Indicators of Biodiversity and Ecological Services

Forest Carbon Stocks

This indicator aims to monitor the amount of carbon stored in forests worldwide. Forests store carbon in their above- and belowground live biomass, dead wood and litter, and soils.   

In this section, we will explore the following questions:

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How much carbon is stored in the world’s forests?

The world’s forests store approximately 861 gigatons of carbon, with 44 percent in soil (to one-meter depth), 42 percent in live biomass (above- and belowground), 8 percent in dead wood, and 5 percent in litter.Pan et al. 2011, https://doi.org/10.1126/science.1201609 . In total, this is equivalent to nearly a century’s worth of current annual fossil fuel emissions. Tropical rainforests account for only 30 percent of global tree cover but contain 50 percent of the world’s carbon stored in trees.See <a href="/gfr/data-and-methods#carbon-stocks">Data and Methods</a>. Tropical forests store most of their carbon in vegetation (biomass), and boreal forests store vast amounts of carbon in soils.Hengl et al. 2017, https://doi.org/10.1371/journal.pone.0169748 .  

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Aboveground carbon density

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The estimates above are based on models rather than spatially explicit data. Numerous maps of forest carbon stocks have been produced, although none covers all forest carbon pools and many do not offer global coverage. Several maps of forest biomass density (of which carbon accounts for approximately 50 percent of live biomass) have been produced over the past decade by combining ground measurements with a variety of remote sensing techniques, with coverage globally,See the GlobBiomass project, http://globbiomass.org/, and the European Space Agency’s Climate Change Initiative Biomass project, http://cci.esa.int/biomass . pantropicallyBaccini et al. 2012, https://doi.org/10.1038/nclimate1354; Saatchi et al. 2011, https://doi.org/10.1073/pnas.1019576108 ., for specific forest types such as mangroves, Simard et al. 2019, https://doi.org/10.1038/s41561-018-0279-1 . and for specific countries such as PeruAsner et al. 2014, https://doi.org/10.1073/pnas.1419550111 . and the Democratic Republic of the Congo.Xu et al. 2017, https://doi.org/10.1038/s41598-017-15050-z . Global maps of soil organic carbon have also been produced, including one  specifically for mangroves.Sanderman et al. 2018, https://doi.org/10.1088/1748-9326/aabe1c . Carbon in belowground biomass (roots) can be mapped as a function of aboveground biomass, but carbon in dead organic matter (dead trees and leaf litter) does not correlate with aboveground biomass in the same way as roots. Therefore, no comprehensive maps are available for carbon stored in dead organic matter, although estimates have been produced using nongeospatial approaches. 

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The Critical Role of Mangrove Forests and Peatlands in Carbon Storage

Given their relatively small total area, tropical mangrove forests and tropical peatlands play a disproportionately large role in climate regulation and adaptation. Some areas of tropical mangroves have accumulated over 1,000 tons of carbon per hectareDonato et al. 2011, http://dx.doi.org/10.1038/ngeo1123 . —about five times more than other forest types—while protecting coastlines from storm surges and sea level rise and providing flood prevention amidst the extreme rainfall expected to increase with a warming climate. Indonesia’s carbon-rich peatlands store 75 gigatons of carbon—about 30 percent more than all of Indonesia’s forest biomass and equivalent to 10 percent of all carbon in the atmosphereWarren et al. 2017, https://doi.org/10.1186/s13021-017-0080-2 .—while also providing critical buffers against flooding during the wet season and insurance against drought in the dry season.

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Limitations and Future Prospects

Several maps of forest aboveground biomass density and soil organic carbon have been produced by different research groups over the past decade by combining ground measurements with a variety of remote sensing data products. Even when the reported error associated with each map is low, differences across maps exist for a variety of reasons, including different spatial resolution; different representative years; and the use of different techniques, training points, and geospatial data when developing each map/model. End users of the data are given no guidance about which map is “best” or which map to use, yet different maps may have very different implications for forest carbon accounting. Although the issue of reconciling different maps is not unique to forest carbon, high-quality reference data against which to compare the quality of different maps for specific geographies are generally lacking,Mitchard et al. 2013, https://doi.org/10.1186/1750-0680-8-10 . making it difficult or impossible to know which map is closest to the “truth” in a given location. In the case of biomass carbon, most maps also currently suffer from bias, where low-carbon-density areas are overestimated and high-carbon-density areas are underestimated. The aboveground live biomass density map currently displayed on Global Forest Watch was produced by the Woods Hole Research Center at 30-meter resolution and is representative of the year 2000. These two properties enable the straightforward colocation of tree biomass carbon present prior to clearing with tree cover loss (also mapped at 30-meter resolution), which is then assumed to be emitted as carbon dioxide upon clearing (see the Soil Stability and Water Regulation Indicator). 

Because carbon-related map products are produced for different representative years, it may appear that they can be directly compared to estimate change. However, for reasons outlined above, this is not a valid approach. Yet future prospects for mapping aboveground carbon stock change directly are emerging. Baccini et al. (2017)Baccini et al. 2017, https://doi.org/10.1126/science.aam5962 . developed a new approach using 12 years of Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data to determine how aboveground biomass changed across the tropics on an annual basis and concluded that tropical forests are a net source of carbon to the atmosphere. However, Hansen et al. (2019)Hansen et al. 2019, https://doi.org/10.1126/science.aar3629 . highlighted that spatial patterns of carbon loss derived using this approach do not correspond to higher-resolution Landsat-derived tree cover loss data. They also noted that changes in the Baccini et al. (2017) biomass change map were likely due to the presence of substantial spatial error rather than actual change. Furthermore, it is difficult to capture and precisely measure relatively small increases in forest biomass across large areas, even on the ground. Thus, satellite-based methods to measure carbon gains will likely result in underestimates of biomass gain until the research community can incorporate information collected from higher-resolution instrumentsFor example, the National Aeronautics and Space Administration launched the GEDI satellite in late 2018 and the European Space Agency’s BIOMASS mission is expected to launch in 2022. with repeat passes over time. 

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{"Glossary":{"51":{"name":"agricultural tree crops","description":"Trees cultivated for their food, cultural, or economic values. These include oil palm, rubber, cocoa, cashew, mango, oranges (citrus), plantain, banana, and coconut.\r\n"},"94":{"name":"biodiversity intactness","description":"The proportion and abundance of a location\u0027s original forest community (number of species and individuals) that remain.\u0026nbsp;\r\n"},"95":{"name":"biodiversity significance","description":"The importance of an area for the persistence of forest-dependent species based on range rarity.\r\n"},"98":{"name":"carbon dioxide equivalent (CO2e)","description":"Carbon dioxide equivalent (CO2e) is a measure used to aggregate emissions from various greenhouse gases (GHGs) on the basis of their 100-year global warming potentials by equating non-CO2 GHGs to the equivalent amount of CO2.\r\n"},"99":{"name":"CO2e","description":"Carbon dioxide equivalent (CO2e) is a measure used to aggregate emissions from various greenhouse gases (GHGs) on the basis of their 100-year global warming potentials by equating non-CO2 GHGs to the equivalent amount of CO2.\r\n"},"1":{"name":"deforestation","description":"The change from forest to another land cover or land use, such as forest to plantation or forest to urban area.\r\n"},"77":{"name":"deforested","description":"The change from forest to another land cover or land use, such as forest to plantation or forest to urban area.\r\n"},"76":{"name":"degradation","description":"The reduction in a forest\u2019s ability to perform ecosystem services, such as carbon storage and water regulation, due to natural and anthropogenic changes.\r\n"},"75":{"name":"degraded","description":"The reduction in a forest\u2019s ability to perform ecosystem services, such as carbon storage and water regulation, due to natural and anthropogenic changes.\r\n"},"79":{"name":"disturbances","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"68":{"name":"disturbed","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"65":{"name":"driver of tree cover loss","description":"The direct cause of forest disturbance.\r\n"},"70":{"name":"drivers of loss","description":"The direct cause of forest disturbance.\r\n"},"81":{"name":"drivers of tree cover loss","description":"The direct cause of forest disturbance.\r\n"},"2":{"name":"forest","description":"Forests include tree cover greater than 30 percent tree canopy density and greater than 5 meters in height as mapped at a 30-meter Landsat pixel scale.\r\n"},"3":{"name":"forest concession","description":"A legal agreement allowing an entity the right to manage a public forest for production purposes.\r\n"},"90":{"name":"forest concessions","description":"A legal agreement allowing an entity the right to manage a public forest for production purposes.\r\n"},"53":{"name":"forest degradation","description":"The reduction in a forest\u2019s ability to perform ecosystem services, such as carbon storage and water regulation, due to natural and anthropogenic changes.\r\n"},"54":{"name":"forest disturbance","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"100":{"name":"forest disturbances","description":"A discrete event that changes the structure of a forest ecosystem.\r\n"},"5":{"name":"forest fragmentation","description":"The breaking of large, contiguous forests into smaller pieces, with other land cover types interspersed.\r\n"},"6":{"name":"forest management plan","description":"A plan that documents the stewardship and use of forests and other wooded land to meet environmental, economic, social, and cultural objectives. Such plans are typically implemented by companies in forest concessions.\r\n"},"62":{"name":"forests","description":"Forests include tree cover greater than 30 percent tree canopy density and greater than 5 meters in height as mapped at a 30-meter Landsat pixel scale.\r\n"},"69":{"name":"fragmentation","description":"The breaking of large, contiguous forests into smaller pieces, with other land cover types interspersed.\r\n"},"80":{"name":"fragmented","description":"The breaking of large, contiguous forests into smaller pieces, with other land cover types interspersed.\r\n"},"74":{"name":"gain","description":"The establishment of tree canopy in an area that previously had no tree cover. Tree cover gain may indicate a number of potential activities, including natural forest growth or the crop rotation cycle of tree plantations.\r\n"},"7":{"name":"hectare","description":"One hectare equals 100 square meters, 2.47 acres, or 0.01 square kilometers and is about the size of a rugby field. A football pitch is slightly smaller than a hectare (pitches are between 0.62 and 0.82 hectares).\r\n"},"66":{"name":"hectares","description":"One hectare equals 100 square meters, 2.47 acres, or 0.01 square kilometers and is about the size of a rugby field. A football pitch is slightly smaller than a hectare (pitches are between 0.62 and 0.82 hectares).\r\n"},"67":{"name":"intact","description":"A forest that contains no signs of human activity or habitat fragmentation as determined by remote sensing images and is large enough to maintain all native biological biodiversity.\r\n"},"78":{"name":"intact forest","description":"A forest that contains no signs of human activity or habitat fragmentation as determined by remote sensing images and is large enough to maintain all native biological biodiversity.\r\n"},"8":{"name":"intact forests","description":"A forest that contains no signs of human activity or habitat fragmentation as determined by remote sensing images and is large enough to maintain all native biological biodiversity.\r\n"},"55":{"name":"land and environmental defenders","description":"People who peacefully promote and protect rights related to land and\/or the environment.\r\n"},"9":{"name":"loss driver","description":"The direct cause of forest disturbance.\r\n"},"10":{"name":"low tree canopy density","description":"Less than 30 percent tree canopy density.\r\n"},"84":{"name":"managed forest concession","description":"Areas where governments have given rights to private companies to harvest timber and other wood products from natural forests on public lands.\r\n"},"83":{"name":"managed forest concession maps for nine countries","description":"Cameroon, Canada, Central African Republic, Democratic Republic of the Congo, Equatorial Guinea, Gabon, Indonesia, Liberia, and the Republic of the Congo\r\n"},"91":{"name":"megacities","description":"A city with more than 10 million people.\r\n"},"57":{"name":"megacity","description":"A city with more than 10 million people."},"56":{"name":"mosaic restoration","description":"Restoration that integrates trees into mixed-use landscapes, such as agricultural lands and settlements, where trees can support people through improved water quality, increased soil fertility, and other ecosystem services. This type of restoration is more likely in deforested or degraded forest landscapes with moderate population density (10\u2013100 people per square kilometer). "},"86":{"name":"natural","description":"A forest that is grown without human intervention.\r\n"},"12":{"name":"natural forest","description":"A forest that is grown without human intervention.\r\n"},"63":{"name":"natural forests","description":"A forest that is grown without human intervention.\r\n"},"82":{"name":"persistent gain","description":"Forests that have experienced one gain event from 2001 to 2016.\r\n"},"13":{"name":"persistent loss and gain","description":"Forests that have experienced one loss or one gain event from 2001 to 2016."},"97":{"name":"plantation","description":"An area in which trees have been planted, generally for commercial purposes.\u0026nbsp;\r\n"},"93":{"name":"plantations","description":"An area in which trees have been planted, generally for commercial purposes.\u0026nbsp;\r\n"},"88":{"name":"planted","description":"A forest composed of trees that have been deliberately planted and\/or seeded by humans.\r\n"},"14":{"name":"planted forest","description":"A forest composed of trees that have been deliberately planted and\/or seeded by humans.\r\n"},"73":{"name":"planted forests","description":"A forest composed of trees that have been deliberately planted and\/or seeded by humans.\r\n"},"15":{"name":"primary forest","description":"Old-growth forests that are typically high in carbon stock and rich in biodiversity. The GFR uses a humid tropical primary rainforest data set, representing forests in the humid tropics that have not been cleared in recent years.\r\n"},"64":{"name":"primary forests","description":"Old-growth forests that are typically high in carbon stock and rich in biodiversity. The GFR uses a humid tropical primary rainforest data set, representing forests in the humid tropics that have not been cleared in recent years.\r\n"},"58":{"name":"production forest","description":"A forest where the primary management objective is to produce timber, pulp, fuelwood, and\/or nonwood forest products."},"89":{"name":"production forests","description":"A forest where the primary management objective is to produce timber, pulp, fuelwood, and\/or nonwood forest products.\r\n"},"87":{"name":"seminatural","description":"A managed forest modified by humans, which can have a different species composition from surrounding natural forests.\r\n"},"59":{"name":"seminatural forests","description":"A managed forest modified by humans, which can have a different species composition from surrounding natural forests. "},"96":{"name":"shifting agriculture","description":"Temporary loss or permanent deforestation due to small- and medium-scale agriculture.\r\n"},"17":{"name":"tree cover","description":"All vegetation greater than five meters in height and may take the form of natural forests or plantations across a range of canopy densities. Unless otherwise specified, the GFR uses greater than 30 percent tree canopy density for calculations.\r\n"},"71":{"name":"tree cover canopy density is low","description":"Less than 30 percent tree canopy density.\r\n"},"60":{"name":"tree cover gain","description":"The establishment of tree canopy in an area that previously had no tree cover. Tree cover gain may indicate a number of potential activities, including natural forest growth or the crop rotation cycle of tree plantations."},"18":{"name":"tree cover loss","description":"The removal or mortality of tree cover, which can be due to a variety of factors, including mechanical harvesting, fire, disease, or storm damage. As such, loss does not equate to deforestation. "},"19":{"name":"tree plantation","description":"An agricultural plantation of fast-growing tree species on short rotations for the production of timber, pulp, or fruit.\r\n"},"72":{"name":"tree plantations","description":"An agricultural plantation of fast-growing tree species on short rotations for the production of timber, pulp, or fruit.\r\n"},"85":{"name":"trees outside forests","description":"Trees found in urban areas, alongside roads, or within agricultural land\u0026nbsp;are often referred to as Trees Outside Forests (TOF).\u202f\r\n"}}}