

All authors contributed to the development of the paper. Y.Y.L. and A.I.J.M.v.D. designed the study. R.A.M.d.J., Y.Y.L. and G.W. prepared the VOD data set. Y.Y.L. conducted the analysis and wrote the Supplementary Information. A.I.J.M.v.D. and J.G.C. summarized the results and wrote the first draft of the paper, with subsequent addition and improvement by all authors.

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The authors declare no competing financial interests.

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