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Issue Profile

Forests

The Change in Forest Cover indicator measures the percent change in forest cover between 2000 and 2012 in areas with greater than 50 percent tree cover. It factors in areas of forest loss (including deforestation), reforestation (forest restoration or replanting), and afforestation (conversion of bare or cultivated land into forest).

 

What it measures: The Change in Forest Cover indicator measures the percent change in forest cover between 2000 and 2012 in areas with greater than 50 percent tree cover.  It factors in areas of forest loss (including deforestation), reforestation (forest restoration or replanting), and afforestation (conversion of bare or cultivated land into forest).

Why we include it: Reduction in the extent of forest cover has significant negative implications for ecosystem services and habitat protection.

Where the data come from: M.C. Hansen, P.V. Potapov, R. Moore, M. Hancher, et al. (2013). High-Resolution Global Maps of 21st-Century Forest Cover Change. Science 15: 342 (6160), 850-853.

What the target is: 0 for Change in Forest Cover. For more information, click here.

Description: Forests are dynamic ecosystems vital to sustaining natural life cycles, biodiversity, and the prosperity of humankind. Approximately 31 percent of the world’s total land area - around 4.033 billion hectares - is covered by forests, of which 93 percent are natural and the other 7 percent are planted. Forests play a critical role in mitigating the effects of climate change and providing integral ecosystem services and products. Policymakers increasingly acknowledge the significance of forest ecosystems as scientists place greater emphasis on the role of forests as carbon sinks to combat global climate change and in regulating the hydrological system.

Forests are threatened by factors such as timber harvesting, urbanization, cattle ranching, and agricultural development. According to Hansen et al. (2013), there was a net loss of 115,400 square kilometers (11.5 million hectares) of forests per year since 2000.1 Although forests are in jeopardy around the world, deforestation is most pronounced in tropical countries such as Brazil, Indonesia, Thailand, the Democratic Republic of Congo, other parts of Africa, as well as parts of Eastern Europe.

In the previous versions of the EPI, the primary source of global data on forest cover change was the FAO Forest Resource Assessment (FRA), but these data have many limitations.2 The UN and FAO have identified several principal areas of concern to measure forest sustainability, but because only a few countries have forest monitoring systems sophisticated enough to produce meaningful reports on these criteria, there is a lack of uniformity in reporting on the global scale. For example, some countries count land as “forest land” based on land use categories regardless of whether or not the land has any tree cover. In the case of forest growing stock change, there are inconsistencies in measurement owing to differences in data collection methods and frequency of assessments. Furthermore, the FAO generally accepts values reported by countries without an independent verification mechanism.3

Partially to compensate for these limitations, the 2014 EPI includes a metric of forest change derived from satellite remote sensing data. Over the past two years, the methodology for collecting this data has been substantially improved and associated estimates of forest gain have been developed.4 With these advancements, satellite-derived estimates represent a marked improvement over the FAO FRA data. Furthermore, the authors of the dataset have a commitment to provide annual updates, providing more regular appraisals than the FRA, which is only updated on a five-year cycle. These data will therefore provide more timely estimates of forest change than the ground-level conducted surveys.  

To produce these data, a research team from the University of Maryland collaborated with Google Earth to create a new high-resolution map of forest loss and gain.5 The “Global Forest Change” project is an interactive mapping tool that uses Google Earth Engine’s enormous archive of Landsat 7 images to calculate change in forest cover from 2000 to 2012. The project required 650,000 Landsat 7 images. This map, according to Hansen, “is the first map of forest change that is globally consistent and locally relevant." The satellite-derived map shows that the world lost 2.3 million square kilometers (km2) of tree cover between 2000 and 2012, but gained 800,000 km2 of new forest during the same time period. The map also reveals that, although tropical forest loss is increasing by 2,101 km2 per year, Brazil shows the best improvement of any country, cutting annual forest loss in half from 2003 to 2004 and 2010 to 2011. By largely removing the uncertainties contained in prior data sources, these estimates are of tremendous value for assessing the effectiveness of country-level forest management programs. However, this is not to say that the Hansen et al. (2013) data are also not without their challenges (see Box: Towards Ideal Forest Indicators).

The new satellite-derived data on global forest loss uncover a number of significant findings in comparison to prior FRA reports. Both Canada and the United States show much higher levels of deforestation than what were previously reported in the FRA, since both countries assessed forest cover change only on officially defined forest lands. China and India officially report significant forest gains that are not readily apparent in time-series satellite imagery. While discrepancies are typically fairly high at the country level, some regions fare much better. The region with the highest correlation between FRA and Landsat-derived net change is Latin America, while European data have the least correlation of the regions examined.6

Prevailing discussions point to policy failure as the main driver of deforestation. In many nations with high rates of forest loss, economic development goals tend to override social and environmental concerns associated with deforestation. Subsidies for agriculture, allowing the invasion of forest lands to avoid land reform elsewhere, lax enforcement of logging concessions, and corruption in the forest sector all contribute to high rates of land clearing. In other areas, it appears as if policy and monitoring are far ahead of operational capabilities. For example, the UN Framework Convention on Climate Change (UNFCCC) Reducing Emissions from Deforestation and Forest Degradation (REDD) program does not have institutional investment and scientific capacity to begin implementing a program that can utilize a global observational record.7

Given the global importance of forests, it is imperative that countries strive to curb deforestation and bolster protection of these valuable ecosystems. It is only through a widespread and concerted global effort to reduce the loss of these ecosystems that the future of forests can be ensured.


[1] Hansen, M. C., Potapov, P. V., Moore, R., et al. (2013) High-resolution global maps of 21st-century forest cover change. Science 342:850-853.

[2] Ibid.

[3] A review of time series data show that many countries repeat the same number for forest growing stock over 5-10 year time periods, which seems improbable.

[4] Hansen, M. C., Potapov, P. V., Moore, R., et al. (2013) High-resolution global maps of 21st-century forest cover change. Science: 342:850-853.

[5] Ibid.

[6] Ibid.

[7] Ibid.

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Methods

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