scholarly journals The end of life on Earth is not the end of the world: converging to an estimate of life span of the biosphere?

2019 ◽  
Vol 19 (1) ◽  
pp. 25-42 ◽  
Author(s):  
Fernando de Sousa Mello ◽  
Amâncio César Santos Friaça
Keyword(s):  
Partial Pressure ◽  
Life Span ◽  
Quantitative Agreement ◽  
C4 Plants ◽  
C3 Plants ◽  
Ocean Mass ◽  
The Future ◽  
Geophysical Processes ◽  
Red Giant ◽  
Life On Earth

AbstractEnvironmental conditions have changed in the past of our planet but were not hostile enough to extinguish life. In the future, an aged Earth and a more luminous Sun may lead to harsh or even uninhabitable conditions for life. In order to estimate the life span of the biosphere we built a minimal model of the co-evolution of the geosphere, atmosphere and biosphere of our planet, taking into account temperature boundaries, CO2 partial pressure lower limits for C3 and C4 plants, and the presence of enough surface water. Our results indicate that the end of the biosphere will happen long before the Sun becomes a red giant, as the biosphere faces increasingly more difficult conditions in the future until its collapse due to high temperatures. The lower limit for CO2 partial pressure for C3 plants will be reached in 170(+ 320, − 110) Myr, followed by the C4 plants limit in 840(+ 270, − 100) Myr. The mean surface temperature will reach 373 K in 1.63(+ 0.14, − 0.05) Gyr, a point that would mark the extinction of the biosphere. Water loss due to internal geophysical processes will not be dramatic, implying almost no variation in the surface ocean mass and ocean depth for the next 1.5 billion years. Our predictions show qualitative convergence and some quantitative agreement with results found in the literature, but there is considerable scattering in the scale of hundreds of millions of years for all the criteria devised. Even considering these uncertainties, the end of the biosphere will hardly happen sooner than 1.5 Gyr.

Life as It Could Be

2020 ◽  
pp. 101-114
Author(s):  
Luis Campos
Keyword(s):  
Synthetic Biology ◽  
Molecular Biology ◽  
The Future ◽  
Forms Of Life ◽  
Life On Earth ◽  
The Universe

This chapter explores the intersection between two related fields: synthetic biology and astrobiology. Pushing the engineering of life past traditional limits in molecular biology and expanding the envelope of life to forms never before extant, synthetic biologists are now beginning to design experimental ways of getting at what astrobiologists have long suspected: that the life known here on Earth is but a subset of vast combinatorial possibilities in the universe. The resonances between the future engineered possibilities of this world and speculations about possible biologies on habitable others are not merely happenstance. Indeed, there is a curious and compelling deeper history interlinking scientific speculation about new forms of life elsewhere in the universe with visions for the human-directed engineering of new forms of life on Earth. For decades, the astrobiological and the synthetic biological have mutually inspired each other and overlapped in powerful genealogical ways.

The Future of Life on Earth

2014 ◽  
pp. 315-327
Author(s):  
Michael Charles Tobias ◽  
Jane Gray Morrison
Keyword(s):  
The Future ◽  
Life On Earth

Elevated Atmosphere Partial Pressure of CO2 and Plant Growth. III. Interactions Between Triticum aestivum (C3) and Echinochloa frumentacea (C4) During Growth in Mixed Culture Under Different CO2, N Nutrition and Irradiance Treatments, With Emphasis on Below-Ground Responses Estimated Using the δ13C Value of Root Biomass

1991 ◽  
Vol 18 (2) ◽  
pp. 137 ◽  
Author(s):  
SC Wong ◽  
CB Osmond
Keyword(s):  
Triticum Aestivum ◽  
Mixed Culture ◽  
Elevated Co2 ◽  
Root Biomass ◽  
Shoot Growth ◽  
Mixed Cultures ◽  
C4 Plants ◽  
C3 Plants ◽  
Δ13c Value ◽  
Echinochloa Frumentacea

Wheat (Triticum aestivum L.), a C3 species, and Japanese millet (Echinochloa frumentacea Link), a C4 species, were grown in pots in monoculture and mixed culture (2 C3 : 1 C4 and 1 C3:2 C4) at two ambient partial pressures of CO2 (320 and 640 μbar), two photosynthetic photon flux densities (PPFDs) (daily maximum 2000 and 500 �mol m-2 s-1) and two levels of nitrogen nutrition (12 mM and 2 mM NO3-). Growth of shoots of both components in mixed culture was measured by physical separation, and the proportions of root biomass due to each component were calculated from δ13C value of total root biomass. In air (320 μbar CO2) at high PPFD and with high root zone-N, the shoot biomass of C3 and C4 components at the first harvest (28 days) was in proportion to the sowing ratio. However, by the second harvest (36 days) the C4 component predominated in both mixtures. Under the same conditions, but with low PPFD, C3 plants predominated at the first harvest but C4 plants had over- taken them by the time of the second harvest. Elevated atmospheric CO2 (640 μbar) stimulated shoot growth of Triticum in 15 of 16 treatment combinations and the stimulation was greatest in plants provided with low NO3-. Root growth of the C3 plants was generally stimulated by elevated CO2, but was only occasionally sensitive to the presence of C4 plants in mixed culture. However, growth of the C4 plants was often sensitive to the presence of C3 plants in mixed culture. In mixed cultures, elevated CO2 plants stimulated growth of C4 plants at high PPFD, high-N and in all low-N treatments but this was insufficient to offset a marked decline in shoot growth with increasing proportion of C3 plants in mixed cultures. The unexpected stimulation of growth of C4 plants by elevated CO2 was correlated with more negative δ13C values of C4 root biomass, suggesting a partial failure of the CO2 concentrating mechanism of C4 photosynthesis in Echinochloa under low-N. These experiments show that for these species nitrogen was more important than light or elevated pCO2 in determining the extent of competitive interactions in mixed culture.

Mating of Helicoverpa armigera (Lepidoptera: Noctuidae) moths and their host plant origins as larvae within Australian cotton farming systems

2012 ◽  
Vol 103 (2) ◽  
pp. 171-181 ◽  
Author(s):  
G.H. Baker ◽  
C.R. Tann
Keyword(s):  
Host Plant ◽  
Helicoverpa Armigera ◽  
Stable Carbon Isotopes ◽  
Production Systems ◽  
Farming Systems ◽  
C4 Plants ◽  
C3 Plants ◽  
Bt Cotton ◽  
Cotton Production ◽  
Helicoverpa Armígera

AbstractTransgenic (Bt) cotton dominates Australian cotton production systems. It is grown to control feeding damage by lepidopteran pests such as Helicoverpa armigera. The possibility that these moths might become resistant to Bt remains a threat. Consequently, refuge crops (with no Bt) must be grown with Bt cotton to produce large numbers of Bt-susceptible moths to reduce the risk of resistance developing. A key assumption of the refuge strategy, that moths from different host plant origins mate at random, remains untested. During the period of the study reported here, refuge crops included pigeon pea, conventional cotton (C3 plants), sorghum or maize (C4 plants). To identify the relative contributions made by these (and perhaps other) C3 and C4 plants to populations of H. armigera in cotton landscapes, we measured stable carbon isotopes (δ13C) within individual moths captured in the field. Overall, 53% of the moths were of C4 origin. In addition, we demonstrated, by comparing the stable isotope signatures of mating pairs of moths, that mating is indeed random amongst moths of different plant origins (i.e. C3 and C4). Stable nitrogen isotope signatures (δ15N) were recorded to further discriminate amongst host plant origins (e.g. legumes from non-legumes), but such measurements proved generally unsuitable. Since 2010, maize and sorghum are no longer used as dedicated refuges in Australia. However, these plants remain very common crops in cotton production regions, so their roles as ‘unstructured’ refuges seem likely to be significant.

DECISION AND DESTINY: THE FUTURE OF LIFE ON EARTH

Zygon® ◽  
1970 ◽  
Vol 5 (2) ◽  
pp. 159-171
Author(s):  
George Wald
Keyword(s):  
The Future ◽  
Life On Earth

scholarly journals Stable carbon isotopic composition of biomass burning emissions – implications for estimating the contribution of C3 and C4 plants

2021 ◽  
Author(s):  
Roland Vernooij ◽  
Ulrike Dusek ◽  
Maria Elena Popa ◽  
Peng Yao ◽  
Anupam Shaikat ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Biomass Burning ◽  
Field Experiments ◽  
Combustion Products ◽  
C4 Plants ◽  
C3 Plants ◽  
Stable Carbon ◽  
Atmospheric Measurements ◽  
C3 And C4 Plants ◽  
Large Variability

Abstract. Landscape fires are a significant contributor to atmospheric burdens of greenhouse gases and aerosols. Although many studies have looked at biomass burning products and their fate in the atmosphere, estimating and tracing atmospheric pollution from landscape fires based on atmospheric measurements is challenging due to the large variability in fuel composition and burning conditions. Stable carbon isotopes in biomass burning (BB) emissions can be used to trace the contribution of C3 plants (e.g., trees or shrubs) and C4 plants (e.g. savanna grasses) to various combustion products. However, there are still many uncertainties regarding changes in isotopic composition (also known as fractionation) of the emitted carbon compared to the burnt fuel during the pyrolysis and combustion processes. To study BB isotope fractionation, we performed a series of laboratory fire experiments in which we burned pure C3 and C4 plants as well as mixtures of the two. Using isotope ratio mass spectrometry (IRMS), we measured stable carbon isotope signatures in the pre-fire fuels and post-fire residual char, as well as in the CO2, CO, CH4, organic carbon (OC), and elemental carbon (EC) emissions, which together constitute over 98 % of the post-fire carbon. Our laboratory tests indicated substantial isotopic fractionation in combustion products compared to the fuel, which varied between the measured fire products. CO2, EC and residual char were the most reliable tracers of the fuel 13C signature. CO in particular showed a distinct dependence on burning conditions; flaming emissions were enriched in 13C compared to smouldering combustion emissions. For CH4 and OC, the fractionation was opposite for C3 emissions (13C-enriched) and C4 emissions (13C-depleted). This indicates that while it is possible to distinguish between fires that were dominated by either C3 or C4 fuels using these tracers, it is more complicated to quantify their relative contribution to a mixed-fuel-fire based on the δ13C signature of emissions. Besides laboratory experiments, we sampled gases and carbonaceous aerosols from prescribed fires in the Niassa special Reserve (NSR) in Mozambique, using an unmanned aerial system (UAS)-mounted sampling set-up. We also provide a range of C3 : C4 contributions to the fuel and measured the fuel isotopic signatures. While both OC and EC were useful tracers of the C3 to C4 fuel ratio in mixed fires in the lab, we found particularly OC to be depleted compared to the calculated fuel signal in the field experiments. This suggests that either our fuel measurements were incomprehensive and underestimated the C3 : C4 ratio in the field, or that other processes caused this depletion. Although additional field measurements are needed, our results indicate that C3 vs C4 source ratio estimation is possible with most BB products, albeit with varying uncertainty ranges.

scholarly journals A kinematic formalism for tracking ice–ocean mass exchange on the Earth's surface and estimating sea-level change

2020 ◽  
Vol 14 (9) ◽  
pp. 2819-2833
Author(s):  
Surendra Adhikari ◽  
Erik R. Ivins ◽  
Eric Larour ◽  
Lambert Caron ◽  
Helene Seroussi
Keyword(s):  
Solid Earth ◽  
Sea Level ◽  
Mass Exchange ◽  
Ice Sheets ◽  
Earth System ◽  
Generic Level ◽  
Ocean Mass ◽  
Geophysical Processes ◽  
Ice Sheet Dynamics ◽  
And Sea Level

Abstract. Polar ice sheets are important components of the Earth system. As the geometries of land, ocean and ice sheets evolve, they must be consistently captured within the lexicon of geodesy. Understanding the interplay between the processes such as ice-sheet dynamics, solid-Earth deformation, and sea-level adjustment requires both geodetically consistent and mass-conserving descriptions of evolving land and ocean domains, grounded ice sheets and floating ice shelves, and their respective interfaces. Here we present mathematical descriptions of a generic level set that can be used to track both the grounding lines and coastlines, in light of ice–ocean mass exchange and complex feedbacks from the solid Earth and sea level. We next present a unified method to accurately compute the sea-level contribution of evolving ice sheets based on the change in ice thickness, bedrock elevation and mean sea level caused by any geophysical processes. Our formalism can be applied to arbitrary geometries and at all timescales. While it can be used for applications with modeling, observations and the combination of two, it is best suited for Earth system models, comprising ice sheets, solid Earth and sea level, that seek to conserve mass.

The Kranz syndrome in the Eragrostideae (Chloridoideae, Poaceae) as indicated by carbon isotopic ratios*

Bothalia ◽  
1984 ◽  
Vol 15 (3/4) ◽  
pp. 587-590
Author(s):  
Hector O. Panarello ◽  
Evangelina Sanchez
Keyword(s):  
Mass Spectrometry ◽  
C4 Photosynthesis ◽  
Leaf Tissue ◽  
C4 Plants ◽  
C3 Plants ◽  
Isotopic Ratios ◽  
Carbon Isotope Ratios ◽  
Carbon Isotopic ◽  
Δ 13C ◽  
Kranz Leaf Anatomy

13C/12C ratios are generally regarded as being very reliable indicators of C3 or C4 photosynthesis. These relative carbon isotope ratios are expressed as a negative δ 3C and fall into two distinct groups: Kranz (or C4) plants with δ between -9°/00 no and -18°/00 and non-Kranz (C3) plants with δ between -22°/00 and -280/00 no. In this paper, 29 taxa, representing 12 genera, of the tribe Eragrostideae were examined by mass spectrometry for their δ 13C in dried leaf tissue. All these taxa proved to be C4, plants with δ13C values ranging between -13,6°/oo and -10.9°/oo. These findings confirmed published leaf anatomical observations which showed that all the studied taxa had characteristic Kranz leaf anatomy.

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