PeerJ Preprints: Climate Change Biologyhttps://peerj.com/preprints/index.atom?journal=peerj&subject=1406Climate Change Biology articles published in PeerJ PreprintsMilankovitch forcing of Early Jurassic wildfireshttps://peerj.com/preprints/279912019-09-272019-09-27Teuntje Parnassia HollaarSarah Jane BakerJean-Francois DeconinckLuke ManderMicha RuhlStephen P HesselboClaire M Belcher
The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming and the frequency of large wildfires appears to be increasing. Recent research has indicated that Quaternary deposits reveal that wildfires respond to orbital forcings; however, to date no study has been able to test whether wildfire activity corresponds to changes over Milankovitch timescales in the deep past.
A high-resolution astrochronology exists for the Upper Pliensbachian in the Llanbedr (Mochras Farm) borehole (NW Wales). Ruhl et al. (2016) show that elemental concentration recorded by hand-held X-ray fluorescence (XRF), changes mainly at periodicities of ~21,000 year, ~100,000 year and ~400,000 year, and which can be related to visually described sedimentary bundles. We have quantified the abundance of fossil charcoal at a high resolution (10-15 cm) to test the hypothesis that these well-preserved climatic cycles influenced fire activity throughout this globally warm period.
Preliminary results suggest that variations in charcoal abundance are coupled to Milankovitch forcings over periods of ~21,000 and ~100,000 years. We suggest that these changes in fire relate to changes in seasonality and monsoonal activity that drove changes in vegetation that are linked to variations in the orbital forcing. Supplementary to the charcoal record, a high-resolution clay mineralogy dataset has been generated to further explain the climatic cyclicity observed in the wildfire record regarding the hydrology on land.
The Early Jurassic was characterized by major climatic and environmental perturbations which can be seen preserved at high resolution on orbital timescales. The Early Jurassic is a period of overall global warmth, and therefore serves as a suitable modern-day analogue to understand changes in the Earth System. Presently, Earth’s climate is warming and the frequency of large wildfires appears to be increasing. Recent research has indicated that Quaternary deposits reveal that wildfires respond to orbital forcings; however, to date no study has been able to test whether wildfire activity corresponds to changes over Milankovitch timescales in the deep past.A high-resolution astrochronology exists for the Upper Pliensbachian in the Llanbedr (Mochras Farm) borehole (NW Wales). Ruhl et al. (2016) show that elemental concentration recorded by hand-held X-ray fluorescence (XRF), changes mainly at periodicities of ~21,000 year, ~100,000 year and ~400,000 year, and which can be related to visually described sedimentary bundles. We have quantified the abundance of fossil charcoal at a high resolution (10-15 cm) to test the hypothesis that these well-preserved climatic cycles influenced fire activity throughout this globally warm period.Preliminary results suggest that variations in charcoal abundance are coupled to Milankovitch forcings over periods of ~21,000 and ~100,000 years. We suggest that these changes in fire relate to changes in seasonality and monsoonal activity that drove changes in vegetation that are linked to variations in the orbital forcing. Supplementary to the charcoal record, a high-resolution clay mineralogy dataset has been generated to further explain the climatic cyclicity observed in the wildfire record regarding the hydrology on land.All change for climate changehttps://peerj.com/preprints/279822019-09-242019-09-24Tony R Walker
Governments, corporations and individuals all need to take immediate action to help change the global economy toward a circular economy. A circular economy which uses fewer resources and based on renewable clean technologies to help limit global warming to 1.5 °C. The 2018 Intergovernmental Panel on Climate Change (IPCC) report warned that limiting global warming to 1.5 °C above pre-industrial levels would require current greenhouse-gas (GHG) emissions to be cut in half by 2030. Yet actions by governments, corporations and individuals are lagging behind. Many countries are failing their obligations made under the 2015 Paris climate agreement. Even the International Maritime Organization, a United Nations agency set a 50% reduction target of GHG emissions for global shipping by 2050, but this falls short of the IPCC target by 20 years. The United Nations climate summit in New York this week (September 2019) needs to send a strong wake up call to the entire world for us all to change. Change makers like Greta Thunberg has already done that. Individual actions to change consumer behaviour can play a major role to help reduce GHG emissions. Even reducing use of single-use plastics (a petroleum derivative) and incineration can help reduce GHG emissions. GHG emissions from plastics could reach 15% of the global carbon budget by 2050 if not curbed. In Europe, plastic production and incineration emits an estimated ~400 million tonnes of CO2 per year. Therefore, reducing single-use plastic use could curb GHG emissions.
Governments, corporations and individuals all need to take immediate action to help change the global economy toward a circular economy. A circular economy which uses fewer resources and based on renewable clean technologies to help limit global warming to 1.5 °C. The 2018 Intergovernmental Panel on Climate Change (IPCC) report warned that limiting global warming to 1.5 °C above pre-industrial levels would require current greenhouse-gas (GHG) emissions to be cut in half by 2030. Yet actions by governments, corporations and individuals are lagging behind. Many countries are failing their obligations made under the 2015 Paris climate agreement. Even the International Maritime Organization, a United Nations agency set a 50% reduction target of GHG emissions for global shipping by 2050, but this falls short of the IPCC target by 20 years. The United Nations climate summit in New York this week (September 2019) needs to send a strong wake up call to the entire world for us all to change. Change makers like Greta Thunberg has already done that. Individual actions to change consumer behaviour can play a major role to help reduce GHG emissions. Even reducing use of single-use plastics (a petroleum derivative) and incineration can help reduce GHG emissions. GHG emissions from plastics could reach 15% of the global carbon budget by 2050 if not curbed. In Europe, plastic production and incineration emits an estimated ~400 million tonnes of CO2 per year. Therefore, reducing single-use plastic use could curb GHG emissions.Organic facies variability and paleoenvironmental interpretation of the Early Toarcian of the Pyrenean Basin: the Bizanet and the Pont de Suert sectionshttps://peerj.com/preprints/279772019-09-242019-09-24Carolina FonsecaJoão Graciano Mendonça FilhoCarine LézinLuís Vítor DuartePhilippe Fauré
The Early Toarcian is characterized by major worldwide environmental changes recorded in an organic-rich black shale sedimentation and carbon cycle disturbances, the so-called Toarcian Oceanic Anoxic Event (T-OAE) (e.g. Jenkyns, 2010). This organic-rich sedimentation is particularly recorded in shallow marine epicontinental basins that developed as part of the Toarcian European epicontinental shelf, paleogeographical framework in which the Pyrenean Basin is incorporated (e.g. Fonseca et al., 2018; McArthur et al., 2008). With these premises, the main objective of this study is to assess the organic facies variability and to define the depositional paleoenvironments of two sections from the Pyrenean Basin (Bizanet and Pont de Suert) during the T-OAE, using palynofacies and geochemical (Total Organic Carbon - TOC and insoluble residue - IR) data. The Pyrenean tectonics that occurred between the latest Cretaceous and the Oligocene, deformed, detached and fragmented the substrate resulting in diverse tectonic units (Faure, 2002). The late Pliensbachian-early Toarcian of the Pont de Suert section, located in the South Pyrenean zone, is characterized by the limestone dominated Barre a Pecten Formation (Fm.), and the carbonate and/or argillaceous-carbonate alternation of its three members (alternations of marl and argillaceous limestone of the Calcaires argileux à Spirifèrines Member (Mb.), the argillaceous limestones and marls of the Calcaires argileux et marnes à Soaresirhynchia Mb., and the marl and argillaceous limestone dominated Calcaires argileux à Telothyris Mb.; Faure, 2002). The Bizanet section is located in the eastern Corbières, and is characterized by a 3m thick succession of late Pliensbachian-early Toarcian sediments comprising, at the base, the limestone dominated Barre a Pecten Fm., followed by a sedimentary gap dated to the Tenuicostatum Chronozone, topped by the marly dominated succession of the Bizanet Fm. (black ferruginous marls intercalated with limestones and topped by dolomitic limestones of the Schistes carton Mb., and the black marls of the Argilites noires litées Mb.; Faure, 2002). The geochemical results evidenced that the Bizanet section presents higher TOC contents than the Pont de Suert section, with values reaching 2.03 wt.%. In the Bizanet section IR ranges between 12 wt.% and 82 wt.% and in the Pont de Suert section varies from 13wt.% to 67 wt.%, displaying a similar average value for the two sections (45 wt.%). The palynofacies assemblage is dominated in both sections by the same components, belonging to the Phylum Cnidaria, Class Hydrozoa and Order Hydroida, and are represented by fragments of colonial and non-colonial sessile polypoid forms and free-swimming medusoid forms, with different degrees of amorphization.
(This abstract has been truncated, please see the complete PDF version)
The Early Toarcian is characterized by major worldwide environmental changes recorded in an organic-rich black shale sedimentation and carbon cycle disturbances, the so-called Toarcian Oceanic Anoxic Event (T-OAE) (e.g. Jenkyns, 2010). This organic-rich sedimentation is particularly recorded in shallow marine epicontinental basins that developed as part of the Toarcian European epicontinental shelf, paleogeographical framework in which the Pyrenean Basin is incorporated (e.g. Fonseca et al., 2018; McArthur et al., 2008). With these premises, the main objective of this study is to assess the organic facies variability and to define the depositional paleoenvironments of two sections from the Pyrenean Basin (Bizanet and Pont de Suert) during the T-OAE, using palynofacies and geochemical (Total Organic Carbon - TOC and insoluble residue - IR) data. The Pyrenean tectonics that occurred between the latest Cretaceous and the Oligocene, deformed, detached and fragmented the substrate resulting in diverse tectonic units (Faure, 2002). The late Pliensbachian-early Toarcian of the Pont de Suert section, located in the South Pyrenean zone, is characterized by the limestone dominated Barre a Pecten Formation (Fm.), and the carbonate and/or argillaceous-carbonate alternation of its three members (alternations of marl and argillaceous limestone of the Calcaires argileux à Spirifèrines Member (Mb.), the argillaceous limestones and marls of the Calcaires argileux et marnes à Soaresirhynchia Mb., and the marl and argillaceous limestone dominated Calcaires argileux à Telothyris Mb.; Faure, 2002). The Bizanet section is located in the eastern Corbières, and is characterized by a 3m thick succession of late Pliensbachian-early Toarcian sediments comprising, at the base, the limestone dominated Barre a Pecten Fm., followed by a sedimentary gap dated to the Tenuicostatum Chronozone, topped by the marly dominated succession of the Bizanet Fm. (black ferruginous marls intercalated with limestones and topped by dolomitic limestones of the Schistes carton Mb., and the black marls of the Argilites noires litées Mb.; Faure, 2002). The geochemical results evidenced that the Bizanet section presents higher TOC contents than the Pont de Suert section, with values reaching 2.03 wt.%. In the Bizanet section IR ranges between 12 wt.% and 82 wt.% and in the Pont de Suert section varies from 13wt.% to 67 wt.%, displaying a similar average value for the two sections (45 wt.%). The palynofacies assemblage is dominated in both sections by the same components, belonging to the Phylum Cnidaria, Class Hydrozoa and Order Hydroida, and are represented by fragments of colonial and non-colonial sessile polypoid forms and free-swimming medusoid forms, with different degrees of amorphization.(This abstract has been truncated, please see the complete PDF version)Public priorities on locally-driven sea level rise planning on the East Coast of the United Stateshttps://peerj.com/preprints/279332019-09-022019-09-02Adam T Carpenter
Sea Level Rise poses a substantial concern to communities worldwide. Increased inundation, storm surge, salt water intrusion, and other impacts create challenges which will require considerable planning to address. Recognizing the broad and differing scope of sea level rise issues and the variability of policy options to address them, local planning frameworks are necessary in addition to tools and resources available from state and federal governments. To help assess priorities and preferences on sea level rise planning, a survey of 503 persons affiliated with coastal communities on the East Coast of the United States was conducted in December 2017. This survey studied key aspects locally-driven sea level rise plans, including planning priorities, funding options, methods to resolve conflict, and potential responses. Six key findings address these and other concerns to provide the foundation of a locally driven framework for public officials.
Sea Level Rise poses a substantial concern to communities worldwide. Increased inundation, storm surge, salt water intrusion, and other impacts create challenges which will require considerable planning to address. Recognizing the broad and differing scope of sea level rise issues and the variability of policy options to address them, local planning frameworks are necessary in addition to tools and resources available from state and federal governments. To help assess priorities and preferences on sea level rise planning, a survey of 503 persons affiliated with coastal communities on the East Coast of the United States was conducted in December 2017. This survey studied key aspects locally-driven sea level rise plans, including planning priorities, funding options, methods to resolve conflict, and potential responses. Six key findings address these and other concerns to provide the foundation of a locally driven framework for public officials.Spatio-temporal patterns of the oceanic conditions and nearshore marine community in the Mid-Atlantic Bight (New Jersey, USA)https://peerj.com/preprints/279202019-08-282019-08-28Juan C Levesque
Oceanic environmental conditions influence, shape, and control the geographical range, spatial distribution, abundance, and size composition of marine fauna. Water temperature, salinity, dissolved oxygen, depth, and sediment type influence select fish life-history characteristics and community structure. Marine communities are vulnerable to major changes in environmental conditions, but the response and severity depends on various biological or ecological factors, such as resilience to stress or adaptation. Researchers around the world have predicted and documented numerous alterations in fish communities caused by ongoing significant physicochemical shifts associated with natural and potentially unnatural sources, but published studies describing the historical conditions are lacking for most regions around the world, including the coastal waters off New Jersey. Given the need to understand these processes, a multifaceted investigation was undertaken to describe, evaluate, and compare the oceanic conditions and nearshore marine fauna community off New Jersey during 1988 through 2015. Findings showed the oceanic conditions varied over time and space. Mean surface water temperature increased significantly about 0.6°C per decade, mean salinity decreased about 1.3 psu per decade, and dissolved oxygen increased 0.09 mg/l per decade. Over 20.4 million fish and invertebrates (1,338.3 mt) representing 214 (water temperature preference classified) species (not including unidentified species) were collected within 15 strata (areas: 12−26) off the coast of New Jersey from 1988 to 2015. Three marine fauna water temperature preference groups (coldwater-adapted, warmwater-adapted, and subtropic-adapted) were identified in the study area. The main coldwater-adapted species collected were longfin squid (Loligo pealei) (n = 2,225,975), Atlantic herring (Clupea harengus) (n = 544,032), and little skate (Leucoraja erinacea) (n = 316,356), while Atlantic butterfish (Peprilus triacanthus) (n = 2,873,138), scup (Stenotomus chrysops) (n = 1,318,569), and northern searobin (Prionotus carolinus) (n = 503,230) represented the warmwater-adapted group. Bay anchovy (Anchoa mitchilli) (n = 9,227,960), striped anchovy (Anchoa hepsetus) (n = 245,214), and Atlantic moonfish (Vomer setapinnis) (n = 38,691) denoted the subtropic-adapted group. Subtropic-adapted species were the most abundant and coldwater-adapted were the least abundant water temperature preference group. The estimated abundance of coldwater-adapted species declined, warmwater-adapted species slightly increased, and subtropic-adapted species decreased with time, which suggest the environmental conditions are influencing and thereby shifting the marine community.
Oceanic environmental conditions influence, shape, and control the geographical range, spatial distribution, abundance, and size composition of marine fauna. Water temperature, salinity, dissolved oxygen, depth, and sediment type influence select fish life-history characteristics and community structure. Marine communities are vulnerable to major changes in environmental conditions, but the response and severity depends on various biological or ecological factors, such as resilience to stress or adaptation. Researchers around the world have predicted and documented numerous alterations in fish communities caused by ongoing significant physicochemical shifts associated with natural and potentially unnatural sources, but published studies describing the historical conditions are lacking for most regions around the world, including the coastal waters off New Jersey. Given the need to understand these processes, a multifaceted investigation was undertaken to describe, evaluate, and compare the oceanic conditions and nearshore marine fauna community off New Jersey during 1988 through 2015. Findings showed the oceanic conditions varied over time and space. Mean surface water temperature increased significantly about 0.6°C per decade, mean salinity decreased about 1.3 psu per decade, and dissolved oxygen increased 0.09 mg/l per decade. Over 20.4 million fish and invertebrates (1,338.3 mt) representing 214 (water temperature preference classified) species (not including unidentified species) were collected within 15 strata (areas: 12−26) off the coast of New Jersey from 1988 to 2015. Three marine fauna water temperature preference groups (coldwater-adapted, warmwater-adapted, and subtropic-adapted) were identified in the study area. The main coldwater-adapted species collected were longfin squid (Loligo pealei) (n = 2,225,975), Atlantic herring (Clupea harengus) (n = 544,032), and little skate (Leucoraja erinacea) (n = 316,356), while Atlantic butterfish (Peprilus triacanthus) (n = 2,873,138), scup (Stenotomus chrysops) (n = 1,318,569), and northern searobin (Prionotus carolinus) (n = 503,230) represented the warmwater-adapted group. Bay anchovy (Anchoa mitchilli) (n = 9,227,960), striped anchovy (Anchoa hepsetus) (n = 245,214), and Atlantic moonfish (Vomer setapinnis) (n = 38,691) denoted the subtropic-adapted group. Subtropic-adapted species were the most abundant and coldwater-adapted were the least abundant water temperature preference group. The estimated abundance of coldwater-adapted species declined, warmwater-adapted species slightly increased, and subtropic-adapted species decreased with time, which suggest the environmental conditions are influencing and thereby shifting the marine community.Ground data confirm warming and drying are at a critical level for forest survival in western equatorial Africahttps://peerj.com/preprints/278482019-07-102019-07-10Emma R BushKathryn JefferyNils BunnefeldCaroline TutinRuth MusgraveGhislain MoussavouVianet MihindouYadvinder MalhiDavid LehmannJosué Edzang NdongLoïc MakagaKatharine A Abernethy
Background.The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2000mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of inability to ground-truth estimates and persistent cloudiness. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests in equatorial Africa under future climate scenarios.
Methods. We have the rare opportunity to analyse a 34-year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in western equatorial Africa. We used linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns.
Results. Lopé’s weather is characterised by a light-deficient, cool, long dry season. Long-term climatic means have changed significantly over the last three decades, with warming occurring at a rate of 0.23°C per decade (minimum daily temperature) and drying at a rate of 50mm per decade (total annual rainfall). Inter-annual variability is highly influenced by sea surface temperatures of the major oceans. In El Niño years Lopé experiences both higher temperatures and less rainfall with increased contrast between wet and dry seasons. Lopé rainfall observations lend support for the role of the Atlantic cold tongue in “dry” models of climate change in the region.
Conclusions. Dry season cloud in western equatorial Africa plays a key role in reducing evaporative demand during seasonal drought and maintaining evergreen tropical forests despite relatively low annual rainfall. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of clouds to ocean temperatures and the viability of humid forests in this dry region should the clouds disappear.
Background.The humid tropical forests of Central Africa influence weather worldwide and play a major role in the global carbon cycle. However they are also an ecological anomaly, with evergreen forests dominating the western equatorial region despite less than 2000mm total annual rainfall. Meteorological data for Central Africa are notoriously sparse and incomplete and there are substantial issues with satellite-derived data because of inability to ground-truth estimates and persistent cloudiness. Long-term climate observations are urgently needed to verify regional climate and vegetation models, shed light on the mechanisms that drive climatic variability and assess the viability of evergreen forests in equatorial Africa under future climate scenarios.Methods. We have the rare opportunity to analyse a 34-year dataset of rainfall and temperature (and shorter periods of absolute humidity, wind speed, solar radiation and aerosol optical depth) from Lopé National Park, a long-term ecological research site in western equatorial Africa. We used linear mixed models and spectral analyses to assess seasonal and inter-annual variation, long-term trends and oceanic influences on local weather patterns.Results. Lopé’s weather is characterised by a light-deficient, cool, long dry season. Long-term climatic means have changed significantly over the last three decades, with warming occurring at a rate of 0.23°C per decade (minimum daily temperature) and drying at a rate of 50mm per decade (total annual rainfall). Inter-annual variability is highly influenced by sea surface temperatures of the major oceans. In El Niño years Lopé experiences both higher temperatures and less rainfall with increased contrast between wet and dry seasons. Lopé rainfall observations lend support for the role of the Atlantic cold tongue in “dry” models of climate change in the region.Conclusions. Dry season cloud in western equatorial Africa plays a key role in reducing evaporative demand during seasonal drought and maintaining evergreen tropical forests despite relatively low annual rainfall. In the context of a rapidly warming and drying climate, urgent research is needed into the sensitivity of clouds to ocean temperatures and the viability of humid forests in this dry region should the clouds disappear.California air resources board forest carbon protocol invalidates offsetshttps://peerj.com/preprints/277982019-06-132019-06-13Bruno D V MarinoMartina MinchevaAaron Doucett
The commercial asset value of sequestered forest carbon is based on protocols employed globally, however, their scientific basis has not been validated. We review and analyze commercial forest carbon protocols and offsets, claimed to have reduced net greenhouse gas emissions, issued by the California Air Resources Board and validated by the Climate Action Reserve (CARB-CAR). CARB-CAR protocol annual offsets, resulting from forest mensuration and growth simulation models, are compared with a population of forest field sites for which annual net ecosystem exchange (NEE) of carbon was measured directly as flux by CO2 eddy covariance, a meteorologically based method integrating forest carbon pools. We characterize differences between the protocols by testing the null hypothesis that the CARB-CAR commercial annual offset data fall within the boundaries of directly measured forest carbon NEE; gC m-2yr-1 are compared for both datasets. Irrespective of geographic location and project type, the CARB-CAR population annual mean value is significantly different from the NEE population mean at the 95% confidence interval, rejecting the null hypothesis. The CARB-CAR population exhibits standard deviation ~5x that of the NEE natural ranges; the variance exceeds the 5% compliance limit for invalidation of CARB-CAR offsets. Exclusion of the soil carbon pool typical for CARB-CAR net carbon budgets pose insuperable carbon accounting uncertainty for offsets that extend to vendor platforms and policies including the United Nations Program on Reducing Emissions from Deforestation and Forest Degradation and the Paris Agreement. NEE methodology for commercial forest carbon offsets ensures in situ molecular specificity, verification of claims for net carbon balance, performance-based pricing and harmonization of carbon protocols for voluntary and compliance markets worldwide, in contrast to continuing uncertainty posed by traditional estimation-based forest carbon protocols.
The commercial asset value of sequestered forest carbon is based on protocols employed globally, however, their scientific basis has not been validated. We review and analyze commercial forest carbon protocols and offsets, claimed to have reduced net greenhouse gas emissions, issued by the California Air Resources Board and validated by the Climate Action Reserve (CARB-CAR). CARB-CAR protocol annual offsets, resulting from forest mensuration and growth simulation models, are compared with a population of forest field sites for which annual net ecosystem exchange (NEE) of carbon was measured directly as flux by CO2 eddy covariance, a meteorologically based method integrating forest carbon pools. We characterize differences between the protocols by testing the null hypothesis that the CARB-CAR commercial annual offset data fall within the boundaries of directly measured forest carbon NEE; gC m-2yr-1 are compared for both datasets. Irrespective of geographic location and project type, the CARB-CAR population annual mean value is significantly different from the NEE population mean at the 95% confidence interval, rejecting the null hypothesis. The CARB-CAR population exhibits standard deviation ~5x that of the NEE natural ranges; the variance exceeds the 5% compliance limit for invalidation of CARB-CAR offsets. Exclusion of the soil carbon pool typical for CARB-CAR net carbon budgets pose insuperable carbon accounting uncertainty for offsets that extend to vendor platforms and policies including the United Nations Program on Reducing Emissions from Deforestation and Forest Degradation and the Paris Agreement. NEE methodology for commercial forest carbon offsets ensures in situ molecular specificity, verification of claims for net carbon balance, performance-based pricing and harmonization of carbon protocols for voluntary and compliance markets worldwide, in contrast to continuing uncertainty posed by traditional estimation-based forest carbon protocols.Drought, freshwater availability and cultural resilience on Easter Island (SE Pacific) during the Little Ice Agehttps://peerj.com/preprints/276812019-05-312019-05-31Valenti Rull
After decades of human-deterministic explanations for the collapse of the ancient Rapanui culture that inhabited Easter Island (Rapa Nui) before European contact (1722 CE), paleoecological studies developed over the last decade have provided sound evidence of climate changes and their potential socioecological impacts. Especially significant is the occurrence of a century-scale (1570-1720 CE) drought occurred during the Little Ice Age. Freshwater is a critical resource on Easter Island that heavily depends on rain, which maintains the only three permanent surficial freshwater sources on the island: two lakes (Rano Kao and Rano Raraku) and a marsh (Rano Aroi). Under these conditions, the LIA drought could have significantly affected human life; however, the Rapanui society remained healthy, showing remarkable resilience. There are two main hypotheses on how the ancient Rapanui could have obtained freshwater to guarantee its continuity. The intra-island migration hypothesis proposes that Rano Raraku, the cultural center of this culture, dried out and the Rapanui were forced to migrate to Rano Kao, which was likely the only surficial freshwater source during the LIA drought. This shift was accompanied by a profound cultural reorganization. The coastal groundwater hypothesis dismisses the use of lakes and other surficial freshwater sources to maintain the water-stressed Rapanui population and contends that the only routine freshwater sources during the LIA drought were the abundant and widespread coastal seeps fed by fresh/brackish groundwater. The pros and cons of these two hypotheses are discussed on the basis of the available archeological and paleoecological evidence, and it is concluded that in the present state of knowledge, neither can be rejected. Therefore, these two proposals could be complementary, rather than mutually exclusive.
After decades of human-deterministic explanations for the collapse of the ancient Rapanui culture that inhabited Easter Island (Rapa Nui) before European contact (1722 CE), paleoecological studies developed over the last decade have provided sound evidence of climate changes and their potential socioecological impacts. Especially significant is the occurrence of a century-scale (1570-1720 CE) drought occurred during the Little Ice Age. Freshwater is a critical resource on Easter Island that heavily depends on rain, which maintains the only three permanent surficial freshwater sources on the island: two lakes (Rano Kao and Rano Raraku) and a marsh (Rano Aroi). Under these conditions, the LIA drought could have significantly affected human life; however, the Rapanui society remained healthy, showing remarkable resilience. There are two main hypotheses on how the ancient Rapanui could have obtained freshwater to guarantee its continuity. The intra-island migration hypothesis proposes that Rano Raraku, the cultural center of this culture, dried out and the Rapanui were forced to migrate to Rano Kao, which was likely the only surficial freshwater source during the LIA drought. This shift was accompanied by a profound cultural reorganization. The coastal groundwater hypothesis dismisses the use of lakes and other surficial freshwater sources to maintain the water-stressed Rapanui population and contends that the only routine freshwater sources during the LIA drought were the abundant and widespread coastal seeps fed by fresh/brackish groundwater. The pros and cons of these two hypotheses are discussed on the basis of the available archeological and paleoecological evidence, and it is concluded that in the present state of knowledge, neither can be rejected. Therefore, these two proposals could be complementary, rather than mutually exclusive.Environment regime influence on Chlorophyll-a abundance and distribution in North Indian Oceanhttps://peerj.com/preprints/276622019-05-062019-05-06Thushani Suleka Madhubha ElepathageDanling Tang
North Indian Ocean region around India and Sri Lanka is a complex and rich coastal ecosystem undergoing various seasonal and inter-annual changes and various pressures. Hence the objective of this study was to assess the scales of coupling between chlorophyll-a concentration (chl-a) and the influencing variables and explore the nature of the spatiotemporal variability of them. The seasonal and annual variations of chl-a along the Bay of Bengal (BoB), Arabian sea (AS) and ocean region around Sri Lanka in relation to the physical and chemical oceanographic variables were analyzed using satellite observations covering the period of 2002-2018. The effects of diffuse attenuation coefficient, photosynthetically available radiation (PAR), sea surface temperature (SST), Wind speed, Eastward wind component, Nitrate, Black carbon column mass density, Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity were considered on a monthly time scale. Wavelet analysis and the Boosted Regression Trees (BRT) were used as the main analysis and modeling methods. The peaks of chl-a, diffuse attenuation coefficient, and nitrate were observed in September. In wind speed and eastward wind it was July and in black carbon column mass density, and PAR in March. In Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity, Diffuse attenuation coefficient for downwelling irradiance, and SST mean maximums were found in June, February, November, September, April respectively. In BRT model the estimated cross validation (cv) deviance, standard error (se), training data correlation, cv correlation, and D2 were 0.003, 0.002, 0.932, 0.949, and 0.846 respectively. According to the results, diffuse attenuation coefficient (90%), eastward wind component (3.7%) and nitrate (3%) were the most positively correlated variables with Chl-a occurrence. SST evidenced an inverse relationship with Chl-a. According to the model built <42 Einsteinm-2day-1 PAR, <0.986 surface emissivity, <70 Wm-2 open water net downward long wave flux, 28.2 -28.5 0C SST , 2 ms-1 Wind speed, 5 ms-1 - 6 ms-1 eastward wind, 4.8 x10-8 -7x10-8 kgm-3 sea salt surface mass concentration, and 0.1-0.5micromoleL-1 nitrate are favourable for the optimum level of phytoplankton occurrence. Since BRT deals robustly with non-linear relationships of the environmental variables it can be used in further studies of ecological modeling.
North Indian Ocean region around India and Sri Lanka is a complex and rich coastal ecosystem undergoing various seasonal and inter-annual changes and various pressures. Hence the objective of this study was to assess the scales of coupling between chlorophyll-a concentration (chl-a) and the influencing variables and explore the nature of the spatiotemporal variability of them. The seasonal and annual variations of chl-a along the Bay of Bengal (BoB), Arabian sea (AS) and ocean region around Sri Lanka in relation to the physical and chemical oceanographic variables were analyzed using satellite observations covering the period of 2002-2018. The effects of diffuse attenuation coefficient, photosynthetically available radiation (PAR), sea surface temperature (SST), Wind speed, Eastward wind component, Nitrate, Black carbon column mass density, Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity were considered on a monthly time scale. Wavelet analysis and the Boosted Regression Trees (BRT) were used as the main analysis and modeling methods. The peaks of chl-a, diffuse attenuation coefficient, and nitrate were observed in September. In wind speed and eastward wind it was July and in black carbon column mass density, and PAR in March. In Sea Salt Surface Mass Concentration, Open water net downward longwave flux, Surface emissivity, Diffuse attenuation coefficient for downwelling irradiance, and SST mean maximums were found in June, February, November, September, April respectively. In BRT model the estimated cross validation (cv) deviance, standard error (se), training data correlation, cv correlation, and D2 were 0.003, 0.002, 0.932, 0.949, and 0.846 respectively. According to the results, diffuse attenuation coefficient (90%), eastward wind component (3.7%) and nitrate (3%) were the most positively correlated variables with Chl-a occurrence. SST evidenced an inverse relationship with Chl-a. According to the model built <42 Einsteinm-2day-1 PAR, <0.986 surface emissivity, <70 Wm-2 open water net downward long wave flux, 28.2 -28.5 0C SST , 2 ms-1 Wind speed, 5 ms-1 - 6 ms-1 eastward wind, 4.8 x10-8 -7x10-8 kgm-3 sea salt surface mass concentration, and 0.1-0.5micromoleL-1 nitrate are favourable for the optimum level of phytoplankton occurrence. Since BRT deals robustly with non-linear relationships of the environmental variables it can be used in further studies of ecological modeling.Evidence for a non-linear carbon accumulation pattern along an Alpine glacier retreat chronosequence in Northern Italyhttps://peerj.com/preprints/277032019-05-062019-05-06Leonardo MontagnaniAysan BadraghiAndrew Francis SpeakCamilla WellsteinLuigimaria BorrusoStefan ZerbeDamiano Zanotelli
Background. The glaciers in the Alps, as in other high mountain ranges and boreal zones, are generally retreating and leaving a wide surface of bare ground free from ice cover. This early stage soil is then colonized by microbes and vegetation in a process of primary succession. It is rarely experimentally examined whether this colonization process is linear or not at the ecosystem scale. Thus, to improve our understanding of the variables involved in the carbon accumulation in the different stages of primary succession, we conducted this research in three transects on the Matsch glacier forefield (Alps, N Italy) at an altitude between 2350 and 2800 m a.s.l.
Methods. In three field campaigns (July, August and September 2014) a closed transparent chamber was used to quantify the net ecosystem exchange (NEE) between the natural vegetation and the atmosphere. On the five plots established in each of the three transects, shading nets were used to determine ecosystem response function to variable light conditions. Ecosystem respiration (Reco) and gross ecosystem exchange (GEE) was partitioned from NEE. Following the final flux measurements, biometric sampling was conducted to establish soil carbon (C) and nitrogen (N) content and the biomass components for each transect.
Results. A clear difference was found between the earlier and the later successional stage. The older successional stages in the lower altitudes acted as a stronger C sink, where NEE, GEE, and Reco were significantly higher than in the earlier successional stage. Of the two lower transects, the sink capacity of intermediate-succession plots exceeded that of the plots of older formation, in spite of the more developed soil. Total biomass (above- and belowground) approached its maximum value in the intermediate ecosystem. Whilst, the later stage of succession predominated in the corresponding belowground organic mass (biomass, N and C).
Outlook. We found that the process of carbon accumulation along a glacier retreat chronosequence is not linear, and after a quite rapid increase in carbon accumulation capacity in the first 150 years, in average 9 g C m-2 y-1, it slows down, taking place mainly in the belowground biomass components. Concurrently, the photosynthetic capacity peaks in the intermediate stage of ecosystem development. If confirmed by further studies on a larger scale, this study would provide evidence for a predominant effect of plant physiology over soil physical characteristics in the green-up phase after glacier retreat, which has to be taken into account in the creation of scenarios related to climate change and future land use.
Background. The glaciers in the Alps, as in other high mountain ranges and boreal zones, are generally retreating and leaving a wide surface of bare ground free from ice cover. This early stage soil is then colonized by microbes and vegetation in a process of primary succession. It is rarely experimentally examined whether this colonization process is linear or not at the ecosystem scale. Thus, to improve our understanding of the variables involved in the carbon accumulation in the different stages of primary succession, we conducted this research in three transects on the Matsch glacier forefield (Alps, N Italy) at an altitude between 2350 and 2800 m a.s.l.Methods. In three field campaigns (July, August and September 2014) aclosed transparent chamber was used to quantify the net ecosystem exchange (NEE) between the natural vegetation and the atmosphere. On the five plots established in each of the three transects, shading nets were used to determine ecosystem response function to variable light conditions. Ecosystem respiration (Reco) and gross ecosystem exchange (GEE) was partitioned from NEE. Following the final flux measurements, biometric sampling was conducted to establish soil carbon (C) and nitrogen (N) content and the biomass components for each transect.Results. A clear difference was found between the earlier and the later successional stage. The older successional stages in the lower altitudes acted as a stronger C sink, where NEE, GEE, and Reco were significantly higher than in the earlier successional stage. Of the two lower transects, the sink capacity of intermediate-succession plots exceeded that of the plots of older formation, in spite of the more developed soil. Total biomass (above- and belowground) approached its maximum value in the intermediate ecosystem. Whilst, the later stage of succession predominated in the corresponding belowground organic mass (biomass, N and C).Outlook. We found that the process of carbon accumulation along a glacier retreat chronosequence is not linear, and after a quite rapid increase in carbon accumulation capacity in the first 150 years, in average 9 g C m-2 y-1, it slows down, taking place mainly in the belowground biomass components. Concurrently, the photosynthetic capacity peaks in the intermediate stage of ecosystem development.If confirmed by further studies on a larger scale, this study would provide evidence for a predominant effect of plant physiology over soil physical characteristics in the green-up phase after glacier retreat, which has to be taken into account in the creation of scenarios related to climate change and future land use.