Low Greenhouse Gas Emission Scenarios Research Articles

Expansion risk of the toxic dinoflagellate Gymnodinium catenatum blooms in Chinese waters under climate change

The paralytic shellfish poison toxin (PST)-producing dinoflagellate, Gymnodinium catenatum, frequently blooms in China, posing a threat to food safety and human health. To understand the drivers of G. catenatum blooms and predict potential habitats for G. catenatum under climate change, samples from occurrence localities and environmental datasets from multiple agencies were aggregated and used to model the habitat suitability of G. catenatum in the China Sea using a maximum entropy model (Maxent). The accumulated variable contributions for the Maxent model were defined to measure the importance of key predictors in the model. The most important environmental variables were distance to the coastline, depth of seawater, and long-term average of the minimum annual temperature. This highlights the main reasons why G. catenatum blooms always occur in coastal waters. Occurrence probabilities higher than 0.66 were defined as habitats with high suitability for shellfish management and aquaculture. Projected habitats with high suitability in Haizhou Bay, coastal waters along the western Taiwan Strait, and Bohai Bay remained stable with increasing temperature by 2100, regardless of the IPCC Representative Concentration Pathways (RCPs). However, those in the China Sea would be reduced overall, leading to a northward movement of the center of integrated habitats. Habitats with a spatial area of >6000 km2 in the Bohai Sea, Yellow Sea, and South China Sea and >23,000 km2 in the East China Sea would be exposed to high risk under low greenhouse gas emission scenarios (RCP2.6).

Optimisation of the insulation thickness for the external walls in Morocco while considering the effect of climate change

The rise in global temperature is a direct consequence of the climate change phenomenon, whose effect on building energy demands can no longer be neglected. In this regard, thermal insulation is considered an efficient design measure to enhance the energy performance of buildings. The key factor for the cost-effective implementation of insulation in buildings is the proper selection of insulation thickness. However, the consideration of the climate change factor in the optimisation of the insulation thickness for building walls has not yet been addressed by researchers. In this work, the optimum insulation thickness of different wall façades is calculated in three principal climate regions in Morocco, while taking into consideration the effect of climate change over the building lifespan. The calculation used a dynamic life cycle costing method to consider the varying climate conditions over time. The future weather data is elaborated based on the medium–low greenhouse gas emissions scenario RCP4.5 of the intergovernmental panel on climate change fifth assessment report. The obtained results show that the optimum insulation layer thickness would vary between 0.04 m and 0.07 m depending on the wall orientation and the climate zone. Considering all walls, the life-cycle energy saving ratio would vary between 49.64 % and 54.87 %.The economic feasibility analysis indicates the payback period would be less than 10 years regardless of the wall orientation and the climate zone. In addition, it is shown that the effectiveness of the insulation would not be adversely affected by the climate change phenomenon in the future.

Analyzing the Joint Effect of Forest Management and Wildfires on Living Biomass and Carbon Stocks in Spanish Forests

Research Highlights: This is the first study that has considered forest management and wildfires in the balance of living biomass and carbon stored in Mediterranean forests. Background and Objectives: The Kyoto Protocol and Paris Agreement request countries to estimate and report carbon emissions and removals from the forest in a transparent and reliable way. The aim of this study is to forecast the carbon stored in the living biomass of Spanish forests for the period 2000–2050 under two forest management alternatives and three forest wildfires scenarios. Materials and Methods: To produce these estimates, we rely on data from the Spanish National Forest Inventory (SNFI) and we use the European Forestry Dynamics Model (EFDM). SNFI plots were classified according to five static (forest type, known land-use restrictions, ownership, stand structure and bioclimatic region) and two dynamic factors (quadratic mean diameter and total volume). The results were validated using data from the latest SNFI cycle (20-year simulation). Results: The increase in wildfire occurrence will lead to a decrease in biomass/carbon between 2000 and 2050 of up to 22.7% in the medium–low greenhouse gas emissions scenario (B2 scenario) and of up to 32.8% in the medium–high greenhouse gas emissions scenario (A2 scenario). Schoolbook allocation management could buffer up to 3% of wildfire carbon loss. The most stable forest type under both wildfire scenarios are Dehesas. As regards bioregions, the Macaronesian area is the most affected and the Alpine region, the least affected. Our validation test revealed a total volume underestimation of 2.2% in 20 years. Conclusions: Forest wildfire scenarios provide more realistic simulations in Mediterranean forests. The results show the potential benefit of forest management, with slightly better results in schoolbook forest management compared to business-as-usual forest management. The EFDM harmonized approach simulates the capacity of forests to store carbon under different scenarios at national scale in Spain, providing important information for optimal decision-making on forest-related policies.

Global vulnerability of marine mammals to global warming

Although extinctions due to climate change are still uncommon, they might surpass those caused by habitat loss or overexploitation over the next few decades. Among marine megafauna, mammals fulfill key and irreplaceable ecological roles in the ocean, and the collapse of their populations may therefore have irreversible consequences for ecosystem functioning and services. Using a trait-based approach, we assessed the vulnerability of all marine mammals to global warming under high and low greenhouse gas emission scenarios for the middle and the end of the 21st century. We showed that the North Pacific Ocean, the Greenland Sea and the Barents Sea host the species that are most vulnerable to global warming. Future conservation plans should therefore focus on these regions, where there are long histories of overexploitation and there are high levels of current threats to marine mammals. Among the most vulnerable marine mammals were several threatened species, such as the North Pacific right whale (Eubalaena japonica) and the dugong (Dugong dugon), that displayed unique combinations of functional traits. Beyond species loss, we showed that the potential extinctions of the marine mammals that were most vulnerable to global warming might induce a disproportionate loss of functional diversity, which may have profound impacts on the future functioning of marine ecosystems worldwide.

Can Acacia mangium and Acacia auriculiformis hinder restoration efforts in the Brazilian Atlantic Forest under current and future climate conditions?

Climate change and biological invasions are two of the most cited factors that may affect species diversity in the coming decades. Here we used five climate scenarios to investigate the potential distribution of two invasive tree species, Acacia mangium and A. auriculiformis, in the Atlantic Forest hotspot. Additionally, we used expansion–contraction maps and maps of potential areas for forest restoration to investigate whether biological invasion could affect restoration efforts. We found A. mangium has a large suitable area in all scenarios (average 268,010.1 km2 ± 25,292.4 SD), while A auriculiformis is confined to a relatively small region (average 13,123.1 km2 ± 361.7 SD). In the low greenhouse gas emissions scenario (RCP 2.6), the suitable area for A. mangium varied from the current scenario of 24.8% of the Atlantic Forest to 26.2% and 25.4% in the years 2050 and 2070, respectively. In the high greenhouse gas emission scenario (RCP 8.5), the suitable area contracted to 23.1% and 20.5% in 2050 and 2070, respectively. Approximately 30.8% of the potential area for restoration currently overlaps the suitable area for A. mangium, and this overlap reaches at least 23.8% of the potential areas for restoration in the future scenarios (RCP 8.5 in 2070). A. mangium has a large suitable area in the Atlantic Forest and can become a barrier to restoration efforts in the coming decades. Expansion–contraction maps should be used to establish environmental policies that promote both forest restoration and prevention of biological invasion in suitable areas.

Thermoregulatory traits combine with range shifts to alter the future of montane ant assemblages.

Predicting and understanding the biological response to future climate change is a pressing challenge for humanity. In the 21st century, many species will move into higher latitudes and higher elevations as the climate warms. In addition, the relative abundances of species within local assemblages are likely to change. Both effects have implications for how ecosystems function. Few biodiversity forecasts, however, take account of both shifting ranges and changing abundances. We provide a novel analysis predicting the potential changes to assemblage-level relative abundances in the 21st century. We use an established relationship linking ant abundance and their colour and size traits to temperature and UV-B to predict future abundance changes. We also predict future temperature driven range shifts and use these to alter the available species pool for our trait-mediated abundance predictions. We do this across three continents under a low greenhouse gas emissions scenario (RCP2.6) and a business-as-usual scenario (RCP8.5). Under RCP2.6, predicted changes to ant assemblages by 2100 are moderate. On average, species richness will increase by 26%, while species composition and relative abundance structure will be 26% and 30% different, respectively, compared with modern assemblages. Under RCP8.5, however, highland assemblages face almost a tripling of species richness and compositional and relative abundance changes of 66% and 77%. Critically, we predict that future assemblages could be reorganized in terms of which species are common and which are rare: future highland assemblages will not simply comprise upslope shifts of modern lowland assemblages. These forecasts reveal the potential for radical change to montane ant assemblages by the end of the 21st century if temperature increases continue. Our results highlight the importance of incorporating trait-environment relationships into future biodiversity predictions. Looking forward, the major challenge is to understand how ecosystem processes will respond to compositional and relative abundance changes.

Evaluation of potential evapotranspiration in the Weihe River Basin based on statistical downscaling

The Hargreaves method of using the average temperature (Tav) was used to calibrate the estimation of potential evapotranspiration (PE) for daily meteorological data of 35 weather stations from 1951 to 2015 in the Weihe River Basin and a statistical downscaling model was applied to downscale the Hadley Centre Sea-Atmosphere Coupled Model (HadCM3) output data to each station. The future temporal and spatial variations of temperature and evapotranspiration under different climate change scenarios were evaluated for the periods of 2016–2039, 2040–2069, and 2070–2099. The results show that the downscaling method is well suited for estimating the PE and that the PE in the Weihe River Basin is larger in May–July and smaller in autumn and winter. The mean annual temperature and annual PE exhibit an increasing trend for the high greenhouse gas emission scenario (RCP8.5) and low greenhouse gas emissions scenario (RCP4.5) and the magnitude of increase is greater for the RCP8.5 scenario. Greater increases in the PE were mainly distributed in the south of the Weihe River, the upper reaches of the Beiluo River, and the middle reaches of the Jinghe River, whereas most of the northern reaches of the Weihe River exhibited smaller changes that were located in the lower reaches of the Jing River. The regional distribution of the PE is consistent with the temperature changes. This study provides the basis for regional water resource management planning.

Simulating Climate Change Induced Thermal Stress in Coldwater Fish Habitat Using SWAT Model

Climate studies have suggested that inland stream temperatures and average streamflows will increase over the next century in New England, thereby putting aquatic species sustained by coldwater habitats at risk. This study uses the Soil and Water Assessment Tool (SWAT) to simulate historical streamflow and stream temperatures within three forested, baseflow-driven watersheds in Rhode Island, USA followed by simulations of future climate scenarios for comparison. Low greenhouse gas emission scenarios are based on the 2007 International Panel on Climate Change Special Report on Emissions Scenarios (SRES) B1 scenario and the high emissions are based on the SRES A1fi scenario. The output data are analyzed to identify daily occurrences where brook trout (Salvelinus fontinalis) are exposed to stressful events, defined herein as any day where Q25 or Q75 flows occur simultaneously with stream temperatures exceeding 21 °C. Results indicate that under both high- and low-emission greenhouse gas scenarios, coldwater fish species such as brook trout will be increasingly exposed to stressful events. The percent chance of stressful event occurrence increased by an average of 6.5% under low-emission scenarios and by 14.2% under high-emission scenarios relative to the historical simulations.

The Greenhouse Gas Footprint of China's Food System: An Analysis of Recent Trends and Future Scenarios

SummaryFood chain systems (FCSs), which begin in agricultural production and end in consumption and waste disposal, play a significant role in China's rising greenhouse gas (GHG) emissions. This article uses scenario analysis to show China's potential trajectories to a low‐carbon FCS. Between 1996 and 2010, the GHG footprint of China's FCSs increased from 1,308 to 1,618 megatonnes of carbon dioxide equivalent (Mt CO2‐eq), although the emissions intensity of all food categories, except for aquatic food, recorded steep declines. We project three scenarios to 2050 based on historical trends and plausible shifts in policies and environmental conditions: reference scenario; technology improvement scenario; and low GHG emissions scenario. The reference scenario is based on existing trends and exhibits a large growth in GHG emissions, increasing from 1,585 Mt CO2‐eq in 2010 to 2,505 Mt CO2‐eq in 2050. In the technology improvement scenario, emissions growth is driven by rising food demand, but that growth will be counterbalanced by gains in agricultural technology, causing GHG emissions to fall to 1,413 Mt CO2‐eq by 2050. Combining technology improvement with the shift to healthier dietary patterns, GHG emissions in the low GHG emissions scenario will decline to 946 Mt CO2‐eq in 2050, a drop of 41.5% compared with the level in 2010. We argue that these are realistic projections and are indeed indicative of China's overall strategy for low‐carbon development. Improving agricultural technology and shifting to a more balanced diet could significantly reduce the GHG footprint of China's FCSs. Furthermore, the transition to a low‐carbon FCS has potential cobenefits for land sustainability and public health.

Carbon, nitrogen, and water response to climate and land use changes in Pennsylvania during the 20th and 21st centuries

Future climate projections indicate that Pennsylvania will get significantly warmer and wetter due to continued increases in atmospheric greenhouse gas (GHG) concentrations. Using the Terrestrial Ecosystem Model version Hydro2 (TEM-Hydro2), this study explores the effect of different climate and land use scenarios on carbon, nitrogen, and water dynamics during the 20th and 21st centuries. TEM-Hydro2 runs are forced by historical 20th century climate data and by 21st century climate projections from the NCAR CCSM3.0 IPCC A2 and B1 scenarios, a relatively high and low GHG emissions scenario, respectively. Regrowing forests are the only ecosystem with positive Net Carbon Exchange (NCE) and sequestered more than 12,000gCm−2 during the 20th century. The highest rates of leaching of dissolved inorganic nitrogen (DIN) occurred in fertilized croplands in the 20th century. Twenty first century runoff increases by 30% in the A2 scenario and 20% in the B1 scenario, but DIN leaching only increases in the A2 scenario. DIN leaching depends upon both runoff and available inorganic nitrogen, which decreases due to high productivity and enhanced plant nitrogen uptake. The effect of increasing urbanization in the 21st century is to reduce NCE by about 34% in both climate scenarios, while water runoff increases by 5% and DIN leaching decreases by 17%. The reduced leaching is the result of converting agricultural land to suburban areas, which are a combination of turflawn and forests, both of which have lower leaching rates than croplands or pastures. Incorporating realistic forest stand age substantially increases the NCE but has little effect on runoff or DIN leaching. Maize yields decrease in the A2 scenario due to the excessive leaching, but increase in the B1 scenario. These results illustrate why it is important to include scenarios of both GHG emissions and realistic land use changes in model projections of the regional impacts of climate change in the 21st century.