Park, Edward

Sand is a vital resource for modern structures but there is limited information on the scale of sand mining or what happens to the sand after it was mined. Here, we focus on Southeast Asia (SEA) as rising affluence and population growth has turned the region into a global sand mining hotspot. We estimated the sand extraction budget in each Southeast Asian country and quantified the volume sand that was exported and imported. In addition, the destinations in which the sand was exported to were detailed and we also clarified the origins of the imported sand. Our analysis revealed that locally mined sand was mostly consumed domestically, and sand was imported if supply was insufficient. In addition, the sand trade in SEA was also predominantly regional. Unfortunately, our understanding of the sand trade in SEA was hampered by limited and inconsistent data. For example, missing data meant that production and trade flows were unavailable for some years. The volume of sand traded between each country was also uncertain due to the mismatch of trade data. Additional information on the type of sand traded was also lacking. The reliability and credibility of existing data should be strengthened to improve material accounting.

Rapid urbanization has dramatically increased the demand for river sand, leading to soaring sand extraction rates that often exceed natural replenishment in many rivers globally. However, our understanding of the geomorphic and social-ecological impacts arising from Sand Mining (SM) remains limited, primarily due to insufficient data on sand extraction rates. Conventionally, bathymetry surveys and compilation of declared amounts have been used to quantify SM budgets, but they are often costly and laborious, or result in inaccurate quantification. Here, for the first time, we developed a Remote Sensing (RS)-based Deep Learning (DL) framework to map SM activities and budgets in the Vietnamese Mekong Delta (VMD), a global SM hotspot. We trained a near real-time object detection system to identify three boat classes in Sentinel-1 imagery: Barge with Crane (BC), Sand Transport Boat (STB), and other boats. Our DL model achieved a 96.1% Mean Average Precision (mAP) across all classes and 98.4% for the BC class, used in creating an SM boat density map at an Intersection over Union (IoU) threshold of 0.50. Applying this model to Sentinel-1, 256,647 boats were detected in the VMD between 2014–2022, of which 17.4% were BC. Subsequently, the annual SM budget was estimated by correlating it with a recent riverbed incision map. Our results showed that, between 2015–2022, about 366 Mm³ of sand has been extracted across the VMD. The annual budget has progressively increased from 34.92 Mm³ in 2015 to 53.25 Mm³ in 2022 (by 52%), with an annual increment of around 2.79 Mm³. At the provincial-scale, Dong Thap, An Giang, Vinh Long, Tien Giang, and Can Tho were the locations of intensive mining, accounting for 89.20% of the total extracted volume in the VMD. Finally, our estimated budgets were validated with previous research that yielded a correlation coefficient of 0.99% (with bias of 2.65%). The automatic DL framework developed in this study to quantify SM budgets has a high potential to be applied to other deltas worldwide also facing intensive SM.

Soil salinization is among the most critical threats to agriculture and food security. Excess of salts adversely affects soil structure and fertility, plant growth, crop yield, and microorganisms. It is caused by natural processes, such as dry climates and low precipitations, high evaporation rate, poor waterlogging, and human factors, such as inappropriate irrigation practices, poor drainage systems, and excessive use of fertilizers. The growing extremization of climate with prolonged drought conditions is worsening the phenomenon. Nature-based solutions (NBS), combined with precision or conservation agriculture, represent a sustainable response, and offer benefits through revitalizing ecosystem services. This perspective explores NBS that can be adopted, along with their challenges and implementation limitations. We also argue that NBS could not be enough to combat hunger in the world’s most vulnerable regions and fully achieve the Sustainable Development Goal – Zero Hunger (SDG2). We therefore discuss their possible combination with salt-tolerant crops based on bioengineering.

his study provides a thorough analysis of the landslides that occurred in the city of São Sebastião, on the northern coast of São Paulo state, Brazil, in February 18th–19th, 2023. The meteorological condition during this event was characterized by a cold front crossing over a warmer-than-normal subtropical South Atlantic, off the coast of São Paulo. Combined with the orographic effect of the Serra do Mar Mountain, the front remained stationary over the northern coastal areas of the state of São Paulo, causing an extreme and historic heavy precipitation event. An unprecedented volume of rain, amounting to 683 mm in less than 15 h, triggered landslides that generated 65 casualties and damages. Although alerts were clearly issued in advance, response among the communities was minimal, indicating the ineffectiveness of current early warning system in place. This calls for improved public policies, communication and the possible adoption of multi-hazard early warning systems to reduce risk in vulnerable areas.

Cambodia has the most fires per area in Southeast Asia, with fire activity have significantly increased since the early 2000s. Wildfire occurrences are multi-factorial in nature, and isolating the relative contribution of each driver remains a challenge. In this study, we quantify the relative importance of each driver of fire by analyzing annual spatial regression models of fire occurrence across Cambodia from 2003 to 2020. Our models demonstrated satisfactory performance, explaining 69 to 81% of the variance in fire occurrence. We found that deforestation was consistently the dominant driver of fire across 48 to 70% of the country throughout the study period. Although the influence of low precipitation on fires has increased in 2019 and 2020, the period is not long enough to establish any significant trends. During the study period, wind speed, elevation, and soil moisture had a slight influence of 6–20% without any clear trend, indicating that deforestation continues to be the main driver of fire. Our study improves the current understanding of the drivers of biomass fires across Cambodia, and the methodological framework developed here (quantitative decoupling of the drivers) has strong potential to be applied to other fire-prone areas around the world.