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Earth

Earth is an international, peer-reviewed, open access journal on earth science published bimonthly online by MDPI.

Quartile Ranking JCR - Q2 (Geosciences, Multidisciplinary | Environmental Sciences)

All Articles (413)

Estimating Soil Hydraulic Properties Using Random Forest Pedotransfer Functions and SoilGrids Data in Mexico

  • Victor M. Rodríguez-Moreno,
  • Josué Delgado-Balbuena and
  • Nuria A. López-Hernández
  • + 2 authors

Field capacity (FC) and permanent wilting point (PWP) thresholds are critical parameters in climate-smart agriculture because they directly relate to soil water availability, which is essential for optimizing water use, improving crop yields, and ensuring resilience against climate variability. Using the continuous mosaic of SoilGrids data, pedotransfer functions based on bulk density, clay content, and sand content were applied to estimate the threshold values of FC and PWP across Mexico utilizing random forest (RF) algorithms. The selection of these parameters was based on their positive contribution to the model’s prediction: bulk density (0.51), clay content (0.21), and sand content (0.16). Soil organic carbon (SOC) contributed negatively; this negative importance score warrants careful interpretation. The 30–60 cm depth was chosen based on the assumption that it is reasonably uniform across other depths and lies below the highly variable surface horizon, which is strongly influenced by management practices and organic matter dynamics. Here we address key technical and scientific critiques regarding the use of SoilGrids for generating FC and PWP data. Additionally, the relevant role of FC and PWP thresholds in the context of climate-smart agriculture is highlighted, from the calculation of available soil water to their role in achieving sustainable development goals.

19 January 2026

Sample mosaic of raster images. The coverage of the Mexico domain is the same for all available depths. Figure 1 shows a single variable at a depth—bulk density (g/cm3) at a depth of 15–30 cm. All mosaics for each variable at each depth were obtained separately using the pedotransfer function (bulk density, sand content, and clay content). PTFs relate the physical and textural properties of the soil to estimate FC and PWP. These equations are empirically derived and vary depending on the dataset and region.

Regional green development requires balancing anthropogenic carbon emissions (CEs) with vegetation carbon sequestration (VCS). Using the CASA model and plant photosynthesis equation, we estimated VCS from net primary productivity (NPP) and proposed a Carbon Balance Pressure Index (CBPI) to quantify the imbalance between carbon sources and sinks. Spatial analysis and a geographic detector were applied to examine influencing factors of CBPI across Sichuan–Chongqing from 2001 to 2017. Results show that CE increased by 178%, while VCS rose by 27%. Regional CBPI thus enhanced from 0.35 to 0.76, aligning with CE trends. The CBPI presented a clear west-low (0–0.2, except Panzhihua), center-high (peak 3.1 in Chengdu), moderate-east (0.1–0.8) pattern. Geographic detector reveals that economic development and urbanization accounted for 80% of CBPI heterogeneity, followed by transportation (65%). Energy-intensive industries dominated developed areas, while construction-land expansion prevailed in developing regions. This study underscores region-specific emission-sink pathways and provides an empirical basis for differentiated low-carbon strategies in similar rapidly urbanizing regions in China.

11 January 2026

Schematic diagram of the study area and urban distribution.

The Iraqi coastline in the northern Persian Gulf is highly vulnerable to the impacts of future sea level rise. This study introduces a novel approach in the Arc Geographic Information System (ArcGIS) for inundation risk of the 58 km Iraqi coast of the northern Persian Gulf through a combination of multi-data sources, machine-learning predictions, and hydrological connectivity by Landsat. The Prophet/Neural Prophet time-series framework was used to extrapolate future sea level rise with 11 satellite altimetry missions that span 1993–2023. The coastline was obtained by using the Landsat-8 Operational Land Imager (OLI) imagery based on the Normalised Difference Water Index (NDWI), and topography was obtained by using the ALOS World 3D 30 m DEM. Global Land Use and Land Cover (LULC) projections (2020–2100) and population projections (2020–2100) were used as future inundation values. Two scenarios were compared, one based on an altimeter-based projection of sea level rise (SLR) and the other based on the National Aeronautics and Space Administration (NASA) high-emission scenario, Representative Concentration Pathway 8.5 (RCP8.5). It is found that, by the IPCC AR6 end-of-century projection horizon (relative to 1995–2014), 154,000 people under the altimeter case and 181,000 people under RCP8.5 will have a risk of being inundated. The highest flooded area is the barren area (25,523–46,489 hectares), then the urban land (5303–5743 hectares), and finally the cropland land (434–561 hectares). Critical infrastructure includes 275–406 km of road, 71–99 km of electricity lines, and 73–82 km of pipelines. The study provides the first hydrologically verified Digital Elevation Model (DEM)-refined inundation maps of Iraq that offer a baseline, in the form of a comprehensive and quantitative base, to the coastal adaptation and climate resilience planning.

8 January 2026

Location of the study area along the Iraqi coastline of the northern Persian Gulf.

Forests play a vital role in the global carbon cycle but face growing anthropogenic pressures, with climate change and forest fragmentation among the most critical. In West Africa, particularly in Ghana, the interaction between increasing aridity and forest fragmentation remains underexplored, despite its significance for forest biomass dynamics and carbon storage processes. This study examined how spatial variation in climatic aridity (Aridity Index, AI) affects above-ground biomass (AGB) in Ghana’s ecological zones, both directly and indirectly through forest fragmentation and biodiversity, using structural equation modeling (SEM) and generalized additive models (GAMs). Results from this study show that AGB declines along the aridity gradient, with humid zones supporting the highest biomass and semi-arid zones the lowest. The SEM analysis revealed that areas with a lower aridity index (drier conditions) had significantly lower AGB, indicating that arid conditions are associated with lower forest biomass. Fragmentation patterns align with this relationship, while biodiversity (as measured by species richness) showed weak associations, likely reflecting both ecological and data limitations. GAMs highlighted nonlinear fragmentation effects: mean patch area (AREA_MN) was the strongest predictor, showing a unimodal relationship with biomass, whereas number of patches (NP), edge density (ED), and landscape shape index (LSI) reduced AGB. Overall, these findings demonstrate that aridity and spatial configuration jointly control biomass, with fragmentation acting as a key mediator of this relationship. Dry and transitional forests emerge as particularly vulnerable, emphasizing the need for management strategies that maintain large, connected forest patches and integrate restoration into climate adaptation policies.

7 January 2026

Map of the study area showing the spatial distribution of vegetation data points obtained from the GBIF database across Ghana. The map outlines Ghana’s national boundary (red dashed line) and regional administrative boundaries (black lines).

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Earth - ISSN 2673-4834