Role In Climate Change Mitigation Research Articles

An unintended ecological benefit from human intervention: The enhancement of carbon storage in seagrass meadows

Abstract Human interventions have had unintended consequences for the diverse functions of various ecosystems. Hydrological interventions have the potential to alter vegetated habitats in coastal nearshore ecosystems, but little is known about the impacts on organic carbon (Corg) sequestration, which plays an important role in climate change mitigation. We examined the effects of past human interventions through artificial inlet opening in a lagoonal seagrass meadow. The sediment profiles of geological and biogeochemical characteristics were measured to obtain the historical changes in the lagoon environment and Corg accumulation rates. Isotopic and elemental signatures and diatom assemblages showed that the interventions increased the duration of seawater exchanges and the extent of the seagrass meadow. Corg accumulation rates increased more than 1.9‐fold after the intervention, resulting in additional Corg storage in the seagrass meadow during last 64 years. Synthesis and applications. Artificial opening of tidal inlet can potentially provide unintended ecological benefits, such as increased carbon sequestration in seagrass meadows. Hydrological interventions could be undertaken intentionally as a potential active intervention to sequester carbon, as well as control flood risk and provide other benefits to people in estuarine systems. Our results illustrate that physical factors such as improving salinity conditions and mineral particle supply have an impact on the feasibility of hydrological interventions for enhancing carbon sequestration. We propose that biogeochemical–physical coupled approach will help stakeholders to evaluate the ecological and social risks and synergies of implementing hydrological interventions.

The contribution of ocean-based solutions to carbon reduction in China

Climate change has become a great challenge for humanity. However, the current climate change mitigation measures, primarily concentrate on land, more or less neglecting the vital role of the ocean-based solutions. While the ocean is a crucial regulator of the global climate, ocean-based solutions could also play an essential role in climate change mitigation and policymaking. This paper developed an Ocean-based Solutions Carbon Reduction Assessment Model (OSCRAM) that addresses coastal ecosystems, ocean energy, marine transportation, fishery, and seabed to estimate the oceanic contribution to climate change mitigation. It has been applied to evaluate the capacity of carbon emission reduction through oceans in China. We found that the total contribution for carbon emission reduction was about 6.86 Tg CO2 per year, and it may reach 139.39 Tg in 2030 under the target scenario. The results indicated that the ocean has huge potential to reduce carbon emissions. The development of marine energy and low-carbon marine shipping may have more potential for emission reduction in China, and the government should also protect and restore coastal wetlands for their enormous carbon storage. It can also provide a reference for the globe and other nations in achieving emission reduction goals.

Historical and future carbon stocks in forests of northern Ontario, Canada

BackgroundForests in the Far North of Ontario (FNO), Canada, are likely the least studied in North America, and quantifying their current and future carbon (C) stocks is the first step in assessing their potential role in climate change mitigation. Although the FNO forests are unmanaged, the latter task is made more important by growing interest in developing the region’s natural resources, primarily for timber harvesting. In this study, we used a combination of field and remotely sensed observations with a land surface model to estimate forest C stocks in the FNO forests and to project their future dynamics. The specific objective was to simulate historical C stocks for 1901–2014 and future C stocks for 2015–2100 for five shared socioeconomic pathway (SSP) scenarios selected as high priority scenarios for the 6th Assessment Report on Climate Change.ResultsCarbon stocks in live vegetation in the FNO forests remained relatively stable between 1901 and 2014 while soil organic carbon (SOC) stocks steadily declined, losing about 16% of their initial value. At the end of the historical simulation (in 2014), the stocks were estimated at 19.8, 46.4, and 66.2 tCha−1 in live vegetation, SOC, and total ecosystem pools, respectively. Projections for 2015–2100 indicated effectively no substantial change in SOC stocks, while live vegetation C stocks increased, accelerating their growth in the second half of the twenty-first century. These results were consistent among all simulated SSP scenarios. Consequently, increase in total forest ecosystem C stocks by 2100 ranged from 16.7 to 20.7% of their value in 2015. Simulations with and without wildfires showed the strong effect of fire on forest C stock dynamics during 2015–2100: inclusion of wildfires reduced the live vegetation increase by half while increasing the SOC pool due to higher turnover of vegetation C to SOC.ConclusionsForest ecosystem C stock estimates at the end of historical simulation period were at the lower end but within the range of values reported in the literature for northern boreal forests. These estimates may be treated as conservatively low since the area included in the estimates is poorly studied and some of the forests may be on peat deposits rather than mineral soils. Future C stocks were projected to increase in all simulated SSP scenarios, especially in the second half of the twenty-first century. Thus, during the projected period forest ecosystems of the FNO are likely to act as a C sink. In light of growing interest in developing natural resources in the FNO, collecting more data on the status and dynamics of its forests is needed to verify the above-presented estimates and design management activities that would maintain their projected C sink status.

Land suitability evaluation for Arenga pinnata cultivation as a source of traditional cuisine, Horog-Horog, in 3 districts of Jepara Regency, Central Java

Arenga pinnata (sugar palm) is an economically and ecologically important palm in Jepara Regency. People of Jepara have been extracting the starch from its stem as the main raw material for traditional cuisine, horog-horog. Sugar palm stands can conserve soil and water. Their large stems store relatively much carbon rather than other agricultural monocot plants. Thus, sugar palm cultivation plays an important role in climate change mitigation. However, the areal of sugar palm cultivation was limited. Thus, land evaluation was needed to predict land performance over time to support sugar palm cultivation. The purposes of the present study were to identify land characteristics and their suitability for sugar palm cultivation. This research was conducted in Bangsri, Kembang, and Pakis Aji Districts. The purposive sampling method was used for the field survey. In total, there were 20 land units (9,232.17 ha) across those three districts. Furthermore, to determine land suitability for sugar palm cultivation, the matching method was applied. Thus, the data from field surveys and laboratory tests were used. The obtained results in the present study indicated that 13 land units were classified as S3 (marginal) and 7 land units were classified as N (not suitable). However, there were some limiting factors in the field that must be addressed to support sugar palm cultivation in S3, such as water availability (wa), rooting condition (rc), and nutrient retention (nr). Furthermore, in the land unit that was classified as N the main limiting factor was slope (>30%).

Rainfall frequency and soil water availability regulate soil methane and nitrous oxide fluxes from a native forest exposed to elevated carbon dioxide

Abstract Free‐air carbon dioxide enrichment (FACE) experiments in terrestrial ecosystems have demonstrated ecological responses of key ecosystem processes to rising atmospheric carbon dioxide (CO2). However, CO2 fertilization responses in field conditions have seldom included methane (CH4) and nitrous oxide (N2O), particularly in natural and mature forests, which are expected to have an important role in climate change mitigation. Herein, we aimed to capture the effect of elevated CO2 (eCO2; ambient vs. +150 ppm) on long‐term temporal dynamics of CH4 and N2O fluxes, followed by identification of climo‐edaphic factors explaining feedback responses. To achieve this, continuous monitoring of greenhouse gas (GHG) fluxes using a manual chamber technique, over a 3‐year period was implemented in a mature dryland Eucalypt forest FACE (EucFACE) facility in Australia. The relationship between CH4 and N2O fluxes with rainfall indices and soil properties was also explored since they directly impact the microbial communities in the soil responsible for CH4 and N2O net emissions. Our results showed that in 3 years of eCO2 treatment, the amount and frequency of rainfall predicted GHG emissions in this native forest. We also found a significant reduction in CH4 sink (15%–25%) for some of the years as well as an overall treatment effect index reduction in N2O emissions under eCO2. Higher frequency of rain events with lower intensity led to highest CH4 sink followed by lowest N2O emissions due to fewer wet–dry cycles. Of all the environmental variables included, soil moisture, rainfall and pH were the main predictors of net CH4 and N2O emissions. Methane flux was also strongly influenced by soil texture. Our findings highlight the need to account for reduced forest CH4 sink under eCO2 in dryland ecosystems, which has implications for GHG budget predictions under future climate conditions. A free Plain Language Summary can be found within the Supporting Information of this article.

Are Municipalities Ready for Integrating Blue Carbon Concepts?: Content Analysis of Coastal Management Plans in the Philippines

The blue carbon ecosystems are gaining salience in the international arena due to their intrinsic role in climate change mitigation. Reviews on management strategies and plans at the local level are largely overlooked, although they are crucial factors in translating commitments to contextualized actions for sustainable management. The primary goal of this study is to investigate the present coastal management plans for blue carbon ecosystem management strategies using content analysis of the local plans of select municipalities in the Philippines. The analysis generated eight (8) clusters based on keywords focusing on mangrove and seagrass ecosystems, namely: ecological profile, ecosystem services, carbon sequestration, tourism, natural threats, anthropogenic threats, laws, policies, & ordinances, and management activities. The management activities cluster has the most coverage while the carbon sequestration cluster is the least mentioned. There is also a distinct gap in the inclusion of mangroves compared to seagrasses in the coastal management plans where these ecosystems are present in the localities concerned. Mangrove ecosystems are frequently mentioned, covering all clusters while seagrass ecosystems are discussed to less extent in only five (5) clusters. This study also showed that the “blue carbon” concept is not yet fully incorporated in the current management plans where carbon sequestration cluster is only discussed under mangrove ecosystems in one of the sites while no discussions for seagrasses’ “blue carbon” functions. The results of this study can serve as a benchmark for local policy-makers in updating their present management plans particularly in branching their focus on integrated management of seagrass ecosystems and advancing technical capacity and knowledge on blue carbon ecosystems.

Potential carbon storage of Indonesian mangroves

Even though it only covers 0.1% of the surface of the continent, mangrove forests recorded as carbon-rich forests on earth. Forest loss and degradation together, especially in the tropics contributes about 12% of the total annual anthropogenic CO2 emissions. Mangrove forests ecosystem have high carbon storage potential. The study results show that the ratio of carbon to area in mangrove ecosystems is almost 13 times greater than that of tropical rainforest ecosystems in Indonesia. This study has used published data recorded in Google Scholar and Science Direct. Indonesia’s mangroves, with a total area of 3.1 million ha, store a total carbon of 5.2 Gt. The average stand biomass or aboveground biomass is around 407.15 tons ha−1, storing carbon as much as 191.36 tons ha−1 which is equivalent to the potential for CO2 absorption (CO2e) by mangrove stands of 702.29 tons ha−1. Papua has the largest mangrove forest in Indonesia that has the potential for CO2e. Assessment of carbon storage in soil needs to be done in estimating the total carbon stored in mangrove ecosystems, given the large potential for stored carbon that plays a role in climate change mitigation.

Multiple drivers of tree and soil carbon stock in the tropical forest ecosystems of Bangladesh

Tropical forest ecosystem act as a carbon sink and plays a vital role in climate change mitigation. The carbon storage capacity of tropical forest ecosystems is declining gradually in recent years. But studies regarding the multiple drivers of tree and soil carbon in the tropical forest ecosystems are scarce. Our study aims to quantify the tree and soil carbon storage capacity and to explore how these carbon storages are associated with both biotic (stand structure, anthropogenic disturbance) and abiotic drivers (climate, topography, and soil) simultaneously in tropical forest ecosystems. The present study was conducted in two forest-protected areas of Bangladesh, namely- Satchari National Park (SNP), and Khadimnagar National Park (KNP). Results showed that tree carbon stock was 72.9 t ha−1 and 58.2 t ha−1 in SNP and KNP, respectively. Besides, soil carbon was 77.1 t ha−1 in SNP and 130.5 t ha−1 in KNP. We found that tree carbon was positively correlated with all stand structure parameters. However, soil carbon was negatively correlated with tree richness, height, and basal area. Anthropogenic disturbance had a negative correlation with tree carbon and a positive correlation with soil carbon stock. No significant correlation was observed between tree carbon and local climatic parameters. But soil carbon had a positive correlation with annual precipitation and a negative correlation with annual mean temperature. Furthermore, tree carbon was positively associated with elevation and slope whereas soil carbon was negatively associated with elevation. Tree carbon was negatively correlated with silt% but positively with sand%. Conversely, soil carbon showed significant positive associations with soil moisture, bulk density, soil pH, and soil silt%. Our study provides a comprehensive insight on the understandings of key drivers of tree and soil carbon storage in the tropical forest ecosystem of Bangladesh. We concluded that anthropogenic disturbance and stand characteristics regulate tree carbon stock while soil carbon is mainly associated with local climate and soil properties in the studied tropical forest ecosystems.

English

Farmers can play an important role in climate change mitigation through sustainable soil management practices. Semi-structured interviews were conducted in the Atwima Nwabiagya municipality of Ashanti region, Ghana, to explore farmers' knowledge and perceptions of their soils, soil fertility, applied management practices, and climate change on soil organic carbon. The interviews included topics related to farmers’ access to training and its impact in adopting and changes in management strategies. Summary for interviews was prepared based on notes and recordings and analyzed with the Qualitative Content Analysis (QCAmap) software using emergent codes. Results show that farmers had a lot of knowledge on soil organic matter (SOM) and how it affects climate and the relationship between SOM and soil fertility. They also acknowledged that their management practices affect quantities of SOM in topsoil and subsoil and soil fertility. The adoption of current and new management practices including, the use of organic and inorganic fertilizers, manure, mulching, and shade management, is a reflection of their newly acquired knowledge and understanding of fertility sustaining processes. The study highlights the relationship between farmers' training and changes in their adopted practices and how management practices affect SOC influencing climate change and soil fertility. Key words: soil organic carbon, cocoa farmers, perception, soil management, soil fertility and climate change.

Projection of material flows and stocks in the urban transport sector until 2050 – A scenario-based analysis for the city of Vienna

The transport sector plays a decisive role in climate change mitigation, especially in cities, as it significantly contributes to global resource and energy consumption. Hence, decarbonising this sector is increasingly recognized as an important means of mitigating climate change, which is reflected in numerous smart city initiatives. However, existing studies thereon have focused almost exclusively on energy and CO2, thereby neglecting the consumption of material resources required to transform urban transport systems so as to be compatible with a low carbon future. In this study, we hence investigate the effects of transforming urban transport systems on future material stock and material flows using the city of Vienna as a case study. For this purpose, a material flow analysis for the infrastructure and vehicles required until 2050 has been conducted taking different scenarios into consideration, which are mainly characterized by different modal splits. The results show that different paths of development among the various transport modes significantly affect the overall material stocks and flows. If the modal split remains constant, the road-infrastructure has to be further expended to provide the transport service needed due to the expected increase in population in Vienna. The material stock per capita for the transport system remains constant at around 54 t/capita for this scenario. If the motorized individual transport can be reduced to a share of less than 10% of all trips (today's share amounts to 25%), the material stock per capita decreases to around 47 t/capita in 2050. As this case allows for infrastructure (e.g. parking infrastructure, road lanes) to be dismantled, the annual material demand for maintenance efforts is also reduced by a fifth (to 460 kg/cap/yr). Despite the reduction in material stocks and flows achievable by changing the current modal split, a significant change in the waste composition in terms of the end-of-life vehicles generated is to be expected in the coming decades. Annual quantities of old batteries, for instance, might rise from today's 1.5 kg/capita up to 70 kg/capita. These changes will definitely challenge the waste management sector, but also represent an opportunity for the recovery of valuable resources. Based on the results, it can be concluded that the transformation of an urban transport system towards lower greenhouse gas emissions also has the potential to reduce future material demand and waste generation. However, this requires a change in the modal split, whereas solely moving to a fossil-free vehicle fleet has the contrary effect.

Exploring Pattern of Green Spaces (GSs) and Their Impact on Climatic Change Mitigation and Adaptation Strategies: Evidence from a Saudi Arabian City

Green spaces (GSs) are significant, nature-based solutions to climate change and have immense potential to reduce vulnerability to heat waves while enhancing the resilience of urban areas in the light of climate change. However, in the Saudi context, the availability of GSs across cities and their perceived role in climate change mitigations and adaptation strategies remain unexplored. This study aimed to examine the per capita availability of GSs in the Jeddah megacity in Saudi Arabia, and their role in climate change mitigation and adaptation strategies. This study assessed the per capita availability of GS in Jeddah city using GIS techniques, and a questionnaire survey (online and an onsite) was conducted to assess the GSs users’ perception of the role of GSs on climate change mitigation and adaptation strategies. Non-parametric tests were also used to find differences in roles based on socio-demographic attributes. The findings of the study revealed that: (i) the per capita availability of GS in Jeddah is relatively low in comparison to international organization recommendations (such as World Health Organization and European Union). As per the survey result, it was reported that GSs play crucial role for climate change mitigation such as temperature regulation, reduction in heat stress, enhancement outdoor thermal comfort, and the maintenance of air quality. More than 85% of the total respondents agreed with the very high importance of GSs for climate change mitigation. More than 80% of respondents in the city highly agreed with climate change adaptation strategies such as the enhancement of accessibility to GSs, ecosystem-based protection of GSs, and the improvement of per capita availability of GSs. The findings of the study will be very helpful to planners and policymakers in implementing nature-based solutions to reduce vulnerability to climate change in Jeddah city, and particularly other cities in a desert environment.

Nuclear energy - The solution to climate change?

With increased awareness of climate change in recent years nuclear energy has received renewed attention. Positions that attribute nuclear energy an important role in climate change mitigation emerge.We estimate an upper bound of the CO2 saving potential of various nuclear energy growth scenarios, starting from our projection of nuclear generating capacity based on current national energy plans to scenarios that introduce nuclear energy as substantial instrument for climate protection. We then look at needed uranium resources.The most important result of the present work is that the contribution of nuclear power to mitigate climate change is, and will be, very limited. At present nuclear power avoids annually 2–3% of total global GHG emissions. Looking at announced plans for new nuclear builds and lifetime extensions this value would decrease even further until 2040. Furthermore, a substantial expansion of nuclear power will not be possible because of technical obstacles and limited resources. Limited uranium-235 supply inhibits substantial expansion scenarios with the current nuclear technology. New nuclear technologies, making use of uranium-238, will not be available in time. Even if such expansion scenarios were possible, their climate change mitigation potential would not be sufficient as single action.

Opportunities for forest sector emissions reductions: a state-level analysis.

The forest sector can play a significant role in climate change mitigation. We evaluated forest sector carbon trends and potential mitigation scenarios in Vermont using a systems-based modeling framework that accounts for net emissions from all forest sector components. These components comprise (1) the forest ecosystem, including land-use change, (2) harvested wood products (HWP), and (3) substitution effects associated with using renewable wood-based products and fuels in place of more emission-intensive materials and fossil fuel-based energy. We assessed baseline carbon trends from 1995 through 2050 using a business as usual (BAU) scenario. Emission reductions associated with different forest management and HWP scenarios were evaluated relative to the BAU scenario from 2020 to 2050. We estimated uncertainty for each forest sector component and used a Monte Carlo approach to estimate the distribution of cumulative total mitigation for each scenario relative to baseline. Our analysis indicates that the strength of the forest sector carbon sink in Vermont has been declining and will continue to decline over coming decades under the BAU scenario. However, several scenarios evaluated here could be effective in reducing emissions and enhancing carbon uptake. Shifting HWP to longer-lived commodities resulted in a 14% reduction in net cumulative emissions by 2050, the largest reduction of all scenarios. A scenario that combined extending harvest rotations, utilizing additional harvest residues for bioenergy, and increasing forest productivity resulted in a 12% reduction in net cumulative emissions. Shifting commodities from pulp and paper to bioenergy showed a 7.3% reduction in emissions. In contrast, shortening rotations to increase harvests for bioenergy use resulted in a 5.5% increase in emissions. In summary, model simulations suggest that net emissions could be reduced by up to 14% relative to BAU, depending on the management and HWP-use scenario. Combining multiple scenarios could further enhance reductions. However, realizing the full climate mitigation potential of these forests may be challenging due to socioeconomic barriers to implementation, as well as alternative management objectives that must be considered along with carbon sequestration.

The role of seagrass ecosystem in small islands as a blue carbon in climate change mitigation in Indonesia (case study: Lembeh Island, Bitung Regency)

Climate change phenomenon has occurred equally and globally all over the world during the last century, including Indonesia, which known as an archipelagic country with more than 17.000 islands, where most of the island considered as small islands. Lembeh Island known by its high biodiversity in marine resources, especially coral reef which associated with other coastal ecosystems such as mangrove and seagrasses and create a healthy environment. Seagrasses as a blue carbon ecosystem can be functioned as a carbon absorber from the atmosphere and storage in the sediment, and supported the climate change mitigation act in Indonesia. Based on field observation, Lembeh Island region has seven species from possible twelve seagrass species found in Indonesia. Enhalus acoroides and Thalassia Hemprichii dominated the seagrass existence in Lembeh Island with certain characteristics live in a sandy substrate, muddy area or coral reefs. Seagrass in Lembeh Island has potency on biomass carbon as much as 0.96 ± 1.327 MgCha−1 (mostly autochthonous), which lower than the potency of carbon stored in sediment reached more than 40 MgCha−1 (mostly allochthonous). Seagrass ecosystem play an important role in climate change mitigation act and should be supported, developed and collaborated with other coastal ecosystems sucha as coral reefs and mangroves.

Climate policies for freight transport: Energy and emission projections through 2050

Reducing energy consumption and emissions from freight transport plays an important role in climate change mitigation. However, there remains a need for enhanced policy making and research to explore decarbonization of freight transport. This research establishes a freight transport model to simulate transport demand, energy consumption and emissions, and applies the model to Ireland with scenarios running out to 2050. This model provides advanced technological details in freight transport modelling, responses of transport demand to economic changes, and behavioural responses in the representation of competition between transport technologies. The results show a strong growth of land freight transport demand in Ireland resulting from economic growth (GDP) despite increasing carbon taxes. The new EU CO2 emission performance standards on light and heavy-duty vehicles have the potential to effectively slow down the growth of energy consumption from 2015 to 2050 but possible technical barriers need to be evaluated to ensure full compliance. In the short term, carbon taxation (or higher fuel prices) may have a greater impact but the effect of emission performance standards will be realised in the longer term as the vehicle stock is replaced with new technology vehicles. Notably, adoption of biofuel and alternative freight vehicles are expected to bring additional reductions in future energy consumption and emissions. For a low carbon future for freight transport, integrated efforts are needed to develop a comprehensive policy agenda (technology specific standards and pricing mechanisms) and promote low or zero emission vehicles technologies, especially for heavy goods vehicles.

Evaluation of different methodologies for the design of the wellfield in shallow geothermal systems

Low enthalpy geothermal resources play an essential role in climate change mitigation. When ensuring the correct future operation of ground-source heat pump systems, an accurate design is mandatory. In this sense, different methodologies can be implemented. Although using sophisticated software constitutes the most optimal solution, its implementation is sometimes inviable in certain projects (the increase of the initial investment required is not justified in small plants). This work is focused on evaluating and comparing procedures used in the design of shallow geothermal systems. Thus, the research includes a simple method based on manual calculations, the Climasoft free application, Earth Energy Designer (EED) software, and the new geothermal tool GES-CAL developed by researchers from the TIDOP Research Group (University of Salamanca). The objective is to evaluate this new software and compare the results of all the detailed methodologies. This comparison derives from applying these tools in the calculation of the same case study (a single-family house placed in Ávila, Spain). Results show that the easiest methods involve oversized well-field schemas that also mean higher initial investments. Regarding GES-CAL, it is considered an accurate and valid alternative for the design of all heat exchanger configurations, especially for those installations placed in the region of Ávila. However, EED is recommended to calculate high-power geothermal systems that require an exhaustive analysis of the ground and the heat carrier fluid behaviour.

On the Atlantic pelagic Sargassum's role in carbon fixation and sequestration

The extensive blooms of the pelagic Sargassum in the Atlantic raised the question of whether this brown seaweed may play an important role in climate change mitigation through carbon fixation and carbon sequestration, as argued in several recent papers. Using simple calculations and published values on Sargassum coverage, biomass density, carbon/biomass ratio, primary productivity, and carbon sequestration efficiency, we show that the total carbon stock in pelagic Sargassum of the entire Atlantic, even during the peak month, is unlikely to exceed 3.61 × 10−3 Pg C, and carbon fixation cannot exceed 6.0 million tons C month−1. While the carbon fixation estimate represents an upper bound, it is still <0.2% of carbon fixation by phytoplankton in the Atlantic Ocean. The carbon stock estimate is 2000 times lower than predicted using a machine learning model in another recent paper. In contrast, carbon sequestration by Sargassum appears significant locally within the Atlantic Sargassum belt. The analysis further suggests that, while the Atlantic pelagic Sargassum may play an important role in affecting local carbon budget and carbon sequestration, its contribution to either carbon stock or carbon sequestration at a global scale may be insignificant. This, however, does not diminish the importance of Atlantic pelagic Sargassum in many other aspects.

Grounding the energy justice lifecycle framework: An exploration of utility-scale wind power in Oaxaca, Mexico

Renewable Energy Technologies (RETs) are often portrayed as inherently just forms of energy production due to their role in climate change mitigation. This paper argues, first and foremost, that this overlooks the contextual struggles associated with renewable energy projects. We do so through critical engagement with an ‘Energy Lifecycle Framework’ approach to understanding claims of energy (in)justice in Oaxaca, Mexico. This framework for energy justice scholarship promises to enable whole systems interpretations related to the potential synergies and manifestations of injustice, existing at stages from resource extraction to waste, as well as opportunities for achieving more holistic forms of justice. Offering the stages of manufacturing and construction as crucial phases of any systemic approach to RETs and discussing the stage of consultation (an obligatory step in Mexico for energy projects in indigenous territories), the paper challenges and questions our ability to generate abstract interpretations of the relationship between energy lifecycles and their associated, contextually grounded, injustices. To do so, we draw upon extensive ethnographic fieldwork around the development of utility-scale wind power (USWP) projects undertaken in Oaxaca, where a number of regional peasant and indigenous groups have led sustained resistance to USWP on the basis of environmental, political and socio-economic impacts. Demonstrating how pre-existent and embedded cultural and environmental relationships determine the way in which energy justice is understood and constructed, the paper demonstrates tension as it simultaneously corroborates the usefulness of the Energy Lifecycle Framework and urges caution towards universalistic and staged approaches to assessing injustices in energy systems.

Carbon Stock Estimation of Urban Trees in Yeka Park and KMU, Addis Ababa

Urban forests contribute to climate regulation by controlling GHG emissions. The objective of this study was to estimate the total carbon stock’s potential of the Yeka Park Kotebe Metropolitan University and their role in climate change mitigation and enhancement of ecosystem services. There were 4064 trees recorded in the selected study sites in which 27.41% of the species were indigenous and 72.59% were exotic trees. The mean above ground and below ground biomass were 160.8 and 69.93 t ha-1 respectively and the mean carbon in the above ground and below ground biomass were 75.56 and 51.75 t ha-1 respectively. The mean CO2 in the above ground and below ground biomass were 580 and 378.3 t ha-1 respectively. Urban trees reduce atmospheric carbon dioxide through sequestration which is important for climate change mitigation; they also provide different ecosystem services. Keywords: Carbon sequestration, urban forests, biodiversity conservation, Addis Ababa DOI: 10.7176/JRDM/74-02 Publication date: March 31 st 2021

Carbon Dioxide and Methane Fluxes from Various Vegetation Communities of a Natural Tropical Freshwater Wetland in Different Seasons

Emission of carbon dioxide (CO2) and methane (CH4) is of interest in tropical wetland studies because the high and relatively stable temperatures year-round enhance both primary productivity and organic matter decomposition. Nonetheless, there is scarcity of data on emission of these carbon-based greenhouse gases from tropical wetlands. We investigated CO2 and CH4 fluxes from a natural tropical freshwater wetland in Uganda under different dominant vegetation communities, i.e., Cyperus papyrus (Papyrus), Typha latifolia (Typha) and Phragmites mauritianus (Phragmites), during the dry and wet seasons. Gas samples were collected using static chambers and analyzed by gas chromatography. Fluxes (mg C m−2 h−1) of both CO2 and CH4 from Papyrus (732.9 ± 48.7 [mean ± standard error] and 14.1 ± 0.8, respectively) and from Typha (759.7 ± 51.4 and 13.5 ± 1.2, respectively) insignificantly varied (p > 0.05) during the dry season. However, CO2 and CH4 fluxes from both vegetation communities during this season were significantly lower and higher (p 0.05) occurred among the three vegetation communities for both CO2 and CH4 fluxes (Phragmites: 691.9 ± 55.8 and 15.6 ± 1.1, Typha: 682.0 ± 53.3 and 16.3 ± 1.2, and Papyrus: 651.2 ± 49.0 and 17.1 ± 1.7, respectively). Water level was the main driver of CO2 and CH4 fluxes from the wetland, suggesting its importance in any efforts to regulate fluxes of both gases in tropical wetlands. We estimated total annual CO2 and CH4 emissions from Uganda’s wetland soils in the ranges of 159.5 × 106–180.2 × 106 t C (tonnes of carbon) and 278.9 × 104–359.7 × 104 t C, respectively. • Vegetation community does not influence CO2 and CH4 fluxes from a tropical freshwater wetland soil under continuous flooding • High water level in a tropical freshwater wetland lowers CO2 flux but increases CH4 flux • A wetland’s role in climate change mitigation is a function of carbon sequestration and emission