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1.
Growing prosperity in the South is accompanied by human diets that will claim more natural resources per capita. This reality, combined with growing populations, may raise the global demand for food crops two- to four-fold within two generations. Considering the large volume of natural resources and potential crop yields, it seems that this demand can be met smoothly. However, this is a fallacy for the following reasons. (i) Geographic regions differ widely in their potential food security: policy choices for agricultural use of natural resources are limited in Asia. For example, to ensure national self-sufficiency and food security, most of the suitable land (China) and nearly all of the surface water (India) are needed. Degradation restricts options further. (ii) The attainable level of agricultural production depends also on socio-economic conditions. Extensive poverty keeps the attainable food production too low to achieve food security, even when the yield gap is wide, as in Africa. (iii) Bio-energy, non-food crops and nature compete with food crops for natural resources. Global and regional food security are attainable, but only with major efforts. Strategies to achieve alternative aims will be discussed. <br>  相似文献   

2.
We estimate the global bioenergy potential from dedicated biomass plantations in the 21st century under a range of sustainability requirements to safeguard food production, biodiversity and terrestrial carbon storage. We use a process‐based model of the land biosphere to simulate rainfed and irrigated biomass yields driven by data from different climate models and combine these simulations with a scenario‐based assessment of future land availability for energy crops. The resulting spatial patterns of large‐scale lignocellulosic energy crop cultivation are then investigated with regard to their impacts on land and water resources. Calculated bioenergy potentials are in the lower range of previous assessments but the combination of all biomass sources may still provide between 130 and 270 EJ yr?1 in 2050, equivalent to 15–25% of the World's future energy demand. Energy crops account for 20–60% of the total potential depending on land availability and share of irrigated area. However, a full exploitation of these potentials will further increase the pressure on natural ecosystems with a doubling of current land use change and irrigation water demand. Despite the consideration of sustainability constraints on future agricultural expansion the large‐scale cultivation of energy crops is a threat to many areas that have already been fragmented and degraded, are rich in biodiversity and provide habitat for many endangered and endemic species.  相似文献   

3.
Cassava is attacked by a complex of arthropod pests across the tropical regions of the world where the crop is grown. Root yield losses have been recorded for several pests, including mites, mealybugs, whiteflies, hornworm, lacebugs, thrips and burrower bugs. Agronomic characteristics such as vegetative propagation, a long growth cycle, drought tolerance, staggered planting dates and intercropping contribute to the considerable diversity of pests that feed on the crop. The dynamics of cassava production are evolving as trends in the food, feed and industrial starch sector are leading to an increased demand for high quality starches. The resulting shift to larger scale production units, expansion of cultivated area and modifications in crop management combined with the effects of climate change, especially warmer temperatures and altered rainfall patterns, affect the occurrence and dynamics of arthropod pests in cassava agro ecosystems. Data is presented to describe the effects of temperature and dry seasons on key pest species. Whiteflies, mites and mealybugs register a suitability increase in the same areas in South America: Northeastern Brazil, Northern Argentina, South-Central Bolivia, and Southwest Peru. In Africa increases are projected in Southeast Africa and Madagascar. In Asia, regions with greater projected suitability for these pest species are Coastal India and Southeast Asia. Future trends and important criteria that will influence the severity and management of key pests are discussed.  相似文献   

4.
As world food demand continues to increase, two broad strategies for agricultural production have been widely discussed: land sparing and land sharing. Reflecting tradeoffs between the extent and intensity of agricultural use, land sparing maximizes the ratio of conserved to agricultural land, whereas land sharing allows more extensive, nature-friendly transformation of the agroecological matrix. Freshwater ecosystems are rarely considered in weighing these strategies, despite being strongly affected by land-use change. Here we analyze how shifting from extensive to intensive agricultural practices is altering dry season riverine nutrient availability and algal growth in upland Southeast Asia, which is experiencing rapid conversion from swidden—or shifting—cultivation to fertilized row crops. In situ algal growth assays and nutrient concentration data from eleven catchments representing a spectrum of land use and population densities show that intensive agriculture is associated with significantly elevated nitrate concentrations but no shift in phosphorus. As a result, nitrogen to phosphorus ratios increases dramatically, shifting algal growth toward colimitation by nitrogen and phosphorus. Geochemical analysis of suspended solids suggested comparable geological inputs across basins, but dissolved rare earth elements reveal that inorganic fertilizers are changing water chemistry in parallel with land use. Taken together, our analyses suggest that the transition from low-input land-sharing management (swidden) to high-input land-sparing practices (intensive row-crop agriculture) underway in Southeast Asia has profound consequences for river ecosystems. Such nutrient loading can affect river productivity and food webs, suggesting that land-use conservation strategies for Southeast Asia need to account for impacts on freshwater ecosystems.  相似文献   

5.
Bioenergy is expected to play an important role in the future energy mix as it can substitute fossil fuels and contribute to climate change mitigation. However, large‐scale bioenergy cultivation may put substantial pressure on land and water resources. While irrigated bioenergy production can reduce the pressure on land due to higher yields, associated irrigation water requirements may lead to degradation of freshwater ecosystems and to conflicts with other potential users. In this article, we investigate the trade‐offs between land and water requirements of large‐scale bioenergy production. To this end, we adopt an exogenous demand trajectory for bioenergy from dedicated energy crops, targeted at limiting greenhouse gas emissions in the energy sector to 1100 Gt carbon dioxide equivalent until 2095. We then use the spatially explicit global land‐ and water‐use allocation model MAgPIE to project the implications of this bioenergy target for global land and water resources. We find that producing 300 EJ yr?1 of bioenergy in 2095 from dedicated bioenergy crops is likely to double agricultural water withdrawals if no explicit water protection policies are implemented. Since current human water withdrawals are dominated by agriculture and already lead to ecosystem degradation and biodiversity loss, such a doubling will pose a severe threat to freshwater ecosystems. If irrigated bioenergy production is prohibited to prevent negative impacts of bioenergy cultivation on water resources, bioenergy land requirements for meeting a 300 EJ yr?1 bioenergy target increase substantially (+ 41%) – mainly at the expense of pasture areas and tropical forests. Thus, avoiding negative environmental impacts of large‐scale bioenergy production will require policies that balance associated water and land requirements.  相似文献   

6.
Climate change in Africa poses a serious threat to many ecosystems and livelihoods, making them vulnerable to climate-related risks. Gum and resin bearing tree species as the genus Boswellia are the main economic and livelihood sources in most dryland areas of Africa. We use species distribution models to find critical sites where Boswellia species may no longer occur in the future. Our models identify potential regions that could benefit from their cultivation and promote conservation efforts for the species to thrive. We projected models to new CMIP6 scenarios and different dispersal profiles. Despite the prevailing aridity already imposed on the species, Boswellia distribution shows a dramatic reduction. Future investments in Boswellia restoration and strategies to promote sustainable extraction of resources may be key to sustain populations and Boswellia dominated forests in many parts of the African continent.  相似文献   

7.
The relative timing and size of regional human population growth following our expansion from Africa remain unknown. Human mitochondrial DNA (mtDNA) diversity carries a legacy of our population history. Given a set of sequences, we can use coalescent theory to estimate past population size through time and draw inferences about human population history. However, recent work has challenged the validity of using mtDNA diversity to infer species population sizes. Here we use Bayesian coalescent inference methods, together with a global data set of 357 human mtDNA coding-region sequences, to infer human population sizes through time across 8 major geographic regions. Our estimates of relative population sizes show remarkable concordance with the contemporary regional distribution of humans across Africa, Eurasia, and the Americas, indicating that mtDNA diversity is a good predictor of population size in humans. Plots of population size through time show slow growth in sub-Saharan Africa beginning 143-193 kya, followed by a rapid expansion into Eurasia after the emergence of the first non-African mtDNA lineages 50-70 kya. Outside Africa, the earliest and fastest growth is inferred in Southern Asia approximately 52 kya, followed by a succession of growth phases in Northern and Central Asia (approximately 49 kya), Australia (approximately 48 kya), Europe (approximately 42 kya), the Middle East and North Africa (approximately 40 kya), New Guinea (approximately 39 kya), the Americas (approximately 18 kya), and a second expansion in Europe (approximately 10-15 kya). Comparisons of relative regional population sizes through time suggest that between approximately 45 and 20 kya most of humanity lived in Southern Asia. These findings not only support the use of mtDNA data for estimating human population size but also provide a unique picture of human prehistory and demonstrate the importance of Southern Asia to our recent evolutionary past.  相似文献   

8.
A growing and more affluent human population is expected to increase the demand for resources and to accelerate habitat modification, but by how much and where remains unknown. Here we project and aggregate global spatial patterns of expected urban and agricultural expansion, conventional and unconventional oil and gas, coal, solar, wind, biofuels and mining development. Cumulatively, these threats place at risk 20% of the remaining global natural lands (19.68 million km2) and could result in half of the world’s biomes becoming >50% converted while doubling and tripling the extent of land converted in South America and Africa, respectively. Regionally, substantial shifts in land conversion could occur in Southern and Western South America, Central and Eastern Africa, and the Central Rocky Mountains of North America. With only 5% of the Earth’s at-risk natural lands under strict legal protection, estimating and proactively mitigating multi-sector development risk is critical for curtailing the further substantial loss of nature.  相似文献   

9.
The growing human population and the increase in per capita food consumption are driving agriculture expansion and affecting natural ecosystems around the world. To balance increasing agriculture production and nature conservation, we must assess the efficiency of land‐use strategies. Soybean production, mainly exported to China and Europe, has become the major driver of deforestation in dry forest/savanna ecosystems of South America. In this article we compared land cover patterns (based on satellite imagery) and land‐use and human population trends (based on government statistics) in regions with two contrasting development pathways in the Chaco dry forests of northern Argentina, since the early 1970s. The area (ca. 13 million hectares) includes one of the largest continuous patches of tropical dry forests and has experienced rapid land‐use change. In the region where land use has been driven by government‐sponsored colonization programs, the expansion of extensive grazing has led to a growing rural population, low food production, and widespread environmental degradation. In contrast, in the region dominated by market‐driven soybean expansion, the rural population has decreased, food production is between 300% and 800% greater, and low‐density extensive cattle production has declined over extensive remaining forested areas, resulting in a land‐use trend that appears to better balance food production and nature conservation.  相似文献   

10.
Human livelihood needs and nature conservation often contradict. Yet, healthy ecosystems are crucial for human livelihood quality. The semi-arid regions of East Africa suffer under demographic pressure and soil depletion. Ecosystem degradation becomes particularly visible along rivers in semiarid regions of south-east Kenya, where former pristine riparian forests have been transformed into agricultural fields and settlements with negative effects on ecosystem services. In this study, we aim to understand how local smallholders perceive the challenges for the riparian ecosystems and what factors affect their engagement in environmental conservation. We surveyed about 200 farmers and performed expert interviews with representatives from governmental institutions from the field of land- and resource management along Nzeeu River in south-east Kenya. We assessed the level of education, land use practices, environmental knowledge, attitudes and the willingness to contribute to nature conservation. We tested for spatial bias to understand smallholders’ perceptions on environmental challenges. Our data show that land division due to inheritance is not perceived as a problem by the farmers. However, owners holding?<?1 ha of land property are less willing to spare some of their land for conservation, as opposed to those holding land plots above this size. Despite a high level of general willingness to conserve ecosystems, our data underline that local people hardly actively engage in conservation action. Furthermore, our data indicate a communication gap between local smallholders and regional governmental officers as well as overconfidence in mass media through the radio which can contradict successful adoption of pro-environment behavior. Sustainable land management in our study area is not a matter of education, but depends from the size of land property. There is an urgent need to bridge this communication gap, as a prerequisite to improve sustainable land management.  相似文献   

11.
Freshwater ecosystems provide vital resources for humans and support high levels of biodiversity, yet are severely threatened throughout the world. The expansion of human land uses, such as urban and crop cover, typically degrades water quality and reduces freshwater biodiversity, thereby jeopardizing both biodiversity and ecosystem services. Identifying and mitigating future threats to freshwater ecosystems requires forecasting where land use changes are most likely. Our goal was to evaluate the potential consequences of future land use on freshwater ecosystems in the coterminous United States by comparing alternative scenarios of land use change (2001–2051) with current patterns of freshwater biodiversity and water quality risk. Using an econometric model, each of our land use scenarios projected greater changes in watersheds of the eastern half of the country, where freshwater ecosystems already experience higher stress from human activities. Future urban expansion emerged as a major threat in regions with high freshwater biodiversity (e.g., the Southeast) or severe water quality problems (e.g., the Midwest). Our scenarios reflecting environmentally oriented policies had some positive effects. Subsidizing afforestation for carbon sequestration reduced crop cover and increased natural vegetation in areas that are currently stressed by low water quality, while discouraging urban sprawl diminished urban expansion in areas of high biodiversity. On the other hand, we found that increases in crop commodity prices could lead to increased agricultural threats in areas of high freshwater biodiversity. Our analyses illustrate the potential for policy changes and market factors to influence future land use trends in certain regions of the country, with important consequences for freshwater ecosystems. Successful conservation of aquatic biodiversity and ecosystem services in the United States into the future will require attending to the potential threats and opportunities arising from policies and market changes affecting land use.  相似文献   

12.
Insects are an important natural resource, both for self-sufficiency and as commercial food products in many parts of the world. The use of edible insects reflects regional preferences and socio-cultural significance, which can be described in terms of regional differences. This study describes some edible insects in three regions: Japan, Southeast Asia and Southern Africa, and focuses on systems of traditional practices as the socio-cultural implications of people's preferences regarding edible insects. The case studies presented here describe such insect-related customs as the continuation of the traditional practice of insect eating in Japan, Southeast Asia and Southern Africa. These case studies describe the uniqueness or special characteristics of the custom, and the significance of its existence in the social sphere. Edible insects are regarded as cultural resources reflecting a rich biodiversity. They represent an alternative source of natural food resources in remote or mountainous areas. People who eat insects have established a broad variety of methods for collecting and cooking the rich diversity of edible insect species that are available. However, increases in demand could lead to competition and overexploitation, resulting in the future decline of these resources. In areas affected by overdevelopment, insect habitats are also likely to decline. It is necessary to raise people's awareness of the importance of the use of insects for food in order to ensure that insects are used in a sustainable manner, and to promote their proper use and conservation.  相似文献   

13.
Gerd Esser 《Plant Ecology》1995,121(1-2):175-188
The High Resolution Biosphere Model (HRBM), which has been developed by the group of the author, was used to investigate the carbon balance of the vegetation and the soil in the ecosystems of Monsoon Asia in comparison to the rest of the world. The HRBM is a global grid-based (0.5 degree resolution) model with a monthly time step. It includes modules for natural vegetation, land use, vegetation fires, vegetation composition. A historical carbon budget was calculated for the period 1860–1978 and, on a global scale, validated using atmospheric CO2 data. Based on the per-country development of the population and their requirements, different reasonable scenarios were used to investigate the potential impacts of land use and deforestation in the period 1990–2050. The HRBM calculates considerable contributions of Monsoon Asia to the global CO2 emissions due to land use changes in the past. Between 1860 and 1978, about 1/4 of the global releases from land use changes came from South Asian and Southeast Asian biota. The future contributions in the period 1990–2050 depend on the assumed development of the agricultural methods. If the intensity of agriculture and the agricultural productivity will stay the same as in the 1980s, there will be a strong need to increase agricultural areas, and thus deforestation will dominate. If there will be a change over to intensive methods of agricultural production, the presently used areas might be sufficient to provide resources to the growing population.  相似文献   

14.
The spatial distribution of populations and settlements across a country and their interconnectivity and accessibility from urban areas are important for delivering healthcare, distributing resources and economic development. However, existing spatially explicit population data across Africa are generally based on outdated, low resolution input demographic data, and provide insufficient detail to quantify rural settlement patterns and, thus, accurately measure population concentration and accessibility. Here we outline approaches to developing a new high resolution population distribution dataset for Africa and analyse rural accessibility to population centers. Contemporary population count data were combined with detailed satellite-derived settlement extents to map population distributions across Africa at a finer spatial resolution than ever before. Substantial heterogeneity in settlement patterns, population concentration and spatial accessibility to major population centres is exhibited across the continent. In Africa, 90% of the population is concentrated in less than 21% of the land surface and the average per-person travel time to settlements of more than 50,000 inhabitants is around 3.5 hours, with Central and East Africa displaying the longest average travel times. The analyses highlight large inequities in access, the isolation of many rural populations and the challenges that exist between countries and regions in providing access to services. The datasets presented are freely available as part of the AfriPop project, providing an evidence base for guiding strategic decisions.  相似文献   

15.
张云芝  胡云锋  韩月琪  战胜 《生态学报》2021,41(19):7599-7613
掌握生态退化区和研究热点区的空间分布、退化区生态系统的演变态势是认识生态问题、开展生态治理的基础,但目前缺乏全球主要生态退化区空间分布图等基础数据和相关知识。应用多源数据集成融合、长时序卫星遥感分析、互联网文献大数据建模分析等方法,对以荒漠化、水土流失、石漠化为代表的全球主要生态退化类型区的空间分布、演变态势、研究关注热度等进行了研究。结果表明:(1)全球荒漠化区面积约15.4×106 km2,水土流失区面积约14.3×106 km2,石漠化区面积约1.1×106 km2;这些生态退化区主要分布在非洲撒哈拉沙漠南北边缘,欧洲西部、地中海沿岸、东欧平原南部,南亚印度河流域,中国西北地区、云贵高原,北美洲落基山脉以及南美洲阿根廷等地区。(2)2000年以来,上述退化区中约有3.9%的面积处于退化加重态势,73.3%的面积处于脆弱平衡状态,22.8%的区域出现好转趋势。(3)全球生态退化研究热点区的分布与全球生态退化区的分布总体呈现一致性。但在沙特阿拉伯中部、哈萨克斯坦北部,巴西大部,安哥拉、南非等生态退化区,存在生态系统继续恶化、缺乏研究界足够关注的情况。研究成果深化了对全球主要生态退化区分布格局的认识,对于防范全球发展和建设中出现加重的生态退化等具有参考价值。  相似文献   

16.
Agricultural expansion is a leading driver of biodiversity loss across the world, but little is known on how future land‐use change may encroach on remaining natural vegetation. This uncertainty is, in part, due to unknown levels of future agricultural intensification and international trade. Using an economic land‐use model, we assessed potential future losses of natural vegetation with a focus on how these may threaten biodiversity hotspots and intact forest landscapes. We analysed agricultural expansion under proactive and reactive biodiversity protection scenarios, and for different rates of pasture intensification. We found growing food demand to lead to a significant expansion of cropland at the expense of pastures and natural vegetation. In our reference scenario, global cropland area increased by more than 400 Mha between 2015 and 2050, mostly in Africa and Latin America. Grazing intensification was a main determinant of future land‐use change. In Africa, higher rates of pasture intensification resulted in smaller losses of natural vegetation, and reduced pressure on biodiversity hotspots and intact forest landscapes. Investments into raising pasture productivity in conjunction with proactive land‐use planning appear essential in Africa to reduce further losses of areas with high conservation value. In Latin America, in contrast, higher pasture productivity resulted in increased livestock exports, highlighting that unchecked trade can reduce the land savings of pasture intensification. Reactive protection of sensitive areas significantly reduced the conversion of natural ecosystems in Latin America. We conclude that protection strategies need to adapt to region‐specific trade positions. In regions with a high involvement in international trade, area‐based conservation measures should be preferred over strategies aimed at increasing pasture productivity, which by themselves might not be sufficient to protect biodiversity effectively.  相似文献   

17.
Aim:  Ecosystems face numerous well‐documented threats from climate change. The well‐being of people also is threatened by climate change, most prominently by reduced food security. Human adaptation to food scarcity, including shifting agricultural zones, will create new threats for natural ecosystems. We investigated how shifts in crop suitability because of climate change may overlap currently protected areas (PAs) and priority sites for PA expansion in South Africa. Predicting the locations of suitable climate conditions for crop growth will assist conservationists and decision‐makers in planning for climate change. Location:  South Africa. Methods:  We modelled climatic suitability in 2055 for maize and wheat cultivation, two extensively planted, staple crops, and overlaid projected changes with PAs and PA expansion priorities. Results:  Changes in winter climate could make an additional 2 million ha of land suitable for wheat cultivation, while changes in summer climate could expand maize suitability by up to 3.5 million ha. Conversely, 3 million ha of lands currently suitable for wheat production are predicted to become climatically unsuitable, along with 13 million ha for maize. At least 328 of 834 (39%) PAs are projected to be affected by altered wheat or maize suitability in their buffer zones. Main conclusions:  Reduced crop suitability and food scarcity in subsistence areas may lead to the exploitation of PAs for food and fuel. However, if reduced crop suitability leads to agricultural abandonment, this may afford opportunities for ecological restoration. Expanded crop suitability in PA buffer zones could lead to additional isolation of PAs if portions of newly suitable land are converted to agriculture. These results suggest that altered crop suitability will be widespread throughout South Africa, including within and around lands identified as conservation priorities. Assessing how climate change will affect crop suitability near PAs is a first step towards proactively identifying potential conflicts between human adaptation and conservation planning.  相似文献   

18.
Commercial cultivation of the red alga Kappaphycus alvarezii (Doty) Doty has been satisfying the demand of the carrageenan industry for more than 40 years. For the past four decades, this species has been globally introduced to many maritime countries for experimental and commercial cultivation as a sustainable alternate livelihood for coastal villagers. Accompanying the introduction is an increasing concern over the species effects on the biodiversity of endemic ecosystems. The introductions of non-endemic cultivars have resulted in the adaptation of quarantine procedures to minimize bioinvasions of additional invasive species. The present review focuses on Kappaphycus farming techniques through the application of biotechnological tools, ecological interactions with endemic ecosystems, future K. alvarezii farming potentials in Asia, Africa, and the Pacific, and the challenges for prospective farmers, i.e., low raw material market value, diseases, grazing, etc. The introduction of Kappaphycus cultivation to tropical countries will continue due to the high production values realized, coastal villages searching for alternative livelihoods, and the increased global industrial demand for carrageenan.  相似文献   

19.
Rangelands are Earth's dominant land cover and are important providers of ecosystem services. Reliance on rangelands is projected to grow, thus understanding the sensitivity of rangelands to future climates is essential. We used a new ecosystem model of moderate complexity that allows, for the first time, to quantify global changes expected in rangelands under future climates. The mean global annual net primary production (NPP) may decline by 10 g C m?2 year?1 in 2050 under Representative Concentration Pathway (RCP) 8.5, but herbaceous NPP is projected to increase slightly (i.e., average of 3 g C m?2 year?1). Responses vary substantially from place‐to‐place, with large increases in annual productivity projected in northern regions (e.g., a 21% increase in productivity in the US and Canada) and large declines in western Africa (?46% in sub‐Saharan western Africa) and Australia (?17%). Soil organic carbon is projected to increase in Australia (9%), the Middle East (14%), and central Asia (16%) and decline in many African savannas (e.g., ?18% in sub‐Saharan western Africa). Livestock are projected to decline 7.5 to 9.6%, an economic loss of from $9.7 to $12.6 billion. Our results suggest that forage production in Africa is sensitive to changes in climate, which will have substantial impacts on the livelihoods of the more than 180 million people who raise livestock on those rangelands. Our approach and the simulation tool presented here offer considerable potential for forecasting future conditions, highlight regions of concern, and support analyses where costs and benefits of adaptations and policies may be quantified. Otherwise, the technical options and policy and enabling environment that are needed to facilitate widespread adaptation may be very difficult to elucidate.  相似文献   

20.

The capacity to assess invasion risk from potential crop pests before invasion of new regions globally would be invaluable, but this requires the ability to predict accurately their potential geographic range and relative abundance in novel areas. This may be unachievable using de facto standard correlative methods as shown for the South American tomato pinworm Tuta absoluta, a serious insect pest of tomato native to South America. Its global invasive potential was not identified until after rapid invasion of Europe, followed by Africa and parts of Asia where it has become a major food security problem on solanaceous crops. Early prospective assessment of its potential range is possible using physiologically based demographic modeling that would have identified knowledge gaps in T. absoluta biology at low temperatures. Physiologically based demographic models (PBDMs) realistically capture the weather-driven biology in a mechanistic way allowing evaluation of invasive risk in novel areas and climes including climate change. PBDMs explain the biological bases for the geographic distribution, are generally applicable to species of any taxa, are not limited to terrestrial ecosystems, and hence can be extended to support ecological risk modeling in aquatic ecosystems. PBDMs address a lack of unified general methods for assessing and managing invasive species that has limited invasion biology from becoming a more predictive science.

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