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- The co-evolution of life and Earth
- Ecosystem-atmosphere CO2 exchange: interpreting signals of change using stable isotope ratios
Trends in Ecology & Evolution, Volume 13, Issue 1, 1 January 1998, Pages 10-14
Lawrence B Flanagan and James R Ehleringer
AbstractChanges in the concentration and stable isotope ratio of atmospheric CO2 can be used to study variations in the net exchange of carbon dioxide in terrestrial ecosystems (net difference between total photosynthesis and respiration). Changes in the timing of seasonal fluctuations in atmospheric CO2 concentration have suggested that net uptake of carbon dioxide has been increasing in northern latitude ecosystems in association with warmer temperatures and a lengthening of the growing season. Stable isotope techniques allow a more detailed separation of differences between ecosystem photosynthesis and respiration because these two processes have contrasting effects on both the carbon and oxygen isotope ratio of atmospheric CO2. Future applications of stable isotope analyses include documenting and monitoring the influence of global environmental change on ecosystem CO2 exchange at regional scales (10–1000km2).
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- The influence of terrestrial ecosystems on climate
Trends in Ecology & Evolution, Volume 21, Issue 5, 1 May 2006, Pages 254-260
Patrick Meir, Peter Cox and John Grace
AbstractTerrestrial ecosystems influence climate by affecting how much solar energy is absorbed by the land surface and by exchanging climatically important gases with the atmosphere. Recent model analyses show widespread qualitative agreement that terrestrial ecological processes will have a net positive feedback effect on 21st-century global warming, and, therefore, cannot be ignored in climate-change projections. However, the quantitative uncertainty in the net feedback is large. The uncertainty in 21st-century carbon dioxide emissions resulting from terrestrial carbon cycle–climate feedbacks is second in magnitude only to the uncertainty in anthropogenic emissions. We estimate that this translates into an uncertainty in global warming owing to the land surface of 1.5°C by 2100. We also emphasise the need to improve our understanding of terrestrial ecological processes that influence land–atmosphere interactions at relatively long timescales (decadal–century) as well as at shorter intervals (e.g. hourly).
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Copyright © 2009 Elsevier Ltd All rights reserved.
Current Biology, Volume 19, Issue 14, R567-R574, 28 July 2009
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The Continuing Puzzle of the Great Oxidation Event
1 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA
2 Department of Biology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Boston, MA 02139, USA
3 Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Boston, MA 02139, USA
4 Howard Hughes Medical Institute, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Boston, MA 02139, USA
- The rise of atmospheric O2 was a milestone in the history of life. Although O2 itself is not a climate-active gas, its appearance would have removed a methane greenhouse present on the early Earth and potentially led to dramatic cooling. Moreover, by fundamentally altering the biogeochemical cycles of C, N, S and Fe, its rise first in the atmosphere and later in the oceans would also have had important indirect effects on Earth's climate. Here, we summarize major lines of evidence from the geological literature that pertain to when and how O2 first appeared in significant amounts in the atmosphere. On the early Earth, atmospheric O2 would initially have been very low, probably <10−5 of the present atmospheric level. Around 2.45 billion years ago, atmospheric O2 rose suddenly in what is now termed the Great Oxidation Event. While the rise of oxygen has been the subject of considerable attention by Earth scientists, several important aspects of this problem remain unresolved. Our goal in this review is to provide a short summary of the current state of the field, and make the case that future progress towards solving the riddle of oxygen will benefit greatly from the involvement of molecular biologists.