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1.
Most scholarship on rural–urban migration in Sub-Saharan Africa demonstrates that migrants tend to move in a “circular” fashion and only spend short periods of time in cities before returning home to rural villages. However, some scholars working on the impacts of climate change on migration suggest that deteriorating environmental conditions may undermine rural livelihoods and lead people to move to cities for longer periods of time. If this is true, then climate change threatens to accelerate urbanisation and lead to renewed stress on urban infrastructure. The purpose of this paper is to explore these positions and we do so by collecting survey [n = 241], in-depth interview [n = 75] and focus group [n = 123 participants] data from rural and urban Malawi. Two key results stand out as significant. The first is that migrants in Malawi's capital city tend to stay in the urban environment for longer periods of time than conventional understandings of migration would predict. The second key result is that climate change may actually lead, in the case of Malawi, to reverse (i.e urban–rural) migration. This is because many of the people in Malawi's cities depend on products produced in rural environments (e.g. food and fuelwood). If climate change undermines rural livelihoods, then many urban residents will find the basis of their livelihoods removed and will likely respond by moving back to rural villages. Overall, our results, therefore, suggest that in at least one case the effect of climate change on migration may not be to increase migration towards cities but to stimulate an exodus from cities and back to the rural countryside. 相似文献
2.
Middle Miocene to Pliocene siliciclastics of the Bare Formation represent a long‐lived (ca. 11 Myr) break in the otherwise carbonate‐dominated shelf of the Northern Carnarvon Basin, Northwest Shelf of Australia. The quartz‐sandstone interval is correlated with the appearance of spectacular clinoform sets mapped on 3D and dense 2D seismic data. Twenty‐seven clinoform sets are interpreted as delta lobes primarily based on their plan‐view morphology (strike‐elongate to lobate features) and their 40–100‐m‐high clinoform amplitudes. The delta lobes were deposited on outer‐shelf to shelf‐edge positions, and the older deltas show evidence of a higher degree wave reworking than the younger deltas. Measurements of the along‐strike (migration) and down‐dip (progradation) movement of these deltas are compared with relative sea‐level behaviour inferred from shelf‐edge trajectory analysis. Delta lobes exhibit greater lateral shifting during relative sea‐level rise, whereas delta lobes are more restricted to dip‐oriented fairways during sea‐level fall, although no major incised valleys have been identified. Long‐term (cumulative) progradation of this delta system and subsequent backstepping correlates with long‐term sea‐level fall and rise during the late middle and late Miocene. In addition, a long‐term northeastward migration trend for these delta lobes was likely a result of localized uplift of an inversion anticline in the Rosemary–Legendre Trend; the growth of this anticline probably steered the fluvial source for the delta system towards the northeast. The Bare Formation siliciclastic influx correlates with other middle Miocene increases in siliciclastic sediment supply worldwide. Global cooling and a shift to more arid conditions, negatively influencing vegetation cover, may have combined with more seasonally variable rainfall to generate the high sediment supply that built the deltas. Retreat of the siliciclastics could correlate with ice‐sheet growth in the Northern Hemisphere and/or increase in the Indonesian Throughflow and Leeuwin Current (ca. 1.6 Ma), which might have modified climate regionally. 相似文献
3.
Jonathon Collins 《The Australian geographer》2014,45(3):289-307
ABSTRACTBangladesh is at the forefront of countries experiencing and debating climate change, despite having contributed little to global emissions, and has the greatest vulnerability to climate change due to inadequate institutional support for the dense population dispersed in low-lying terrain. A micro-level study of livelihoods in the Panpatti Union, a district of the coastal zone exposed to climate stress and an array of other social, economic and political stresses, demonstrated that adaptation strategies to a range of shocks were both reactive and proactive. The persistent nature of shocks, and the limited margins in which to respond, meant that achieving sustainable long-term livelihoods was unusually difficult. Despite cases of dynamism and flexibility, where livelihoods had been effectively diversified, rural people largely failed to reduce their exposure to vulnerability. That was especially true of extremely poor, landless and female-headed households. In such challenging circumstances external interventions were required to ensure sustainable development, but were unlikely because of the isolation of Panpatti and the number of villages and people in similar circumstances. This emphasised the need to develop a more robust livelihoods framework to support the most vulnerable communities in severe economic and environmental contexts where climate change is likely to exacerbate all existing problems. 相似文献
4.
Dryland ecosystems are highly vulnerable to environmental changes. Monitoring is vital in order to evaluate their response to fluctuating rainfall and temperature patterns for long-term ecosystem safeguarding. Monitoring of long term changes of normalized difference vegetation index (NDVI) and climate variables are fundamental for better understanding of change trajectories in dryland ecosystem, and to ascertain their potential interaction with anthropogenic drivers. In this study, we identify determinant factors of dryland changes by using MODIS NDVI, precipitation and temperature data for Breaks for Additive Seasonal and Trend (BFAST) and Mann Kendall test statistic. BFAST predicts iteratively time and number of changes within a time series data to depict the size and direction of changes. Analysis of NDVI, precipitation and temperature time series data showed substantial changes during the study period of 2000–2014. There is a reduction trend in vegetation showed by the decline in NDVI, with significant breakpoints till 2009 and recovery afterwards, without a significant change in annual trends of precipitation (α < 0.05) for the same study period. Furthermore 2 positive climate trends were founded: a) a significant positive trend on long term annual rainfall during the main rainy seasons and; 2) a significant (α < 0.05) annual increment of the long term mean minimum and mean maximum temperature of 0.03 °C/year and 0.04 °C/year, respectively. This assessment showed that climate variables cannot be considered as the main factors in explaining the observed patterns of vegetation dynamics. Seasonal and interannual precipitation changes have a lower weight as driving factors for the reduction in vegetation trends. Hence, the decline in vegetation productivity of the region can be attributed to the increasing pressure of human activities. 相似文献
5.
Craig E. Colten 《Geographical review》2019,109(3):416-435
Adaptation is a key concept in long‐term human adjustments to climate change. Despite the centrality of human decisions and actions in adaptation, much of the climate change literature is thin on humanities and social science which are the primary approaches for understanding human activity. This situation is particularly pronounced in Louisiana's discussions about its disappearing coast line where research has concentrated in understanding biophysical processes and solutions prioritize short‐term adaptations. This paper reviews the relationship of adaptation and long‐term transitions in the global change discussion and traces how disjointed adaptations in coastal Louisiana have contributed to a perilous environmental situation there. It proposes a shift from discrete adaptations to efforts that incorporate interrelated biophysical and human adaptations that can sustain long‐term transitions. 相似文献
6.
Evolution of the Kivu Rift,East Africa: interplay among tectonics,sedimentation and magmatism 
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下载免费PDF全文 Douglas A. Wood Hubert J. Zal Christopher A. Scholz Cynthia J. Ebinger Irénée Nizere 《Basin Research》2017,29(Z1):175-188
The seismically and volcanically active Kivu Rift, in the western branch of the East African Rift System, is a type locale for studies of high‐elevation, humid‐climate rift basins, as well as magmatic basin development. Interpretations of offshore multi‐channel seismic (MCS) reflection data, terrestrial radar topography, lake bathymetry and seismicity data recorded on a temporary array provide new insights into the structure, stratigraphy and evolution of the Kivu rift. The Kivu rift is an asymmetric graben controlled on its west side by a ca. 110 km‐long, N‐S striking border fault. The southern basins of the lake and the upper Rusizi river basin are an accommodation zone effectively linking 1470 m‐high Lake Kivu to 770 m‐high Lake Tanganyika. MCS data in the eastern Kivu lake basin reveal a west‐dipping half graben with at least 1.5 km of sedimentary section; most of the ca. 2 km of extension in this sub‐basin is accommodated by the east‐dipping Iwawa normal fault, which bounds an intrabasinal horst. Lake Kivu experienced at least three periods of near desiccation. The two most recent of these approximately correlate to the African Megadrought and Last Glacial Maximum. There was a rapid lake level transgression of at least 400 m in the early Holocene. The line load of the Virunga volcanic chain enhances the fault‐controlled basin subsidence; simple elastic plate models suggest that the line load of the Virunga volcanic chain depresses the basin by more than 1 km, reduces flank uplift locally and broadens the depocentre. Not only do the voluminous magmatism and degassing to the lake pose a hazard to the riparian population, but our studies demonstrate that magmatism has important implications for short‐term processes such as lake levels, inflow and outlets, as well as long term modification of classic half‐graben basin morphology. 相似文献
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8.
Freddy J. Gathorne-Hardy Egill Erlendsson Peter G. Langdon Kevin J. Edwards 《Journal of Paleolimnology》2009,42(3):413-426
Ecosystem variability must be assessed over a range of timescales in order to fully understand natural ecosystem processes.
Long-term climate change, at millennial and centennial scales, is a major driver of natural ecosystem variability, but identifying
evidence of past climate change is frequently confounded by human-induced impacts on the ecosystem. Iceland is a location
where it is possible to separate natural from anthropogenic change in environmental archives, as the date of settlement is
accepted to be around AD 874, prior to which the island was free from proven human impacts. We used a lake sediment core from
Breieavatn, near Reykholt, a major farm of the Norse period in western Iceland, to examine landscape development. A change
in pollen concentration in the sediments, especially the decline in Betula, indicated initial landscape degradation immediately post-settlement, whereas the chironomid fauna and reconstructed temperatures
were relatively complacent during this period. The pollen evidence is corroborated by 14C analyses, which indicate an increase in older carbon entering the lake, inferred to have been caused by increased erosion
following settlement. Further decreases in Betula pollen occurred around AD 1300, pre-dating a drop in chironomid-inferred temperatures (CI-T) of ~1°C over 100–200 years.
The CI-T reconstruction also shows a significant cooling after ~AD 1800, likely indicative of the coldest phase of the Little
Ice Age. The evidence suggests that the chironomid record was relatively unaffected by the increased landscape degradation
and hence reveals a temperature reconstruction independent of human impact. 相似文献
9.
10.
Fiona Miller 《The Australian geographer》2014,45(3):309-324
ABSTRACTChange has been at the heart of the livelihoods concept since its inception, allowing for a clear focus on how people perceive, respond to and experience risk. The ardent focus on ‘the local’ within livelihoods work, both in research and programmatic terms, has to some extent overshadowed attention on the role of wider-scale political economic and environmental processes in generating change and determining responses to change. Livelihoods in the Mekong Delta have never been ‘local’, having long been historically embedded in international, regional and national economic, political and environmental transformations. Drivers of change at these wider scales have intensified, complicating local responses to change, whether through economic, social or political means. A more nuanced appreciation of how scaled relations can be supported is required to better anticipate and respond to the political ecology of risk. 相似文献
11.
Eutrophication is perhaps the most pervasive form of pollution. Here we first review its effects on lake ecosystems based largely on modern ecological investigation. The longer time scale afforded by palaeolimnological investigation has seen an increase in the number of the publications since 1990 with a disproportionate increase in citations demonstrating the increasing use and usefulness of palaeolimnology to help understand lakes ecosystems and their response to eutrophication. We summarise briefly the history and origins of palaeolimnological investigation into eutrophication and its impacts in lakes. Then we review quantitative and qualitative palaeolimnological methods for tracking change in nutrient concentrations, algal community and abundance, macrophyte community composition and abundance and zooplanktivorous fish density. The usefulness of stable isotope analysis on sediment organic matter to track eutrophication is assessed and alternative methods discussed. A current challenge is to determine the effects of recent climate change on lake ecosystems. The impacts of climate change and eutrophication on the ecology of lakes have many similarities making it difficult to disentangle the impact of one from the other, in particular where the eutrophication impacts are greatest. We review a number of recent palaeolimnological studies, in particular those integrating long term monitoring data, which have gone some way to identifying when nutrients or climate may be having the greatest impact. Finally, we discuss possible future directions for the discipline, such as the greater integration of studies of evolutionary change using molecular techniques. 相似文献
12.
Thomas Birk 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2014,114(1):59-75
This article assesses the vulnerability to climatic and socioeconomic stresses in the Reef Islands, Solomon Islands, an atoll island group in the Southwest Pacific. Climate change and the associated sea-level rise are often seen as the most pressing challenges to atoll communities, yet this study aims at critically re-assessing this view by placing climate in the context of a range of other internal and external stressors affecting local livelihoods, including population growth, inadequate land use practices, and lack of economic potential, as well as external factors such as poorly developed infrastructure, economic marginalization and weak governance of Solomon Islands. Findings suggest that some of these non-climatic stresses are currently – and in the short term – more important determinants of local vulnerability than climate change and sea-level rise. Certainly, these stresses are likely to be exacerbated by different elements of climate change in the short, medium and long term, but generally speaking climate change does not appear to be a major driver of the current changes in the islands. On the basis of these observations, the possible adaptation options, relevant to different time scales, are discussed. 相似文献
13.
A high resolution multi-proxy record of pronounced recent environmental change at Baker Lake,Nunavut
A. S. Medeiros C. E. Friel S. A. Finkelstein R. Quinlan 《Journal of Paleolimnology》2012,47(4):661-676
Arctic aquatic systems are considered to be especially sensitive to anthropogenic disturbance, which can have cascading effects
on biological communities as aquatic food-web structure is altered. Bio-indicators that respond to major limnological changes
can be used to detect and infer major environmental change, such as climate warming, with the use of paleolimnological techniques.
A multi-proxy approach was used to quantify recent environmental changes at Baker Lake, Nunavut, Arctic Canada. Analyses of
fossilized remains of chironomids and diatoms were conducted on a sediment core of 20 cm in length sampled at 0.5-cm intervals.
A new surface sediment training set of subfossil chironomid assemblages from 65 lakes across the eastern Canadian Arctic generated
a robust (r
jack2 = 0.79) surface water paleotemperature transfer function. The transfer function was applied to stratigraphic intervals from
the Baker Lake sediment core to generate a paleotemperature reconstruction of sub-decadal resolution. The surface water temperature
reconstruction inferred a 2°C increase in mid-summer surface water temperature for Baker Lake over the last 60 years, which
was corroborated by the local instrumental record spanning the period of 1950–2007 AD. The chironomid record shows a recent
decline of several cold-water taxa and appearance of warm-water indicators. This shift in community structure began circa
1906 AD, and intensified after 1940 AD. The corresponding fossil diatom record showed an increase in small planktonic Cyclotella taxa over the past 60 years, intensifying in the last 5 years, which also suggests a warmer climate and longer ice-free periods.
The shifts in the diatom assemblages began later than the shifts in the chironomid assemblages, and were of lower magnitude,
reflecting differences in the mechanisms in which these two indicators respond to environmental change. 相似文献
14.
Modest diatom responses to regional warming on the southeast Tibetan Plateau during the last two centuries 总被引：1，自引：0，他引：1
Juliane Wischnewski Anson W. Mackay Peter G. Appleby Steffen Mischke Ulrike Herzschuh 《Journal of Paleolimnology》2011,46(2):215-227
A general mean annual temperature increase accompanied with substantial glacial retreat has been noted on the Tibetan Plateau
during the last two centuries but most significantly since the mid 1950s. These climate trends are particularly apparent on
the southeastern Tibetan Plateau. However, the Tibetan Plateau (due to its heterogeneous mountain landscape) has very complex
and spatially differing temperature and precipitations patterns. As a result, intensive palaeolimnological investigations
are necessary to decipher these climatic patterns and to understand ecological responses to recent environmental change. Here
we present palaeolimnological results from a 210Pb/137Cs-dated sediment core spanning approximately the last 200 years from a remote high-mountain lake (LC6 Lake, working name)
on the southeastern Tibetan Plateau. Sediment profiles of diatoms, organic variables (TOC, C:N) and grain size were investigated.
The 210Pb record suggests a period of rapid sedimentation, which might be linked to major tectonic events in the region ca. 1950.
Furthermore, unusually high 210Pb supply rates over the last 50 years suggest that the lake has possibly been subjected to increasing precipitation rates,
sediment focussing and/or increased spring thaw. The majority of diatom taxa encountered in the core are typical of slightly
acidic to circumneutral, oligotrophic, electrolyte-poor lakes. Diatom species assemblages were rich, and dominated by Cyclotella sp., Achnanthes sp., Aulacoseira sp. and fragilarioid taxa. Diatom compositional change was minimal over the 200-year period (DCCA = 0.85 SD, p = 0.59); only a slightly more diverse but unstable diatom assemblage was recorded during the past 50 years. The results indicate
that large-scale environmental changes recorded in the twentieth century (i.e. increased precipitation and temperatures) are
likely having an affect on the LC6 Lake, but so far these impacts are more apparent on the lake geochemistry than on the diatom
flora. Local and/or regional peculiarities, such as increasing precipitation and cloud cover, or localized climatic phenomena,
such as negative climate feedbacks, might have offset the effects of increasing mean surface temperatures. 相似文献
15.
Global climate change is causing the majority of large lakes on the Tibetan Plateau to expand. While these rising lake levels and their causes have been investigated by hydrologists and glaciologists, their impacts on local pastoral communities have mostly been ignored. Our interviews with pastoralists in central Tibet reveal their observations and beliefs about Lake Serling’s expansion, as well as how its effects are interacting with current rangeland management policies. Interviewees reported that the most negative effects on their livelihoods have been reduced livestock populations and productivity due to the inundation of high-quality pastures by saline lake water. However, pastoralists’ collective efforts based on traditional values and norms of sharing, assistance, and reciprocity have helped them cope with these climate change impacts. These local, traditional coping strategies are particularly worthy of attention now, given that the transformation of traditional pastoralism is a goal of current government development initiatives. 相似文献
16.
Rainfall is the major driver of crop growth in Mediterranean agricultural regions and its spatial and temporal distributions determine yield potential. This study uses a long term spatial archive of rainfall observations for the Eyre Peninsula (South Australia) to estimate the spatial and temporal impacts of climate change on wheat yield. The three step process involved: (1) cluster analysis and statistical comparison to spatially distinguish heterogeneous “hazardscapes” (places that represent the physical susceptibility to hazards (Khan, 2012)); (2) using historical rainfall reliabilities to estimate the probability of receiving rainfall within a range of predefined thresholds and season for each hazardscape; (3) applying 2030 and 2070 climate change projections to determine the potential future impacts on rainfall. Nine hazardscapes were spatially differentiated each having temporally different historical seasonal rainfall reliabilities. Variations over space and time mean that the impacts of climate change will be spatially explicit. Projected rainfall reductions for 2030 showed marginal impact on hazardscapes with low seasonal reliabilities, primarily in winter and spring. The 2070 projections showed that some hazardscapes were unlikely to receive past rates of rainfall thus limiting the ongoing prospects of current and perhaps the potential adoption of alternative rain-fed land uses. Reductions in rainfall for hazardscapes with higher historical rainfall reliabilities will cause negative impacts on crop development. The ability to quantify the potential spatial and temporal impacts of climate change on seasonal trends will inform land managers' climate change mitigation and adaptation pathways. 相似文献
17.
Palaeoecological studies have identified the broad patterns of environmental and climate change in highland south‐eastern Australia, but the detail of human impact on a variety of parameters and their interlinkages is largely missing. This study compares the erosion, productivity, fire and vegetation history in prehistoric and historical times at Burraga Swamp in montane rainforest in New South Wales. The known human impact is meagre; the major presently sustained impacts involve forestry in the surrounding sclerophyll forests and a low level of visits to the swamp by day‐walkers. While no significant changes in the largely oligotrophic conditions or in fire frequency were detected, changes in erosion rates and some vegetation change can be attributed to impacts since European settlement. There has been a small decline in eucalypts and a loss of fern cover, while grasses, Urtica and exotic species have expanded. It is clear that upland sites are sensitive to environmental change including low‐level human impact. 相似文献
18.
Climate variability and rural livelihoods: assessing the impact of seasonal climate forecasts in Lesotho 总被引：7，自引：0，他引：7
Climate variability acutely affects rural livelihoods and agricultural productivity, yet it is just one of many stresses that vulnerable rural households have to cope with. A livelihood approach is used to assess the potential role that seasonal climate forecasts might play in increasing adaptive capacity in response to climate variability, using Lesotho as a case study. An examination of the assets and strategies that rural households employ enables a holistic assessment of the impact seasonal forecasts could have on rural livelihoods. This research thereby bridges macro-level variability with local-level impacts and adaptation to provide insight into the dynamics of forecast use and impact among vulnerable groups. 相似文献
19.
Potential distributional changes of invasive crop pest species associated with global climate change
This study investigated the potential global distributional shifts of poikilothermic invasive crop pest species associated with climate change, aiming to understand if their overall global distributions will expand or contract, and how the species distributions will vary across different regions. An ecological niche modelling analysis was conducted for 76 species. The potential distributional changes of the species in 2050 and 2070 were scrutinized for two climate change scenarios, which were further examined across different temperature and precipitation ranges. Results showed that averages of the mean probabilities of presence of the 76 crop pest species were predicted to increase. Higher species turnovers were predicted mostly to occur in areas with increasing predicted species richness. Lower species turnovers, however, were predicted mostly to occur in areas with decreasing predicted species richness. Species richness increases were predicted to occur more often in currently lower temperature (annual mean temperature approximately < 21 °C) or lower precipitation (annual precipitation approximately < 1100 mm) regions. Areas with the current annual mean temperatures at around 27 °C and 7.5 °C, respectively, were predicted to experience the highest decrease and increase in species richness as the climate warms. In conclusion, climate change is likely to expand the pest species’ overall distribution across the globe. It could have more profound impacts on the species distributions of those regions where species richness increases are expected, by altering the species’ community compositions. 相似文献
20.
This study explored the impacts of sustained heavy grazing in six vegetation types across an altitudinal and rainfall gradient in the Kamiesberg mountain range in Namaqualand. The study was carried out across the fence separating the Leliefontein communal area and surrounding privately owned farms. The communal area has been stocked over decades at approximately twice the government recommended stocking rate, while adjacent privately owned farms have generally adhered to recommended rates. Plant community data were collected from 66, 0.1 ha modified Whittaker plots and analysed for diversity and compositional changes. Consideration of community-wide responses through NMDS ordination showed that heavy grazing did not result in the dominance of a few wide-spread, weedy species in communal areas. Species richness at the 0.1 ha scale was also not affected by different land use practices. However, there was a significant compositional shift away from large woody and succulent shrubs, and an associated increase in dwarf shrubs and herbaceous perennial plants on the communal areas. This shift was only evident on the sandy lowland habitats, while a reduction in perennial grass was recorded in the rocky upland habitats on the communal areas. Compositional shifts towards smaller and more ephemeral species in the communal area are indicative of a system more closely dependent on rainfall. This has implications for people's livelihoods in the region, particularly in light of predicted climate change. 相似文献