## 4. Changes in Tropical Forest Cover  
Estimating carbon losses and gains from deforestation and degradation, and regenerating secondary forests in the tropics, plays a critical role in contemporary carbon budget monitoring [141]. However, it is highly uncertain to obtain spatially explicit and consistent information on carbon exchange, due to dynamic forest cover and land-use changes in tropical ecosystems. Nonetheless, various studies have attempted to quantify tropical forest cover changes and associated carbon fluxes using remote sensing observations at various spatial and temporal scales. For instance, Figure 4 represents a Landsat-based assessment of status and distribution of tropical woodlands and forests indicates the distribution of intact (a minimum mosaic of forest and naturally treeless ecosystems of 500 km\({}^{2}\) with no sign of human activity), fragmented/managed, deforested and degraded tropical woodlands and forests [142]. The study reported that the loss of intact tropical landscape is increased by three times during 2011-2013 than during 2001-2003 [83; 142; 143]. In 2002, [PERSON] et al. [93] quantified tropical forest cover changes from 1982 to 2000 using coarse resolution (8 km) daily satellite images of NOAA's AVHRR. They estimated yearly sub-pixel level Percent Tree Cover (PTC) from the satellite time series, and used median values of the PTC to derive forest cover changes in three intervals, 1982-87, 1988-92 and 1993-99. Later, they integrated the PTC with \"bookkeeping terrestrial carbon mode [144]\" to estimate pixel-level carbon flux dynamics in the tropical forests. They found the net annual rate of tropical deforestation has increased by \(\sim\)10% (accelerated deforestation) from 5.04 million ha yr\({}^{-1}\) in the 1980s to 5.563 million ha yr\({}^{-1}\) in 1990s, which resulted in a net annual carbon flux loss of 0.6 Pg (600 Mt) and 0.9 Pg (900 Mt). Notably, these estimates of the rate of deforestation are lesser by 35.3% and 62.6% from the estimates of 13.463 million ha yr\({}^{-1}\) and 8.6 million ha yr\({}^{-1}\) by the FRA reports for the 1980s and 1990s. Similarly, a Landsat-based assessment, at the spatial resolution of 30 m, of tropical forest cover changes, indicated tropical deforestation at an annual rate of 0.49% with a gross loss of 8.0 million ha yr\({}^{-1}\) from 1990 to 2000 and 7.6 million ha yr\({}^{-1}\) from 2001 to 2010 [145]. This work was carried through a systematic sampling approach and statistical extrapolation of the results. Notably, 54% of the forest loss during the 2000s occurred in humid tropics which occupies 64% of the tropical forests [145]. Besides, overlay analysis of these change maps with pan-tropical biomass maps (Figure 5) resulted in a net loss of 883.5 MtC [0.88 PgC] per year from 1990 to 2010 [145]. On the other hand, the emergence of the secondary tropical forests on abandoned agricultural land has removed 106 MtC (0.11 PgC) annually [145]. Furthermore, based on 5444 Landsat images acquired during 1990, 2000, 2005, and 2010, [PERSON] et al. [15] observed a 62% acceleration in deforestation rates in the humid tropic from the 1990s to 2000s. Conversely, there is a more general agreement emphasizing the decreasing trend in deforestation in the humid tropics during the 1990s to 2010s [6,145]. [PERSON] et al. (2014) also used the Landsat images for 1990, 2000 and 2010 to estimate tropical forest cover change. They used an image segmentation approach with an MMU of 5 ha and reported a reduction in deforestation in tropical forests from 8.0 million ha in the 1990s to 7.6 million ha in the 2000s. According to FAO's FRA 2020 [146], the rate of net global forest loss has reduced gradually from 7.8 million ha during the 1990s to 4.7 million during 2010s. The largest proportion (90%) of global deforestation was in tropical countries. Interestingly, the rate of deforestation has gradually decreased from 13.8 million ha in the 1990s to 13.2 million ha in the 2000s.