The Big Questions in Geography

In noting his fondness for geography, John Noble Wilford, science correspondent for The New York Times, nevertheless challenged the discipline to articulate those big questions in our field, ones that would generate public interest, media attention, and the respect of policymakers. This article presents our collective judgments on those significant issues that warrant disciplinary research. We phrase these as a series of ten questions in the hopes of stimulating a dialogue and collective research agenda for the future and the next generation of geographic professionals.     

Chinese Industrial and Science Parks: Bridging the Gap

This article proposes the addition of a “bridge high technology” stage to Park's (1996) Asian development model, based upon field research and analysis of four “science and technology parks” in different regions of China: Shenzhen, Shanghai, Suzhou, and Xi’an. Initially established as learning districts to foster technology transfer from foreign to domestic enterprises, these specially configured spaces exhibit a variety of interactions indicating an increasing shift toward domestically generated technology for native companies. The mix and type of companies in parks at different locations within China reflect the locational comparative advantages of each place, whether as an outgrowth of local research or by government design.     

Resilience and justice: planning for New York City

New York City has developed recent policy initiatives under the rubric of resilience. I consider the implications of extending the concept of resilience beyond the physical environment, analyze the effect of planning for adaptation rather than prevention, and finally examine the positive role played by community groups organized for environmental justice in responding to resiliency planning. My argument is that use of the term resilience tends to obscure distributional impacts and, even under a progressive mayor, supports neoliberal policy initiatives.     

Multiproxy surface wetness records from replicate cores on an ombrotrophic mire: implications for Holocene palaeoclimate records

Ombrotrophic mires can provide records of palaeoclimate over the mid- to late- Holocene in several areas of the world. Their potential is currently partly limited by difficulties with scaling indices based on plant macrofossils and humification, and the need to account for the internal variability of the mire system. This paper explores the use of testate amoebae analysis as a third technique and assesses the minimum within-site variability by comparing results from two closely spaced cores. Reconstruction of surface wetness changes was carried out on cores from the centre of an intermediate raised-blanket mire, Coom Rigg Moss, Northumberland, by analysis of testate amoebae, plant macrofossils and humification. Surface wetness changes were expressed as mean annual water table changes inferred from testate amoebae assemblages, two separate indices based on plant macrofossils and percentage transmission of humification extracts. Comparisons between the proxies suggest good agreement of general trends in Sphagnum peats but some differences in monocot and ericaceous peats. The magnitude of surface wetness changes also differs within Sphagnum peats. The records from the separate cores converge over time and replicability between cores is best in the last 1000 yr. Changes over this period are similar to those shown by estimates based on documentary sources. Good agreement is obtained between a normalised plant macrofossil index and normalised reconstructed water-table values and it is suggested that this approach could form the basis for improved composite, multiproxy records from peatlands. Copyright © 1999 John Wiley & Sons, Ltd.     

Regional and species specific sexual reproductive patterns of three zooxanthellate scleractinian corals across the Eastern Tropical Pacific

Sexual reproduction of zooxanthellate scleractinian corals in the Eastern Tropical Pacific (ETP) is influenced by the interactive effects of regional and local oceanographic conditions, as well as a variety of other environmental factors. Differences in spatial and temporal gamete development and reproductive patterns of three widespread scleractinian corals of this region—Pocillopora damicornis (branching colony morphology, characterized as hermaphrodite broadcaster), Pavona gigantea (massive colonies, characterized as gonochoric broadcaster/sequential co‐sexually hermaphroditic) and Porites panamensis (encrusting colonies, characterized as gonochoric brooder)—were evaluated at local and regional scales across the ETP. This area extended from the Gulf of California (24°N) to the southern coast of Ecuador (–1°S), including offshore islands, using existing data pooled from prior studies. Predictive models were employed based on environmental variables: sea surface temperature, daylight hours, diffuse attenuation co‐efficient at 490 nm and photosynthetically active radiation. Datasets were extracted from satellite images ( https://oceancolor.gsfc.nasa.gov ) and analysed using WAM_STATIST ver. 6.33® software to obtain monthly average data from each site. The spatial (region, sub‐region and site) and seasonal (wet, dry) variation in reproductive activity (% colonies with gametes) differed among the three species; significant interactions were season × sub‐region for P. damicornis, season × site (sub‐region) for P. gigantea, and season × site for P. panamensis, for which sub‐region was not considered as a factor. The predictive models also suggest that gamete production/maturation of P. damicornis and P. gigantea is influenced by local differences in sea surface temperature and daylight hours. Porites panamensis was not correlated with any environmental variable examined. Variations in local and regional reproductive developmental patterns are likely an acclimatization response by each species imposed by the timing and duration of local stressor events. This analysis has provided insights into the diverse local and regional physical drivers that affect species responses and acclimatization in sexual reproduction across the ETP.     

Using Resin‐Based 3D Printing to Build Geometrically Accurate Proxies of Porous Sedimentary Rocks

Three‐dimensional (3D) printing is capable of transforming intricate digital models into tangible objects, allowing geoscientists to replicate the geometry of 3D pore networks of sedimentary rocks. We provide a refined method for building scalable pore‐network models (“proxies”) using stereolithography 3D printing that can be used in repeated flow experiments (e.g., core flooding, permeametry, porosimetry). Typically, this workflow involves two steps, model design and 3D printing. In this study, we explore how the addition of post‐processing and validation can reduce uncertainty in the 3D‐printed proxy accuracy (difference of proxy geometry from the digital model). Post‐processing is a multi‐step cleaning of porous proxies involving pressurized ethanol flushing and oven drying. Proxies are validated by: (1) helium porosimetry and (2) digital measurements of porosity from thin‐section images of 3D‐printed proxies. 3D printer resolution was determined by measuring the smallest open channel in 3D‐printed “gap test” wafers. This resolution (400 µm) was insufficient to build porosity of Fontainebleau sandstone (～13%) from computed tomography data at the sample's natural scale, so proxies were printed at 15‐, 23‐, and 30‐fold magnifications to validate the workflow. Helium porosities of the 3D‐printed proxies differed from digital calculations by up to 7% points. Results improved after pressurized flushing with ethanol (e.g., porosity difference reduced to ～1% point), though uncertainties remain regarding the nature of sub‐micron “artifact” pores imparted by the 3D printing process. This study shows the benefits of including post‐processing and validation in any workflow to produce porous rock proxies.     

Understanding fracture distribution and its relation to knickpoint evolution in the Rio Icacos watershed (Luquillo Critical Zone Observatory,Puerto Rico) using landscape-scale hydrogeophysics

The Rio Icacos watershed in the Luquillo Mountains (Puerto Rico) is unique due to its extremely rapid weathering rates. The watershed is incised into a quartz diorite that has developed a large knickzone defining the river profile. Regolith thickness within the watershed generally decreases from 20 to 30 m at the ridges to several meters in the quartz diorite-dominated valley to tens of centimeters near the major river knickpoint, as determined from previous studies. Above the knickzone, we observe spheroidal corestones, but below this weathering is much less apparent. Measured erosion rates from previous studies are also high in the knickzone compared with upper elevations within the river profile. A suite of near-surface geophysical methods (i.e. ground penetrating radar and terrain conductivity) capable of fast data acquisition in rugged landscapes, was deployed at kilometer scales to characterize critical zone structure. Concentrations of chaotic ground penetrating radar (GPR) reflections and diffraction hyperbolas with low electrical conductivity were observed in vertical zones that outcrop at the land surface as areas of intense fracturing and spheroidally weathered corestones. The width of these fractured and weathered zones showed an increase with proximity to the knickpoint, and was attributed to dilation of these sub-vertical fractures near the knickpoint, as postulated theoretically by a stress model calculated for the topographic variability across the knickzone in the Rio Icacos, and that shows a release of compressive stress near the knickpoint. We hypothesize that erosion rates increase in the knickzone because of this inferred dilation of fractures. Specifically, opened fractures could enhance access of water and in turn promote spalling, erosion, and spheroidal weathering. This study shows that ground-based hydrogeophysical methods used at the landscape-scale (traditionally applied at smaller scales) can be used to explore critical zone architecture at the scales needed to explain the extreme variability in erosion rates across river profiles. © 2018 John Wiley & Sons, Ltd.     

Postglacial to Holocene landscape evolution and process rates in steep alpine catchments

Climate change and high magnitude mass wasting events pose adverse societal effects and hazards, especially in alpine regions. Quantification of such geomorphic processes and their rates is therefore critical but is often hampered by the lack of appropriate techniques and the various spatiotemporal scales involved in these studies. Here we exploit both in situ cosmogenic beryllium-10 (¹⁰Be) and carbon-14 (¹⁴C) nuclide concentrations for deducing exposure ages and tracing of sediment through small alpine debris flow catchments in central Switzerland. The sediment cascade and modern processes we track from the source areas, through debris flow torrents to their final export out into sink regions with cosmogenic nuclides over an unprecedented five-year time series with seasonal resolution. Data from a seismic survey and a 90 m core revealed a glacially overdeepened basin, filled with glacial and paraglacial sediments. Surface exposure dating of fan boulders and radiocarbon ages constrain the valley fill from the last deglaciation until the Holocene and show that most of the fan existed in early Holocene times already. Current fan processes are controlled by episodic debris flow activity, snow (firn) and rock avalanches. Field investigations, digital elevation models (DEMs) of difference and geomorphic analysis agree with sediment fingerprinting with cosmogenic nuclides, highlighting that the bulk of material exported today at the outlet of the subcatchments derives from the lower fans. Cosmogenic nuclide concentrations steadily decrease from headwater sources to distal fan channels due to the incorporation of material with lower nuclide concentrations. Further downstream the admixture of sediment from catchments with less frequent debris flow activity can dilute the cosmogenic nuclide signals from debris flow dominated catchments but may also reach thresholds where buffering is limited. Consequently, careful assessment of boundary conditions and driving forces is required when apparent denudation rates derived from cosmogenic nuclide analysis are upscaled to larger regions. © 2018 John Wiley & Sons, Ltd.     

Multi‐method (14C, 36Cl, 234U/230Th) age bracketing of the Tschirgant rock avalanche (Eastern Alps): implications for absolute dating of catastrophic mass‐wasting

Correct and precise age determination of prehistorical catastrophic rock‐slope failures prerequisites any hypotheses relating this type of mass wasting to past climatic regimes or palaeo‐seismic records. Despite good exposure, easy accessibility and a long tradition of absolute dating, the age of the 230 million m³ carbonate‐lithic Tschirgant rock avalanche event of the Eastern Alps (Austria) still is relatively poorly constrained. We herein review the age of mass‐wasting based on a total of 17 absolute ages produced with three different methods (¹⁴C, ³⁶Cl, ²³⁴U/²³⁰Th). Chlorine‐36 (³⁶Cl) cosmogenic surface exposure dating of five boulders of the rock avalanche deposit indicates a mean event age of 3.06 ± 0.62 ka. Uranium‐234/thorium‐230 (²³⁴U/²³⁰Th) dating of soda‐straw stalactites formed in microcaves beneath boulders indicate mean precipitation ages of three individual soda straws at 3.20 ± 0.26 ka, 3.04 ± 0.10 ka and 2.81 ± 0.15 ka; notwithstanding potential internal errors, these ages provide an ‘older‐than’ (ante quam) proxy for mass‐wasting. Based on radiocarbon ages (nine sites) only, it was previously suggested that the present rock avalanche deposit represents two successive failures (3.75 ± 0.19 ka bp , 3.15 ± 0.19 ka bp ). There is, however, no evidence for two events neither in surface outcrops nor in LiDAR derived imagery and drill logs. The temporal distribution of all absolute ages (¹⁴C, ³⁶Cl, ²³⁴U/²³⁰Th) also does not necessarily indicate two successive events but suggest that a single catastrophic mass‐wasting took place between 3.4 and 2.4 ka bp . Taking into account the maximum age boundary given by reinterpreted radiocarbon datings and the minimum U/Th‐ages of calcite precipitations within the rock avalanche deposits, a most probable event age of 3.01 ± 0.10 ka bp can be proposed. Our results underscore the difficulty to accurately date catastrophic rock slope failures, but also the potential to increase the accuracy of age determination by combining methods. Copyright © 2016 John Wiley & Sons, Ltd.