Many islands throughout SE Asia are experiencing rapid development and land-cover conversion that potentially threaten sensitive coastal ecosystems, such as seagrasses, through increased loading of sediment and nutrients originating from disturbed catchments draining to the sea. To evaluate this threat for one such island in Southern Thailand (Yao Yai), we perform sediment source tracing via end-member mixing analysis using stable isotopes δ13C and δ15N in organic matter to explore sediment loading in a seagrass meadow. The analysis indicates that sedimentary material in the meadow originates mostly from ocean-associated sources (∼62% from seagrass detritus, seston, and ocean sediments). Terrestrial material comprises ∼19% of the organic material found in the seagrass meadow, with another 20% originating from an adjacent mangrove forest. Approximately one-fourth of the seagrass meadow material (24%) is detritus that has been (re)deposited internally. The high contribution of terrestrial-derived organic matter deposited near the river mouth demonstrates that substantial quantities of sediment are being transferred from upslope erosion sources into the seagrass meadow. However, only a small amount of this material is deposited throughout the entire bay because much of the terrestrial- and mangrove-derived sediment is transferred to the open ocean via channels that are periodically dredged to allow boat access to two small inland harbours. This positive affect of dredging has not received very much attention in existing literature. River water flowing to the channels during falling tide delivers sediment to these efficient pathways, where much of it bypasses the seagrass meadow at periods of time when sediment deposition would normally be the greatest. There is growing concern that ongoing land-cover changes and planned urbanization related to tourism and agriculture on the island may boost sediment/nutrients above a critical threshold, beyond that revealed in our baseline survey. Our tracer-based sediment source approach did not corroborate our observations of substantial erosion and land degradation in the upper catchment—but this could be a result of sediment flushing through the dredged channels. We encourage others to combine such methods with sediment budgeting approaches to triangulate results for consistency. Finally, from an ecological perspective, the high presence of seagrass detritus we found in bay sediments suggests seagrass is potentially a key source of nutrients for the meadow itself, as well as other connected ecosystems.

Myanmar is a country of huge biodiversity importance that is undergoing major political change, bringing with it new international engagement. This includes access to international markets, which will likely spur investment in export-oriented agriculture, leading to increased pressures on already threatened ecosystems. This scenario is illustrated in the Ayeyarwady Delta, the country's agricultural heartland sustaining high deforestation rates. Using the Delta as a model system, we use an integrated approach to inquire about whether and how imminent agricultural reforms associated with an internationally-engaged Myanmar could introduce new actors and incentives to invest in agricultural expansion that could affect deforestation rates. We use a novel remote sensing analysis to quantify deforestation rates for the Delta from 1978 to 2011, develop business-as-usual deforestation scenarios, and contextualize those results with an analysis of contemporary policy changes within Myanmar that are expected to alter the principal drivers of land-cover change. We show that mangrove systems of Myanmar are under greater threat than previously recognized, and that agriculture has been the principle driver of deforestation on the Delta. The centrality of agriculture to the Myanmar economy indicates that emerging policies are likely to tip the scales towards agricultural expansion, agroindustrial investment and potentially greater rates of deforestation due to the introduction of well-funded investors, insufficient land tenure agreements, and low governance effectiveness. The broad national challenge is to initiate environmental governance reforms (including safeguards) in the face of significant pressures for land grabbing and opportunistic resource extraction. (C) 2013 Elsevier Ltd. All rights reserved.

Physical habitat complexity regulates the structure and function of biological communities, although the mechanisms underlying this relationship remain unclear. Urbanisation, pollution, unsustainable resource exploitation and climate change have resulted in the widespread simplification (and loss) of habitats worldwide. One way to restore physical complexity to anthropogenically simplified habitats is through the use of artificial substrates, which also offer excellent opportunities to explore the effects of different components (variables) of complexity on biodiversity and community structure that would be difficult to separate in natural systems. Here, we describe a software program (CASU) that enables users to visualise static, physical complexity. CASU also provides output files that can be used to create artificial substrates for experimental and/or restoration studies. It has two different operational modes: simple and advanced. In simple mode, users can adjust the five main variables of informational complexity (i.e. the number of object types, relative abundance of object types, density of objects, variability and range in the objects' dimensions, and their spatial arrangement) and visualise the changes as they do so. The advanced mode allows users to design artificial substrates by fine-tuning the complexity variables as well as alter object-specific parameters. We illustrate how CASU can be used to create tiles of different designs for application in a marine environment. Such an ability to systematically influence physical complexity could greatly facilitate ecological restoration by allowing conservationists to rebuild complexity in degraded and simplified habitats.

Mangroves play a disproportionately large role in carbon sequestration relative to other tropical forest ecosystems. Accurate assessments of mangrove biomass at the site-scale are lacking, especially in mainland Southeast Asia. This study assessed tree biomass and species diversity within a 151 ha mangrove ecosystem on the Andaman Coast of Thailand. High-resolution GeoEye-1 satellite imagery, medium resolution ASTER satellite elevation data, field-based tree measurements, published allometric biomass equations, and a suite of machine learning techniques were used to develop spatial models of mangrove biomass. Field measurements derived a whole-site tree density of 1313 trees ha(-1), with Rhizophora spp. comprising 77.7% of the trees across forty-five 400 m(2) sample plots. A support vector machine regression model was found to be most accurate by cross-validation for predicting biomass at the site level. Model-estimated above-ground biomass was 250 Mg ha(-1); below-ground root biomass was 95 Mg ha(-1). Combined above-ground and below-ground biomass for the entire 151-ha stand was 345 (+/- 72.5) Mg ha(-1), equivalent to 155 (+/- 32.6) Mg C ha(-1). Model evaluation shows the model had greatest prediction error at high biomass values, indicating a need for allometric equations determined over a larger range of tree sizes. (C) 2013 Elsevier Ltd. All rights reserved.

Hydrological ProcessesVolume 26, Issue 11 p. 1748-1750 Invited Commentary Floods, false hope, and the future Alan D. Ziegler, Corresponding Author Alan D. Ziegler [email protected] National University of Singapore, Singapore, Singapore Alan D. Ziegler, Department of Geography, National University of Singapore, Singapore, Singapore. E-mail: [email protected]Search for more papers by this authorLim Han She, Lim Han She National University of Singapore, Singapore, SingaporeSearch for more papers by this authorChatchai Tantasarin, Chatchai Tantasarin Department of Conservation, Faculty of Forestry, Kasetsart University, Bangkok, ThailandSearch for more papers by this authorNick R. Jachowski, Nick R. Jachowski National University of Singapore, Singapore, SingaporeSearch for more papers by this authorRobert Wasson, Robert Wasson National University of Singapore, Singapore, SingaporeSearch for more papers by this author Alan D. Ziegler, Corresponding Author Alan D. Ziegler [email protected] National University of Singapore, Singapore, Singapore Alan D. Ziegler, Department of Geography, National University of Singapore, Singapore, Singapore. E-mail: [email protected]Search for more papers by this authorLim Han She, Lim Han She National University of Singapore, Singapore, SingaporeSearch for more papers by this authorChatchai Tantasarin, Chatchai Tantasarin Department of Conservation, Faculty of Forestry, Kasetsart University, Bangkok, ThailandSearch for more papers by this authorNick R. Jachowski, Nick R. Jachowski National University of Singapore, Singapore, SingaporeSearch for more papers by this authorRobert Wasson, Robert Wasson National University of Singapore, Singapore, SingaporeSearch for more papers by this author First published: 11 February 2012 https://doi.org/10.1002/hyp.9260Citations: 41Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Citing Literature Volume26, Issue1130 May 2012Pages 1748-1750 This article also appears in:HPToday: Invited Commentaries RelatedInformation

Padang, West Sumatra, Indonesia is considered to have one of the highest tsunami risks in the world. Currently, the strategy to prepare for a tsunami in Padang is focused on developing early warning systems, planning evacuation routes, conducting evacuation drills, and educating the public about its tsunami risk. Although these are all necessary efforts, they are not sufficient. Padang is located so close to the Sunda Trench and has such flat terrain that a large portion of its populace will not be able to reach safe ground in the interval—less than 30 minutes—between the time the earthquake shaking stops and the tsunami arrives at the shore. It is estimated that over 100,000 inhabitants of Padang will be unable to evacuate in that time, even if they head for safe ground immediately following the earthquake. Given these circumstances, other means to prepare for the expected tsunami must be developed. With this motivation, GeoHazards International and Stanford University partnered with Indonesian organizations— Andalas University in Padang, the Laboratory for Earth Hazards (LIPI), and the Ministry of Marine Affairs and Fisheries (KKP)—in an effort to evaluate the need for and feasibility of developing Padang’s tsunami evacuation infrastructure. This project team designed and conducted a course at Stanford University, undertook several field investigations in Padang, and participated in a reconnaissance trip following the September 30, 2009 earthquake. The team concluded that: 1) the tsunami-generating earthquake is still a threat, despite the recent M7.6 earthquake; 2) Padang’s tsunami evacuation capacity is currently inadequate, and evacuation structures need to be implemented as part of an effective evacuation plan; 3) it is likely that previous estimates of the number of people unable to evacuate in time are grossly low; and 4) a more engineering-based approach is Project Manager, GeoHazards International, Palo Alto, CA 94301 2 Graduate Student, Dept. of Civil Engineering, Stanford University, Stanford, CA 94305 3 Professor, Dept. of Civil Engineering, Stanford University, Stanford, CA 94305 4 Project Engineer, Tipping Mar, Berkeley, CA 94704 5 Professor, Dept. of Civil Engineering, Andalas University, Padang, Indonesia 6 Graduate Student, Dept. of Civil Engineering, Andalas University, Padang, Indonesia needed to evaluate the appropriateness of existing buildings to serve as evacuation sites.

Studies on upper ocean plankton production and respiration in oligotrophic ecosystems are taken to imply that these regions are net heterotrophic (i.e. gross primary production [GPP] < respiration [R]). In this study we examined the hypothesis that the regularly observed state of net heterotrophy in the oligotrophic North Pacific Ocean may be interrupted by periodic bursts of net autotrophy when GPP becomes decoupled from R. To examine this hypothesis, we conducted a series of nutrient addition experiments in the oligotrophic North Pacific Subtropical Gyre (NPSG) in which nutrient-replete deep seawater was mixed with nutrient-depleted mixed-layer water. We monitored time-dependent changes in rates of GPP and R as well as dynamics of chlorophyll and nutrient concentrations. Our results consistently demonstrated that following the addition of nutrients: (t) phytoplankton biomass (chl a) and primary production increase; (2) the photoautotrophic plankton assemblage shifts from small (< 2 mu m diameter) to large (> 10 mu m diameter), chl c-containing and Si-utilizing cells; and (3) community metabolism shifts from near balance, or slightly net heterotrophic, to demonstrably net autotrophic metabolism. These results suggest that nutrient availability partly regulates plankton community structure and dynamics, and could serve as a mechanism to temporally and spatially decouple GPP and R in oligotrophic open ocean ecosystems.