The role of urbanization in the flooding and surface water chemistry of Puerto Rico’s mangroves

ABSTRACT

In this study, water level models are constructed to characterize mangrove flooding across urban gradients in Puerto Rico. The most urban sites exhibited 95% longer hydroperiods, 23% lower flood frequencies, and 110% lower depths than the least urban sites. Rainfall importance was explained more by geomorphology and tidal connectivity than by urbanization, but there was evidence for changes in tidal amplitudes along the urban gradient. Relationships between surface water chemical metrics and land cover contradicted previous studies by suggesting lower nutrients and biochemical oxygen demand with increasing urbanization. However, much of this changed with the exclusion of potential outlier sites, as well as under different statistical comparisons. These results reinforce the understanding that the most important drivers of urban mangrove hydrology and water quality in Puerto Rico are likely geomorphology and tidal connectivity, with some influence from surrounding land cover. Results should be considered alongside the reported errors stemming from digital elevation and rainfall response models.     

The open veins of Latin America: Long-term physical trade flows (1900–2016)

Latin America has long played a key role in the global provision of natural resources. Most of the continent's economies are net exporters of low-value, primary products and importers of manufactured goods at a high price. This pattern of specialised trade has highly negative consequences for economic development, the environment, and the local population’s wellbeing. Yet to date, little empirical evidence has been collected on Latin America’s total contribution to the rest of the world's regions in historical perspective. Applying the Material Flow Accounting methodology, this paper estimates the physical and monetary trade of 16 Latin American economies between 1900 and 2016. Our results show that: (i) yearly net exports of materials went from 4 Mt to 610 Mt between 1900 and 2016, and greatly accelerated since the World War II. (ii) Latin America is a net exporter of most types of materials (fossil fuels, non-energy minerals and biomass), so it harbours socio-environmental problems associated with different types of extractivism. (iii) Different regional export patterns exist: Andeans export subsoil (mining and energy carriers) while the rest export soil (land-based products). The countries with the lowest net exports are the smallest in size and with the highest population density. (iv) Europe and the USA have historically received most of the imports, but since the end of the twentieth century, the Southeast Asia region is the biggest importer of materials from Latin America. (v) The price received for exported material is much lower than the price paid for imported material; and (vi) various historical periods can be differentiated regarding the relationship between economic growth and physical trade balance.     

地理协同论——从理解“人—地关系”到设计“人—地协同”

本文从地球进入"人类世"(Anthropocene)之后,实现世界可持续发展、建设人类命运共同体的角度出发,就地表系统的复杂性、人类面临的各种灾难以及将要面临的各种资源短缺和环境风险等问题,提出发展"地理协同论",即:地球表层系统与区域可持续性机理、过程与动力学,以实现地理学研究从理解"人—地关系"到设计"人—地协同"的转变。着眼于"人类世"时代地球表层系统由多尺度、多过程等组成的复杂性,回顾了区域论、综合论、系统论等经典地理学理论,从自然单元与社会单元的结合、自然资源利用与自然灾害防御、人类功与过的评价、自然地图与行政地图间的关系、动力学与非动力学的耦合等主题入手,深入讨论了现代地理科学与技术问题。通过理解灾害系统及其致灾成害机理、过程和动力学,构建凝聚度指标,量化综合减灾系统的复杂性。利用协同宽容、约束、放大和分散原理,以灾害风险防范共识最高、成本最低、福利最大、风险最小化为目标,构建以政府为主导、企业为主体和社区全面参与的综合灾害风险防范凝聚力模式。在分析都江堰工程如何实现除害与兴利并举的基础上,综合阐释了"人类世"时代"适度改造自然",以实现人与自然的协同。     

“人类世”的提出与争议

“人类世”(The Anthropocene)一词自2000年以来逐渐流行并越来越多地见诸于环境科学、地球科学以及社会和人文学科的各种期刊文章和书籍。本研究简要介绍有关“人类世”概念的提出、科学意义和相关的最新进展, 特别是国际地层委员会第四纪地层分委员会的人类世工作组(Anthropocene Working Group)正在推进将“人类世”作为一个正式地质年代单位的工作; 同时也介绍与之有关的争议, 例如关于如何界定“人类世”的底界, 以及“人类世”是否应当被看作是一个地质事件, 而不是一个新的地质年代单位。分析认为, 人类活动已经对地球环境造成极为深远的影响, 但现今是否已经进入了一个新的地质年代尚待确定。学术界应当搁置争议, 将注意力集中于研究人类活动对地球环境影响的事实和机制, 为人类社会减缓和适应日益加剧的全球环境变化做出贡献。

     

人类世的地球化学标志——沉积物中的持久性有机污染物

确定人类世地层标志物是选取全球层型剖面和点（GSSP）的重要前提。目前水系沉积记录作为人类世GSSP的候选表现出显著优越性。水系沉积物中的持久性有机污染物（POPs）可以连续、高分辨率地反映人类活动影响和强度变化,通过横向对比全球POPs历史变化可以获取潜在标志物的高速增长起点。本次研究收集了3类POPs的69套数据,通过分析数据的时间趋势重建其沉积记录,以求获得全球范围内各类POPs的增长特征。全球沉积记录显示20世纪40~60年代间不同类型的POPs开始展现出不同程度的快速增长,其中多环芳烃（PAHs）和多氯联苯（PCBs）可以作为潜在的标志物指示沉积物中化学地层的界限,有机氯农药（OCPs）中只有滴滴涕（DDTs）具备这种特性。同时,这3类POPs的沉积记录可以反映人类能源消耗、农业生产和工业品商品制造等方面活动,作为标志物体现人类多种活动营力在地球系统中留下的证据。

     

An observation-based method to quantify the human influence on hydrological drought: upstream–downstream comparison

In this present era of the Anthropocene, human activities affect hydrology and droughts. Quantifying this human influence improves our understanding and builds fundamental knowledge for water resource management. Analysis of observation data is useful in progressing this knowledge as these human activities and feedbacks are intrinsically included. Therefore, here we present an observation-based approach, the upstream–downstream comparison, to quantify changes in hydrological drought downstream of a human activity. We demonstrate this approach in a basin in northern Chile, where a reservoir was introduced. A sensitivity analysis is performed to assess how different choices of drought analysis threshold can affect the results and interpretation. We find that many commonly used choices do not exclude human activities from the threshold and therefore could be underestimating the change detected due to the human influence. The upstream–downstream comparison avoids this through the application of the upstream station threshold rather than the human-influenced downstream station.     

Creating a thinking space for the rising stars of Australian urban geography

The Institute of Australian Geographers Urban Study Group and Australian Geographer present the first essay in our Leading Insights/Thinking Space partnership. We discuss Dr Natalie Osborne's 2018 essay, flag Dr Marilu Melo's 2019 essay and talk about creating a thinking space for the rising stars of Australian urban geography.     

A Five-stage Evolution of Earth's Phosphorus Cycle

Phosphorus(P) is a key biological nutrient and probably the ultimate limiter of marine productivity during Earth history.In recent years,a wealth of new knowledge has revolutionized our understanding of the global P cycle,yet its longterm evolution remains incompletely documented.In this paper,we review the effects of three major controlling factors on the long-term evolution of the global P cycle,i.e.,tectonics,marine redox conditions,and bio-evolution,on the basis of which a five-stage model i...     

Bio-cultural refugia—Safeguarding diversity of practices for food security and biodiversity

Food security for a growing world population is high on the list of grand sustainability challenges, as is reducing the pace of biodiversity loss in landscapes of food production. Here we shed new insights on areas that harbor place specific social memories related to food security and stewardship of biodiversity. We call them bio-cultural refugia. Our goals are to illuminate how bio-cultural refugia store, revive and transmit memory of agricultural biodiversity and ecosystem services, and how such social memories are carried forward between people and across cohorts. We discuss the functions of such refugia for addressing the twin goals of food security and biodiversity conservation in landscapes of food production. The methodological approach is first of its kind in combining the discourses on food security, social memory and biodiversity management. We find that the rich biodiversity of many regionally distinct cultural landscapes has been maintained through a mosaic of management practices that have co-evolved in relation to local environmental fluctuations, and that such practices are carried forward by both biophysical and social features in bio-cultural refugia including; genotypes, artifacts, written accounts, as well as embodied rituals, art, oral traditions and self-organized systems of rules. Combined these structure a diverse portfolio of practices that result in genetic reservoirs—source areas—for the wide array of species, which in interplay produce vital ecosystem services, needed for future food security related to environmental uncertainties, volatile financial markets and large scale conflicts. In Europe, processes related to the large-scale industrialization of agriculture threaten such bio-cultural refugia. The paper highlights that the dual goals to reduce pressures from modern agriculture on biodiversity, while maintaining food security, entails more extensive collaboration with farmers oriented toward ecologically sound practices.     

Empirical models for describing recent sedimentation rates in lakes distributed across broad spatial scales

Over the last 20 years there has been a surge of interest in paleolimnology and as a result a large accumulation of lake sedimentation records. This emerging archive has allowed us to develop empirical models to describe which variables explain significant variation in sedimentation rates over the past ∼150 years across large spatial scales. We hypothesized that latitude would be a significant explanatory variable of profundal zone lake sedimentation rates across a temperate to polar gradient. We further hypothesized that along a more longitudinally-constrained dataset (i.e. east coast of North America), latitude would explain a greater proportion of the variance. To test these hypotheses, we collated data from 125 natural, average-sized lakes (with surface area <500 km²) by recording authors’ estimates of sedimentation rates (measured as mm/year) or by digitizing recent sediment profiles and calculating sedimentation rates over the past ∼150 years. We found that, at both scales, latitude was the strongest predictor of lake sedimentation rates (full dataset: r ² = 0.28, P = 0.001, n = 125; east coast dataset: r ² = 0.58, P < 0.001, n = 43). By conducting a multiple linear regression analysis, we found that 70% of the variance in sedimentation rates from the east coast transect was explained by latitude and elevation alone. This latter model is of sufficient strength that it is a robust predictive tool. Given that climate and land-use strongly co-vary with latitude and that both of these factors have previously been shown to influence lake sedimentation rates, it appears that latitude is a surrogate measure for climate and land-use changes. We also show support for land-use as an important variable influencing sedimentation rates by demonstrating large increases in recent versus Holocene accumulation rates. These results indicate that it is possible to make generalizations about sedimentation rates across broad spatial scales with even limited geographic data.