scholarly journals Historical geomorphic analysis of Someșul Mic River (NW Romania) channel spatial and temporal behavior, as a background for the assessment of present day morphological state of the river

2019 ◽  
Vol 21 (1) ◽  
pp. 59-76
Author(s):  
Ioana PERȘOIU ◽  
Maria HOSU
Keyword(s):  
Human Impacts ◽  
River Management ◽  
Temporal Response ◽  
Fluvial Systems ◽  
Channel Dynamics ◽  
The Past ◽  
Management Actions ◽  
Geological Conditions ◽  
Decadal Scale ◽  
Morphological State

In the context of the increased interest on integrating the complex spatial and temporal response of fluvial systems to human impacts into the process of assessing the ecological state of the rivers and in promoting a sustainable river management European countries have developed a multi–scalar, hierarchical, process based hydro–morphological framework focused on understanding the river functioning and evolution as a basis for interpreting current conditions. In this context, the goal of this paper is to demonstrate the usefulness of systematic historic and present day geomorphic analysis along channel reaches with distinct typologies in order to generate a better image of river morphology as a background for assessing its present morphological state. The historical geomorphic analysis of Someșul Mic River’s channel dynamics during the past 250 years has shown that the main controlling factor is climate through its centennial – decadal scale variations in magnitudes and amplitudes of flood events, while the local geological conditions and hydrotechnical works having subordinate effects. The reference condition in assessing the present day morphological state of the river was defined based on channel typology and dynamics between AD 1860 – AD 1970, reflecting a river state far from a pristine condition, but characterized trough human impacts maintained bellow the river sensitivity to disturbances. The Morphological Quality Index (MQI) was calculated for 17 distinct channel reaches. Its values indicate the high geomorphic degradation of the river induced by hydrotechnical interventions along the channel. Very poor conditions are concentrated mainly along the upper reaches of the river, while further downstream the river is in a dominantly moderate deterioration state. The resulted image has the potential to better identify the critical reaches along this river, and the main disturbatory elements acting on them, in order to support better projections on possible channel trajectories andsubsequently river management actions.

scholarly journals Indigenous impacts on North American Great Plains fire regimes of the past millennium

2018 ◽  
Vol 115 (32) ◽  
pp. 8143-8148 ◽  
Author(s):  
Christopher I. Roos ◽  
María Nieves Zedeño ◽  
Kacy L. Hollenback ◽  
Mary M. H. Erlick
Keyword(s):  
North American ◽  
Human Impacts ◽  
Fire Regimes ◽  
Human Populations ◽  
The Past ◽  
Fire Use ◽  
Decadal Scale ◽  
Fire Activity ◽  
Prairie Fire ◽  
Past Millennium

Fire use has played an important role in human evolution and subsequent dispersals across the globe, yet the relative importance of human activity and climate on fire regimes is controversial. This is particularly true for historical fire regimes of the Americas, where indigenous groups used fire for myriad reasons but paleofire records indicate strong climate–fire relationships. In North American grasslands, decadal-scale wet periods facilitated widespread fire activity because of the abundance of fuel promoted by pluvial episodes. In these settings, human impacts on fire regimes are assumed to be independent of climate, thereby diminishing the strength of climate–fire relationships. We used an offsite geoarchaeological approach to link terrestrial records of prairie fire activity with spatially related archaeological features (driveline complexes) used for intensive, communal bison hunting in north-central Montana. Radiocarbon-dated charcoal layers from alluvial and colluvial deposits associated with driveline complexes indicate that peak fire activity over the past millennium occurred coincident with the use of these features (ca. 1100–1650 CE). However, comparison of dated fire deposits with Palmer Drought Severity Index reconstructions reveal strong climate–fire linkages. More than half of all charcoal layers coincide with modest pluvial episodes, suggesting that fire use by indigenous hunters enhanced the effects of climate variability on prairie fire regimes. These results indicate that relatively small, mobile human populations can impact natural fire regimes, even in pyrogeographic settings in which climate exerts strong, top-down controls on fuels.

Managing rivers for conservation and ecotourism in the Kruger National Park

1995 ◽  
Vol 32 (5-6) ◽  
pp. 227-233 ◽  
Author(s):  
F. J. Venter ◽  
A. R. Deacon
Keyword(s):  
National Park ◽  
Good Condition ◽  
Kruger National Park ◽  
Rapid Expansion ◽  
Natural Environments ◽  
The West ◽  
The Past ◽  
Management Actions ◽  
Flow Through ◽  
Three Rivers

Six major rivers flow through the Kruger National Park (KNP). All these rivers originate outside and to the west of the KNP and are highly utilized. They are crucially important for the conservation of the unique natural environments of the KNP. The human population growth in the Lowveld during the past two decades brought with it the rapid expansion of irrigation farming, exotic afforestation and land grazed by domestic stock, as well as the establishment of large towns, mines, dams and industries. Along with these developments came overgrazing, erosion, over-utilization and pollution of rivers, as well as clearing of indigenous forests from large areas outside the borders of the KNP. Over-utilization of the rivers which ultimately flow through the KNP poses one of the most serious challenges to the KNP's management. This paper gives the background to the development in the catchments and highlights the problems which these have caused for the KNP. Management actions which have been taken as well as their results are discussed and solutions to certain problems proposed. Three rivers, namely the Letaba, Olifants and Sabie are respectively described as examples of an over-utilized river, a polluted river and a river which is still in a fairly good condition.

scholarly journals Fluvial Geomorphology and River Management

Water ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1608
Author(s):  
Salvatore Ivo Giano
Keyword(s):  
Human Activities ◽  
River Restoration ◽  
Fluvial Geomorphology ◽  
Landscape Evolution ◽  
River Management ◽  
Special Issue ◽  
Fluvial Systems ◽  
The Impact

This Special Issue deals with the role of fluvial geomorphology in landscape evolution and the impact of human activities on fluvial systems, which require river restoration and management [...]

scholarly journals Supporting Restoration Decisions through Integration of Tree-Ring and Modeling Data: Reconstructing Flow and Salinity in the San Francisco Estuary over the Past Millennium

Water ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2139
Author(s):  
Paul H. Hutton ◽  
David M. Meko ◽  
Sujoy B. Roy
Keyword(s):  
San Francisco ◽  
Tree Ring ◽  
San Francisco Estuary ◽  
Salinity Intrusion ◽  
Estuarine Ecosystem ◽  
Freshwater Flow ◽  
The Past ◽  
Decadal Scale ◽  
Tree Ring Data ◽  
Past Millennium

This work presents updated reconstructions of watershed runoff to San Francisco Estuary from tree-ring data to AD 903, coupled with models relating runoff to freshwater flow to the estuary and salinity intrusion. We characterize pre-development freshwater flow and salinity conditions in the estuary over the past millennium and compare this characterization with contemporary conditions to better understand the magnitude and seasonality of changes over this time. This work shows that the instrumented flow record spans the range of runoff patterns over the past millennium (averaged over 5, 10, 20 and 100 years), and thus serves as a reasonable basis for planning-level evaluations of historical hydrologic conditions in the estuary. Over annual timescales we show that, although median freshwater flow to the estuary has not changed significantly, it has been more variable over the past century compared to pre-development flow conditions. We further show that the contemporary period is generally associated with greater spring salinity intrusion and lesser summer–fall salinity intrusion relative to the pre-development period. Thus, salinity intrusion in summer and fall months was a common occurrence under pre-development conditions and has been moderated in the contemporary period due to the operations of upstream reservoirs, which were designed to hold winter and spring runoff for release in summer and fall. This work also confirms a dramatic decadal-scale hydrologic shift in the watershed from very wet to very dry conditions during the late 19th and early 20th centuries; while not unprecedented, these shifts have been seen only a few times in the past millennium. This shift resulted in an increase in salinity intrusion in the first three decades of the 20th century, as documented through early records. Population growth and extensive watershed modification during this period exacerbated this underlying hydrologic shift. Putting this shift in the context of other anthropogenic drivers is important in understanding the historical response of the estuary and in setting salinity targets for estuarine restoration. By characterizing the long-term behavior of San Francisco Estuary, this work supports decision-making in the State of California related to flow and salinity management for restoration of the estuarine ecosystem.

scholarly journals Have Human Impacts Changed Alpine Zooplankton Diversity over the past 100 Years?

2001 ◽  
Vol 33 (4) ◽  
pp. 467 ◽  
Author(s):  
Monika Winder ◽  
Michael T. Monaghan ◽  
Piet Spaak
Keyword(s):  
Human Impacts ◽  
The Past ◽  
Alpine Zooplankton

scholarly journals Temporal refuges differ between anthropogenic and natural top down pressures in a subordinate carnivore

2020 ◽  
Author(s):  
Rumaan Malhotra ◽  
Samantha Lima ◽  
Nyeema C. Harris
Keyword(s):  
Human Impacts ◽  
Temporal Response ◽  
Apex Predators ◽  
Top Down ◽  
Anthropogenic Pressures ◽  
Multiple Camera ◽  
Disturbed Systems ◽  
Food Subsidies ◽  
Predator Guild ◽  
Fear Effects

ABSTRACTApex predators structure communities through consumptive and non-consumptive pathways. In the carnivore guild, this can result in a within-guild cascade through the suppression of mesocarnivores. As the top-down influences of apex predators wane due to human-driven declines, landscape level anthropogenic pressures are rising. Human impacts can be analogous to apex predators in that humans can drive increased mortality in both prey species and carnivores, and impact communities through indirect fear effects and food subsidies. Here, we evaluate whether anthropogenic top-down pressures can structure communities in a similar manner as apex predators in shaping the interactions of mesocarnivores. Specifically, we expect anthropogenic forces to induce comparable effects as occurrence of apex predators in driving spatiotemporal partitioning between two mesocarnivores. Using multiple camera-trap surveys, we compared the temporal response of a small carnivore, the raccoon (Procyon lotor), to the larger coyote (Canis latrans) at four sites across Michigan that represented opposing gradients of pressure from humans and apex predators. Contrary to our expectations, we found that raccoons shifted their activity pattern in response to coyotes at sites with higher anthropogenic pressures and exhibited no temporal response at sites with apex predators. Temporal shifts were characterized by raccoons being more diurnal in areas of high coyote activity. We conclude that despite superficial similarities, anthropogenic forces do not replace the function of native apex predators in structuring the mesocarnivore guild. As such, an intact and functioning native predator guild remains necessary to preserve spatiotemporal community structure, in natural and disturbed systems alike.

scholarly journals A multi-proxy investigation of late-Holocene temperature change and climate-driven fluctuations in sediment sourcing: Simpson Lagoon, Alaska

The Holocene ◽  
2018 ◽  
Vol 28 (6) ◽  
pp. 984-997 ◽  
Author(s):  
Andrea JM Hanna ◽  
Timothy M Shanahan ◽  
Mead A Allison ◽  
Thomas S Bianchi ◽  
Kathryn M Schreiner
Keyword(s):  
Environmental Changes ◽  
Clay Mineralogy ◽  
Ice Cores ◽  
Temperature Reconstruction ◽  
Ice Age ◽  
Fluvial Systems ◽  
Arctic Regions ◽  
Coastal Marine ◽  
Decadal Scale ◽  
Climate Events

The significant and ongoing environmental changes in Arctic regions demonstrate the need for quantitative, high-resolution records of pre-industrial climate change in this climatically sensitive region; such records are fundamental for understanding recent anthropogenic changes in the context of natural variability. Sediment contained within Arctic coastal environments proximal to large fluvial systems has the ability to record paleoclimate variability on subdecadal to decadal scale resolution, on par with many other terrestrial climate archives (i.e. lake sediments, ice cores). Here, we utilize one such sediment archive from Simpson Lagoon, Alaska, located adjacent to the Colville River Delta to reconstruct temperature variability and fluctuations in sediment sourcing over the past 1700 years. Quantitative reconstructions of summer air temperature are obtained using the branched glycerol dialkyl glycerol tetraether (brGDGT)-derived methylation index of branched tetraethers (MBT’)/cyclization ratio of branched tetraether (CBT) paleothermometer and reveal temperature departures correlative with noted climate events (i.e. ‘Little Ice Age’, ‘Medieval Climate Anomaly’). In addition, temporal variability in sediment sourcing to the lagoon, determined using a multi-proxy approach (i.e. granulometry, elemental analysis, clay mineralogy), broadly corresponds with temperature fluctuations, indicating relative increases in fluvial sediment discharge during colder intervals and decreased river discharge/increased coastal erosion during warmer periods. The Simpson Lagoon record presented in this study is the first temperature reconstruction, to our knowledge, developed from coastal marine sediments in the Alaskan Beaufort Sea.

scholarly journals How predictable is extinction? Forecasting species survival at million-year timescales

2019 ◽  
Vol 374 (1788) ◽  
pp. 20190392 ◽  
Author(s):  
Peter Smits ◽  
Seth Finnegan
Keyword(s):  
Fossil Record ◽  
Human Impacts ◽  
Rank Order ◽  
Extinction Risk ◽  
Geographical Range ◽  
The Past ◽  
The Future ◽  
Out Of Sample ◽  
Extinction Events ◽  
Over Time

A tenet of conservation palaeobiology is that knowledge of past extinction patterns can help us to better predict future extinctions. Although the future is unobservable, we can test the strength of this proposition by asking how well models conditioned on past observations would have predicted subsequent extinction events at different points in the geological past. To answer this question, we analyse the well-sampled fossil record of Cenozoic planktonic microfossil taxa (Foramanifera, Radiolaria, diatoms and calcareous nanoplankton). We examine how extinction probability varies over time as a function of species age, time of observation, current geographical range, change in geographical range, climate state and change in climate state. Our models have a 70–80% probability of correctly forecasting the rank order of extinction risk for a random out-of-sample species pair, implying that determinants of extinction risk have varied only modestly through time. We find that models which include either historical covariates or account for variation in covariate effects over time yield equivalent forecasts, but a model including both is overfit and yields biased forecasts. An important caveat is that human impacts may substantially disrupt range-risk dynamics so that the future will be less predictable than it has been in the past. This article is part of a discussion meeting issue ‘The past is a foreign country: how much can the fossil record actually inform conservation?’

scholarly journals Diatoms in a sediment core from a flood pulse wetland in Malaysia record strong responses to human impacts and hydro‐climate over the past 150 years

2020 ◽  
Vol 7 (1) ◽  
Author(s):  
Charlotte L. Briddon ◽  
Suzanne McGowan ◽  
Sarah E. Metcalfe ◽  
Virginia Panizzo ◽  
Jack Lacey ◽  
...  
Keyword(s):  
Sediment Core ◽  
Human Impacts ◽  
Flood Pulse ◽  
The Past

Human impacts on hydrology in the Pantanal wetland of South America

2002 ◽  
Vol 45 (11) ◽  
pp. 35-44 ◽  
Author(s):  
S.K. Hamilton
Keyword(s):  
South America ◽  
Human Activities ◽  
Human Impacts ◽  
Structure And Function ◽  
Natural State ◽  
Ecological Structure ◽  
The Past ◽  
Influences Of Human Activities ◽  
And Function ◽  
Pantanal Wetland

Inundation patterns in the Pantanal remain in a relatively natural state, yet a number of significant human influences have occurred in the past, and there is potential for more severe human impacts as development of the region continues in the future. The objectives of this paper are 1) to briefly review the linkages between hydrology and ecological structure and function in the Pantanal; 2) to review some documented cases of historical influences of human activities on hydrology in the region; and 3) to consider potential future impacts, particularly in regard to the recently proposed navigation project known as the Paraguay-Paraná Waterway (or Hidrovía).

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