Net Land Research Articles

Damming-Induced Hydrogeomorphic Transition in Downstream Channel and Delta: A Case Study of the Yellow River, China

River dynamics and sediment budget play a crucial role in shaping geomorphic variability of river channels and deltaic environments. Basin-scale human activities, including dam construction, induce alterations in river flow and sediment dynamics in the downstream channels and to the delta, and quantification of sediment source shift along downstream fluvial-deltaic systems is often uncertain. This study analyzed the river regime changes and sediment dynamics of a typical sediment-laden fluvial-deltaic system—the lower Yellow River (LYR) and the Yellow River Delta (YRD) —to assess the integrated effects of dam impoundment and dam-based river regulation schemes on downstream hydrogeomorphic transition processes. The Xiaolangdi (XLD) Reservoir, which was completed in 2000 with a total storage of 12.7 km3, is the final reservoir located in the middle Yellow River and plays an important role in flood control and energy supply. Following the full operation of XLD Reservoir, the relationship between water and sediment in the LYR became more balanced, with a drastic decline of sediment input and seasonal migrations of floodwaters. The interannual variability of water levels at downstream hydrological stations indicated a geomorphic transition in the LYR from net deposition to erosion state. The building of the XLD Reservoir caused a downstream shift of river-originated sediment source and 48% of the total sediment delivered to the YRD was derived from the LYR. However, the reduced sediment delivery since 2000 has still triggered net land loss regarding the YRD system, with a strong spatial variability which is dominated by the reduced accretion at the active delta front and erosion at the abandoned river mouth and coastal engineering zone. Compared with other environmental factors, the construction of upstream dams contributed the most to the decline of downstream sediment delivery over the past decades. The challenge for sustainable sediment management is the gradual decline of scouring efficiency as the riverbed sediment is coarsening. Our study suggests that future river regulation strategies should consider the geomorphic sustainability of both the LYR and the YRD system.

The Warming Effect of Urbanization in the Urban Agglomeration Area Accelerates Vegetation Growth on the Urban–Rural Gradient

Urbanization has changed the environmental conditions of vegetation growth, such as the heat island effect, which has an indirect impact on vegetation growth. However, the extent to which the direct and indirect effects of the thermal environment changes caused by urbanization on vegetation growth are unclear. In this study, taking the example of the Guangdong–Hong Kong–Macao Greater Bay Area, a fast-growing national urban agglomeration in China, the relationship between vegetation growth and warming conditions during the period from 2001 to 2020 were explored by the net primary productivity (NPP) and land surface temperature (LST), based on the vegetation growth theory, in urban environments. The results show that there is a significant exponential relationship between the warming and the growth of large-scale vegetation. This relationship is mainly attributable to thermal environmental factors, since their multi-year average contribution rate on the interannual scale is 95.02%. The contribution rate varies on the seasonal scale, according to which the contribution rate is the largest in autumn and the smallest in winter. This research is of great significance for predicting the potential response of vegetation growth to future climate warming and improving vegetation growth in urban areas.

Prospects of Biochar for Sustainable Agriculture and Carbon Sequestration: An Overview for Eastern Himalayas

The net arable land area is declining worldwide rapidly due to soil erosion, drought, loss of soil organic carbon, and other forms of degradation. Intense rainfall, cultivation along steep slopes, unscientific land-use changes, shifting cultivation, soil acidity, and nutrient mining in hills and mountains make agriculture unsustainable and less profitable. Hills and mountain ecosystems of the Eastern Himalayan Region (EHR) are further prone to the impact of climate change posing a serious threat to agricultural production and the environment. Increasing soil carbon reserves contributes to multiple ecosystem services, improves soil nutrient and water-holding capacities, and advances climate-resilient agriculture. Thus, carbon sequestration is increasingly becoming an important aspect of farming among researchers in the region. The EHR predominantly practices shifting cultivation that degrades the ecosystem and promotes land degradation and biodiversity loss. Leaching of exchangeable bases is highly favored due to excess rainfall which in turn creates an acidic soil accounting for >84% of the region. Application of lime to raise the soil acidity for the cultivation of crops did not get adequate acceptance among the farming community due to multiple issues such as cost involvement, non-availability in time and place, and transportation issues. The application of biochar as soil amendments is widely known to improve soil’s physical, chemical, and biological properties. Biochar has also emerged as a potential candidate for long-term carbon sequestration due to its inbuilt structure and higher stability. Shift from traditional “slash and burn” culture to “slash and char” might lead to the sequestration of carbon from the atmosphere. Around 0.21 Pg of carbon (12% of the total anthropogenic carbon emissions by land-use change) can be sequestered in the soil if the traditional “slash and burnt” practice is converted to “slash and char”. The objective of this review is to provide detailed information about the role of biochar in altering the soil properties for sustaining agriculture and carbon sequestration, especially for hills and mountain ecosystems.

SATELLITE OBSERVATIONS REVEAL MORPHOLOGICAL CHANGES IN ASIAN DELTAS FROM 1986 TO 2018

Abstract. Asian deltas are densely populated and richly bio-diversified regions with significant social, economic, ecological and environmental importance across the globe. These low-lying and fertile floodplains support substantial food production. Because of sediment supply reductions, sea-level rising, subsidence, and frequent storm surges, many deltas are rapidly sinking and shrinking, which will threaten survival of millions of populations. It’s of great significance to monitor the delta morphological evolution and understand the relationship between their shoreline migrations and sediment supplies. However, quantifying the delta morphological changes is challenging due to its nature of high dynamics. In this study, we developed a methodology integrated by a time-series algorithm of water frequency and a spatial analysis to track the morphological changes of 11 major Asian deltas from 1986 to 2018.The results show that the deltas of Yellow, Yangtze, Pearl, Red, Mekong, Ganges-Brahmaputra, and Chao Phraya have experienced a net land gain at the total of 1829.3 km2, with China’s three major deltas accounting for 73 percent of all. The deltas of Mahanadi, Irrawaddy, Indus, and Godavari-Krishna have undergone a net land loss at the total of 295.1 km2, of which the Indus River Delta accounted for 65 percent. Most of the shorelines in the Yangtze River Delta were constantly advancing seaward at a rate of over 30 m/year, whereas, many ones in the rest of Asian deltas were significantly being eroded at a rate of over 20 m/year. These changes in delta morphology are closely related to sediment supplies and management policies. These results also suggest that rational wetland reclamation with auxiliary projects of ecological restoration can enhance the deltaic ability of sustainable development.

Econometric Analysis of Fluted Pumpkin Production in Nigeria; Empirical In-Depth Analysis

A study was carried out to investigate the econometric analysis of fluted pumpkin, Telfairia occidentalis production in South East, Nigeria. For this study, multi-stage random sampling was used to select 222 fluted pumpkin farmers using structured questionnaires and interview schedules. Data were analyzed using both descriptive and inferential statistics. It was observed in the study that the majority of the fluted pumpkin growers were females, married, relatively educated, and within productive age. A high productivity ratio was recorded by 39% of the fluted pumpkin growers due to exposure to agricultural forums and extension visits. Productivity differences across the state varied significantly with higher productivity estimates. Overall total factor productivity (TFP) and partial factor productivity (PFP) values were 11.33 and 111.2. The Majority, 52.2% of the fluted pumpkin farmers disposed of their produce in the local market due to proximity. The profit function analysis result gave N145,309.1, indicating economic viability and profitability of fluted pumpkin. Age, gender, household size, farm size, education, and farming experience influenced both the net returns and land productivity of the fluted pumpkin farmers. Farmers should be encouraged to embrace fluted pumpkin cultivation due to its economic viability, profitability, productivity, and sustainability. Government should also assist in subsidizing and providing the needed inputs to encourage fluted pumpkin growers and enhance production as well.

Vulnerability of Coastal Communities to Sea Level Rise in Brass Local Government Area, Nigeria

Coastal communities are continuously under threat of survival due to sea level rise, which has increased their vulnerability to inundation resulting to loss of livelihood, property and land area. Hence, this study investigated the vulnerability of the communities in the Brass coast to the impacts of sea level rise. Three communities (Twon-Brass, Okpoama and Diema) located within 0 – 1.2km from the shoreline, and where economic activities are prominent were purposively selected for the study. To assess the level of vulnerability of these communities to sea level rise, the coastal vulnerability index method comprising of six variables (topography, geomorphology, relative sea level rise rate, annual shoreline erosion rate, proximity to coast and population growth rate) were adopted. Landsat imageries at 10years interval for the period 1999 to 2019 were acquired to analyze the Brass shoreline dynamics. The results revealed that for a period of 20 years (1999-2019), the Brass coast has experienced a net land loss of 364.0km2 and a projected land loss of 910km2 by 2050, based on the current scenario. The study further revealed that Twon-Brass and Okpoama communities have high risk of inundation due to sea level rise with a calculated coastal vulnerability index values of 23.1 and 25.3, respectively; while Diema community had moderate risk of being inundated with a coastal vulnerability index value of 21.9. The study recommends the development of an integrated mitigation and adaptation strategy that would increase the resilience of the coastal communities to withstand the threat of sea level rise.

Definitions and methods to estimate regional land carbon fluxes for the second phase of the REgional Carbon Cycle Assessment and Processes Project (RECCAP-2)

Abstract. Regional land carbon budgets provide insights into the spatial distribution of the land uptake of atmospheric carbon dioxide and can be used to evaluate carbon cycle models and to define baselines for land-based additional mitigation efforts. The scientific community has been involved in providing observation-based estimates of regional carbon budgets either by downscaling atmospheric CO2 observations into surface fluxes with atmospheric inversions, by using inventories of carbon stock changes in terrestrial ecosystems, by upscaling local field observations such as flux towers with gridded climate and remote sensing fields, or by integrating data-driven or process-oriented terrestrial carbon cycle models. The first coordinated attempt to collect regional carbon budgets for nine regions covering the entire globe in the RECCAP-1 project has delivered estimates for the decade 2000–2009, but these budgets were not comparable between regions due to different definitions and component fluxes being reported or omitted. The recent recognition of lateral fluxes of carbon by human activities and rivers that connect CO2 uptake in one area with its release in another also requires better definitions and protocols to reach harmonized regional budgets that can be summed up to a globe scale and compared with the atmospheric CO2 growth rate and inversion results. In this study, using the international initiative RECCAP-2 coordinated by the Global Carbon Project, which aims to be an update to regional carbon budgets over the last 2 decades based on observations for 10 regions covering the globe with a better harmonization than the precursor project, we provide recommendations for using atmospheric inversion results to match bottom-up carbon accounting and models, and we define the different component fluxes of the net land atmosphere carbon exchange that should be reported by each research group in charge of each region. Special attention is given to lateral fluxes, inland water fluxes, and land use fluxes.

Impact of anthropogenic disturbances on carbon cycle changes in terrestrial‐aquatic‐estuarine continuum by using an advanced process‐based model

AbstractRecent research has shown that inland water—including rivers, lakes, and groundwater—may play some role in carbon cycling, although the extent of its contribution has remained uncertain due to the limited amount of reliable data available. To evaluate global changes in the carbon cycle due to anthropogenic factors, such as application of fertilizer and manure, in major rivers including 130 tidal estuaries over an 18‐year period (1998–2015), the present study used an advanced process‐based model derived by coupling a process‐based national integrated catchment‐based eco‐hydrology (NICE) model with various biogeochemical cycle models (NICE‐BGC). Generally, total nitrogen and phosphorus transports in overland flow were found to increase. In contrast, total suspended sediment in overland flow decreased in some regions because the vegetation was able to expand to cover the ground, resulting in less erosion. NICE‐BGC simulated the difference in carbon budget in major rivers with and without nutrient application. Generally, CO2 degassing across the water‐air interface decreased and particulate organic carbon (POC) increased in most rivers through variations in carbon budget, where excess nutrients might stimulate gross primary production of carbon‐rich algal biomass. The simulated result also showed that the estuarine carbon cycle was sensitive to intense anthropogenic disturbances reflected by nutrient load, seawater temperature, increases in sea level, and ocean acidification. Extension of previous studies only by categorizing MARgins and CATchments Segmentation (MARCATS) segment numbers showed that the estimated total CO2 flux from the world's estuaries was 0.14 Pg C/year. Generally, the simulation showed that incorporation of the nutrient cycle into the terrestrial‐aquatic‐estuarine continuum improved estimates of net land flux and carbon budget in inland waters, thus emphasizing that the effect of estuarine inland water should be explicitly included in the global carbon model to minimize the range of uncertainty.

The Variability of Air-sea O2 Flux in CMIP6: Implications for Estimating Terrestrial and Oceanic Carbon Sinks

The measurement of atmospheric O2 concentrations and related oxygen budget have been used to estimate terrestrial and oceanic carbon uptake. However, a discrepancy remains in assessments of O2 exchange between ocean and atmosphere (i.e. air-sea O2 flux), which is one of the major contributors to uncertainties in the O2-based estimations of the carbon uptake. Here, we explore the variability of air-sea O2 flux with the use of outputs from Coupled Model Intercomparison Project phase 6 (CMIP6). The simulated air-sea O2 flux exhibits an obvious warming-induced upward trend (∼1.49 Tmol yr−2) since the mid-1980s, accompanied by a strong decadal variability dominated by oceanic climate modes. We subsequently revise the O2-based carbon uptakes in response to this changing air-sea O2 flux. Our results show that, for the 1990–2000 period, the averaged net ocean and land sinks are 2.10±0.43 and 1.14±0.52 GtC yr−1 respectively, overall consistent with estimates derived by the Global Carbon Project (GCP). An enhanced carbon uptake is found in both land and ocean after year 2000, reflecting the modification of carbon cycle under human activities. Results derived from CMIP5 simulations also investigated in the study allow for comparisons from which we can see the vital importance of oxygen dataset on carbon uptake estimations.

Conflicting Interests between Local Governments and the European Target of No Net Land Take

Conflicting Interests between Local Governments and the European Target of No Net Land Take

Influence of Key Environmental Drivers on the Performance of Sediment Diversions

A Delft3D morphodynamic model for Barataria Bay, Louisiana, USA is used to quantify a plausible range of land change in response to a proposed sediment diversion under a range of environmental drivers. To examine the influence of environmental drivers, such as Mississippi River water hydrographs, mineral and organic sediment loading, sea level rise rates, subsidence, and a projected implementation (or operation) date, 240 multi-decadal (2020–2100) numerical experiments were used. The diversion was assumed to begin operation in 2025, 2030, or 2035. The experiments revealed persistent benefits of the sediment diversion through 2100. Start data of 2025 result in a median net positive land change of 32 km2 by 2100; whereas the 90th, and 10th percentiles are 69 and 10 km2. A delay in the operation date of the diversion to 2030 or 2035 would reduce the net positive land change by approximately 15–20% and 20–30%, respectively.

Agricultural landscape change impact on the quality of land: An African continent-wide assessment in gained and displaced agricultural lands

Agricultural land area is increasing globally despite the loss of productive agricultural lands in some world regions. We examine the case of Africa where the knowledge about major agricultural land transitions and the impacts on the quality of land is still very limited. A comprehensive assessment of change in agricultural landscapes was conducted at the African continental scale. We identify influencing factors and model the quality of land associated with agricultural land gains and losses between 2000 and 2018. Land quality was established based on spatially-explicit analysis of varying Net Primary Productivity, soil organic carbon content, crop suitability and percent yield change for major crops of global importance grown across Africa such as maize, rice, soybean, wheat, and alfalfa. Distance to settlements was important in explaining agricultural land dynamics. Most land areas that transitioned to cropland in Africa were associated with large distances away from major roads. Poor access to major roads suggests the remoteness of gained croplands. Land quality was better in gained croplands than in those lost, whereas gained grasslands were of lesser quality compared to areas of grassland loss. Five typologies of African countries were developed based on net yield and amount of land cultivated per crop in cropland change areas. Type 1 typifies net yield increase and cultivated land decrease, while type 2 is characterized by yield increase consequent upon cropland expansion. Net yield and land remain unchanged in type 3, while in type 4 cultivated land increased but yield decreased as in 40% of African countries for maize, and in type 5, both yield and land area decreased. This study thus provides evidence about the quality of land in gained and lost agricultural areas and generalizable insights on their dynamics across Africa.

Where Has All the Carbon Gone?

Carbon is among the most abundant substances in the universe; although severely depleted on Earth, it is the primary structural element in biochemistry. Complex interactions between carbon and climate have stabilized the Earth system over geologic time. Since the modern instrumental CO2record began in the 1950s, about half of fossil fuel emissions have been sequestered in the oceans and land ecosystems. Ocean uptake of fossil CO2is governed by chemistry and circulation. Net land uptake is surprising because it implies a persistent worldwide excess of growth over decay. Land carbon sinks include ( a) CO2fertilization, ( b) nitrogen fertilization, ( c) forest regrowth following agricultural abandonment, and ( d) boreal warming. Carbon sinks in both land and oceans are threatened by warming and are likely to weaken or even reverse as emissions fall with the potential for amplification of climate change due to the release of previously stored carbon. Fossil CO2will persist for centuries and perhaps many millennia after emissions cease. ▪ About half the carbon from fossil fuel combustion is removed from the atmosphere by sink processes in the land and oceans, slowing the increase of CO2and global warming. These sinks may weaken or even reverse as climate warms and emissions fall. ▪ The net land sink for CO2requires that plants have been growing faster than they decay for many decades, causing carbon to build up in the biosphere over and above the carbon lost to deforestation, fire, and other disturbances. ▪ CO2uptake by the oceans is slow because only the surface water is in chemical contact with the air. Cold water at depth is physically isolated by its density. Deep water mixes with the surface in about 1,000 years. The deep water does not know we are here yet! ▪ After fossil fuel emissions cease, much of the extra CO2will remain in the atmosphere for many centuries or even millennia. The lifetime of excess CO2depends on total historical emissions; 10% to 40% could last until the year 40,000 AD.

Preface

The International Conference 2021 (INAFOR 2021 Stream 2) was held on 7-8 September 2021 in a virtual format via zoom meetings due to the COVID-19 pandemic situation. It was conducted virtually to align with the biannual agenda of The 6th International Conference of Indonesia Forestry and Environment Researchers (INAFOR), which previously was carried out by The Agency for Standardization of Environment and Forestry Instruments, Ministry of Environment of Forestry, Indonesia. This is the first international conference hosted by The Center for Standardization of Sustainable Forest Management Instruments, Bogor, West Java, Indonesia. This conference was an important medium for sharing information and experiences and encouraging collaboration in sustainable forest management.The theme “Managing Forest and Natural Resources, Meeting Sustainable and Friendly Use”, strategically supports Indonesia’s commitment to Net Sink Forestry and Land Use (FoLU) 2030. The INAFOR 2021 Stream 2 was attended by approximately 750 participants, invitees, keynote speakers, scientists, and academicians from Indonesia, South Korea, the Netherland and Australia. The conference took place with a plenary session featuring six Keynote Speakers that presented exciting and practical information relevant to the theme. Also, a parallel session was divided into 12 separate zoom spaces according to the topics and number of participants. The presenters had ten minutes to present their papers and followed by interactive and engaging discussion.This proceeding presents 78 papers of research results on various topics, including biodiversity conservation, livelihoods, climate resilience, timber, and non-timber forest products. Those valuable pieces of information and recommendations can be modalities and references for the preparation and development of standards for sustainable forest management instruments and the development of science, technology, and innovation.Thank you.Dr. Wening Sri WulandariActing Director of Center for Standardization of Sustainable Forest ManagementInstruments Scientific Committee Prof. (Ris.) Dr. Sri Suharti; Prof. (Ris.) Dr. Pratiwi; Prof. (Ris.) Dr. Hendra Gunawan; Prof. (Ris.) Dr. Maman Turjaman; Prof. (Ris.) Dr. Haruni Krisnawati; Prof. (Ris). Dr. R. Garsetiasih; Prof. (Ris). Dr. Murniati; Prof. (Ris). Dr. Nina Mindawati; Prof. (Ris). Chairil Anwar Siregar; Prof. (Ris). Dr. Gustan Pari; Prof. (Ris). Dr. AYPBC Widyatmoko; Prof. (Ris). Dr. Liliana Baskorowati ; Asep Hidayat, Ph.D.; Henti Hendalastuti Rachmat, Ph.D.; Krisdianto, Ph.D.; Jamaludin Malik, Ph.D.; Dr. Neo Endra Lelana; Dr. Rozza Tri Kwatrina; Dr. Budi Hadi Narendra; Dr. Wa Ode Muliastuty Arsyad; Dr. Rizki Maharani; Dr. Arif Nirsatmanto; Dr. Dede Sudrajat; Denny, S. Hut., M.P.; Rinaldi Imanuddin, S.Hut., M.Si.; Irma Yeni, S.P., M.Sc.; Drs. Bugi Sumirat, M.Phil.

Impact of merging of historical and future climate data sets on land carbon cycle projections for South America

AbstractEarth System Models (ESMs) project climate change, but they often contain biases in their estimates of contemporary climate that propagate into simulated futures. Land models translate climate projections into surface impacts, but these will be inaccurate if ESMs have substantial errors. Bias concerns are relevant for terrestrial physiological processes which often respond non‐linearly (i.e. contain threshold responses) and are therefore sensitive to absolute environmental conditions as well as changes. We bias‐correct the UK Met Office ESM, HadGEM2‐ES, against the CRU–JRA observation‐based gridded estimates of recent climate. We apply the derived bias corrections to future projections by HadGEM2‐ES for the RCP8.5 scenario of future greenhouse gas concentrations. Focusing on South America, the bias correction includes adjusting for ESM estimates that, annually, are approximately 1 degree too cold, for comparison against 21st Century warming of around 4 degrees. Locally, these values can be much higher. The ESM is also too wet on average, by approximately 1 mm·day−1, which is substantially larger than the mean predicted change. The corrected climate fields force the Joint UK Land Environment Simulator (JULES) dynamic global vegetation model to estimate land surface changes, with an emphasis on the carbon cycle. Results show land carbon sink reductions across South America, and in some locations, the net land–atmosphere CO2 flux becomes a source to the atmosphere by the end of this century. Transitions to a CO2 source is where increases in plant net primary productivity are offset by larger enhancements in soil respiration. Bias‐corrected simulations estimate the rise in South American land carbon stocks between pre‐industrial times and the end of the 2080s is ∼12 GtC lower than that without climate bias removal, demonstrating the importance of merging historical observational meteorological forcing with ESM diagnostics. We present evidence for a substantial climate‐induced role of greater soil decomposition in the fate of the Amazon carbon sink.

Land take in environmental assessments: Recent advances and persisting challenges in selected EU countries

In this paper, we present results from an in-depth questionnaire survey, in which experts from ten EU Member States and the UK assessed the progress towards the EU’s ‘no net land take by 2050’ target within their countries. The survey focused in particular on how Directive 2014/52/EU has been implemented at national level. The revised directive stipulates for the first time explicitly that Environmental Impact Assessments (EIAs) should consider ‘land’ in addition to ‘soil’, thereby opening up the possibility that EIAs will play a more significant role in curbing land take. However, the results from our survey suggest that the impact from including the factor ‘land’ in EIAs has remained limited so far. Against this background, we discuss likely reasons for this observation, highlight persistent challenges for tackling land take effectively, and reflect on options to mitigate barriers on the way toward the European ‘no net land take by 2050’ target.

The land footprint of the global food trade: Perspectives from a case study of soybeans

The potential adverse impact of international trade on the environment has received growing attention in recent years. Growing environmental pressure poses significant challenges to sustainable development, further highlighting the need for a comprehensive response to tackling the unsustainable food use driven by the soybean trade. Although a significant amount of literature on trade-related land footprints already exists, globally, there has been only a limited amount of research seeking to identify the main issues related to agriculturally driven land-use change and food trade flows that have high land-use impacts. In addition, existing research does not fully reveal the ecological significance of land footprints but instead focuses mainly on physical quantities. There have been few studies that shed any light on the underlying correlations between environmental footprints and the food trade. To address these challenges, in this study, a multi-region input-output (MRIO) model was used to study agricultural land use and changes in carbon losses related to the soybean trade along global supply chains in 2013; the bilateral flows of land and economic value between countries were also modeled. The empirical results of this research indicate that the total land footprint embodied in the global soybean trade in 2013 amounted to 16.51 Mha. Globally, China used the most land resources for the soybean trade and accounted for 9.69 Mha of this footprint. The countries where the soybean trade had the greatest impact on the land and the economy were the USA and Brazil, where 6.74 Mha and 5.76 Mha of land were used for soybeans, respectively. Most of the soybeans from these countries were exported to China. The situation on the supply side was similar as China was also ranked in the top ten countries on the supply side; however, its supply-side land footprint was sufficient to meet internal demand. To further assess the environmental impact of the international soybean trade, carbon loss values (represented by the loss of carbon sequestration capacity) were estimated for the soybean trade at a country level. The total global carbon loss and the social cost of carbon due to the soybean trade in 2013 were estimated at $93.27 billion and $15.48 billion, respectively, with Brazil, the USA, and other countries in South America having the largest figures. It was found that, following a peak in the expansion of the amount of cropland used for planting soybeans, these ecological costs had declined since 2005. Based on these results, we suggest that soybean exporting countries should focus more on improving land-use efficiency and ecological protection in order to minimize the net land footprint of soybeans.

Diurnal and Seasonal Mapping of Water Deficit Index and Evapotranspiration by an Unmanned Aerial System: A Case Study for Winter Wheat in Denmark

Precision irrigation is a promising method to mitigate the impacts of drought stress on crop production with the optimal use of water resources. However, the reliable assessment of plant water status has not been adequately demonstrated, and unmanned aerial systems (UAS) offer great potential for spatiotemporal improvements. This study utilized UAS equipped with multispectral and thermal sensors to detect and quantify drought stress in winter wheat (Triticum aestivum L.) using the Water Deficit Index (WDI). Biennial field experiments were conducted on coarse sand soil in Denmark and analyses were performed at both diurnal and seasonal timescales. The WDI was significantly correlated with leaf stomatal conductance (R2 = 0.61–0.73), and the correlation was weaker with leaf water potential (R2 = 0.39–0.56) and topsoil water status (the highest R2 of 0.68). A semi-physical model depicting the relationship between WDI and fraction of transpirable soil water (FTSW) in the root zone was derived with R2 = 0.74. Moreover, WDI estimates were improved using an energy balance model with an iterative scheme to estimate the net radiation and land surface temperature, as well as the dual crop coefficient. The diurnal variation in WDI revealed a pattern of the ratio of actual to potential evapotranspiration, being higher in the morning, decreasing at noon hours and ‘recovering’ in the afternoon. Future work should investigate the temporal upscaling of evapotranspiration, which may be used to develop methods for site-specific irrigation recommendations.

Productivity and Profitability Assessment of Lemon Based Agroforestry Systems in Bangladesh

A field experiment was conducted from May 2017 to February 2018 at the research farm of Bangabandhu Sheikh Mujibur Rahman Agricultural University to evaluate the performance and profitability of three seasonal (Broccoli, Cabbage and Okra) and two annual crops (ginger and turmeric) in lemon-based agroforestry systems. The experiment was laid out in a Randomized Complete Block Design (RCBD) and replicated thrice. For seasonal crops the treatments were sole field (T0), 50 cm distance from tree base (DTB) with ginger (T1), 50 cm DTB with turmeric (T2), 100 cm DTB with ginger (T3) and 100 cm DTB with turmeric (T4). For annual crops (ginger and turmeric) the treatments were sole field (T0) and four distance regimes (50, 100, 150 and 200 cm) from the lemon tree base in agroforestry systems. The results of the study revealed that the yield of seasonal crops decreased and the yield of annual crops and perennial trees increased in agroforestry than respective sole cropping systems. The yield performance of crops component was significantly decreased with the decreasing distance towards tree base in agroforestry systems. The economic analysis showed that the net return, benefit-cost ratio (BCR) and land equivalent ratio (LER) was higher in the lemon-based agroforestry system than sole cropping. Therefore, the cultivation of cabbage, broccoli, okra, ginger and turmeric under lemon-based agroforestry systems are economically profitable.

The climate impact of COVID-19-induced contrail changes

Abstract. The COVID-19 pandemic caused significant economic disruption in 2020 and severely impacted air traffic. We use a state-of-the-art Earth system model and ensembles of tightly constrained simulations to evaluate the effect of the reductions in aviation traffic on contrail radiative forcing and climate in 2020. In the absence of any COVID-19-pandemic-caused reductions, the model simulates a contrail effective radiative forcing (ERF) of 62 ± 59 mW m−2 (2 standard deviations). The contrail ERF has complex spatial and seasonal patterns that combine the offsetting effect of shortwave (solar) cooling and longwave (infrared) heating from contrails and contrail cirrus. Cooling is larger in June–August due to the preponderance of aviation in the Northern Hemisphere, while warming occurs throughout the year. The spatial and seasonal forcing variations also map onto surface temperature variations. The net land surface temperature change due to contrails in a normal year is estimated at 0.13 ± 0.04 K (2 standard deviations), with some regions warming as much as 0.7 K. The effect of COVID-19 reductions in flight traffic decreased contrails. The unique timing of such reductions, which were maximum in Northern Hemisphere spring and summer when the largest contrail cooling occurs, means that cooling due to fewer contrails in boreal spring and fall was offset by warming due to fewer contrails in boreal summer to give no significant annual averaged ERF from contrail changes in 2020. Despite no net significant global ERF, because of the spatial and seasonal timing of contrail ERF, some land regions would have cooled slightly (minimum −0.2 K) but significantly from contrail changes in 2020. The implications for future climate impacts of contrails are discussed.