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Southeast Asia is a region known for active land-use changes (LUC) over the past 60 years; yet, how trends in net CO2 uptake and release resulting from LUC activities (net LUC flux) have changed through past decades remains uncertain. The level of uncertainty in net LUC flux from process-based models is so high that it cannot be concluded that newer estimates are necessarily more reliable than older ones. Here, we examined net LUC flux estimates of Southeast Asia for the 1980s−2010s from older and newer sets of Dynamic Global Vegetation Model simulations (TRENDY v2 and v7, respectively), and forcing data used for running those simulations, along with two book-keeping estimates (H&N and BLUE). These estimates yielded two contrasting historical LUC transitions, such that TRENDY v2 and H&N showed a transition from increased emissions from the 1980s to 1990s to declining emissions in the 2000s, while TRENDY v7 and BLUE showed the opposite transition. We found that these contrasting transitions originated in the update of LUC forcing data, which reduced the loss of forest area during the 1990s. Further evaluation of remote sensing studies, atmospheric inversions, and the history of forestry and environmental policies in Southeast Asia supported the occurrence of peak emissions in the 1990s and declining thereafter. However, whether LUC emissions continue to decline in Southeast Asia remains uncertain as key processes in recent years, such as conversion of peat forest to oil-palm plantation, are yet to be represented in the forcing data, suggesting a need for further revision.

An integrated understanding of the biogeochemical consequences of climate extremes and land use changes is needed to constrain land-surface feedbacks to atmospheric CO2 from associated climate change. Past assessments of the global carbon balance have shown particularly high uncertainty in Southeast Asia. Here, we use a combination of model ensembles to show that intensified land use change made Southeast Asia a strong source of CO2 from the 1980s to 1990s, whereas the region was close to carbon neutral in the 2000s due to an enhanced CO2 fertilization effect and absence of moderate-to-strong El Niño events. Our findings suggest that despite ongoing deforestation, CO2 emissions were substantially decreased during the 2000s, largely owing to milder climate that restores photosynthetic capacity and suppresses peat and deforestation fire emissions. The occurrence of strong El Niño events after 2009 suggests that the region has returned to conditions of increased vulnerability of carbon stocks.

We present a synthesis of the land-atmosphere carbon flux from land use and land cover change (LULCC) in Asia using multiple data sources and paying particular attention to deforestation and forest regrowth fluxes. The data sources are quasi-independent and include the U.N. Food and Agriculture Organization-Forest Resource Assessment (FAO-FRA 2015; country-level inventory estimates), the Emission Database for Global Atmospheric Research (EDGARv4.3), the 'Houghton' bookkeeping model that incorporates FAO-FRA data, an ensemble of 8 state-of-the-art Dynamic Global Vegetation Models (DGVM), and 2 recently published independent studies using primarily remote sensing techniques. The estimates are aggregated spatially to Southeast, East, and South Asia and temporally for three decades, 1980-1989, 1990-1999 and 2000-2009. Since 1980, net carbon emissions from LULCC in Asia were responsible for 20%-40% of global LULCC emissions, with emissions from Southeast Asia alone accounting for 15%-25% of global LULCC emissions during the same period. In the 2000s and for all Asia, three estimates (FAO-FRA, DGVM, Houghton) were in agreement of a net source of carbon to the atmosphere, with mean estimates ranging between 0.24 to 0.41 Pg C yr-1, whereas EDGARv4.3 suggested a net carbon sink of -0.17 Pg C yr-1. Three of 4 estimates suggest that LULCC carbon emissions declined by at least 34% in the preceding decade (1990-2000). Spread in the estimates is due to the inclusion of different flux components and their treatments, showing the importance to include emissions from carbon rich peatlands and land management, such as shifting cultivation and wood harvesting, which appear to be consistently underreported.

Background: Although endoscopic submucosal dissection (ESD) provides a high rate of curative resection, the remaining gastric mucosa after ESD is at risk for metachronous superficial gastric epithelial neoplasms (MSGENs). It leaves room for risk factors for developing MSGENs after ESD. This study aimed to identify clinicopathological risk factors for the occurrence of MSGENs, and to evaluate the association of Helicobacter pylori (H. pylori) with the MSGENs. Methods: We conducted a retrospective cohort study including 369 patients with 382 lesions that underwent ESD for adenoma/early gastric cancer. Results: Twenty-seven MSGENs occurred. The subjects were divided into MSGEN and not-MSGEN groups. There was a significantly higher frequency of histological intestinal metaplasia (HIM) and initial neoplasm location in the upper or middle parts (INUM) in the MSGEN group. The HIM and INUM groups had a significantly higher cumulative incidence of MSGENs. We compared 27 patients from the MSGEN group and 27 patients from the not-MSGEN group that were matched to the MSGEN group for variables including HIM and INUM. There was a significantly higher frequency of the spontaneous disappearance of H. pylori in the MSGEN group. Conclusions: HIM, INUM, and the spontaneous disappearance of H. pylori may be clinicopathological risk factors for developing MSGENs after ESD. [ABSTRACT FROM AUTHOR]

Background and Aim: Small gastric subepithelial lesions (SELs) are sometimes encountered in daily esophagogastroduodenoscopy (EGD) practice, but whether once-annual or twice-annual endoscopy can provide sufficient follow-up remains unclear. Because follow-up based on small-SEL characteristics is important, this study clarified the natural history of gastric SELs less than 20 mm. Methods: This retrospective multicenter observation study conducted at 24 Japanese hospitals during April 2000 to March 2020 examined small gastric SELs of ≤20 mm diameter. The primary outcome was the rate of size increase of those SELs detected using EGD, with growth times assessed irrespective of SEL pathological diagnoses. Results: We examined 824 cases with tumors of 1–5 mm diameter in 298 (36.2%) cases, 6–10 mm in 344 (41.7%) cases, 11–15 mm in 112 (13.6%) cases, and 16–20 mm in 70 (8.50%) cases. An increase of small gastric SELs was observed in 70/824 patients (8.5%). The SELs larger than 6 mm increased, even after 10 years. No-change and increasing groups had no significantly different malignant findings at diagnosis. In cases of gastrointestinal stromal tumors (GISTs), internal cystic change in endoscopic ultrasound (EUS) is a risk factor for an increased tumor size. The predictive tumor growth cutoff size at initial diagnosis was 13.5 mm. Conclusions: Small gastric SELs less than 20 mm have an approximately 8.5% chance of increase. Predictive markers for GIST growth are tumor size ≥13.5 mm and internal cystic change in EUS. [ABSTRACT FROM AUTHOR]