Springer Old Growth Forests - Chapter 18

Chapter 18 Detecting Intact Forests from Space: Hot Spots of Loss, Deforestation and the UNFCCCChanges in forest cover have become recognised as an important global environmental issue. This chapter aims to synthesise what is known about areas and rates of forest-cover change in the tropics and boreal Eurasia from the 1990s onwards
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Springer Old Growth Forests - Chapter 18Chapter 18Detecting Intact Forests from Space: Hot Spotsof Loss, Deforestation and the UNFCCC ´ ´Frederic Achard, Hugh Eva, Danilo Mollicone, Peter Popatov, Hans-JurgenStibig, Svetlana Turubanova, and Alexey Yaroshenko18.1 IntroductionChanges in forest cover have become recognised as an important global environ-mental issue. This chapter aims to synthesise what is known about areas and rates offorest-cover change in the tropics and boreal Eurasia from the 1990s onwards,based on data compiled from expert opinion and earth observation technology.Since the early 1990s, changes in forest area can be measured with confidence fromspace from the global to the regional scale (Mollicone et al. 2003). Forest-cover change (including deforestation) at the regional scale is the process ofland-cover change that is most frequently measured. During the 1990s, rates of forest-cover change were much higher in the tropics than in other parts of the world. Inparticular, the Amazon basin and Southeast Asia contain a concentration of defores-tation hotspots, and more regional remote sensing studies cover the tropics than borealzones. However, forest degradation in Eurasia, related mostly to unsustainablelogging activities or increases in fire frequency, has been growing in recent years. In addition to reviewing the results from Earth observation studies, this chapterpresents a potential accounting mechanism in the context of the United NationsFramework Convention on Climate Change (UNFCCC) question of reducing emis-sions from deforestation in developing countries (UNFCCC 2006), which builds onrecent scientific achievements related to the estimation of tropical deforestationrates from Earth observation technology.18.2 Monitoring of Forest Areas from the Global to the Regional Scale using Satellite ImageryCombined with ground measurements, remote sensing plays a key role in determin-ing the loss of forest cover. Technical capabilities have advanced since the early1990s and operational forest monitoring systems at the national level are now aC. Wirth et al. (eds.), Old‐Growth Forests, Ecological Studies 207, 411DOI: 10.1007/978‐3‐540‐92706‐8 18, # Springer‐Verlag Berlin Heidelberg 2009412 F. Achard et al.feasible goal for most developing countries (DeFries et al. 2006). Several appropri-ate methods are now available to analyse satellite data to measure changes in forestcover. These methods range from visual photo-interpretation to sophisticated digi-tal analysis, and from wall-to-wall mapping to hot spot analysis and statisticalsampling. Clearings for large-scale mechanised agriculture are detectable withmedium resolution data (hundreds of metres spatial resolution), whereas smallagricultural or settlement clearings of 0.5 1 ha require higher resolution data(tens of metres) to be detected accurately. Analysis of remotely sensed satellite data is the only practical approach tomeasure changes in forest area at the regional to global scale. High resolutiondata, with almost complete global coverage, are available at low or no cost for the1990s, early 2000s and around year 2005, in particular Landsat satellite data fromNASA (https://zulu.ssc.nasa.gov/mrsid), the USGS (http://edc.usgs.gov/products/satellite/landsat ortho.html) or from the University of Maryland’s Global LandCover Facility (http://glcfapp.umiacs.umd.edu/). It has been demonstrated thatestimates of deforestation can be provided by using such data at the global orcontinental level (Achard et al. 2002; FAO 2001), or at national level for very largecountries such as Brazil or India (INPE 2005; Forest Survey of India 2004).Deforestation, defined as the conversion of forest land to non-forest land, is mosteasily monitored. Estimating forest degradation resulting from practices such asunsustainable timber production, harvesting of wood for fuel, and fires clearing theedge of forest fragments is more technically challenging than measuring deforesta-tion. Quantifying the accuracy of the result and ensuring that consistent methods areapplied at different time intervals is critical. Accuracies of 80 95% are achievablefor monitoring with high resolution imagery to discriminate between forest andnon-forest (DeFries et al. 2006). Accuracies can be assessed through in-situ obser-vations or analysis of very high resolution aircraft or satellite data.18.3 Information on Global Forest Extent and Deforestation Rates18.3.1 Distribution of Forest Areas at Global ScaleIn the late 1990s, data from AVHRR (advanced very high resolution radiometer)sensors at 1.1 km resolution on board the United States National Oceanic and Atmo-spheric Administration’s polar orbiting meteorological satellites were used to producepan-tropical forest maps at around 1 km resolution (Fig. 18.1) with classificationtechniques adapted to the ecological conditions of these areas, e.g. low seasonalityand nearly permanent cloud coverage (Achard et al. 2001). Recently, theVEGETATION sensor on board SPOT-4 and SPOT-5 satellites, and the MODIS sensoron board the Terra and Aqua satellites allowed for a spatial and thematic refinement ofthe previous global maps. In the framework of the Global Land-Cover 2000 project18 Detecting Intact Forests from Space 413(GLC-2000), teams of regional experts mapped each continent independently usingVEGETATION data for the year 2000 at 0.01 geographic resolution, i.e. at around1.1 km resolution at the equator (Bartalev et al. 2003; Eva et al. 2004; Latifovicet al. 2004; Mayaux et al. 2004; Stibig et al. 2003, 2004). To complement mappingdata, a ‘‘vegetation continuous fields’’ algorithm has been developed using MODISdata to map the global ...