Research ArticleENVIRONMENTAL STUDIES

Degradation and forgone removals increase the carbon impact of intact forest loss by 626%

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Science Advances  30 Oct 2019:
Vol. 5, no. 10, eaax2546
DOI: 10.1126/sciadv.aax2546
  • Fig. 1 Areas of tropical forest that remained intact in 2013 or were lost between 2000 and 2013 (2).

    (A to C) Inset maps with orange borders show remnant and lost parcels of intact forest across Latin America, Central Africa, and Asia-Pacific. The second row of inset maps (black borders) shows the spatial distribution of activities that cause carbon emissions and forgo carbon removal in intact forest areas. Forest clearance and burned areas were sourced from (14) and (21), respectively. Selectively logged areas were simulated inside lost parcels by applying a 1-km buffer around roads mapped in the OpenStreetMap dataset (www.openstreetmap.org). New forest edges were simulated by applying 500-m buffers around footprints of burned area and forest clearance.

  • Fig. 2 Full accounting of the carbon impact of intact forest loss.

    (A, red segments) Conventionally, only emissions from readily observed forest clearance are considered. Forest clearance in intact forest between 2000 and 2013 led to the emission of 338 (372 to 208) Tg C. (B, orange segments) Less readily observed degradation processes that follow forest clearance, including selective logging, edge effects, and defaunation, are rarely accounted for in emission estimates. We expect that these events occurring in intact forest between 2013 and 2050 will lead to the emission of 806 (878 to 465) Tg C. (C, green stippled segments) Forgone carbon removal—carbon sequestration that could have occurred had cleared or degraded forest areas remained intact beyond 2000—is not considered in conventional emission accounting frameworks. If the forested area affected by clearance, logging, or edge effects remained intact beyond 2000, then it could have sequestered 972 (1604 to 331) by 2050. Full accounting of these additional factors (i.e., selective logging, cryptic emissions, and forgone enhancement) led to a 626% increase in cumulative net carbon impact from intact forest loss. Histogram plot shows carbon impacts for the 10 countries with the highest estimated impacts.

  • Table 1 Pantropical and regional estimates of the full carbon impact of intact forest loss.

    Pulse emissions include those from forest clearance and fire observed between 2000 and 2013. Disturbance inside intact forests will lead to numerous sources of emissions between 2013 and 2050, including selective logging, edge effects, and defaunation, herein collectively referred to as committed emissions. Committed emissions shown here also account for some carbon sequestration from forest regrowth between 2013 and 2050 (see Materials and Methods). Emission estimates were based on a synthesis map of pantropical aboveground biomass of woody vegetation (22). Upper and lower uncertainty bounds were based on rerunning emission calculations with two original biomass maps (23, 24). Forgone removals are an estimate of the amount of carbon that cleared or degraded forests could have sequestered had they remained intact beyond 2000. Forgone removal estimates and 95% confidence intervals were based on carbon sequestration rates in intact tropical forests estimated for the 2000s (4).

    Carbon emissions (Tg C)Forgone (Tg C)
    RegionCarbon impact (Tg C)Net (2000–2050)Pulse (2000–2013)Committed (2013–2050)Total (2000–2050)
    Pantropics2116 (2854–1004)1114 (1250–673)338 (372–208)806 (878–465)972 (1604–331)
    Latin America1132 (1633–455)677 (766–420)263 (294–168)414 (472–252)455 (867–35)
    Africa517 (681–239)236 (239–117)31 (32–15)205 (207–103)281 (442–122)
    Asia-Pacific467 (540–310)231 (245–135)44 (46–25)188 (199–110)236 (295–175)

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/10/eaax2546/DC1

    Fig. S1. Estimated annual rate of carbon sequestration inside intact forests under alternative scenarios.

    Fig. S2. Full accounting of the carbon impact of intact forest loss assuming the onset of carbon saturation in intact forests in Latin America by 2030.

    Fig. S3. Full accounting of the carbon impact of intact forest loss assuming the onset of carbon saturation in all tropical intact forests by 2030.

    Table S1. Country-level estimates on the proportion of selective logging that uses responsible forest management techniques and emission factors for responsible and conventional logging practices.

    Table S2. Intact forest landscape reduction between 2000 and 2013 in countries across the global tropics.

    Table S3. Country-level statistics required to estimate carbon emissions from defaunation.

    Table S4. Regional carbon sequestration rates for intact forest areas and reforestation.

    Table S5. Assumed time scales and trajectories of carbon dynamics from different forest processes.

    References (6583)

  • Supplementary Materials

    This PDF file includes:

    • Fig. S1. Estimated annual rate of carbon sequestration inside intact forests under alternative scenarios.
    • Fig. S2. Full accounting of the carbon impact of intact forest loss assuming the onset of carbon saturation in intact forests in Latin America by 2030.
    • Fig. S3. Full accounting of the carbon impact of intact forest loss assuming the onset of carbon saturation in all tropical intact forests by 2030.
    • Table S1. Country-level estimates on the proportion of selective logging that uses responsible forest management techniques and emission factors for responsible and conventional logging practices.
    • Table S2. Intact forest landscape reduction between 2000 and 2013 in countries across the global tropics.
    • Table S3. Country-level statistics required to estimate carbon emissions from defaunation.
    • Table S4. Regional carbon sequestration rates for intact forest areas and reforestation.
    • Table S5. Assumed time scales and trajectories of carbon dynamics from different forest processes.
    • References (6583)

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