Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Lectures by Greg Podgorski, Utah State University Methane, Plants and Climate Change Scientific American Current Issues in Biology Volume 5

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change What do you do when you find something that contradicts the textbooks? Frank Keppler and Thomas Röckmann faced this question when they found a new source of methane – living plants. Their answer? Repeat your experiments to be sure of your results, then tell the world through a publication reviewed by other scientists. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Methane (CH 4 ) is best known as “natural gas.” Methane is an important greenhouse gas. Pound-for-pound, methane is 23 times more effective than carbon dioxide in trapping heat. Human activities have tripled the levels of atmospheric methane over the past 150 years. Roughly 600 million metric tons of methane are produced annually. Knowing all sources of methane is essential if its levels are to be controlled. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change The finding that plants produce methane flew in the face of conventional wisdom. By 2001, the Intergovernmental Panel on Climate Change (IPCC) believed all major sources of methane had been identified. Plants were not on the list. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Prior to Keppler and Röckmann’s discovery, the major known sources of methane were: Anaerobic bacteria (including those that live in the digestive systems of cows and other ruminants) Forest and savannah fires Burning of fossil fuels But based on these sources, fluctuations in methane levels before humans started burning fossil fuel (during the Industrial Revolution) could not be explained. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change The discovery that living plants produce methane was accidental. Keppler and Röckmann were interested in chloromethane, a gas that destroys ozone. They knew that decaying plant material produced chloromethane, and wondered if it also made methane. They found that tiny amounts of methane were produced by dried plant material. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change What about living plants? They found that living plants produced 10 to 100 times more methane than dried plant material. The amount of methane produced by each plant is small, but the cumulative amount is huge. Keppler and Röckmann estimated that plants produce 60 – 240 million metric tons of methane annually. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Concept Review According to these figures, plants could be responsible for 10% to 40% of global methane emissions. Keppler and Röckmann knew that current views about methane production would make it difficult for many scientists to accept these figures. Strengthening their case, two independent lines of evidence were discovered that supported links between plants, methane, and climate change.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Satellite observations showed huge clouds of methane over tropical forests that couldn’t be explained by existing models. A reanalysis of previous data showed massive releases of methane from tropical savannah, which is explained by plant methane production. Even so, many scientists remain skeptical of the magnitude of methane production by plants and are repeating Keppler and Röckmann’s studies. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Understanding that plants produce methane explains previous puzzling observations. Methane levels were known to vary in step with the Earth’s temperatures. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change The plant-methane link also means that global warming will drive further increases in temperature. Concept Review Warmer EarthMore plants More methane

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change The media ran headlines like “Global Warming – Blame the Forests.” Plants have been emitting methane for hundreds of millions of years. They have not caused the sharp increase in methane output seen since the Industrial Revolution. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Plants are an essential source of the oxygen on which life as we know it depends. The major cause of global warming is not plants – it’s the burning of fossil fuels. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Plant production of methane raises a serious concern. Which is greater – the benefit of carbon sequestration from planting forests, or the harm caused by the methane those forests give off? Calculations show that the benefit of planting more trees is greater. Concept Review

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Methane is also known as: a) chlorofluorocarbon. b) chloromethane. c) natural gas. d) liquefied butane.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Methane is also known as: c) natural gas

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Methane is: a) becoming toxic to plants at its current levels. b) more effective than carbon dioxide at trapping heat. c) a major contributor to acid rain. d) taken up by plants for use in photosynthesis.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Methane is: b) more effective than carbon dioxide at trapping heat.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension The discovery that living plants produce methane happened by accident when scientists were studying: a) the sources of an ozone-destroying gas. b) how plants produce oxygen during photosynthesis. c) how plants absorb carbon dioxide. d) the ecology of savannah ecosystems.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension The discovery that living plants produce methane happened by accident when scientists were studying: a) the sources of an ozone-destroying gas.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Knowing that plants produce methane solves the long- standing mystery of: a) the winter ozone hole over the Antarctic. b) global warming. c) why plant biomass increased during interglacial periods. d) the coupling between atmospheric methane and changes in Earth’s temperature.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension Knowing that plants produce methane solves the long- standing mystery of: d) the coupling between atmospheric methane and changes in Earth’s temperature.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings If not interrupted, the cycle above leads to: a) a spread of plants across every land area. b) the destruction of all large life forms. c) ever-increasing global temperatures. d) an equilibrium between global temperature, plant life, and methane levels. Methane, Plants and Climate Change Testing Your Comprehension Warmer EarthMore plants More methane

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Testing Your Comprehension If not interrupted, the cycle above leads to: c) ever-increasing global temperatures. Warmer EarthMore plants More methane

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Biology and Society When the media misinterprets scientific findings, it is the fault of scientists, who should have explained the meaning of their work more clearly. Disagree Agree Strongly A B C D E Strongly

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Thinking About Science Calculations show that in terms of global warming, the positive effect of carbon sequestration by reforestation outweighs the negative effect of methane production by plants. In addition to knowing the amount of carbon taken up by growing trees, what else would you need to know to make these calculations? (Hint: more than one answer may be correct.) a) The amount of methane produced by growing trees. b) The relative heat-trapping properties of carbon dioxide and methane. c) The growth rate of trees in different global regions. d) The current rate of world-wide temperature increase.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Thinking About Science Calculations show that in terms of global warming, the positive effect of carbon sequestration by reforestation outweighs the negative effect of methane production by plants. In addition to knowing the amount of carbon taken up by growing trees, what else would you need to know to make these calculations? (Hint: more than one answer may be correct.) a) The amount of methane produced by growing trees. b) The relative heat-trapping properties of carbon dioxide and methane.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Interpreting Charts and Graphs What conclusion can be drawn from comparison of the two graphs? a) There has been no change in the amount of biomass burned. b) The amount of methane produced from wetlands has increased. c) There are fewer termites in modern times. d) There was more burning of biomass in preindustrial times.

Copyright © 2009 Pearson Education, Inc. publishing as Benjamin Cummings Methane, Plants and Climate Change Interpreting Charts and Graphs What conclusion can be drawn from comparison of the two graphs? b) The amount of methane produced from wetlands has increased.