Earth, Volume 3, Issue 3 (September 2022) – 18 articles

Hydroclimatic processes such as precipitation, temperature, wind speed and dew point are usually considered to be independent of each other. In this study, the cross–correlations between key hydrological-cycle processes are examined, initially by conducting statistical tests, then adding the impact of long-range dependence, which is shown to govern all these processes. Subsequently, an innovative stochastic test that can validate the significance of the cross–correlation among these processes is introduced based on Monte-Carlo simulations. The test works as follows: observations obtained from numerous global-scale timeseries were used for application to, and a comparison of, the traditional methods of validation of statistical significance, such as the t-test, after filtering the data based on length and quality, and then by estimating the cross–correlations on an annual-scale. The proposed method has two main benefits: it negates the need of the pre-whitening data series which could disrupt the stochastic properties of hydroclimatic processes, and indicates tighter limits for upper and lower boundaries of statistical significance when analyzing cross–correlations of processes that exhibit long-range dependence, compared to classical statistical tests. The results of this analysis highlight the need to acquire cross–correlations between processes, which may be significant in the case of long-range dependence behavior. Full article

Bush encroachment is a habitat change phenomenon that threatens savanna and grassland ecosystems worldwide. In Africa, large carnivores in bush encroached landscapes must adjust to increasing woody plant cover and biomass, which could affect predation success at multiple stages through complex and context-dependent pathways. We highlight, interpret, and compare studies that assessed how bush encroachment or related habitat parameters affect the predation stages of large African carnivores. Bush encroachment may directly or indirectly affect predation success in various ways, including by: (1) altering habitat structure, which may affect hunting efficiency and prey accessibility; (2) changing prey abundance/distribution, with smaller species and browsers being potentially favoured; (3) influencing interference competition within the carnivore guild. For habitat or dietary specialists, and subordinate predators that are vulnerable to both top-down and bottom-up ecosystem effects, these alterations may be detrimental and eventually incur population fitness costs. As the threat of bush encroachment continues, future studies are required to assess indirect effects on competitive interactions within the large African carnivore guild to ensure that conservation efforts are focused. Additionally, to better understand the effects of bush encroachment across Africa, further research is necessary in affected areas as overall little attention has been devoted to the topic. Full article

Dry-mesic old-growth oak forests are widely distributed remnants across the eastern U.S. and are expected to increase in number and extent as second-growth forests mature. In this study, we synthesize published and unpublished information to better define the species, structure and extent of these forests. Mean site tree density for trees ≥10 cm dbh ranged from 341–620 trees ha⁻¹. In the eastern part of the region, most stand basal areas were >23 m² ha⁻¹, compared to ≤23 m² ha⁻¹ in the westernmost stands. Overall, woody species diversity was relatively low compared to old-growth oak forests on moister sites, with tree species per forest ranging from 5–18. The most common species among the stands were white oak (Quercus alba), northern red oak (Quercus rubra), and black oak (Quercus velutina). Shrub and vine species per forest ranged from 1–10, with common species or genera including Virginia creeper (Parthenocissus quinquefolia), poison ivy (Toxicodendron radicans), Vaccinium spp., and grapevines (Vitis spp.). Within the southern Appalachian Mountains, rosebay rhododendron (Rhododendron maximum) and mountain laurel (Kalmia latifolia L.) were common. Herbaceous species per stand ranged from 4–51, with the highest richness occurring in a southern Appalachian oak-hickory forest. The maximum within-stand age of the large trees ranged from 170 to over 365 years. The mean density of standing dead trees ≥10 cm dbh ranged from 31–78 ha⁻¹ and the volume of coarse woody debris ≥10 cm in diameter averaged 52 m³ ha⁻¹. We more fully describe the characteristics of these forests and fill gaps in the collective knowledge of this increasingly important forest type. However, over the past 20 years, there has been scant research on these forests, and older research studies have used a variety of research plots and methods. A uniform approach to surveying these sites is needed to gain a better understanding of these forests before we are faced with caring for an increase in old-growth forest areas. Full article

On the first several days of October 2013, daily chlorophyll a (chl a) data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the National Aeronautics and Space Administration (NASA) Aqua satellite detected a marked increase in chlorophyll a concentrations (chl a) in the vicinity of Chuuk Lagoon and the Federated States of Micronesia. Such an increase, likely indicative of a phytoplankton bloom, has not been observed in this location at any other time during the MODIS-Aqua mission, which commenced in 2002 and continues to present. Examination of sea surface wind data from the Modern Era Retrospective analysis for Research and Applications Version 2 (MERRA-2) reanalysis dataset indicated that the region experienced a sequence of alternating elevated and very low wind speed events prior to the observation of the bloom. The influence of the winds can be seen in MERRA-2 sea surface skin temperature data. Elevated windspeeds for several days likely induced a mixing of deeper waters with higher nutrient levels to the surface, which was followed by stratification and phytoplankton growth during low wind intervals and finally transport induced by a brief high windspeed event. Analysis of hourly MERRA-2 maximum windspeed data over a 40-year period indicated that this sequence was climatologically rare. Full article

Drystone terraces offer a series of ecosystem services including both biological and cultural benefits. The aesthetic contribution towards the landscape and the increase in biodiversity levels, constitute drystone terraces and other similar constructions, as important biocultural assets. The low maintenance and the eventual abandonment of drystone terraces cause a series of drawbacks regarding the sustainability of agricultural environments. The main goal of this research was to assess the effect of drystone terrace maintenance level on biodiversity. For that reason, two closely distant agricultural areas of Lesbos Island (North Aegean, Greece) in which olive grove drystone terraces dominate were compared. The non-intrusive method of ecoacoustics was selected, and the levels of the acoustic complexity and acoustic diversity were statistically analyzed for areas that included highly maintained and poorly maintained olive grove drystone terraces. The results indicated an increase in acoustic biodiversity levels in the poorly maintained drystone terraces area. At this early stage, the results highlighted the fact that the increased resources in the poorly maintained drystone terraces, in terms of nesting and feeding opportunities, increased the biodiversity levels. Nevertheless, the spatiotemporal expansion of this research is undeniably important. Full article

Animal based-food products represent an essential source of protein supply in overall diets, and livestock provide 25% of the total protein content consumed by humans as food. Concurrently, livestock significantly impacts the environment, being responsible for 10–12% of total anthropogenic CO₂ emissions. Among livestock, pork is considered one that accounts for the greatest impact in terms of emissions, about 4.62 kg CO₂ eq/kg. Furthermore, the growing global demand for protein sources has led to a widespread need to find agri-food solutions that meet the demand for food through sustainable production systems. The high nutritional quality of edible insects, in terms of amino acids, fats, minerals, and vitamins, is comparable with meat products. This study aims to compare protein production from pork and mealworm, assessing the degree of substitution and environmental impacts of the two production systems. To assess the impacts of protein production from mealworms and pork on the ecosystem, resources, and human health, an LCA was conducted using the ReCiPe 2016 Endpoint method, with a 100-year hierarchical perspective (H) V1.05. It emerged that pork production is characterized by high impacts on the ecosystem, land use, climate-altering emissions, and fossil resources, in contrast with mealworm protein production. The low impact of insect protein production and the high nutritional values make edible insects a sustainable solution to growing food demand and economic benefits render edible insects globally a major potential future food. Full article

Pawara area is a mining district in the eastern region of Cameroon. Mining in the area is generally artisanal and semi-mechanized, practiced by the local miners and immigrants from neighboring African countries and China. The lack of strict regulations and control of mining activities permits the miners to use illegal substances, especially Hg in gold separation. These expose the area to toxic and heavy metals pollution. This study highlights the source of heavy metals concentration in the Pawara soils and the potential adverse effects of Hg on gold separation to the environment and health. Three mining sites and one control site were investigated, namely Site A, Site B and Site C. The control Site 0 (background) is an area where no mining and agricultural activities have taken place. Soil samples were collected at depth of 20 cm, with six from each site (24 samples). Samples were analyzed for Al, Cd, Cr, Cu, Fe, Hg, Pb, Cd and Zn content using atomic absorption spectrophotometry in a graphite furnace. The metals, except for Fe, show high values for all three sites exceeding the background levels in the soils. Hg shows the highest concentration on Site A with a value of 1590 mg kg⁻¹. Pb is highest on Site B with a concentration of 12,274 mg kg⁻¹. The contamination degree was assessed with the help of contamination indices (Igeo—index of geo-accumulation; PLI—pollution load index; RI—potential ecological risk; Eri—ecological risk; Pi—single pollution index; CF—contamination factor) and all parameters show a high degree of contamination on all three sites compared to the control site. Hg, Pb, Cd, Cr and Cu as single pollutants show the highest ecological risk on Site A and Site B where intense mining is taking place. The absence of industrial and large-scale agricultural activities in the Pawara area, the nonexistence of contaminants on the control site and the presence of contaminants on Site C where farming is high and mining is low jointly show that the discharge of mine wastes onto the soils and stream channels are the main source of contaminants and potential pollutants of the Pawara ecological environment. Full article

Regenerative agriculture is a potential alternative to conventional agricultural systems. It integrates the components of zero-tillage, permanent soil cover, diverse crop rotations and rotational or mob-grazing by ruminant livestock. Earthworms are beneficial soil macrofauna and function as indicators of soil health. A need exists to identify how earthworm populations are affected when all four regenerative agriculture components are implemented simultaneously. This study investigates earthworm abundance in three split-plot treatments located on adjacent land within the same farm: (1) ungrazed permanent grassland, (2) a three-year grass-clover ley within an arable zero tillage system without grazing and (3) identical to treatment 2 but with mob-grazing. Earthworms were sampled using soil pits and classified into four functional groups: epigeic (surface dwellers), endogeic (sub-surface), anecic (deep soil) and juveniles. The total earthworm count, epigeic and juvenile functional groups were significantly (p ≤ 0.05) higher in treatment (3), the arable zero tillage system with mob-grazing. Mob-grazing increases the diversity of carbon sources available to earthworms and has a positive impact on earthworm abundance and functional group diversity within the arable rotation under evaluation. Full article

Although environmental sustainability provides a foundation for maintaining economic and social sustainability, it is often neglected in favor of economic sustainability. Ameliorating water impairment is costly, and policymakers do not always prioritize this problem because its economic benefits are often intangible. This study explored the potential economic value for Tokyo’s regional economy of past improvements in the water quality of its rivers. Transitioning the rivers from their previous role as sewage drainage pipes to venues for spending leisure time created economic incentives in the local economy. An input-output analysis showed that in 1985, the inland navigation sector in the Sumida River generated 1.5 times the economic output by increasing demand. While this impact decreased to 1.3 times in 2005, the results clearly indicate that the regional economy can generate amenity values by improving the environmental quality. This study provides useful information to guide policymakers in allocating the budget for environmental management. In particular, it allows them to envision possible development plans to promote the livelihood of urban residents as well as understand the linkage between the environment and the economy. Full article

Information on the relationship between rainfall intensity, duration and accumulation frequency or return period (IDF) is commonly utilized in the design and management of urban drainage systems. Can Tho City, located in the Vietnamese Mekong Delta, is a city which has recently invested heavily in upgrading its stormwater drainage systems in the hope of preventing reoccurring flood events. Yet, much of these works were designed based on obsolete and outdated IDF rainfall curves. This paper presents an updated IDF curve for design rainfall for Can Tho City. For each duration and designated return period, a cumulative distribution function (CDF) was developed using the Pearson III, Log-Pearson III, and Log-Normal distribution functions. In order to choose the best IDF rainfall curve for Can Tho City, the CDF rainfall curve and empirical formulas used in Vietnam and Asia (Vietnamese standard 7957:2008, Department of Hydrology, Ministry of Transportation, Talbot, Kimijima, and Bermard) were compared. The goodness of fit between the IDF relationship generated by the frequency analysis (CDF curve), and that predicted by the IDF empirical formulas was assessed using the efficiency index (EI), and the root mean squared error (RMSE). The IDF built from Vietnam’s standard TCVN 7957:2008 with new parameters (A = 9594, C = 0.5, b = 26, n = 0.96) showed the best performance, with the highest values of EI (0.84 $\le$EI$\le$ 0.93) and the lowest values of RMSE (2.5 $\le$RMSE$\le$ 3.2), when compared to the other remnants. Full article

Soil quality can directly influence the health, yield, and quality of a particular crop species, and agrochemicals are often used to boost soil micro- and macro-nutrients. The excessive application of agrochemicals, however, is often the cause of imbalances in acidity and nutrient concentration and can cause soil to deteriorate. The presence of multiple shade trees in farmland can positively influence soil quality. Here, we evaluate the effect of agrochemical use (i.e., organic, mixed, and intensive) and shade tree complexity (i.e., sun, low, and high) on soil quality (i.e., pH, macronutrients, and micronutrients) in 56 coffee home gardens in Indonesia. We found that Al, Fe, K, and Mn were significantly higher in farms that used agrochemicals, and pH was more acidic in fields with intensive use of agrochemicals. C:N ratio and Mn were higher in soils with high shade complexity than in sun-exposed soils. The use of agrochemicals, however, is not sustainable as it increases the Al concentration and decreases pH, both of which are associated with poor coffee growth and reduced soil quality. Shade tree removal and the use of invasive, non-native species, such as eucalyptus, can also negatively influence soil quality, and thus the maintenance of complex shade cover with native trees should be prioritised. Full article

With the aim of contributing to the knowledge of soil organic carbon stocks in dry areas, this work is based on a quantification of SOC stocks in gypsum-bearing soils whose vertical and spatial heterogeneity greatly limits inferring the total SOC stocks solely from soil surface information. Public databases of soil profiles were key to this quantification, through which it was estimated which amounts of organic carbon can potentially be excluded from calculations associated with soil C cycle models in the absence of information regarding deep soil horizons. These databases include two key factors in the quantification of SOC stocks, which are often excluded: the volume of coarse fragments and the thickness of all sampled soil horizons where SOC concentration was determined. The observed average value of SOC stocks in the studied subsurface horizons reaches 73% of the whole soil. Climate, relief, and land use influence the quantity and heterogeneity of SOC stocks in these soils. Information based on the mere surface of the soil is not relevant to quantify the total SOC; however, the calculation of stocks through soil pits of medium depth (30 cm) has proven to be potentially useful as a complementary approach to these stocks. Full article

With a growing interest in the study of urban life and health, evidence indicates that the quality of the environment in which we live can have implications for our subjective well-being and health. This study assesses the potential impacts of perceptions of visual air pollution, olfactory air pollution, and noise pollution on self-perceived health, self-perceived happiness, and satisfaction with life, through the calculation of ordinal logistic regressions, using the information of an online survey carried out in Quito, Ecuador. We found that perceptions of unpleasant odors and noise pollution influence self-perceived health, self-perceived happiness, and satisfaction with life. The obtained results may support the incorporation of citizens’ perspectives to better understand environmental pollution and to enrich local planning for urban sustainability. Full article

Water quality management of rivers is one of the challenges in the analysis of water resource systems. The optimal operation of the pollutant carrying capacity of these systems provides significant economic value and could reduce treatment costs. In this study, the application of the trading ratio system is investigated to control the cost of pollutants in a river and make a fair deal. In this regard, transfer coefficients between pollution sources, along with the trade coefficients, are determined, considering the system limitations and each pollutant’s contaminant impact. To provide allowable limits of river water quality concentrations, the total cost of all sources and the system is minimized, using the linear programming method. Finally, the new trading discharge permits are calculated for each source. The proposed method is successfully applied to Dez River as a case study. Results show that using a trading ratio system could maintain water quality at a standard level containing economic benefits for the participants of this program. Full article

Gelidium corneum (Giant Gelidium or Atlantic agar) is a well-known red seaweed harvested for its high-quality agar content. Agar is a mixture of the polysaccharides used in the food industry as a gelling, thickener, clarifying, and stabilizer agent. The best agar quality is also used in the laboratory as bacteriological agar. Yet, in recent years, the species has been studied for many other applications. Examples of uses are pharmaceuticals, cosmetics, food supplements, bioremediation, biofuels, biofertilizers and biostimulants, biomaterials, and nanocrystals, among others. The use of this biomass, though, raises concerns about the sustainability of the resource, since this is not a cultivated species, being harvested in the wild. Thus, other uses of G. corneum biomass increase pressure on wild stocks already stressed due to climate change. However, in a biorefinery approach, a new trend is emerging, using waste biomass rather than harvested biomass to produce new bio-based materials. These are smart solutions that transform waste into innovative products, useful for various sectors of society while reducing the impact of biomass exploitation. The aim of this review paper, thus, is to address the current state of G. corneum biology, ecology, threats, its current uses and market, and the ongoing research on innovative proposals in a circular economy framework. Full article

Habitat condition is a vital ecological attribute in wildlife conservation and management in protected areas, including the Burunge wildlife management areas in Tanzania. Traditional techniques, including satellite remote sensing and ground-based techniques used to assess habitat condition, have limitations in terms of costs and low resolution of satellite platforms. The Normalized Difference Vegetation Index (NDVI) and Green NDVI (GNDVI) have potential for assessing habitat condition, e.g., forage quantity and quality, vegetation cover and degradation, soil erosion and salinization, fire, and pollution of vegetation cover. We, therefore, examined how the recently emerged Unmanned Aerial Vehicle (UAV) platform and the traditional Sentinel-2 differs in indications of habitat condition using NDVI and GNDVI. We assigned 13 survey plots to random locations in the major land cover types: three survey plots in grasslands, shrublands, and woodlands, and two in riverine and mosaics cover types. We used a UAV-mounted, multi-spectral sensor and obtained Sentinel-2 imagery between February and March 2020. We categorized NDVI and GNDVI values into habitat condition classes (very good, good, poor, and very poor). We analyzed data using descriptive statistics and linear regression model in R-software. The results revealed higher sensitivity and ability of UAV to provide the necessary preliminary diagnostic indications of habitat condition. The UAV-based NDVI and GNDVI maps showed more details of all classes of habitat conditions than the Sentinel-2 maps. The linear regressions results showed strong positive correlations between the two platforms (p < 0.001). The differences were attributed primarily to spatial resolution and minor atmospheric effects. We recommend further studies to test other vegetation indices. Full article

Water resources are paramount for the maintenance of the Earth’s system equilibrium; however, they face various threats and need increased conservation and better management. To restore water resources, nature-based solutions can be applied. Nevertheless, it is unclear which solution promotes greater water supply resilience: restoring riparian vegetation, improving management practices in key areas for water recharge, or both? In addition, how significant are these results in the face of climate change effects? To answer this, we used the SWAT (Soil and Water Assessment Tool) model to simulate and compare four different land use scenarios under three climate conditions (i.e., observed climate and two of the IPCC’s future climate projections). Focusing on key areas contributed more to increasing water supply resilience than forest restoration. Applying both solutions, however, yielded the greatest increases in resilience and groundwater recharge and the greatest decreases in surface runoff and sediment loads. None of the solutions caused a significant difference in streamflow and water yield. Furthermore, according to both of the IPCC climate projections evaluated, by the end of this century, the average annual streamflow will be lower than the historical mean for the region. Climate adaptation strategies alone will be insufficient to ensure future water access, highlighting the need for implementing drastic mitigation actions. Full article