Nakayama T.,Japan National Institute of Environmental Studies
River Research and Applications | Year: 2010
The Kushiro Mire in subarctic Japan has significantly reduced in size because of the complex interaction of many processes, including snowmelt runoff, sediment transport and vegetation dynamics. This study uses a coupled integrated catchment-based eco-hydrology model with a mass transport process (NICE-MASS) to investigate the influence of hydrologic and geomorphic changes on the Kushiro Mire. Coefficients of the sediment-rating curve in the snowmelt runoff are very different from those in the snow-free period. This empirical relation shall underestimate the observed suspended sediment (SS) concentration in the snowmelt period, indicating a difference in runoff mechanisms between the two periods and the necessity of a process-based model. The simulation model reproduced well the spatial distribution of elevation aggradations by sediment deposits from rivers flowing into the mire. NICE-MASS clarified that river channelization works carried out in the past resulted in groundwater degradation and drying phenomenon in the downstream area because of increased sedimentation and a decrease of seepage infiltration from the river to the aquifer. It is assumed that these hydrologic and geomorphic changes are closely related to the invasion of alder (Alnus japonica) into the mire. The occupation rate of alder is positively correlated with groundwater degradation relative to the ground surface. The model simulation derived by addition of this limiting factors related to submerged depth is important for prediction of vegetation succession when devising future policies for restoration of meandering river channels. © 2009 John Wiley & Sons, Ltd.
Hongo C.,Japan National Institute of Environmental Studies
Quaternary Science Reviews | Year: 2012
The geological record of key coral species that contribute to reef formation and maintenance of reef ecosystems is important for understanding the ecosystem response to global-scale climate change and anthropogenic stresses in the near future. Future responses can be predicted from accumulated data on Holocene reef species identified in drillcore and from data on raised reef terraces. The present study analyzes a dataset based on 27 drillcores, raised reef terraces, and 134 radiocarbon and U-Th ages from reefs of the Northwest Pacific, with the aim of examining the role of key coral species in reef growth and maintenance for reef ecosystem during Holocene sea-level change. The results indicate a latitudinal change in key coral species: arborescent Acropora (Acropora intermedia and Acropora muricata) was the dominant reef builder at reef crests in the tropics, whereas Porites (Porites australiensis, Porites lutea, and Porites lobata) was the dominant contributor to reef growth in the subtropics between 10,000 and 7000 cal. years BP (when the rate of sea-level rise was 10 m/ka). Acropora digitifera, Acropora hyacinthus, Acropora robusta/. A. abrotanoides, Isopora palifera, Favia stelligera, and Goniastrea retiformis from the corymbose and tabular Acropora facies were the main key coral species at reef crests between 7000 and 5000 cal. years BP (when the rate of sea-level rise was 5 m/ka) and during the following period of stable sea-level. Massive Porites (P. australiensis, P. lutea, and P. lobata) contributed to reef growth in shallow lagoons during the period of stable sea level. Key coral species from the corymbose and tabular Acropora facies have the potential to build reefs and maintain ecosystems in the near future under a global sea-level rise of 2-6 m/ka, as do key coral species from the arborescent Acropora facies and massive Porites facies, which show vigorous growth and are tolerant to relatively deep-water, low-energy environments. However, these species are likely to experience severe mortality in upcoming decades due to natural and anthropogenic stresses. Consequently, this damage will lead to a collapse in reef formation and the maintenance of reef ecosystems in the near future. This study emphasizes the need for research into the conservation of key coral species. © 2012 Elsevier Ltd.
Bagan H.,Japan National Institute of Environmental Studies |
Yamagata Y.,Japan National Institute of Environmental Studies
Remote Sensing of Environment | Year: 2012
Combining remote sensing data and socio-economic data to quantitatively analyze urban growth is a topic growing in importance. We used square grid cells to investigate the spatial and temporal dynamics of urban growth in the Tokyo, Japan, metropolitan area by using remote sensing imagery from 1972 to 2011 and census population data from 1970 to 2010. First, we used the subspace classification method to produce land-cover maps by using Landsat images from 1972, 1987, 2001, and 2011. Next, we integrated the land-cover maps with basic grid cell maps (using the standard 1km 2 grid cell system of Japan) to represent the proportion of each land-cover category within each 1km 2 grid cell area. Finally, we combined the proportional land-cover maps and population census data to investigate the relationship between land-cover changes and population density change based on grid cells. By using grid cells it is straightforward to (i) integrate remote sensing, geographic information system (GIS), and statistical data within the cells; (ii) quantify land-cover changes in terms of the percentage of area affected and rates of change and compare them with population census data; and (iii) analyze the spatial-temporal dynamics of urban growth patterns. Between 1972 and 2011 the rapid expansion of the urban area was accompanied by extensive shrinking of the agricultural area around the new settlements. As a result, the urban growth rate exceeded the population growth rate by more than a factor of 2.6. We used the grid cells to investigate the spatial relationship between the changes of land-cover classes and population density change, and then calculated the correlation coefficients of land-cover categories and population density changes for 3 intervals between 1972 and 2011 (1972-1987, 1987-2001, and 2001-2011). The results showed that the urban/built-up density decreased in the metropolitan inner core as the city center experienced depopulation. Spatial correlation analysis showed a strong positive correlation between urban expansion and population density change (r=0.59), and that urban expansion was strongly negatively correlated with cropland change (r=-0.77). The results also demonstrated that grid cells allow remote sensing and statistics data to be combined, improving the knowledge, understanding, and analysis of urban dynamics. © 2012 Elsevier Inc.
Peregon A.,Japan National Institute of Environmental Studies |
Yamagata Y.,Japan National Institute of Environmental Studies
Remote Sensing of Environment | Year: 2013
The estimates of above-ground forest biomass (AGB) in Northern Eurasia are highly uncertain, despite the global importance of AGB for ecosystem services and its role as carbon stores. In this paper, we demonstrate the potential of ALOS/PALSAR (Advanced Land Observing Satellite/Phased Array L-band Synthetic Aperture Radar), for the estimation of AGB in the range of 10-190tons (dry matter)/ha in mixed and deciduous forests at the southern edge of the boreal region in Western Siberia. Various regression models were tested to determine the relationship between forest biomass derived from field measurements and radar backscatter. The best results were obtained using HV-polarized backscatter with the Water Cloud model, giving estimation errors in terms of root mean square errors (RMSE) between 25% and 32% of the mean biomass, and coefficient of determination (R2) between 0.35 and 0.49 for the whole range of SAR backscatter used in the analysis. The method displayed a higher prediction accuracy with RMSE of 15%, and the R2 between 0.55 and 0.72 when restricted to SAR backscatter (σ0)<-12.6dB where the model was clearly defined. The SAR-based estimates offer a potential of rapid, high resolution and low cost mapping of the lower biomass woody vegetation (sparse or young forests on shallow peat) in Siberia, the area where more accurate national or large scale forest inventories hardly exist. © 2013 Elsevier Inc.
Oda T.,Japan National Institute of Environmental Studies |
Maksyutov S.,Japan National Institute of Environmental Studies
Atmospheric Chemistry and Physics | Year: 2011
Emissions of CO2 from fossil fuel combustion are a critical quantity that must be accurately given in established flux inversion frameworks. Work with emerging satellite-based inversions requires spatiotemporally-detailed inventories that permit analysis of regional natural sources and sinks. Conventional approaches for disaggregating national emissions beyond the country and city levels based on population distribution have certain difficulties in their application. We developed a global 1 kmÃ-1 km annual fossil fuel CO2 emission inventory for the years 1980ĝ€"2007 by combining a worldwide point source database and satellite observations of the global nightlight distribution. In addition to estimating the national emissions using global energy consumption statistics, emissions from point sources were estimated separately and were spatially allocated to exact locations indicated by the point source database. Emissions from other sources were distributed using a special nightlight dataset that had fewer saturated pixels compared with regular nightlight datasets. The resulting spatial distributions differed in several ways from those derived using conventional population-based approaches. Because of the inherent characteristics of the nightlight distribution, source regions corresponding to human settlements and land transportation were well articulated. Our distributions showed good agreement with a high-resolution inventory across the US at spatial resolutions that were adequate for regional flux inversions. The inventory can be extended to the future using updated data, and is expected to be incorporated into models for operational flux inversions that use observational data from the Japanese Greenhouse Gases Observing SATellite (GOSAT). © 2011 Authors.
Ito A.,Japan National Institute of Environmental Studies |
Ito A.,Japan Agency for Marine - Earth Science and Technology
Global Change Biology | Year: 2011
Net primary productivity (NPP) is one of the most important ecosystem parameters, representing vegetation activity, biogeochemical cycling, and ecosystem services. To assess how well the scientific community understands the biospheric function, a historical meta-analysis was conducted. By surveying the literature from 1862 to 2011, I extracted 251 estimates of total terrestrial NPP at the present time (NPP T) and calculated their statistical metrics. For all the data, the mean±standard deviation and median were 56.2±14.3 and 56.4PgCyr -1, respectively. Even for estimates published after 2000, a substantial level of uncertainty (coefficient of variation by ±15%) was inevitable. The estimates were categorized on the basis of methodology (i.e., inventory analysis, empirical model, biogeochemical model, dynamic global vegetation model, and remote sensing) to examine the consistency among the statistical metrics of each category. Chronological analysis revealed that the present NPP T estimates were directed by extensive field surveys in the 1960s and 1970s (e.g., the International Biological Programme). A wide range of uncertainty remains in modern estimates based on advanced biogeochemical and dynamic vegetation models and remote-sensing techniques. Several critical factors accounting for the estimation uncertainty are discussed. Ancillary analyses were performed to derive additional ecological and human-related parameters related to NPP. For example, interannual variability, carbon-use efficiency (a ratio of NPP to gross photosynthesis), human appropriation, and preindustrial NPP T were assessed. Finally, I discuss the importance of improving NPP T estimates in the context of current global change studies and integrated carbon cycle research. © 2011 Blackwell Publishing Ltd.
Fukasawa K.,Japan National Institute of Environmental Studies
Proceedings. Biological sciences / The Royal Society | Year: 2013
Invasive species and anthropogenic habitat alteration are major drivers of biodiversity loss. When multiple invasive species occupy different trophic levels, removing an invasive predator might cause unexpected outcomes owing to complex interactions among native and non-native prey. Moreover, external factors such as habitat alteration and resource availability can affect such dynamics. We hypothesized that native and non-native prey respond differently to an invasive predator, habitat alteration and bottom-up effects. To test the hypothesis, we used Bayesian state-space modelling to analyse 8-year data on the spatio-temporal patterns of two endemic rat species and the non-native black rat in response to the continual removal of the invasive small Indian mongoose on Amami Island, Japan. Despite low reproductive potentials, the endemic rats recovered better after mongoose removal than did the black rat. The endemic species appeared to be vulnerable to predation by mongooses, whose eradication increased the abundances of the endemic rats, but not of the black rat. Habitat alteration increased the black rat's carrying capacity, but decreased those of the endemic species. We propose that spatio-temporal monitoring data from eradication programmes will clarify the underlying ecological impacts of land-use change and invasive species, and will be useful for future habitat management.
Yamagata Y.,Japan National Institute of Environmental Studies |
Seya H.,Japan National Institute of Environmental Studies
Applied Energy | Year: 2013
Designing a future smart city (FSC) that copes with the reduction of CO2 has become one of the urgent tasks of the next 20years. One promising approach to achieve FSC is to combine appropriate land use (compact city with energy efficient buildings and photovoltaic panels (PVs)), transportation (electric vehicles (EVs) and public transportation system) and energy systems (smart grid systems), because of the interaction between these elements. However, there are few models which simulate these elements in an integrated manner. This paper presents the concept of the integrated model, and shows the land use-energy part of the model created for the Tokyo metropolitan area, which is the largest Mega city in the world. Firstly, a spatially explicit land use model (urban economic model) is constructed for the study area, and the model is calibrated using existing statistical data. Secondly, possible future compact/dispersion city scenarios for the year 2050 are created using the model. Thirdly, intra-day dynamics (hourly) of electricity demand and supply from PVs, which is assumed to be installed to the roofs of all detached houses in the study area, under two urban scenarios is simulated. The obtained results suggest that  "compact" urban form may contribute to the reduction of electricity demand from the residential sector, but  PV-supply under the scenario may also be reduced because of the decreased share of detached houses. Hence in the compact city scenario, it is important to discuss the effective use of vacant areas in suburbs, which may be used for large PV installations, or be re-vegetated to mitigate urban heat island effects. © 2013 Elsevier Ltd.
Kawashima Y.,Japan National Institute of Environmental Studies
Environmental Economics and Policy Studies | Year: 2014
This paper aims to assess Japan’s decision-making process to finalize its proposal for the Kyoto Protocol by comparing it to a similar decision in 1990–1992. The processes of the two periods are analyzed at both the international and domestic levels of decision making. At the domestic level, the process is divided into three areas—decision-making factors, the decision itself, and the process itself—to clarify the comparison.It is concluded that Japan’s decision in 1997 may have been effective in mediating between the United States and the EU for a short time, but not in the last phase of the negotiation when countries started bargaining toward an agreement. The process may also not be suitable if Japan wants to take the lead in the climate-change debate. To overcome these weaknesses it is necessary to make changes in the decision-making process to involve more domestic stakeholders in the process, and to strengthen the capacity of such stakeholders. © 2000, Springer Japan.
Dhakal S.,Japan National Institute of Environmental Studies
Current Opinion in Environmental Sustainability | Year: 2010
A large body of literature has been published on urban carbon emissions and management in the last few years. This paper searches for answers to two broad questions: what do we know about the GHG emissions from urbanization at multiple scales and what are the key opportunities to mitigate GHG from cities and their efficient governance? The review suggests that the quantification of urban contribution to global, regional and national GHGs are limited to few regions and for CO2 only. The GHG emissions of urban areas differ widely for the accounting methods, scope of GHGs, emission sources and urban definition, thus, making place-based comparisons difficult. The urban system has large indirect carbon flows across the administrative and agglomeration boundaries with important policy implications. We also observed that an integrated system perspective is needed in future studies to integrate all sources, sinks, and opportunities for infrastructure and technology for carbon management. In particular, the multiple benefit assessment of climate change mitigation in cities including the potentials for combined response to the mitigation and adaptation are necessary and the research related to efficient urban carbon governance by ascertaining who can influence the urban carbon mitigation by what extent is important. © 2010 Elsevier B.V.