首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 62 毫秒
1.
In this paper we develop a novel, comprehensive method for estimating the global human carrying capacity in reference to food production factors and levels of food consumption. Other important interrelated dimensions of carrying capacity such as energy, non-renewable resources, and ecology are not considered here and offer opportunities for future work. Use of grain production (rain-fed/irrigated), animal product production (grazing/factory farm), diet pattern (grain/animal products), and a novel water accounting method (demand/supply) based on actual water consumption and not on withdrawal, help resolve uncertainties to find better estimates. Current Western European food consumption is used as a goal for the entire world. Then the carrying capacity lies in the range of 4.5–4.7 billion but requiring agricultural water use increase by 450–530% to 4725–5480 km3, the range based on different estimates of available water. The cost of trapping and conveying such water, will run 4.5–13.5 trillion over 50 years requiring an annual spending increase of 150–400%, straining the developing world where most of the population increase is expected. We reconfirm estimates in the literature using a dynamic model. ‘Corner scenarios’ with extreme optimistic assumptions were analyzed using the reasoning support software system GLOBESIGHT. With a hypothetical scenario with a mainly vegetarian diet (grazing only with 5% animal product), the carrying capacity can be as high as 14 billion. Ecological deterioration that surely accompanies such a population increase would negatively impact sustainable population. Using our approach the impact of ecological damage could be studied. Inter- and intra-regional inequities are other considerations that need to be studied.  相似文献   

2.
农村人口转移及城市集群发展加速城镇化进程,把握农村人口转移趋势,导引农村人口有序转移是推动新型城镇化建设的关键。长株潭城市群一体化发展具有典型性和代表性,基于此,本文选择湖南省和长株潭城市群作为研究对象,探讨农村人口转移趋势及其空间指向。本文选择人口发展方程和回归分析两种常见的人口总量预测方法测算湖南省2016—2030年人口总量,比较测算结果发现人口发展方程虽然在年增长率的预设上具有一定的主观性,但在长期人口预测中表现出更好的适用性。在城镇化率预测上,Logistic增长模型具有广泛的适用性。因此本文选择人口发展方程和Logistic增长模型,预测湖南省和长株潭城市群2016—2030年的人口总量和城镇化率,在此基础上计算出人口城乡分布的大致状况,进而估算农村人口转移趋势。预测结果显示2016—2030年间,湖南省和长株潭城市群分别有大约980万和567万农村人口向城市转移,长株潭城市群城镇化率和农村人口转移进程均领先于湖南省平均水平,尤其是城市群中心城市。据此,可得出结论:城镇化进程中的城市群发展在推动农村人口转移中的作用突显,农村人口转移空间指向城市群集聚,即城市群是引领城镇化进程的空间经济主体形态,是农村人口转移的"牵引力",是农村人口转移空间指向的"内聚力"。同时,农村人口加快向城市群聚集的趋势也呼吁城市治理理念和治理模式的创新,智慧城市或是这一变革的最优方案。  相似文献   

3.
Will Limits of the Earth's Resources Control Human Numbers?   总被引:1,自引:1,他引:0  
The current world population is 6 billion people. Even if we adopted a worldwide policy resulting in only 2.1 children born per couple, more than 60 years would pass before the world population stabilized at approximately 12 billion. The reason stabilization would take more than 60 years is the population momentum – the young age distribution – of the world population. Natural resources are already severely limited, and there is emerging evidence that natural forces already starting to control human population numbers through malnutrition and other severe diseases. At present, more than 3 billion people worldwide are malnourished; grain production per capita has been declining since 1983; irrigation per capita has declined 12% during the past decade; cropland per capita has declined 20% during the past decade; fish production per capita has declined 7% during the past decade; per capita fertilizer supplies essential for food production have declined 23% during the past decade; loss of food to pests has not decreased below 50% since 1990; and pollution of water, air, and land has increased, resulting in a rapid increase in the number of humans suffering from serious, pollution-related diseases. Clearly, human numbers cannot continue to increase.  相似文献   

4.
The present research investigated the relationship between nitrate–nitrogen (NO3–N) in river water and the land use/land cover (hereafter, land use) in the Teshio River watershed located in northern Hokkaido island to understand the effect of human activities such as agriculture, forestry, industry, and urbanization in the drainage basin on the river ecosystem quality and services. River water was sampled at nine points seasonally during a 2-year period and the nutrients concentration was measured. Land use profiles were estimated at two spatial scales, riparian and sub-catchment, for each sampling station. The spatial pattern of water quality in the Teshio River showed increased NO3–N levels associated with agriculture and urban expansion, and forest reduction in the watershed. Land use at the riparian scale closely reflected that at the sub-catchment scale, which masked the unique riparian buffer effect on the river water condition. The increased agricultural and reduced forest area in the riparian zone, especially in the upper middle reach, could be a possible reason for a decline of ecosystem service for the provisioning of clean water and habitat for aquatic organisms. Measures towards sustainable and more nature-friendly agricultural management are necessary in the area to protect the Teshio River ecosystem and its ecosystem services.  相似文献   

5.
This paper assesses sea-level rise impacts on Africa at continental and national scales including the benefits of mitigation and of applying adaptation measures, considering four scenarios of global mean sea-level rises from 64 to 126 cm in the period of 1995–2100. We find that in 2100, 16–27 million people are expected to be flooded per year, and annual damage costs range between US5 and US 5 and US 9 billion, if no adaptation takes place. Mitigation reduces impacts by 11–36%. Adaptation in the form of building dikes to protect against coastal flooding and nourishing beaches to protect against coastal erosion reduces the number of people flooded by two orders of magnitude and cuts damage costs in half by 2100. Following such a protection strategy would require substantial investment. First, Africa’s current adaptation deficit with respect to coastal flooding would need to be addressed. DIVA suggests that a capital investment of US300 billion is required to build dikes adapted to the current surge regime and US 300 billion is required to build dikes adapted to the current surge regime and US 3 billion per year for maintenance. In addition, between US2 and US 2 and US 6 billion per year needs to be spent on protecting against future sea-level rise and socio-economic development by 2100. This suggests that protection is not effective from a monetary perspective but may still be desirable when also taking into account the avoided social impact. We conclude that this issue requires further investigation including sub-national scale studies that look at impacts and adaptation in conjunction with the development agenda and consider a wider range of adaptation options and strategies.  相似文献   

6.
It has become increasingly evident over the past several decades that there is a growing tension between two seemingly irreconcilable trends: (1) moderate to conservative demographic projections that world population size could easily reach 9 billion (or more) by the mid-to-late twenty-first century; and (2) prudent and increasingly reliable scientific estimates suggesting that the Earth's long-term sustainable carrying capacity (at an 'adequate to comfortable' standard of living) may not be much greater than 2–3 billion. I therefore argue that it is now time – indeed, past time – to develop and implement a set of well-conceived, clearly articulated, broadly equitable and internationally coordinated sociopolitical initiatives that go beyond merely slowing the growth – or even the stabilization – of global human numbers. After summarizing a number of 'inescapable realities' that the human species must soon confront, and notwithstanding the considerable difficulties involved in establishing rational and defensible global population optimums, I conclude with several suggestions relevant to the next logical step: how best to bring about a very significant reduction in global population size over the next two to three centuries. To the extent that there is still time to choose whether this dramatic decrease will be under conscious control or essentially chaotic, these proposals are cautiously optimistic.  相似文献   

7.
Anthropogenic climate and land-use change are leading to irreversible losses of global biodiversity, upon which ecosystem functioning depends. Since total species' well-being depends on ecosystem goods and services, man must determine how much net primary productivity (NPP) may be appropriated and carbon emitted so as to not adversely impact this and future generations. In 2005, man ought to have only appropriated 9.72 Pg C of NPP, representing a factor 2.50, or 59.93%, reduction in human-appropriated NPP in that year. Concurrently, the carbon cycle would have been balanced with a factor 1.26, or 20.84%, reduction from 7.60 Gt C/year to 5.70 Gt C/year, representing a return to the 1986 levels. This limit is in keeping with the category III stabilization scenario of the Intergovernmental Panel for Climate Change. Projecting population growth to 2030 and its associated basic food requirements, the maximum HANPP remains at 9.74 ± 0.02 Pg C/year. This time-invariant HANPP may only provide for the current global population of 6.51 billion equitably at the current average consumption of 1.49 t C per capita, calling into question the sustainability of developing countries striving for high-consuming country levels of 5.85 t C per capita and its impacts on equitable resource distribution.  相似文献   

8.
In the mountainous regions of northern Laos, shifting cultivation, or slash-and-burn agriculture, is widely practiced. However, the crop–fallow rotation cycle is becoming shorter owing to forest conservation policies and population pressure, causing loss of productivity that deleteriously affects farmers’ livelihoods in the region. To investigate regional land use conditions, we have developed a method of identifying the crop–fallow rotation cycle from Landsat Thematic Mapper (TM) and Enhanced Thematic Mapper+ (ETM+) data. We assessed the impact of the identified cycle on plant production measured by Normalized Difference Vegetation Index (NDVI). The study site was an area in Luang Prabang Province. Using eight TM and ETM+ images acquired annually from 1995 to 2003, except for 1998, when cloud-free data were not collected, we classified land use in each year as crop or fallow by the presence of vegetation in the late dry season. Conformity with fallow age determined by field investigation was 69.1%. The cultivation frequency from 1995 to 2002 showed that 77,000 ha (17.3% of the study site) had not been used for cropping during the period, but 41,000 ha (9.2%) had been used every year. Of the study site, 129,000 ha (29.1%) was cultivated one or two times, 83,000 ha (18.7%) was three or four times, and 54,000 ha (12.2%) was five or six times. The NDVI of crops in November did not provide sufficient evidence to prove the assumption that a longer fallow period would result in better crop yields. Instead, the regeneration of fallow vegetation was evidenced by the higher NDVI values after longer fallow. More than 8 years would be needed to reach the same NDVI as forest. From the produced maps indicating fallow age and cultivation frequency, we found that areas with high potential for regeneration decreased as cultivation frequency increased. Areas near rivers were intensively used, and fallow length was accordingly short. Low-potential areas were found in the western basin of the Mekong River. This spatial information can be used to detect areas where biomass productivity is at high risk of deteriorating. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.  相似文献   

9.
An improved energy demand forecasting model is built based on the autoregressive distributed lag (ARDL) bounds testing approach and an adaptive genetic algorithm (AGA) to obtain credible energy demand forecasting results. The ARDL bounds analysis is first employed to select the appropriate input variables of the energy demand model. After the existence of a cointegration relationship in the model is confirmed, the AGA is then employed to optimize the coefficients of both linear and quadratic forms with gross domestic product, economic structure, urbanization, and technological progress as the input variables. On the basis of historical annual data from 1985 to 2015, the simulation results indicate that the proposed model has greater accuracy and reliability than conventional optimization methods. The predicted results of the proposed model also demonstrate that China will demand approximately 4.9, 5.6, and 6.1 billion standard tons of coal equivalent in 2020, 2025, and 2030, respectively.  相似文献   

10.
Between the tenth and twentieth century the population of Paris city increased from a few thousand to near 10 million inhabitants. In response to the growing urban demand during this period, the agrarian systems of the surrounding rural areas tremendously increased their potential for commercial export of agricultural products, made possible by a surplus of agricultural production over local consumption by humans and livestock in these areas. Expressed in terms of nitrogen, the potential for export increased from about 60 kg N/km2/year of rural territory in the Middle Ages, to more than 5,000 kg N/km2/year from modern agriculture. As a result of the balance between urban population growth and rural productivity, the rural area required to supply Paris (i.e. its food-print) did not change substantially for several centuries, remaining at the size of the Seine watershed surrounding the city (around 60,000 km2). The theoretical estimate of the size of the supplying hinterland at the end of the eighteenth century is confirmed by the figures deduced from the analysis of the historical city toll data (octroi). During the second half of the twentieth century, the ‘food-print’ of Paris reduced in size, owing to an unprecedented increase in the potential for commercial export associated with modern agricultural systems based on chemical N fertilization. We argue that analysing the capacity of territories to satisfy the demand for nitrogen-containing food products of local or distant urban population and markets might provide new and useful insights when assessing world food resource allocation in the context of increasing population and urbanization.  相似文献   

11.
This study focuses on analyses of greenhouse gas (GHG) emission reductions, from the perspective of interrelationships among time points and countries, in order to seek effective reductions. We assessed GHG emission reduction potentials and costs in 2020 and 2030 by country and sector, using a GHG emission reduction-assessment model of high resolution regarding region and technology, and of high consistency with intertemporal, interregional, and intersectoral relationships. Global GHG emission reduction potentials relative to baseline emissions in 2020 are 8.4, 14.7, and 18.9 GtCO2eq. at costs below 20, 50, and 100 $/tCO2eq., corresponding to +19, −2, and −7 %, respectively, relative to 2005. The emission reduction potential for 2030 is greater than that for 2020, mainly because many energy supply and energy-intensive technologies have long lifetimes and more of the current key facilities will be extant in 2020 than in 2030. The emission reduction potentials in 2030 are 12.6, 22.0, and 26.6 GtCO2eq. at costs below 20, 50, and 100 $/tCO2eq., corresponding to +19, −2, and −7 %, respectively, relative to 2005. The emission reduction potential for 2030 is greater than that for 2020, mainly because many energy supply and energy-intensive technologies have long lifetimes and more of the current key facilities will be extant in 2020 than in 2030. The emission reduction potentials in 2030 are 12.6, 22.0, and 26.6 GtCO2eq. at costs below 20, 50, and 100 /tCO2eq., corresponding to +33, +8, and −3 %, respectively, relative to 2005. Global emission reduction potentials at a cost below 50 $/tCO2eq. for nuclear power and carbon capture and storage are 2.3 and 2.2 GtCO2eq., respectively, relative to baseline emissions in 2030. Longer-term perspectives on GHG emission reductions toward 2030 will yield more cost-effective reduction scenarios for 2020 as well.  相似文献   

12.
Climatic disaster-induced migration and its effects on land exploitation of new settlements is a crucial topic that needs to be researched to better understand the impact of climate change and human adaptation. This paper focuses on the process and mechanism of migrant–reclamation in Northeast China in response to climatic disasters over the past 300 years. The research used comparative analysis of key interlinked factors in this response involving drought/flood events, population, cropland area, farmer revolts, administrations establishment, and land reclamation policies. It draws the following conclusions: (1) seven peaks of migrants–reclamation in Northeast China were evident, most likely when frequent climatic disasters happened in North China, such as the drought–flood in 1851–1859, drought in 1875–1877, and drought 1927–1929; (2) six instances of policy transformation adopted to cope with extreme climatic events, including distinctive examples like changing to a firm policy prohibiting migration in 1740 and a subsequent lifting of that prohibition in 1860; and (3) the fast expansion of the northern agricultural boundary since the middle of the nineteenth century in this area benefited from a climate change trend from a cold period into a warm period. Altogether, over the past 300 years, extreme climatic disasters in North China have deepened the contradiction between the limited land resources and the rapidly increasing population and have resulted in migration and reclamation in Northeast China. Climate, policy, and reclamation constructed an organic chain of response that dominated the land use/cover change process of Northeast China.  相似文献   

13.
Yang  Liyang  Wu  Ying  Zhang  Jing  Liu  Sumei  Deng  Bing 《Regional Environmental Change》2011,11(3):707-714
Organic geochemical proxies (OC, OC/TN, δ13C, and lignin oxidation products) were measured in a 271 cm long sediment core collected from central Jiaozhou Bay, northern China, to study the response of terrestrial and marine organic carbon burials to the surrounding urbanization. Terrestrial organic carbon content was constantly low from the bottom of the core to ~150 cm depth, indicating a stable and low level of terrestrial input before urbanization. Thereafter, it increased up to ~20 cm depth, suggesting that increased human activities and land-use changes during urbanization likely enhanced the flux of terrestrial organic carbon to the bay. Overall, 5–38% of the total organic carbon was terrigenous, which was derived from a mixture of woody and non-woody angiosperms and moderately degraded. Marine organic carbon content did not increase notably during urbanization. It increased from the bottom of the core to ~180 cm and stayed at high levels until it decreased in the top 20 cm. It was affected by multiple factors, including grain size and nutrient composition. These results demonstrate the different influences of urbanization on terrestrial and marine organic carbon cycles and suggest the importance of discriminating between these two organic carbon pools in the reconstruction of their historical changes.  相似文献   

14.
The industrial sector is usually the largest economy sector for carbon emissions in many countries, which made it the sector with greatest potential for carbon reduction although the process duration might be very long. Studying the potential of industrial emission reduction has great significance in estimating the carbon emission peak of China on the one hand, and adjusting its strategy in international climate change negotiations. By employing the economic accounting method, this article estimates the emission reduction potential of China’s Industrial sector for the period of 2010–2050. It reveals that, taking 2030 as the year when the emission reaches the peak, the total reduction can be 8.38 billion tons (bts) for the period of 2010–2030, with 3.12 bts from structural reduction while 5.26 bts from intensity reduction. Afterwards, reduction will continue with a total amount of 6.59 bts for the period of 2030–2050, where the structural reduction accounts for 2.47 bts, and intensity reduction 4.115 bts. If both industrial and energy consumption structures are improved during the above period, the reduction potential can be even greater, e.g. the emission peak can arrive five years earlier (in the year of 2025) and the peak value can decline by about 8% as compared to the original estimation. Reviewing the trajectory of emission changes in developed countries indicates that the industry sector can contribute to the overall reduction targets through the dual wheels of structural reduction and intensity reduction, even beyond the emission peak. This article concludes with the following policy suggestions. (1) Our estimation on the emission peak of the industrial sector suggests that China should avoid any commitment earlier than 2030 on the timeline of the overall emission peak; (2) the great potential of industrial emission reduction can improve the situation of China in climate change negotiation, where the intensity reduction can serve as an important policy option. (3) Reduction potential can be further enhanced through technology advancement, which requires furthering of market oriented reforms and improvement of institutional design. (4) To secure the reduction effects of the industrial structure adjustment, the balanced development among different regions should be encouraged in order to avoid the reverse adjustment caused by industrial transferring. (5) International cooperation promoting the application and development of industrial emission reduction technologies, including carbon capture, utilization and storage, should be encouraged.  相似文献   

15.
经济发展中人口城市化与经济增长相关分析比较研究   总被引:32,自引:1,他引:31  
本文利用OECD国家和世界其他主要国家的人口城市化与经济增长的数据,对人口城市化与经济增长进行了相关分析,以揭示人口城市化与经济增长的关系模式。判断得到我国人口城市化仍处于低增长水平的线性阶段,城市化水平,大大滞后于经济发展水平;大大落后于发达国家同等经济水平时的城市化水平,经济发展与人口城市化的相互促进作用还没有得到充分发挥。为此,文章提出了要加快我国城市化发展,超前于经济的增长是一个理性选择。  相似文献   

16.
对中国农村人口问题有两种不弼的理论主张和政策导向:一是城市化。二是城镇化。由于“城镇化”模型的基本结构是:“城镇化”=“城市化“ “乡镇化”其框架所明含的“乡镇化”倾向必然存在下述显著弊端:选择了不可能从根本上解决农民问题的农村化乡镇框架;将会对中国现代化进程中的农村人口压力产生短期缓解而长期困抗的不良后果;将会导致资泊配置的浪费;将会导致后果严重的长期环境污染;违背了农村人口的最优化理性选择;乡镇企业存在和发展主妻理由已经基本上不复存在。中国农村人口目艇t性发展的战略框架是:必须和只能走新型城市化道路;尽快理智而清晰地确立城市化的惟一发展战略;尽快建构“教育化 城市化”的提升国民素质的社会发展框架;尽快把县级城市作为中国城市化发展战略的根本空间选择和主要社会载体。中国在这方面具有广阔的制度创新空间。应尽快通过镧度现代化而开辟出一条农民市民化和人口现代化的制度通道。  相似文献   

17.
BackgroundMotor vehicle emissions contribute nearly a quarter of the world's energy-related greenhouse gases and cause non-negligible air pollution, primarily in urban areas. Changing people's travel behaviour towards alternative transport is an efficient approach to mitigate harmful environmental impacts caused by a large number of vehicles. Such a strategy also provides an opportunity to gain health co-benefits of improved air quality and enhanced physical activities. This study aimed at quantifying co-benefit effects of alternative transport use in Adelaide, South Australia.MethodWe made projections for a business-as-usual scenario for 2030 with alternative transport scenarios. Separate models including air pollution models and comparative risk assessment health models were developed to link alternative transport scenarios with possible environmental and health benefits.ResultsIn the study region with an estimated population of 1.4 million in 2030, by shifting 40% of vehicle kilometres travelled (VKT) by passenger vehicles to alternative transport, annual average urban PM2.5 would decline by approximately 0.4 μg/m3 compared to business-as-usual, resulting in net health benefits of an estimated 13 deaths/year prevented and 118 disability-adjusted life years (DALYs) prevented per year due to improved air quality. Further health benefits would be obtained from improved physical fitness through active transport (508 deaths/year prevented, 6569 DALYs/year prevented), and changes in traffic injuries (21 deaths and, 960 DALYs prevented).ConclusionAlthough uncertainties remain, our findings suggest that significant environmental and health benefits are possible if alternative transport replaces even a relatively small portion of car trips. The results may provide assistance to various government organisations and relevant service providers and promote collaboration in policy-making, city planning and infrastructure establishment.  相似文献   

18.
Long-term (1985–1999) stationary observations on a polymorphic population of northern mole voles (Ellobius talpinus Pall.) in Kurgan oblast, Russia, using a mark-recapture method yielded original data on the population dynamics and population structure of a polymorphic colony consisting of animals of three color morphs (black, brown, and intermediate or transitional). The period when the northern mole vole population dynamics was studied (15 years) consisted of five distinct three-year population phases: depression, growth, peak (stabilization), decline to depression, and the next growth phase. It was shown that the population dynamics and changes in the population structure of northern mole voles in the Kurtamysh colony are cyclic.  相似文献   

19.
This paper describes the informal groundwater market existing in the urban–peri-urban interface of Chennai. The private water tanker suppliers and packaged water industries utilize the land and water resources of the peri-urban villages. Thus, the groundwater sources in peri-urban areas play a significant role in meeting the growing urban demand. The villages that are experiencing the groundwater market are highly influenced by the urbanization and its related activities, due to their proximity to the city. The transfer of groundwater from the peri-urban villages not only deprives the peri-urban areas of their water rights but also leads to environmental damage. Agriculture declined in the water marketed villages in the range of 20–95 per cent during 1990–2007. The pre-monsoon and post-monsoon groundwater level fluctuation varied from 2–6 m to 0–5 m, respectively, during 1971–2007. The declining trend of the groundwater table and agriculture is highly significant in the water marketing villages. Moreover, the present groundwater quality is also in a susceptible state due to over extraction. Hence, strengthening the legal and institutional framework to ensure an equitable access to water for both urban and peri-urban areas is urgently required. This paper also describes the characteristics of the groundwater transfer, quantification of the marketed water, the role of the existing regulatory framework, and the institutional mechanisms. Many stakeholder’s meeting and focus group discussions have been conducted in the villages under study for understanding the socio-economic implications of the water market. The study ultimately emphasized a sustainable groundwater extraction/market which will safeguard the interests of the peri-urban and urban communities.  相似文献   

20.
发达地区人口、土地与经济城镇化协调发展度研究   总被引:8,自引:0,他引:8  
江苏省作为中国东部沿海经济发达地区省份的典型代表,正处于城镇化加速发展的关键时期。新时期的城镇化是一个融合人口、土地与经济的复杂系统,不能从单方面衡量城镇化发展水平。在归纳总结城镇化内涵的基础上,选择人口城镇化、土地城镇化和经济城镇化为切入点,从三个方面衡量江苏省的城镇化水平的变化过程,研究不同时空城市在人口、土地和产业三方面协调发展的状态。结果显示,1998-2009年12年间江苏省人口城镇化、土地城镇化和经济城镇化的发展都呈现上升趋势,但在不同阶段处于主导地位的城镇化驱动力量不同,协调发展度也处于上升状态,从衰退发展阶段(1998-2003)逐渐发展到过渡阶段(2004-2005),最后到达协调发展阶段(2006-2009);在空间分布上,以2009年为例,综合评价结果显示,江苏省的城镇化水平和协调发展度总体水平较高,但是也存在区域分异明显的特点。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号