Earth

Soil health is the sustained ability of soil to function as a vital ecosystem that supports plants, animals, and humans. Conventional agricultural practices, such as intensive tillage and monocropping, degrade soils by depleting organic matter, causing erosion, and reducing biodiversity. Agroforestry systems, by contrast, mimic natural ecosystems and offer a viable solution to restore and protect this crucial resource. The purpose of this review was to explore agroforestry’s effects on soil health in the context of sustainable agriculture. By restoring and building soil health, the review revealed that agroforestry provides a solution to combat soil degradation, enhance biodiversity, and increase agricultural sustainability. Benefits to soil are diverse and include improving its physical, chemical, and biological aspects, which boosts ecosystem services and resilience. Despite its clear advantages, agroforestry has not been widely adopted. Challenges to adoption include time lag for trees to mature, insecure land tenure and lack of expertise and institutional support. Overcoming these barriers through supportive policies, financial incentives and farmer participatory approaches offers clear pathways towards more resilient and profitable farming systems. This will require site-specific studies to optimize species selection and system designs compatible with local conditions. Long-term agroforestry success is determined by aligning site-specific conditions (soil, slope, climate) with appropriate species selection, expert management, and farmer knowledge. In conclusion, intentionally combining trees and crops provides a powerful solution for building resilient soil ecosystems and ensuring agricultural sustainability.

The Seulawah Agam volcano, located in Aceh, hosts one of Indonesia’s largest unexploited geothermal resources that is included in the Indonesian Green Energy Program. Previous studies of the Seulawah geothermal system (SGS) have used partial data and methods without developing a comprehensive conceptual model of the reservoir and its fluid flow and heat transfer patterns. This study aims to characterize the groundwater flow and heat transfer patterns of the SGS through numerical modeling based on integrated geological, geophysical, and geochemical data. Numerical modeling was conducted along two representative transects: Ie Seum, Ie Jue, and Kawah van Heutsz manifestations. MODFLOW 6 was used to model groundwater flow and heat transfer using a new conceptual model derived from magnetotelluric data, chemical composition and physical properties of the fluid, isotopic data, and mineragraphic data. The low resistivity anomalies are closely related to fluid discharges beneath the Ie Seum and Ie Jue areas. The depth of the Ie Seum reservoir is around 1.0–2.5 km, with estimated temperatures of 120–242 °C, while the depth of the Ie Jue and Kawah van Heutsz reservoirs is between 0.8 and 2.5 km, with estimated temperatures of 150–316 °C. The modeling suggests that the Ie Seum and the Ie Jue–Kawah van Heutsz systems represent regional groundwater and intermediate-local flow regimes, respectively. It is suggested that drilling be conducted around the local Ie Jue hydrothermal system, which is more economical given the shallower reservoir and higher temperature.

Hazard risk monitoring of groundwater depletion and land subsidence due to excessive groundwater extraction is crucial for groundwater resource development, especially in densely populated, small-island developing sites. The island of Bali, Indonesia, represents such an urban environment at risk of land subsidence arising from groundwater depletion. The total percentage of groundwater depletion was calculated and interpolated spatially using measurements of groundwater level from 2008 to 2017 at 18 monitoring well sites available in the area. Furthermore, time-series synthetic-aperture radar (SAR) interferometry processing was applied to estimate the temporal change in land displacement using the Phased Array type L-band SAR (PALSAR) data from 2007 to 2010. The result of downward displacement, signifying subsidence, corresponded with the Global Navigation Satellite System (GNSS) data measurements at stations distributed in the observed subsided areas, i.e., CDNP and CPBI. The displacement varied consistently with changes in groundwater level. In regard to maintaining groundwater utilization, the hazard–risk relation of the groundwater depletion, i.e., low (<10%), moderate (10–25%), and high (>25%), and the presence/absence of subsidence were utilized to classify groundwater conservation into safe, vulnerable, critical, and damaged zones. This application can be considered effective in providing spatial information for sustainable groundwater management.