Marine birds breeding in Penny Strait and Queens Channel, Nunavut, Canada

Surveys of breeding birds on small islands in Penny Strait and Queens Channel, Nunavut Territory, Canada, were conducted in July 2002 and 2003. Approximately 3600 marine birds were observed, with the most common species being Arctic terns ( Sterna paradisaea , N=2400) and common eiders ( Somateria mollissima borealis , N=620). We observed no Ross's gulls ( Rhodostethia rosed ) in either year, and we found ivory gulls ( Pagophila eburned ) only in 2003, even though these species commonly bred here in the 1970s. This previously unsurveyed region supports numerous breeding marine birds, but reproductive success on these small islands may be dependent on annual ice conditions and consequent movements of Arctic foxes ( Alopex lagopus ).     

Medium‐term fluvial island evolution in a disturbed gravel‐bed river (Piave River,Northeastern Italian Alps)

River islands are defined as discrete areas of woodland vegetation surrounded by either water‐filled channels or exposed gravel. They exhibit some stability and are not submerged during bank‐full flows. The aim of the study is to analyze the dynamics of established, building, and pioneer islands in a 30‐km‐long reach of the gravel‐bed Piave River, which has suffered from intense and multiple human impacts. Plan‐form changes of river features since 1960 were analyzed using aerial photographs, and a LiDAR was used to derive the maximum, minimum and mean elevation of island surfaces, and maximum and mean height of their vegetation. The results suggest that established islands lie at a higher elevation than building and pioneer islands, and have a thicker layer of fine sediments deposited on their surface after big floods. After the exceptional flood in 1966 (RI > 200 years) there was a moderate increase in island numbers and extension, followed by a further increase from 1991, due to a succession of flood events in 1993 and 2002 with RI > 10 years, as well as a change in the human management relating to the control of gravel‐mining activities. The narrowing trend (1960–1999) of the morphological plan form certainly enhanced the chance of islands becoming established and this explains the reduction of the active channel, the increase in established islands and reduction of pioneer islands.     

经济形态演变对海洋海岛生态环境的影响——以美国海峡群岛为例

海洋海岛生态环境脆弱,一旦遭受破坏难以修复。人类社会历经原始经济时代、农业经济时代、工业经济时代和知识经济时代,经济形态的演变影响着人类生存的生态环境。以美国海峡群岛为例,以时间和事件两个维度对海岛生态环境破坏、生态修复和环境保护进行梳理,侧重于知识经济时代在国家公园管理局管理下的生态修复和环境保护。其中信息知识、生态文明、高新技术是海峡群岛实现生态回归的重要因素。海峡群岛的发展历程和后期的生态修复与管理为其他国家海洋海岛经济发展提供借鉴。     

The formation and evolution of the barrier islands of Inhaca and Bazaruto, Mozambique

The barrier islands of Inhaca and Bazaruto are related to the extensive coastal dune system of the Mozambican coastal plain, south-east Africa. Optically stimulated luminescence (OSL) dating of key stratigraphic units indicates that accretion of sediment within these systems is episodic. Both islands appear to have been initiated as spits extending from structural offsets in the coastline. Superposition of significant quantities of sediment upon these spits during subsequent sea-level highstands formed the core of the islands, which were anchored and protected by beachrock and aeolianite formation. At least two distinct dune-building phases occurred during Marine Oxygen Isotope Stage (MIS) 5, tentatively attributed to marine transgressions during sub-stages 5e and 5c. Although some localized reactivation of dune surfaces occurred prior to the Holocene, large quantities of sediment were not deposited on either island during the low sea-levels associated with MIS 2. Significant dune-building and sediment reworking occurred immediately prior to and during the Holocene, though it is not clear whether these processes were continuous or episodic. Significant erosion of the eastern shoreline of Bazaruto suggests that it is far less stable than Inhaca and may suffer further large-scale erosion. A model is presented for the formation of barrier islands along the Mozambican coastal plain.     

Population and resources on the minor Danish islands 1860, 1900, and 1960

Mørch, H., 1975: Population and resources on the minor Danish islands. Geografisk Tidsskrift 74: 21–35. København, juni 1, 1975.

An investigation made on the basis of a simple, linear regression of the relationship between resources—defined as areas after different criteria—and size of population on the minor Danish islands 1860, 1900, and 1960.     

Drowned shelf-edge deltas, barrier islands and related features along the outer continental shelf north of the head of De Soto Canyon, NE Gulf of Mexico

Four drowned shelf-edge delta complexes, two drowned shelf deltas, three drowned barrier islands, large areas of “hardground”, and fields of bedforms on the mid and outer continental shelf and uppermost slope north of the head of De Soto Canyon, NE Gulf of Mexico were mapped with high-resolution multibeam echosounder. Deltas formed not during the last eustatic low stand, but during one or more interstadials when eustatic sea levels were only 60 to 80 m below present sea level. The barrier islands and deltas must have been cemented prior to rapid falls of eustatic sea level that occurred during global glaciations. Cementation is necessary to have preserved the barrier islands from erosion and subsequent destruction by the rapid sea-level rise during the last deglaciation. The preservation of the relict bathymetry is so good that features that superficially resemble trough blowouts are found in association with one of the relict barrier islands. Asymmetric bedforms on the midshelf in water depths of 50 to 60 m indicate transport directions to the SW but asymmetric bedforms in water depths of the upper slope between 100 and 120 m on the S and SE flanks of the drowned shelf-edge deltas indicate a different current direction, a separate flow that is a continuation of a SW-flowing current that was previously found on the upper slope off NW Florida.     

Endemic avifaunal biodiversity and tropical forest loss in Makira, a mountainous Pacific island

Anthropogenic habitat changes and the introduction of pigs, dogs, cats and rats have caused a catastrophic decline in the terrestrial biodiversity of Pacific archipelagos. At present, economic globalization and an increased demand for timber are promoting industrial logging and plantation expansion. Commercial logging can be sustainable but in practice it more often leads to land degradation, especially on small flat islands. On large and mountainous islands, however, more modest impacts can be expected as the narrowly endemic species tend to inhabit montane forests where logging is difficult. In this study we use ornithological data collected at different elevations to assess the extent to which the avifauna of Makira, a large mountainous island in Melanesia, will be affected by deforestation of the lowlands, most of which are under timber concessions. Our data suggest that a majority of the endemic bird species use lowland forest to some extent and that this may even apply to species hitherto associated with montane forest. If current commercial forestry programmes are continued, the forest habitat may be disturbed or lost over large parts of Makira, potentially undermining the natural resource base for the local subsistence economy, exacerbating climate change and threatening the integrity of one of the most important areas for biodiversity conservation on earth. Our study highlights the importance of understanding the habitat requirements of endemic species and the urgency of establishing and effectively managing community-based protected areas in suitable lowland forests of the Pacific.     

日本离岛管理制度及其对我国的启示

边远海岛对于维护国家海洋权益和促进海岛地区社会经济发展具有重要意义。我国边远海岛发展与管理面临着缺少发展规划、基础设施薄弱、产业发展滞后、人口流失严重等问题,急需加强发展和管理。日本离岛也面临着人口数量减少、老龄化现象突出以及农林水产业、旅游业等传统产业下滑的趋势,本文介绍了日本离岛振兴管理的主要制度和措施,提出了我国边远海岛管理的借鉴和启示:开展边远海岛详细调查和分析、制定边远海岛扶持计划并进行适时调整、建立边远海岛扶持机制、制定鼓励边远海岛定居的有关政策、重视扶持渔业和旅游业等特色产业发展、重视无居民的边远海岛振兴。日本离岛的管理可为我国提供实践借鉴。     

南沙岛礁及周边港口可达性评价模型研究

中国的南沙群岛位于南海南部,岛礁星罗棋布,但受到岛礁自身面积及其他自然条件的限制,自持力和承载能力都较差,需要外界的持续补给才能维持大量人口的活动。南沙岛礁远离大陆,分布于被称为“危险地带”的珊瑚礁丛中,补给受到很大影响。目前,南沙群岛的岛礁部分被菲律宾、越南和马来西亚等国非法侵占,这些被其他国家非法控制的岛屿和沙洲的控制态势对其周边的海域产生一定的控制,并且将对通过的船舶产生较大的影响。针对南沙岛礁补给困难和控制态势复杂的现状,本文从南沙岛礁的自然条件和控制态势入手,提出了一种基于最小累积成本距离和加权Voronoi图的综合可达性指数,通过建立水深与航行成本的分级对应关系,构建了南沙岛礁及周边港口可达性评价模型,计算了南沙23个岛礁和周边国家9个重要港口之间的综合可达性指数,通过分析南沙主要岛礁和周边国家重要港口之间的综合可达性的优劣,可以为中国在南沙建设补给和中转基地选址提供决策参考。可以为中国开发和管理南沙群岛、制定海洋发展战略提供依据。     

长山群岛水环境基本特征与水资源开发研究

长山群岛特有的地质，地理环境肽其气候条件决定其水环境容量水，水资源有限。海岛区域开发协调发展的道路，水资源开发不应以损害水环境炒代价，必须走水资源持续利用的开发模式     

Anabranching in mixed bedrock-alluvial rivers: the example of the Orange River above Augrabies Falls, Northern Cape Province, South Africa

Anabranching is characteristic of a number of rivers in diverse environmental settings worldwide, but has only infrequently been described from bedrock-influenced rivers. A prime example of a mixed bedrock-alluvial anabranching river is provided by a 150-km long reach of the Orange River above Augrabies Falls, Northern Cape Province, South Africa. Here, the perennial Orange flows through arid terrain consisting mainly of Precambrian granites and gneisses, and the river has preferentially eroded bedrock joints, fractures and foliations to form multiple channels which divide around numerous, large (up to 15 km long and 2 km wide), stable islands formed of alluvium and/or bedrock. Significant local variations in channel-bed gradient occur along the river, which strongly control anabranching style through an influence on local sediment budgets. In relatively long (>10 km), lower gradient reaches (<0.0013) within the anabranching reach, sediment supply exceeds local transport capacity, bedrock usually only crops out in channel beds, and channels divide around alluvial islands which are formed by accretion in the lee of bedrock outcrop or at the junction with ephemeral tributaries. Riparian vegetation probably plays a key role in the survival and growth of these islands by increasing flow roughness, inducing deposition, and stabilising the sediments. Less commonly, channels may form by eroding into once-continuous island or floodplain surfaces. In shorter (<10 km), higher gradient reaches (>0.0013) within the anabranching reach, local transport capacity exceeds sediment supply, bedrock crops out extensively, and channels flow over an irregular bedrock pavement or divide around rocky islands. Channel incision into bedrock probably occurs mainly by abrasion, with the general absence of boulder bedforms suggesting that hydraulic plucking is relatively unimportant in this setting. Mixed bedrock-alluvial anabranching also occurs in a number of other rivers worldwide, and appears to be a stable and often long-lived river pattern adjusted to a number of factors commonly acting in combination: (1) jointed/fractured granitoid rock outcrop; (2) erosion-resistant banks and islands; (3) locally variable channel-bed gradients; (4) variable flow regimes.     

基于场强模型的南沙岛礁战略地位评价

南沙岛礁及附近海域蕴含丰富的资源,是中国海洋权益的重要组成部分。在南海主权争端日益激烈的形式下,根据岛礁自然特征和所处空间的资源条件,对南沙诸岛进行战略地位评价,有利于量化各岛礁价值,有重点地维护中国海洋权益。研究选取131 座符合评价条件的南沙岛礁,结合其自然属性以及南海空间的资源、航道等因素,使用场强模型,量化其在空间中的主权法律意义、军事价值和资源条件,获得了各岛礁的战略地位得分,可为研判南海局势提供参考。评价结果表明：部分具有显著战略地位和区域重要意义的南沙岛礁至今无人驻守,需重点关注;人工建设可明显提升岛礁的战略地位;在现有格局下,加大岛礁建设力度有助于维护中国南海的海洋权益。     

Impact of the Arctic Fox Alopex lagopus on nesting success of geese in southeast Svalbard, 1989

Goose populations, with special emphasis on Light-bellied Brent Geese Branta bernicla hrota , were censured in Tusenøyane and Tjuvfjorden, southeast Svalbard, July-August 1989. A total of 425 non-breeding Brent Geese, 210 Barnacle Geese Branta leucopsis and 421 Pink-footed Geese Anser bra-chyrhynchus and 11, 2 and 3 families of the three species, respectively, were counted. Brent Geese attempted to nest on 6 of the 20 islands surveyed, and were successful on four. Barnacle Geese attempted to nest on three islands and were successful on two. Many islands known to be traditional nesting sites were entirely void of geese. Pink-footed Geese were only seen in Tjuvfjorden. The breeding failure on the islands was linked to the presence of the Arctic Fox Alopex lagopus which probably caused the geese to completely give up the attempt to nest. On one island the fox had apparently arrived after nest initiation and ravaged 45 Brent Goose and Barnacle Goose nests. It is likely that the foxes stranded on the islands during ice break-up. As a consequence of the presence of foxes on most of Tusenøyane, more than half of the potential breeding segment of the Svalbard Brent Goose population failed to nest in the summer of 1989.     

南沙他国侵占岛礁战略价值及空间格局评价

从建岛潜力、岛礁辐射能力和岛礁承载能力3个方面选取26个指标,采用主客观综合赋权法确定各因子权重,利用线性加权法获得被越南、菲律宾、马来西亚、文莱等国所侵占的南沙44个岛礁的战略价值,并对结果进行空间插值,分析其空间格局特征。结果表明：1）被马来西亚侵占的弹丸礁、越南侵占的南威岛、以及菲律宾侵占的中业岛,其战略价值位列前3,评价得分分别为100、98.42和97.09。2）岛礁辐射能力空间分布格局呈现“NW—SE条带式”,“最高”和“高”等级的区域由研究区西北延伸至东南,然后向东北、西南两侧递减,辐射能力格局中有2个核心区域和2个次级核心区域。承载能力空间分布格局呈现“横向条带式”,由北向南越来越低,有1个核心区域和2个次级核心区域。建岛潜力空间分布格局有3个核心区域及2个次级核心区域。3）岛礁战略价值空间分布格局有3个核心区域,分布于研究区中部、北部及南部,与越南、菲律宾、马来西亚密切相关的核心区域各有1个。越南侵占岛礁最多且空间分布较广,有2个次级核心区域也与越南密切相关,越占岛礁若进一步建设,将形成多核心协同的战略格局,需密切关注。     

Alexander the Great's tombolos at Tyre and Alexandria, eastern Mediterranean

Tyre and Alexandria's coastlines are today characterised by wave-dominated tombolos, peculiar sand isthmuses that link former islands to the adjacent continent. Paradoxically, despite a long history of inquiry into spit and barrier formation, understanding of the dynamics and sedimentary history of tombolos over the Holocene timescale is poor. At Tyre and Alexandria we demonstrate that these rare coastal features are the heritage of a long history of natural morphodynamic forcing and human impacts. In 332 BC, following a protracted seven-month siege of the city, Alexander the Great's engineers cleverly exploited a shallow sublittoral sand bank to seize the island fortress; Tyre's causeway served as a prototype for Alexandria's Heptastadium built a few months later. We report stratigraphic and geomorphological data from the two sand spits, proposing a chronostratigraphic model of tombolo evolution.     

HABITAT ISLANDS AND THE PRESERVATION OF NEW ZEALAND'S AVIFAUNA*

ABSTRACT. Numerous avifauna species face extinction on New Zealand's two main islands, owing largely to forest clearance and to introduced mammals. In response, New Zealand selects certain offshore islands for the relocation of threatened native birds, first purging them of mammalian predators. Over the past few decades, this procedure has evolved to become fairly successful. Protected habitat “islands” within mainland forested areas are also being created, but with success less certain. As historic habitats are lost, small biopreservation islands may become a standard mechanism for protecting threatened species, a process that can be termed the “miniaturization” of nature.     

Characteristics of freshly deposited sand and finer sediments along an island-braided, gravel-bed river: The roles of water, wind and trees

Over the past two decades there has been a growing interest in the geomorphological mosaic along large floodplain rivers where channel dynamics are seen to drive habitat-patch creation and turnover and to contribute to high biological diversity. This has required a new perspective on fluvial geomorphology that focuses on biological scales of space and time. This study examines the spatial pattern of surface fine sediment accumulations along a reach of a large gravel-bed river, the Tagliamento River in NE Italy; an area with a moist Mediterranean climate and seasonal flow regime. The study investigates changes in sediment characteristics during the summer low-flow period between April and September. Focussing on five areas representing a gradient from open, bar-braided to wooded island-braided morphologies, the paper demonstrates the importance of riparian vegetation and aeolian–fluvial interactions.Significant contrasts in particle size distributions and organic content of freshly deposited sand and finer sediments were found between sampling areas, geomorphological settings, and sampling dates. In particular, wooded floodplain and established islands supported consistently finer sediment deposits than both open bar surfaces and the lee of pioneer islands, and in September significantly finer sediments were also found in deposits located in the lee of pioneer islands than on open bar surfaces. Overall, the September samples had a greater variability in particle size characteristics than those obtained from the same sites in April, with a general coarsening of the D₅ (φ) (i.e., the coarse tail of the particle size distribution). Also in September, crusts of fine sediment (30 μm < D₅₀ < 64 μm) had formed on the surface of some of the open bar and pioneer island deposits within the more open sampling areas along the study reach. These crusts possessed similar particle size characteristics to aeolian crusts found in more arid environments. They were significantly finer than April samples and September subcrust samples obtained from the same sites and had similar particle size characteristics to some samples taken from wooded floodplain, established island surfaces and the lee of pioneer islands that were not crusted.Local climatological and river level data confirm significant wind and rainfall events during a period of consistently low river levels between the April and September sampling periods. These support deflation, deposition and rain wash of finer sediment during the summer, with windblown sediments being deposited on bar surfaces and in the lee of pioneer islands where wood and young trees provide foci for accelerated sedimentation and island growth as well as on marginal floodplains and established islands. We conclude that along braided rivers in moist settings but with a distinct dry season, aeolian reworking of sediment deposits may have a more important role in driving habitat dynamics than previously considered.     

Questions of emigration,circulation and return: mobility between the French Caribbean and France

"The last four decades have seen the establishment of close migratory links between the French Caribbean islands of Martinique and Guadeloupe and the metropole.... The present paper focuses on the...complex migratory links--including continuing emigration from the islands for work and education, return migration and circulation--which have come to characterise the 1980s.... The paper aims also to contribute to the broader conceptualisation of migration and mobility. The principal conclusions reveal that the more straightforward labour migration of the years from 1963 to 1981 has been replaced by some considerable return migration (amongst young adults particularly) and circulation.... The paper also demonstrates that the role of migration in reducing population growth and fertility in the islands has been much altered during the course of the 1980s."     

Channel and island change in the lower Platte River, Eastern Nebraska, USA: 1855–2005

The lower Platte River has undergone considerable change in channel and bar characteristics since the mid-1850s in four 20–25 km-long study stretches. The same net effect of historical channel shrinkage that was detected upstream from Grand Island, Nebraska, can also be detected in the lower river but differences in the behaviors of study stretches upstream and downstream from major tributaries are striking. The least relative decrease occurred downstream from the Loup River confluence, and the stretch downstream from the Elkhorn River confluence actually showed an increase in channel area during the 1940s. Bank erosion was also greater downstream of the tributaries between ca. 1860 and 1938/1941, particularly in stretch RG, which showed more lateral migration. The cumulative island area and the ratio of island area to channel area relative to the 1938/1941 baseline data showed comparatively great fluctuations in median island size in both downstream stretches. The erratic behavior of island size distributions over time indicates that large islands were accreted to the banks at different times, and that some small, newly-stabilized islands were episodically “flushed” out of the system. In the upstream stretches the stabilization of mobile bars to create new, small islands had a more consistent impact over time. Channel decrease by the abandonment of large, long-lived anabranches and by the in-place narrowing resulting from island accretion were more prominent in these upstream stretches. Across all of the study area, channel area appears to be stabilizing gradually as the rate of decrease lessens. This trend began earliest in stretch RG in the late 1950s and was accompanied by shifts in the size distributions of stabilized islands in that stretch into the 1960s. Elsewhere, even in the easternmost study stretch, stabilizing was occurring by the late 1960s, the same time frame documented by investigations of the Platte system upstream of the study area. Comprehensive management plans for the lower Platte River should account, at least in theory, for the observed differences in stream behavior upstream and downstream of the major eastern tributaries.     

Seabird guano influences on desert islands: soil chemistry and herbaceous species richness and productivity

An understanding of the effects of guano deposition on arid soil chemistry and the consequences for plant communities is lacking. This study examined patterns of herbaceous species richness and productivity, soil chemistry, soil moisture and soil respiration on 11 islands in the Gulf of California, six of which receive seabird guano deposition. Species richness was significantly lower on islands with guano (“Bird” islands) than islands without guano (“Non-bird” islands), with very little overlap in species composition; however, productivity was significantly greater on Bird than on Non-bird islands. As expected, Bird island soils had higher concentrations of NO₃⁻, NH₄⁺ and total nitrogen (N) than Non-bird island soils; and, measurements of δ¹⁵N indicate that the higher concentrations of N were derived from guano. We also found that soil moisture and respiration were significantly higher, but pH was significantly lower, on Bird than Non-bird islands. These results suggest that guano deposition in deserts stimulates productivity—even in dry years—due to elevated N and, indirectly, soil moisture. Guano deposition also results in a decrease in species richness and a change in species composition probably due to elevated N, N toxicity, or low pH. However, we also found that pH varied more on Bird than on Non-bird islands; and that salinity—while not different between island types—was significantly patchier on Bird than on Non-Bird islands. These results suggest that guano deposition affects not only the general chemical composition of soils, but also results in greater spatial variation in soil chemical composition, which may ultimately affect species richness and composition. Therefore, understanding spatial patterning in soil chemistry as a result of guano deposition is critical for understanding guano effects on plant richness and productivity.