Twenty Years of Working Towards a Sustainable Southeast Asia: 1993 -- 2013

The Southeast Asia program first set about testing hypotheses applicable to each of the three ecosystem zones. On the forest margins, the hypothesis was that complex agroforests provided a superior alternative for small-scale farmers to either food-crop systems or monocultural plantations of perennials. As an alternative to slash and burn, complex agroforests increased production sustainability, increased biodiversity, reduced production risks and increased returns to labour compared to continuous food crops or monocultural plantations. The second hypothesis stated that rehabilitating Imperata grasslands with small-scale agroforestry systems would be superior to plantation reforestation in terms of production, equitability and participation. For hilly farmlands, the team hypothesised that there were several pathways to sustainable farming. Among these, contour hedgerow systems initiated through natural vegetative strips provided distinct advantages as a superior, least-cost foundation upon which to build agroforestry-based, conservation farming

Forest Landscape Restoration and Ecosystem Services in A Luoi District, Thua Thien Hue Province, Vietnam

Abstract The Government of Vietnam has invested efforts to increase the forest cover, and to conserve biodiversity through different forest development projects and programs. Losing natural forests and landscapes in the context of the “exhaust” of ecosystem services has been seen as burden in many mountainous areas. The Decision No.16 on ecosystem restoration, which was adopted by the Conference of the Parties to the Convention on Biological Diversity (CBD) at the 11th meeting (December 5th, 2012) stated that ecosystem restoration requires the application of suitable technologies and the fully-effective participation of local entities. This serves to identify obstacles while attempting to restore, regenerate ecosystem services and biodiversity, which have been degraded and lost in the recent decades. Furthermore, Vietnam’s National Forest Development Strategy targeted to achieve a forest area of 16.2 million hectares by the year 2020. Local people living adjacent to forests depend on the forest ecosystem services supplied from various natural forest landscapes in the area. This holds true especially for the people of Central Vietnam where the terrestrial area is narrow due to the country shape. In this area, agriculture practices play an essential role although the agricultural land is very limited due to the topographic conditions. The distinct land-uses reflect the natural distribution of plant and animal species as well as human interventions. In Vietnam, the forest ecosystems have been classified into three categories according to their main functions: special-use forest for nature conservation; protection forest for the watershed and protective measures; and production forest for commercial operations. This study was conducted in the A Luoi District, Thua Thien Hue Province. Ground truth samples were inventoried in three forest types from 150 m to 1162 m above sea level (a.s.l.) and steep slopes from 5 to 48 degrees. The elevation range was divided into the lower elevation level H1 ranging from 150 m – 699 m and into the higher elevation level H2 from 700 m-1162 m a.s.l.. The slopes were stratified into level S1 from 5-20 degrees, and into S2 from 21-48 degrees. The forest cover was classified into the types: undisturbed forest (UF), low disturbed forest (LF), and heavily disturbed forest (DF). To strengthen the classification of forest types, a t-test of extracted vegetation indices between ground truth plots and training sample plots was done. Up to date, no remote sensing-based work on ecological stratification of the natural forest landscapes has been conducted. Finding the tree species distribution, species diversity, and species composition over the sub-stratification of the elevations, slopes, and the forest types - by applying remote sensing - are necessary to classify the land-use types and to map out the availability of natural resources, especially the ecosystem services supply and demand of local people. Land-use and forest type classification may contribute remarkably to long-term planning, which has been assigned to local authorities, and which should include local communities. The entire study consists of four main parts. The first part aimed at evaluating the influence of topography on tree species diversity, distribution, and composition of the forests in Central Vietnam. A significant difference of species richness and species diversity was found in shallower and steeper slopes (p < 0.05) and a relatively high correlation of the species distribution, the number of stems, and the number of tree families with the elevation factor was found. The lower elevation and shallower slope showed higher species richness (p < 0.05) but not a significant difference between the number of families and the evenness. The dominance and the abundance of tree species among the topographic attributes were significantly different (p < 0.05). Lower elevation and shallower slope showed higher species richness and species diversity than the higher elevation and steeper slope. The most dominant and abundant tree families from different elevations and slopes included the Myrtaceae, Dipterocarpaceae, Burseraceae, Fagaceae, Moraceae, Cornaceae, Apocynaceae, Sapindaceae, Cannabaceae, Juglandaceae, Lauraceae, Myristicaeae, Annonaceae, Ebenaceae, Meliaceae, Rubiaceae, and the Rosaceae. The second part aimed at assessing the soil qualities, which belong to the most essential elements for land-use planning and agricultural production. 155 soil samples from different land-use types and topographic aspects were collected in order to compare information on soil organic carbon (SOC), soil total nitrogen (STN), and soil acidity (pH) at two soil depths. The SOC of arable land and forest plantation land was found to be higher than those of grassland and of natural forests (p < 0.05). The total nitrogen in the natural forests was significantly less, compared to the other land-use types. No significant differences in the total nitrogen content (p < 0.05) were found among arable land, plantation forest, and grassland. The soil organic carbon and the total nitrogen were high in the upper soil and less downwards, within all land-use types. The soil pH in the plantation forest and the arable land-use types showed no significant change among soil depth categories. Significant differences were not found in topographic aspects and the soil organic carbon content; however, differing trends of soil organic carbon and land-use types and aspects were found. The impact of the slope, elevation, farming system and soil texture accounted for the main differences of soil indicators under varying land-use types in the A Luoi District. The third part of this study was designed to apply remote sensing data from Landsat-8 and Sentinel-2 sources in order to classify land-cover and land-use classes (including three forest types UF, LF, and DF) in the study area by using machine learning algorithms. Further, vegetation indices were applied to find possible correlations and regressions of both, vertical and horizontal structures of the dominant forest tree species within different forest types. It was found that the vegetation indices between the ground-truth plots and the training sample plots were significantly different (p<0.05). The most dominant and abundant tree families in the context of the vertical structure were the Dipterocaparceae, Combretaceae, Moraceae, Leguminosae, Burseraceae, and the Polygalaceae. These, in the context of the horizontal structure were the Fagaceae, Lauraceae, Leguminosae, Dipterocaparceae, Myrtaceae, Myristicaceae, Euphorbiaceae, and the Clusiaceae. The results of the land cover and the land-use classification of Sentinel-2 were found to be more precise than those of Landsat-8 with the Random Forest algorithm: (Sentinel-2 with out-of-bag error of 14.3%, overall accuracy of 85.7%, kappa of 83% and Landsat-8 with out-of-bag error 31.6%, overall accuracy of 68%, kappa of 67.5%). The study found relationships (from 43% up to 66%) between four (out of ten) vegetation indices within horizontal and vertical structures of the forest stands: the Enhanced Vegetation Index (EVI), the Difference Vegetation Index (DVI), the Perpendicular Vegetation Index (PVI), and the Transformed Normalized Difference Vegetation Index (TNDVI). The fourth part evaluated potential provisioning services of the current natural forests - apart from wood and timber supply. It (i) assessed and compared the amount of non-timber forest tree species (NTFP species) in the different investigated forest types and elevations as potential resources; explored (ii) the respective demands of local people and (iii) their personal views concerning the importance of natural forests and the satisfaction with their provisioning services; and finally (iv) gathered their awareness of limited consequences of former forest development and requirements for forest landscape restoration. Thirty-nine NTFP tree species were found for various uses such as food, medicine, and resin or oil. Random on-site interviews of 120 out of 627 local households were conducted in a commune with high dependency on local natural forest products. Their importance and satisfaction ranking of natural forests - considering different target groups with respect to gender, income, age-class, and education - was commenced. Multiple methods were used to assess an array of gathering information, which are related to (a) the forest resources importance and (b) the local people satisfaction. These were set into context with the involvement of non-timber forest goods extraction, landslides, goods declination, and the perception for natural forest landscapes restoration, in order to clarify perspectives on forest provisioning services. The results revealed remarkable differences among target groups, adjustment, perceptions. The insufficient supply of NTFPs, particularly profitable natural medicine provision, urges for adapted silvicultural measures. The results imply that NTFPs from natural forests are not only very important to the local communities, but also contribute to the enrichment of biodiversity. The participation of local people in practical forest management and forest improvement should be considered in the decision-making process for natural forest landscape restoration of remote mountainous areas. The findings of this study can support sustainable forest management; natural forest landscape restoration with the involvement of local communities; conservation practices of biodiversity, based on topographic conditions; land-use planning; identification of dominant tree species using vegetation indices’ values, and land cover and land-use classification using open source satellite images. This final component will be aided by application of machine learning algorithms in the current study area and in the central mountainous area of Vietnam.2021-07-2

Forest cover changes in lao tropical forests: physical and socio-economic factors are the most important drivers

Lao People’s Democratic Republic (PDR) has been experiencing significant forest depletion since the 1980s, but there is little evidence to demonstrate the major causes and underlying drivers for the forest cover changes. In this study, we investigated the relationship between forest cover decrease and increase in the south of Lao PDR between 2006 and 2012 and selected physical and socio-economic factors. We used a map of forest cover changes derived from analysis of Landsat ETM+ imagery in 2006 and 2012, together with socio-economic and physical environmental data from the national authorities. The study area has experienced noticeable forest cover changes: both forest decreases and increases were unevenly distributed throughout the region. Logistic regression models were used to test relationships between forest cover decrease or increase and selected physical and socio-economic factors. Forest clearance was associated strongly with elevation, distance to main roads and shifting cultivation practices. Meanwhile, forest cover increase was more likely to correlate with rubber plantations. Native forest and shifting cultivation lands were vulnerable to being converted into rubber plantations. This research provides much-needed information on which to base forestry policy and decision making to minimize and prevent current deforestation, as well as manage potential risks in the future.Chittana Phompila, Megan Lewis, Bertram Ostendorf and Kenneth Clark

Farms or forests? understanding and mapping shifting cultivation using the case study of West Garo hills, India

Attempts to study shifting cultivation landscapes are fundamentally impeded by the difficulty in mapping and distinguishing shifting cultivation, settled farms and forests. There are foundational challenges in defining shifting cultivation and its constituent land-covers and land-uses, conceptualizing a suitable mapping framework, and identifying consequent methodological specifications. Our objective is to present a rigorous methodological framework and mapping protocol, couple it with extensive fieldwork and use them to undertake a two-season Landsat image analysis to map the forest-agriculture frontier of West Garo Hills district, Meghalaya, in Northeast India. We achieve an overall accuracy of ~80% and find that shifting cultivation is the most extensive land-use, followed by tree plantations and old-growth forest confined to only a few locations. We have also found that commercial plantation extent is positively correlated with shortened fallow periods and high land-use intensities. Our findings are in sharp contrast to various official reports and studies, including from the Forest Survey of India, the Wastelands Atlas of India and state government statistics that show the landscape as primarily forested with only small fractions under shifting cultivation, a consequence of the lack of clear definitions and poor understanding of what constitutes shifting cultivation and forest. Our results call for an attentive revision of India’s official land-use mapping protocols, and have wider significance for remote sensing-based mapping in other shifting cultivation landscapes

Spatiotemporal analysis of deforestation patterns and drivers reveals emergent threats to tropical forest landscapes

As deforestation breaches into new tropical frontiers, proactive conservation strategies require a trifecta of information on where deforestation is accelerating (emergent), how drivers of deforestation vary spatiotemporally, and where to focus limited conservation resources in protecting the most integral yet threatened forested landscapes. Here we introduce Emergent Threat Analysis, a process integrating Emerging Hot Spot Analysis of deforestation, visual classification of deforestation outcomes over time, and spatial quantification of contemporary forest condition. We applied Emergent Threat Analysis to tropical Southeast Asia, a global epicentre of biodiversity threatened by deforestation. We found that emergent hot spots (EHS)-a subset of hot spots characterized by strong, recent, and clustered patterns of deforestation-accounted for 26.1% of total forest loss from 1992 to 2018, with deforestation within EHS proceeding at 2.5 times the regional rate of gross loss. Oil palm and rubber plantation expansion were the principal drivers of deforestation within EHS of insular and mainland SE Asia, respectively. Over the study period, oil palm shifted in importance from Sumatra and Sarawak to Papua and Kalimantan, whereas rubber became prominent in Cambodia and Tanintharyi from 2006 to 2015. As of 2019, more than 170 000 km(2) of SE Asia's remaining forest occurred within EHS, of which 21.7% was protected. High and medium-integrity forest constituted 19.2% and 49.1% of remaining EHS forest, respectively, but of these, 35.0% of high-integrity and 23.9% of medium-integrity EHS forest were protected. Because we anticipate that tree plantation expansion will continue to drive deforestation in SE Asia, significantly heightened protection is needed to secure the long-term preservation of high and medium-integrity forest, especially in highly contested forest frontier regions. Finally, as a flexible, integrated process, Emergent Threat Analysis is applicable to deforestation fronts across the global tropics.Peer reviewe

Measuring and modelling carbon stocks in rubber (Hevea brasiliensis) dominated landscapes in Subtropical China

Rubber plantation has been rapidly expanded in Montane Mainland South East Asia in past decades. Limited by long-term monitoring data availability, the impacts of environmental change on rubber trees carbon stock development still not fully understood. Against global warming background, in order to better facilitate regional forest management, we applied synergetic approach combining field survey and modelling tools to improve predictions of dynamic carbon stock changes. The trade-off analysis regarding to rubber carbon stock and latex production optimization was further discussed in view of sustainable rubber cultivation. The first study explored the impact of regional land-use changes on landscape carbon balances. The Naban River Watershed National Nature Reserve (NRWNNR), Xishuangbanna, China, was selected as a case study location. Carbon stocks were evaluated using the Rapid Carbon Stock Appraisal (RaCSA) method based on tree, plot, land use and landscape level assessments of carbon stocks, integrating field sampling with remote sensing and GIS technology. The results showed that rubber plantations had larger time-averaged carbon stocks than non-forest land use types (agricultural crops, bush and grassland) but much lower than natural forest. During 23 years (1989-2012), the whole landscape of the nature reserve (26574 ha) gained 0.644 Tg C. Despite rubber expansion, the reforestation activities conducted in NRWNNR were able to enhance the carbon stocks. Regional evaluation of the carbon sequestration potential of rubber trees depends largely on the selection of suitable allometric equations and the biomass-to-carbon conversion factor. The second study developed generic allometric equations for rubber trees, covering rotation lengths of 4-35 years, within elevation gradient of 621-1,127 m, and locally used rubber tree clones (GT1, PRIM600, Yunyan77-4) in mountainous South Western China. Allometric equations for aboveground biomass (AGB) estimations considering diameter at breast height (DBH), tree height, and wood density were superior to other equations. We also tested goodness of fit for the recently proposed pan-tropical forest model. The results displayed that prediction of AGB by the model calibrated with the harvested rubber tree biomass and wood density was more accurate than the results produced by the pan-tropical forest model adjusted to local conditions. The relationships between DBH and height and between DBH and biomass were influenced by tapping, therefore biomass and C stock calculations for rubber have to be done using species-specific allometric equations. Based on the analysis of environmental factors acting at the landscape level, we noticed that above- and belowground carbon stocks were mostly affected by stand age, soil clay content, aspect, and planting density. The results of this study provide reference for reliable carbon accounting in other rubber-cultivated regions. In the last study, we explored how rubber trees growth and production response to climate change and regional management strategies (cultivation elevation, planting density). We applied the process-based Land Use Change Impact Assessment tool (LUCIA) calibrated with detailed ground survey data to model tree biomass development and latex yield in rubber plantations at the tree, plot and landscape level. Model simulation showed that during a 40-year rotation, lowland rubber plantations (< 900m) grew quicker and had larger latex yield than highland rubber (&#8807;900m). High planting density rubber plantations showed 5% higher above ground biomass than those at low- and medium-planting density. The mean total biomass and cumulative latex yield per tree over 40 years increased by 28% and 48%, respectively, when climate change scenarios were modelled from baseline to highest CO2 emission scenario (RCP 8.5). The same trend of biomass and latex yield increase with climate change was observed at plot level. Denser plantations had larger biomass, but the cumulative latex production decreased dramatically. The spatially explicit output maps produced during modelling could help maximize carbon stock and latex production of regional rubber plantations. Overall, rubber-based system required for appropriate monitoring scale in both temporal aspect (daily-, monthly-, and yearly-level) and in spatial aspect (pixel-, land use-, watershed-, and landscape- level). The findings from present study highlighted the important application of ecological modelling tools in nature resources management. The lessons learned here could be applicable for other rubber-cultivated regions, by updating with site-specific environmental variables. The significant role of rubber tree not limited in its nature latex production, it also lies in its great carbon sequestration potential. Our results here provided entry point for future developing comprehensive climate change adaption and mitigation strategies in South East Asia. By making use of interdisplinary cooperation, the sustainable rubber cultivation in Great Mekong Regions could be well realized.In den vergangenen Jahrzehnten wurde der Kautschukanbau in den Bergregionen des südostasiatischen Festlandes rasch ausgebaut. Die Auswirkungen von Umweltveränderungen auf die Entwicklung des Kohlenstoffbestandes von Kautschukbäumen sind durch die eingeschränkte Verfügbarkeit von Langzeit-Monitoring-Daten noch nicht vollständig geklärt. Vor dem Hintergrund der globalen Erwärmung und um die regionale Waldbewirtschaftung zu unterstützen, haben wir einen synergetischen Ansatz angewandt, der Feldmessungen und Modellierungswerkzeuge kombiniert, um die Vorhersage dynamischer Veränderungen der Kohlenstoffbestände zu verbessern. Die Kosten-Nutzen Abwägung für einen nachhaltigen Kautschukanbau bezüglich der Kautschuk-Kohlenstoffvorräte und der Optimierung der Latexproduktion wird im Weiteren diskutiert. Die erste Studie untersuchte die Auswirkungen regionaler Landnutzungsänderungen auf die Kohlenstoffbilanz der Landschaft. Das Naban River Watershed National Nature Reserve (NRWNNNR), Xishuangbanna, China, wurde als Fallstudienstandort ausgewählt. Die Bewertung der Kohlenstoffvorräte erfolgte mit der Rapid Carbon Stock Appraisal (RaCSA)-Methode. Diese basiert auf der Bewertung von Kohlenstoffvorräten auf dem Niveau von Bäumen, Grundstücken, Landnutzung und Landschaft, mit Einbindung von Feldprobennahme verbunden mit Fernerkundung und GIS-Technologie. Die Ergebnisse zeigten, dass Kautschukplantagen einen größeren zeitgemittelten Kohlenstoffvorrat hatten als nicht-forstliche Landnutzungsarten (Ackerland, Busch- und Grünland), aber viel weniger als natürliche Wälder. Während 23 Jahren (1989-2012) gewann das gesamte Gebiet des Naturschutzgebietes (26574 ha) 0,644 Tg C hinzu. Trotz Ausdehnung der Kautschukanbauflächen konnten die Aufforstungsaktivitäten in NRWNNR die Kohlenstoffvorräte erhöhen. Die regionale Bewertung des Kohlenstoffsequestrierungspotenzials von Kautschukbäumen hängt wesentlich von der Auswahl geeigneter allometrischer Gleichungen und des Biomasse-Kohlenstoff-Umwandlungsfaktors ab. Die zweite Studie entwickelte allgemeine allometrische Gleichungen für Kautschukbäume, basierend auf Daten aus Kautschukplantagen mit Umtriebszeiten von 4-35 Jahren, Höhenlagen von 621-1.127 m und lokal verwendeten Kautschukbaumklonen (GT1, PRIM600, Yunyan77-4) im bergigen Südwesten Chinas. Allometrische Gleichungen zur Berechnung der oberirdischen Biomasse (AGB), welche den Durchmesser in Brusthöhe (DBH), Baumhöhe und Holzdichte berücksichtigten, waren anderen Gleichungen überlegen. Wir haben auch die Anpassungsgüte des kürzlich vorgeschlagene pan-tropische Waldmodell getestet. Die Ergebnisse zeigten, dass die Vorhersage der AGB durch das mit der destruktiv bestimmten Biomasse und der Holzdichte kalibrierte Modell genauer war als die Ergebnisse des pan-tropischen Waldmodells, das an die lokalen Bedingungen angepasst wurde. Die Beziehungen zwischen DBH und Höhe, und DBH und Biomasse wurden durch die Anzapfung der Bäume beeinflusst. Aufgrund dessen müssen Biomasse- und C-Bestandsberechnungen für Kautschuk mit artspezifischen allometrischen Gleichungen durchgeführt werden. Basierend auf der Analyse von Umweltfaktoren, die auf Landschaftsebene wirken, stellten wir fest, dass die ober- und unterirdischen Kohlenstoffvorräte vor allem durch das Bestandsalter, den Tongehalt des Bodens, die Hanglage und die Pflanzdichte beeinflusst wurden. Die Ergebnisse dieser Studie liefern Anhaltspunkte für eine zuverlässige Kohlenstoffbilanzierung in anderen Kautschukanbaugebieten. In der letzten Studie haben wir untersucht, wie Kautschukbäume auf den Klimawandel und regionalen Managementstrategien (Anbauhöhe, Pflanzdichte) reagieren. Wir setzten das prozessbasierte Land Use Change Impact Assessment Tool (LUCIA) ein, das mit detaillierten Bodenuntersuchungsdaten kalibriert wurde, um die Entwicklung der Baumbiomasse und den Latexertrag in Kautschukplantagen auf Baum-, Parzelle- und Landschaftsebene zu modellieren. Die Modellsimulation zeigte, dass während einer 40-jährigen Rotationzeit die Flachland-Kautschukplantagen (< 900m) schneller wuchsen und eine höhere Latexausbeute hatten als die Hochland-Kautschukplantagen (&#8807;900m). Kautschukplantagen mit hoher Pflanzdichte zeigten eine um 5% höhere oberirdische Biomasse als solche mit niedriger und mittlerer Pflanzdichte. Der durchschnittliche Gesamtertrag an Biomasse und der kumulative Latexertrag pro Baum stieg in 40 Jahren um 28% bzw. 48%, wenn die Klimaszenarien vom Basisszenario bis zum höchsten CO2-Emissionsszenario (RCP 8. 5) durchsimuliert wurden. Dieser Trend der Zunahme der Biomasse- und Latexausbeute mit verstärktem Klimawandel wurde auch auf der Ebene der Parzelle beobachtet. Dichtere Plantagen hatten eine größere Biomasse, aber die kumulative Latexproduktion ging drastisch zurück. Die während der Modellierung erstellten räumlich expliziten Output-Karten könnten helfen, die Kohlenstoffvorräte und die Latexproduktion regionaler Kautschukplantagen zu maximieren. Allgemein ist für ein angemessenes Monitoring ein Kautschuk-basiertes System erforderlich, das sowohl in zeitlicher Hinsicht (Tages-, Monats- und Jahresebene) als auch in räumlicher Hinsicht (Pixel-, Landnutzungs-, Wassereinzugs- und Landschaftsebene) geeignet ist. Die Ergebnisse der vorliegenden Studie verdeutlichen die Bedeutung ökologischer Modellierungswerkzeuge im Naturressourcenmanagement. Die hier gemachten Erfahrungen könnten auch auf andere Kautschukanbaugebiete übertragen werden, indem sie mit standortspezifischen Umweltvariablen aktualisiert werden. Die bedeutende Rolle des Kautschukbaums ist nicht nur auf dieHerstellung von Naturlatex beschränkt, sondern liegt auch in seinem großen Potenzial zur Kohlenstoffbindung. Unsere Ergebnisse lieferen den Ausgangspunkt für die künftige Entwicklung umfassender Strategien zur Anpassung an den Klimawandel und zur Eindämmung des Klimawandels in Südostasien. Durch interdisziplinäre Zusammenarbeit könnte der nachhaltige Kautschukanbau in den Großen Mekong-Regionen realisiert werden