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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. Source

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. Source

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. Source

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. Source

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. Source

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