Tendencies in the dynamics of harvested northern fur seal (Callorhinus ursinus) population on the Tyulenii Island have been analyzed in detail. The results show that retardation of reproduction (decrease in the numbers of pups) and decline in the survival of young females (up to 3 years of age) by the late 1980s resulted in a reduction of the total number of females and a significant increase in the proportion of older females. This tendency changed during the later observation period (after 1988–1989) due to increase in the survival of young females: the female population has gradually recovered, with the proportion of young females increasing at the expense of old females (aged over 10 years). The age composition of males has also changed: the proportion of young animals has decreased, while that of large mature males (bulls) has increased. Moreover, the number of bulls continues to increase and has already exceeded the level that formerly provided for the well-being of the population. This, a paradoxical situation has arisen: the numbers of females and bulls are increasing, whereas pup production remains at a low level.
Russian Journal of Ecology - Abstract—The study of the effect of mycorrhiza symbiosis on the transformation of carbon and nitrogen compounds in soils is important in view of the necessity to... 相似文献
Russian Journal of Ecology - Temporal and spatial variations of phytoplankton community in Lake Erhai were investigated from May 2010 to April 2011. A total of 124 species belonging to 8 phyla and... 相似文献
This paper investigates multi-stakeholder arrangements initiated by businesses and NGOs from the North that aim to enhance a more sustainable agricultural production at specific localities in Southern countries. We aim to better understand the search for concerted action in multi-actor arrangements. Therefore, this paper presents a diagnostic framework with three strategic challenges the partnership projects are facing: linking global economic objectives to local needs, values and interests; bridging public and private interests and responsibilities; and seeking trade-offs between social, environmental and economic values. Starting from the partnerships’ Theory of Change, this diagnostic framework is applied to comparative case studies of partnership projects in the cocoa sector in Indonesia, which are part of a Northern-based public–private partnership to improve farmers’ prospective. It is concluded that the economic reality faced by the farmers differs from that of the Northern actors; collaboration with governments is difficult because of different organizational cultures; and the partnership projects underestimate the strength of vested social relations the smallholders are part of. Overall, the initiators of the partnerships seem to work with a too restricted economic interpretation of the local reality. 相似文献
The aim of the study is to assess the agricultural drought risk condition in the context of global climate change in the western part of Bangladesh that covers about 45% area of the country for the period of 1960–2011. Drought Index (DI) and Drought Hazard Index (DHI) have been calculated by Markov Chain analysis and that of Drought Vulnerability Index (DVI) from socioeconomic and physical indicators. The DI values show that the northern part in general is more drought-prone, having less crops prospect, whereas the southern part is less drought-prone with high crop potentiality. The probability of extreme drought occurrence increases in recent decades in some parts as a result the drought events become more frequent in the areas. The DHI ranges from 15 to 32, and northern part suffers from more extreme drought hazards than that of southern part. DVI also indicates that northern part is exposed to high to very high drought vulnerability as higher percentage of illiterate people are involved in agricultural practices and high percentage of irrigation to cultivable land, but southern part exposed to moderate to low vulnerability because of low values of vulnerability indicators. Finally, agricultural drought exists at high risk condition in northern part and low in southern parts and 21.63, 26.54 and 29.68% of the area poses very high, high and moderate risk, respectively. So, immediate adaptation measures are needed keeping in mind climate features like rainfall and temperature variability, drought risk and risk ranking to make viable adaptation measures. 相似文献
Prawn aquaculture industry is one of the developing economic activities in the Philippines. Generally, a wide range of microalgae typically grow and proliferate in many aquaculture ponds. However, certain species of microalgae have the ability to form harmful algal blooms (HABs) which often bring damaging consequences to the aquaculture industry, food safety, and the environment. The study aims to identify and characterize the composition of microalgae (particularly Cyanophyta) that are capable of forming HABs in selected freshwater prawn culture ponds in Central Luzon, Philippines, using morphological, ultrastructural, and molecular characterizations. From water samples collected in ten selected ponds across Central Luzon (Bulacan, Nueva Ecija, Pampanga, Tarlac, and Zambales), potential HAB formers such as Oscillatoria agardhii, O. princeps, Microcystis aeruginosa, and M. wesenbergii were observed to have occurred mostly, while Anabaena circinalis was only observed in one site. Both morphological and ultrastructural methods brought upon some challenges and limitations while molecular methods using 16S rRNA gene and phylogenetic analysis which were optimized in this study offered better and more efficient ways of identification and were helpful in resolving genus-level and species-level relationships. The influence of physicochemical properties of pond water, especially nutrient levels (nitrate, nitrite, and orthophosphate) on the occurrence of these cyanobacteria was also analyzed. As a pioneering study on freshwater HABs in aquaculture ponds in the country, results of the study can provide information to improve the knowledge in bloom occurrence and prediction, and to develop freshwater HAB prevention and control methods. 相似文献
Drought in the northern part of Cyprus has become a recurrent phenomenon. In the last few decades, Cyprus has experienced significantly severe drought events occurring periodically, and this trend is now continuing. With rainfall distribution varying considerably across the region and frequent drought conditions, the water resources, agriculture, economy and the environment have been adversely affected. This study aims to investigate spatial–temporal characteristic of drought using Standardized Precipitation Index (SPI) at multiple timescales (3, 6 and 12 months). Monthly time series of 36 years (1977–2013) rainfall data from nine weather stations are used to derive SPI values. Based on different drought categories, this study focuses on propagation of drought from one timescale to another and estimating critical rainfall values during moderate, severe and extreme drought conditions. The analysis revealed that there is a strong correlation among different timescales in detecting drought events. On average, 79 and 78% of 3-month timescale drought propagated into 6- and 12-month drought events, respectively, while 90% of 6-month timescale drought events propagated into 12-month drought events. The derived critical rainfall value for extreme droughts over a 12-month timescale was less than 255 mm/year in the town of Alsancak, while for Guzelyurt, a major citrus growing city, this figure was less than 135 mm/year. The results are validated through drought events detected at various regions of the Mediterranean basin and local flood occurrences during the wet periods and decline in water tables at drought seasons. 相似文献
This paper tests the hypothesis that relocation of pig production within the EU27 can reduce the external costs of nitrogen (N) pollution. The external cost of pollution by ammonia and nitrate from agriculture in the European Union (EU27) in 2008 was estimated at 61–215 billion € (0.5 to 1.8% of the GDP). Per capita it ranged from more than 1000 € in north-west EU27 to 50 € in Romania. The average contribution of pig production was 15%. Using provincial data (224 NUTS2 regions in EU27), the potential reduction of external N cost by relocation of pig production was estimated at 14 billion € (10% of the total). Regions most eligible for decreasing the pig stock were in western Germany, Flemish region, Denmark, the Netherlands and Bretagne, while Romania is most eligible for increasing pig production. Relocating 20 million pigs (13% of the total EU stock) decreased average external costs per capita from 900 to 785 € in the 13 NUTS2 regions where pigs were removed and increased from 69 to 107 € in 11 regions receiving pigs. A second alternative configuration of pig production was targeted at reducing exceedance of critical N deposition and closing regional nutrient cycles. This configuration relocates pigs within Germany and France, for example from Bretagne to Northern France and from Weser-Ems to Oberbayern. However, total external cost increases due to an increase of health impacts, unless when combined with implementation of best N management practices. Relocation of the pig industry in the EU27 will meet many socio-economic barriers and realisation requires new policy incentives. 相似文献
Despite the often mentioned environmental benefits associated with transition from fossil fuels to renewable energy sources, their use for electricity production has non-negligible negative environmental impacts. The most commonly mentioned in surveys concern different types of landscape impacts, impacts on the fauna and flora, and noise. These impacts differ by size and location of plants, and by source of energy, rendering the policy decision complex. In addition, there are other welfare issues to take into consideration, as positive and negative environmental impacts are not evenly distributed among population groups. This paper proposes to compare the welfare impacts of renewable energy sources controlling for the type of renewable as well as the specific environmental impact by source. To this end, two discrete-choice experiments are designed and applied to a national sample of the Portuguese population. In one case, only individual negative impacts of renewables are used, and in another case, the negative impacts interact with a specific source. Results show the robustness of discrete-choice experiments as a method to estimate the welfare change induced by the impacts of renewable energy sources. Overall, respondents are willing to pay to reduce the environmental impacts, thus making compensation for local impacts feasible. Moreover, the estimations reveal that respondents are significantly sensitive to the detrimental environmental effects of specific renewable energy sources, being willing to pay more to use these sources of energy relative to others. 相似文献