Abstract
Insular Southeast Asia is a hotspot of humid tropical forest cover loss. A sample-based monitoring approach quantifying forest cover loss from Landsat imagery was implemented to estimate gross forest cover loss for two eras, 1990–2000 and 2000–2005. For each time interval, a probability sample of 18.5 km × 18.5 km blocks was selected, and pairs of Landsat images acquired per sample block were interpreted to quantify forest cover area and gross forest cover loss. Stratified random sampling was implemented for 2000–2005 with MODIS-derived forest cover loss used to define the strata. A probability proportional to x (πpx) design was implemented for 1990–2000 with AVHRR-derived forest cover loss used as the x variable to increase the likelihood of including forest loss area in the sample. The estimated annual gross forest cover loss for Malaysia was 0.43 Mha/yr (SE = 0.04) during 1990–2000 and 0.64 Mha/yr (SE = 0.055) during 2000–2005. Our use of the πpx sampling design represents a first practical trial of this design for sampling satellite imagery. Although the design performed adequately in this study, a thorough comparative investigation of the πpx design relative to other sampling strategies is needed before general design recommendations can be put forth.
Highlights
Humid tropical forests are mostly found in Brazil, Congo, Indonesia and Malaysia [1]
This is not necessarily a surprising result given that the strata and sample size allocation used for Malaysia were constrained to align with the stratified design implemented to estimate global humid tropical forest cover loss [1]
Considerable forest cover loss was detected by Landsat in the first two strata which, according to the Moderate Resolution Imaging Spectroradiometer (MODIS)-based stratification, should have contained very little loss. These results suggest that Malaysia had a pervasive dynamic of small forest clearings that were not detected at the coarse-scale change threshold specified for the MODIS stratification variable, but were detectable by Landsat
Summary
Humid tropical forests are mostly found in Brazil, Congo, Indonesia and Malaysia [1]. Humid tropic forests cover less than ten percent of the earth’s land area, they contain some of the most bio-diverse terrestrial ecosystems [1,2,3]. Deforestation is a major concern for many developing countries [4,5]. A large amount of humid tropical forest in South Asia has been lost due to one of the world’s highest rates of deforestation since the 1980s including Malaysia and Indonesia [6]. Land use changes through agriculture expansion, commercial logging, plantation development, mining and road building are among many factors in causing the loss of valuable tropical forest cover [7]. Malaysia encompasses 32.9 million ha of land area and in 2005 had a population of about 25 million [8,9]
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