Indicators of Forest Condition

Forest Degradation

This indicator aims to monitor the area of forest worldwide that has experienced degradation due to natural or human causes. Since it is not currently possible to measure forest degradation directly at a global scale, this indicator employs three different measures of disturbed forest area as a proxy for where degradation may have occurred, acknowledging that not all forest disturbance results in forest degradation. The three measures of disturbed forest area are not mutually exclusive (i.e., areas of different kinds of disturbance often overlap), and they are therefore estimated individually but not summed.

How much forest has experienced partial loss of canopy cover?

Worldwide, 185 million hectares (Mha) of forest experienced a partial reduction of tree canopy cover (more than 20 percent but less than 90 percent as measured at 250-meter [m] resolution via satellite imagery) between 2001 and 2012, affecting 5 percent of global forest area.FAO 2016, http://www.fao.org/3/a-i4793e.pdf; Van Lierop et al. 2005, https://doi.org/10.1016/j.foreco.2015.06.010 . Common causes of partial canopy cover loss include fire, wood removals, small clearances, and insect damage. Climate change also exacerbates conditions that lead to increased fires and outbreaks of forest pests and diseases. The tropical region experienced the most partial canopy cover loss with 9 percent of forest area affected.

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The Impacts of Forest Degradation

Forest degradation can diminish a forest’s ability to support local human populations through ecosystem services, such as soil stability, water regulation, and local economic development, as well as to provide recreational and cultural amenity value. Forest degradation can also impact biodiversity and the ability of forests to sequester and store carbon. Degradation is often a precursor to forest conversion.Thompson et al. 2013, https://www.ecologyandsociety.org/vol18/iss2/art20/ . Degraded forests are less resilient in the face of natural disturbances such as droughts, fires, storms, and pests, particularly as such events become more severe and more frequent due to climate change. Human causes of degradation include destructive logging practices, encroachment, extensive firewood collection, overhunting, and the introduction of invasive species.

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Tropical forests experienced the highest levels of partial canopy cover loss between 2000 and 2012<fn>FAO 2016, <a href="http://www.fao.org/3/a-i4793e.pdf">http://www.fao.org/3/a-i4793e.pdf</a>.</fn>

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How much forest has been affected by wildfire?

Worldwide, 86 Mha of tree cover loss were associated with fire between 2001 and 2019, affecting 2.1 percent of global tree cover area. In an effort to reflect only those forests that will be allowed to recover following a fire event, this statistic intentionally excludes fire-related tree cover loss that was followed by a new land use such as agriculture. Canada, Russia, and the United States together accounted for 94 percent of all tree cover loss related to fire. Although fires occur naturally in many temperate and boreal forest ecosystems, human-caused fires and the drying effects of climate change have led to hotter and more frequent fires in some areas, with potential adverse effects on forest ecosystems.Joyce et al. 2014, https://nca2014.globalchange.gov/report/sectors/forests#statement-16387 .  

Tropical forests have also been heavily affected by fires in recent years,Weisse and Goldman 2017, https://www.wri.org/blog/2017/10/global-tree-cover-loss-rose-51-percent-2016 . with 2019 blazes in Brazil and Indonesia resulting in massive media attention. Fires in humid tropical forests such as the Amazon are not natural—these fires are almost always set by humansCochrane 2011, https://link.springer.com/chapter/10.1007%2F978-3-642-05383-2_7; Cochrane and Laurance 2008, https://www.nrem.iastate.edu/class/assets/nrem390-10/Cochrane%26Laurance_Tropics_Fire.pdf . —though they often only burn out of control under drought conditions. Since tropical ecosystems are not adapted to fire, the blazes may cause adverse impacts on those forests for years to come.Rappaport et al. 2018, https://doi.org/10.1088/1748-9326/aac331 . These tropical forest fires also result in major climate-damaging emissions,Harris et al. 2015, https://www.wri.org/blog/2015/10/indonesia-s-fire-outbreaks-producing-more-daily-emissions-entire-us-economy . resulting in a potential positive feedback loop between climate change and fires.Le Page et al. 2017, https://www.earth-syst-dynam.net/8/1237/2017/esd-8-1237-2017.pdf . 
 

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How much has the area of intact forest been reduced?

Large, undisturbed forest areas often play an outsized role in storing terrestrial carbon, harboring biodiversity, regulating hydrological regimes, and providing other ecosystem functions in comparison with smaller tracts of forest. A widely cited global data set on intact forest landscapesSee Intact Forest Landscapes, http://www.intactforests.org/ . sets a minimum threshold of 50,000 ha for an undisturbed forest to be considered “intact”; dropping below this threshold is a potential indication that the ability of that forest to provide these benefits could be diminished. Loss of “intactness” could result from fragmentation (such as a new road cutting through a forest) or from outright deforestation (such as conversion of forest for agriculture). 

Worldwide, 120 Mha of forest area that were considered intact in 2000 could no longer be considered intact in 2016, corresponding to a reduction of approximately 7.5 Mha of intact forest per year and a total reduction of 9 percent of intact forest area. Russia experienced the largest reduction of intact forest area (29 Mha), primarily due to fire.See <a href="/gfr/data-and-methods#forest-degradation">Data and Methods</a>. Romania saw the largest percentage decline, with its last remaining tract of intact forest fragmented by new transport infrastructure. Paraguay also experienced a notable decline, with an 80 percent decrease in forest area that could be considered intact between 2000 and 2016 due to the clearing of the Chaco for cattle ranching.
 

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Reduction of intact forest area by country

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Tree cover loss caused by cattle ranching in northern Paraguay causes many forest areas to lose their “intact” status

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Limitations and Future Prospects

There is no simple or widely accepted method for measuring forest degradation or assessing the resulting forest quality. Forest degradation is notoriously difficult to define due to varied perceptions of which forest attributes matter most.Thompson et al. 2013, https://unfccc.int/files/land_use_and_climate_change/redd/submissions/application/pdf/redd_20130704_cpf_working_group_on_forest_degradation.pdf . The condition of forests may decline for different reasons, and degradation in one dimension of forest quality (e.g., water regulation) will not necessarily correlate with degradation in another (e.g., biodiversity). A further challenge is that forest degradation is incremental and often involves subtle changes that are difficult to measure, especially using medium-resolution satellite imagery typically used in global forest monitoring systems. Finally, measuring forest degradation requires methods that can distinguish short-term fluctuations due to changing seasons or natural disturbances—such as fires, floods, and droughts—from persistent trends that are more likely indicative of long-term degradation.  

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The three measures of forest disturbance used in this indicator are only proxies, indicating where degradation may have occurred. They are not direct measures of the extent of degradation that has occurred. As new data sets are developed, a multidimensional framework, such as that shown in the diagram below, could enable degradation in a specific forest to be measured against a suite of values, and targets could be set according to the management priorities for that forest.

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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"},"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"},"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."},"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"}}}