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Drainage of Organic Soils and GHG Emissions, 1990 – 2019

Rome, April 20 2020. FAO releases today new estimates of the amount of area of organic soils drained for agriculture and the resulting anthropogenic greenhouse gas (GHG) emissions to the atmosphere. Data are disseminated by gas and land use class: emissions of N2O on cropland and grassland are disseminated under the domain Cultivation of Organic soils of FAOSTAT Emissions-agriculture; whereas emissions of CO2 on Cropland and Grassland are disseminated within the FAOSTAT Emissions-Land use domain.

Organic soils  are, generally speaking, wet soils ecosystems, characterized by very high levels of organic matter, which accumulates under the anoxic conditions that exist in the presence of water. They include tropical and boreal peatlands, high-latitude bogs, ferns and mires. Indeed, while organic soils cover globally a mere 3 percent of the terrestrial land area, they represent up to 30 percent of the total soil carbon, playing an important role in maintaining the earth’s carbon balance. Drainage of organic soils releases large quantities of carbon dioxide (CO2) and nitrous dioxide (N2O) into the atmosphere and for several decades after the drainage event, due to the increased oxydation rates of the underlying organic matter. Agriculture is a major cause of drainage of organic soils around the world, especially since 1990 for the cultivation of permanent crops such as oil palm and cacao. Restoration of degraded organic soils is currently a priority in several countries as part of their commitments under the climate convention. Measuring current trends, globally and with country detail, is therefore important to identify and quantify existing and fast-developing new hotspots of degradation and to help reduce emissions from drained organic soils in future decades.

Estimates of area drained and subsequent emissions are computed at pixel level, using available geospatial information on soils characteristics, land cover, land use and climate conditions. The FAOSTAT estimates use histosols as proxy for presence of organic soils, in agreement with IPCC guidelines (Fig. 1).

Data are aggregated at national level for 101 countries and 4 territories, representing the subset of FAOSTAT countries and territories where organic soils are present. Statistics are disseminated in three separate domains, over the period 1990 – 2019, in line with country reporting requirements to the Climate Convention, following the Intergovernmental Panel on Climate Change Guidelines (IPCC, 2006).  These FAOSTAT statistics represent the only avaialble global dataset in the world today showing country, regional and global time series on drained organic soils.

 

Figure 1. Global extent of organic soils – histosols

 

HIGHLIGHTS

GLOBAL

•    In 2019, the world total area of drained organic soils reached 25 million hectares (ha), up from 23 million ha in 1990. Of this total, about 14 million ha were in temperate and boreal areas of the northern hemisphere, while the remainder were tropical peatlands, mostly in the southern hemisphere

•    The corresponding world total GHG emissions were 833 Mt CO2eq, with CO2 and N2O gas contributing 87 percent and 13 percent ot this amount, respectively. Emissions from drainage of organic soils represented nearly 8 percent of total agriculture emissions. About three quarters of the global area of organic soils drained for agriculture was for cultivation  of both temporary and permanent crops. The remainder one quarter was drained for livestock grazing.

•    The past two decades marked a significant increase in the area of drained organic soils, largely due to drainage of tropical peatlands in South-East Asia. Emissions were 10 percent higher in 2019 compared to 2000 and 13 percent higher compared to 1990 (Fig. 2)

 

Figure 2. Global emissions from drained organic soils, 1990 – 2019

REGIONAL

•    As of 2019, the area of drained organic soils for agriculture was largest in Eastern and Northern Europe (11 M ha in total), representing 45 percent of the world total. It was followed by Asia (8 Mha), with nearly 6 Mha were in South-East Asia alone. Smaller contributions came from North America (3 Mha), Africa, South America and Oceania (1 Mha)

•    Conversely, GHG emissions were larger in tropical Asia, due to the fact that carbon loss from oxydation is faster in warmer climates. In 2019, drained organic soils in Asia were responsible for emissions of 466 Mt CO2eq, more than half of the world total, followed by emissions from Europe (167 Mt CO2eq), Africa and North America (71 and 74 Mt CO2eq, respectively). Drained tropical peatlands in South-East Asia were the world single largest emission source (417 Mt CO2eq) (Fig. 3)

 

Figure 3. Regional and sub-regional emissions from drained organic soils, 1990-2019

•    Since 1990, emissions from drained organic soils increased mainly in South-East Asia, by more than 100 Mt CO2eq, representing a relative growth of 25% over the period 1990-2010. Albeit starting from much lower absolute values, relative growth was also strong in South America (30%) and Oceania (15%). As shown in Fig. 4, emissions increases were instead quite small in Africa (3%), North America and Europe (where they remained virtually unchanged). While still poorly studied, the estimated growth rates in South America, Oceania and Africa are consistent with recent literature on recent degradation of organic soils due to agriculture in these regions. The low growth rates in Europe and North America reflect the fact that organic soils in these regions have already been drained.

 

Figure 4. Percent change in emissions from drained organic soils by region and sub-region, 1990 – 2019

COUNTRY

•    In 2019, Indonesia had the world largest annual emissions from drained organic soils, totaling 343 Mt CO2eq (41 percent of the world total). These emissions are from about 5 Mha of drained tropical peatlands, largely for oil palm cultivation. Substantial contributions were estimated for Malaysia (48 Mt CO2eq), the United States of America (47 Mt CO2eq), Russian Federation (35 Mt CO2eq) and Belarus (27 Mt CO2eq).

•   Indonesia also had largest absolute increase in emissions from drained organic soils during the 1990 – 2019 period, corresponding to 273 Mt CO2eq (26 percent relative increase). Malaysia had a smaller yet still significant increase over the same period, of 31 Mt CO2eq, representing the highest relative increase among large emitters (54 percent). Fig. 5 illustrates the increase over time in the area of drained organic soils in both countries

•   Finally, the world highest relative increases were computed for Peru (+150 percent drainded area; +100 percent emissions), although these changes happened with respect to low initial values.

 

Figure 5. Extent of drained organic soils in Indonesia and Malaysia over time, showing total drained area in 1995 and successive additions by 2005, 2015 and 2018

 

 

 

 

EXPLANATORY NOTES

The FAOSTAT domains Cultivation of Organic soils, Cropland Organic Soils and Grassland Organic Soils contain estimates of nitrous oxide (N2O) and CO2 emissions associated with the drainage of organic soils for agriculture. Data is computed geospatially, using the Tier 1 default factors defined by the Intergovernmental Panel on Climate Change (IPCC, 2006). Estimates are available by country, with global coverage and relative to the period 1990 – 2019.

Disseminated information includes emissions, implied emission factors and the underlying activity data, i.e. area of histosols (in ha) drained in agricultural areas. GHG estimates are available in Gg of N2O and in corresponding Gg of CO2 equivalents. Conversion to CO2eq is made via Global Warming Potentials (GWP) coefficients, from: a) Second Assessment Report (SAR)(IPCC, 1996); b) IPCC Fourth Assessment Report (AR4) (IPCC, 2007); and c) IPCC Fifth Assessment Report (AR5)(IPCC, 2014). Data are estimated for the 103 countries and 4 territories where organic soils exist according the the world soil map used in this analysis. In only two of these, Mozambique and Saint Pierre & Miquelon, organic soils had not been drained for agriculture.

Estimates are available by country, by FAOSTAT regional aggregation and special group, including the Annex I and Non-Annex I Parties to the United Nations Framework Convention on Climate Change (UNFCCC).

Geospatial data are obtained through the stratification of the following spatial datasets:

i. map derived from the Harmonized World Soil Database (HWSD-FAO et al., 2012), with percentages of the pixel area with histosols (both as dominant and secondary soil type). The area covered by histosols is used as proxy, as per IPCC guidelines, for organic soils. Methods relevant to the development and use of this spatial layer are discussed in Tubiello et al. (2016) for previous comparable GHG estimates.

ii. Annual land cover maps (for the period 1993–2018) produced by the Catholic University of Louvain Geomatics as part of the Climate Change Initiative of the European Spatial Agency (vesion 2.0, CCI UCL Geomatics, 2017) and version 2.1 updates under the European Copernicus program (2019). Cropland area is identified from the CCI-LC yearly maps, applying specific proportions to pixel area in the relevant land cover categories. The approach follows primarily a land cover perspective as in the FAOSTAT “Land Cover” domain.  The cropland area is identified from the CCI-LC yearly maps, applying specific proportions to pixel area in the relevant land cover categories.

iii. For grassland, the trampling of grazing animals on organic soils is associated with drainage, and N2O and C release from degraded organic soils. The presence of livestock is derived from the spatial distribution of cattle, goats and sheep from the FAO Gridded Livestock of World (Robinson et al., 2014).

Methodological notes with additional technical details for each of the three FAOSTAT Organic Soils domains is available in FAOSTAT.

REFERENCES

IPCC SAR 1996. Climate Change 1995. The Science of Climate Change. Houghton, J.T., Meira Filho, L.G., Callander, B.A., Harris, N., Kattenberg, A. and K. Maskell (eds.). Contribution of WGI to the Second Assessment Report of the Intergovernmental Panel on Climate Change. Available at: http://www.ipcc.ch 

IPCC 2006. 2006 IPCC Guidelines for National Greenhouse Gas Inventories, Prepared by the National Greenhouse Gas Inventories Programme, Eggleston H.S., Buendia L., Miwa K., Ngara T. and Tanabe K. (Eds), IGES, Hayama, Japan. Available at: http://www.ipcc-nggip.iges.or.jp/public/2006gl/index.html

IPCC AR4 2007. Fourth Assessment Report Climate Change 2007. GWP values. Available at: https://www.ipcc.ch/publications_and_data/ar4/wg1/en/ch2s2-10-2.html

FAO/IIASA/ISRIC/ISSCAS/JRC, 2012. Harmonized World Soil Database (version 1.2). FAO, Rome, Italy and IIASA, Laxenburg, Austria. Available at: http://www.fao.org/soils-portal/soil-survey/soil-maps-and-databases/harmonized-world-soil-database-v12/it/

IPCC AR5 2014. Climate Change 2014: Mitigation of Climate Change. Contribution of Working Group III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Edenhofer, O., R. Pichs-Madruga, Y. Sokona, E. Farahani, S. Kadner, K. Seyboth, A. Adler, I. Baum, S. Brunner, P. Eickemeier, B. Kriemann, J. Savolainen, S. Schlömer, C. von Stechow, T. Zwickel and J.C. Minx (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Available at: http://www.ipcc.ch/report/ar5/wg3/

Robinson, T.P., Wint G.R.W., Conchedda G., Van Boeckel T.P., Ercoli V., Palamara E., Cinardi G., D’Aietti L., Hay S.I., and Gilbert M., 2014. “Mapping the Global Distribution of Livestock.” PloS One 9 (5): e96084. Available at: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096084

Tubiello, N.F., Biancalani, R., Salvatore, M., Rossi, S., Conchedda, G., 2016. A Worldwide Assessment of Greenhouse Gas Emissions from Drained Organic Soils. Sustainability 2016, 8 (4). Available at: http://www.mdpi.com/2071-1050/8/4/371 

Land Cover CCI Product User Guide Version 2.0, 2017.  UCL Geomatic (Université catholique de Louvain; Friederich-Schille-Universität Jena; Wageningen University; Max-Planck-Institut für Meteorologie; JRC European Commission; Met Office. Deliverable ref: D3.3. Belgium. Available at: http://maps.elie.ucl.ac.be/CCI/viewer/download/ESACCI-LC-Ph2-PUGv2_2.0.pdf.

Copernicus Climate Change Service, 2019. Documentation for version 2.1 of the dataset. Land cover classification gridded maps from 1992 to present derived from satellite observations. Available at: https://cds.climate.copernicus.eu/cdsapp#!/dataset/satellite-land-cover?tab=doc 

 

This analytical brief was prepared by Francesco Nicola Tubiello and Giulia Conchedda 

Cover photo: ©Ramadian Bachtiar/CIFOR – under CC license

 

 

 

 

 

DATA

 

RELATED DATA 

 

 

 

 

 

 

European Space Agency

 

 

Global Soils Partnership