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7.2.2.2.g
Forestry – This section deals with global carbon dioxide before introducing the role of forests.
Ontario forests are discussed later in the section.
One way to reduce the effects of emissions, or mitigate the effects of climate change, is to improve natural carbon storage or “carbon sinks”. The process of photosynthesis uses carbon dioxide as a raw material. Photosynthesis locks up CO2 in bigger molecules such as glucose for energy and cellulose for cell walls a natural carbon sink. More trees or better forestry practices can improve carbon sinks.
The Kyoto definition of carbon sinks includes human activities that increase the amount of carbon dioxide naturally stored by both land and oceans. “Carbon sources” are processes that release carbon to the atmosphere such as the respiration of all living organisms and the burning of fossil fuels.
All green plants from algae to maples – carry on the process of photosynthesis as their way of making food using sunlight, carbon dioxide and water. Chlorophyll makes cells look green, whether on land or in the ocean. All cells that have chlorophyll use this “green magic” to trap light energy. The energy is then used to lock up carbon dioxide in glucose- a natural carbon sink.
The oxygen we breathe is released to the atmosphere by the same process – photosynthesis. This oxygen is the surplus produced after the cells uses what it needs to stay alive! (I.e. 50% for respiration) We live and breathe using green cell leftovers! Note: The chemical structure of chlorophyll bears some resemblance to hemoglobin! Both are very active molecules!!
The Kyoto Îsinks’ – include human activities that remove carbon dioxide from the air by improving carbon storage in natural reservoirs – land and oceans. The world’s carbon is shown below as a global carbon budget.
Source: IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK. P 188
ACTIVITY 1
1. What is meant by a global budget? Hint – check the fine print!
2. What is meant by global flux? Hint – check the fine print!
3. How much is a GtC? Hint – check the fine print!
Research: Review the Carbon Cycle and list the processes involved in carbon release and carbon storage as sources and sinks. Add the above numbers to the diagram. Hint don’t forget to add the geological storage and release check out limestone, acid rain, carbonic acid, carbonates etc.
The graph below shows why scientists are concerned about the amount of carbon dioxide now being added to the atmosphere by human activities. Before the industrial period, the past 10,000 years, the very stable atmospheric concentration of carbon dioxide. This means that the natural flow of CO2 into and out of the atmosphere was generally equal or balanced. This is like a bank account, where the account balance stays the about the same, as long as the money going in and out of the account are generally equal, no matter how much money is being moved.
Carbon Dioxide concentration in parts per million (ppm)
Source: Adapted from IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK. p 201.
Since the industrial revolution, small amounts of CO2 emissions from human sources have caused a growing imbalance in this natural budget. This imbalance has resulted in gradual buildup of excess CO2 in the atmosphere. Atmospheric concentrations of CO2 have now increased by 30% compared to pre-industrial levels. See after 1850 in the above graph.
This level is already higher than any found in geological records from the last 200,000 years, even the last 20,000,000 years. Research clearly shows the burning of fossil fuels during the last century is the main reason for this increase. Note: During the same period, methane has increased 145% and nitrous oxide by 15%, relative to pre-industrial levels.
Our use of the land is one way to reduce the net amount of carbon dioxide added to the atmosphere.
Improving present carbon sinks on land may include protection of threatened landscapes and adaptation to newly planted landscapes. New technology and practices for managed landscapes of forestry and agriculture will be needed. Human improvements in forestry and agriculture to remove and store more carbon help to balance human caused carbon dioxide emissions. See the graphs for new tree growth at the end of this section.
Changes in land use such as reforestation (replanting areas) and aforestation (planting new areas) increase carbon sinks while deforestation (tree cutting) reduces them. Forest fires are a source of carbon dioxide. Reduction in the number and size of forest fires is considered in smaller countries to be part of forest management. Our failure to suppress forest fires in Ontario might be considered a source of carbon. See also Agriculture 7.2.2.2d regarding Carbon Sources and Sinks.
To understand the scientific basis for considering biological sinks, they must be put into the context of global carbon reservoirs and natural exchanges between them. Both the natural global carbon reservoirs and the natural exchanges between these reservoirs are very large (note that 1 tonne of carbon is equivalent to about 3.7 tonnes of CO2).
The bar graph below shows both global carbon sources and sinks for the 1990’s.
Source: IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK. p208
ACTIVITY 2
1. In the 1990’s oceans and ecosystems have offset human emissions through natural sinks During the 1990s, CO2 emissions from human sources were estimated to be:
- 6.4 +/-0.4 GtC/yr from the combustion of fossil fuels and the production of cement;
- 1.6 +/-0.8 GtC/yr source from deforestation (1989-98 estimate).
1. What is total GtC released to the atmosphere by human activities?
2. How much was removed from the atmosphere by the natural sinks?
3. What % of the total natural carbon sink does the ocean provide?
An atmospheric perspective of the terrestrial carbon budget is shown below.
Source: IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK
ACTIVITY 3
1. About half of Gross Primary Production is rapidly released by terrestrial plant respiration. How many Gigatonnes (GtC) of carbon is this per year?
2. If 55 GtC/year is released by biomass decay, how much was left in growing ecosystems?
3. Wild fires and human changes of land use release about 4 GtC/yr into the atmosphere. How many gigatonnes of carbon are actually used for increased growth by global ecosystems?
ACTIVITY 4 Research
1. What % of the Gross Primary Production is the #3 answer? How is this like bank interest?
2. Human emissions release about 8 GtC into the atmosphere each year. This about 5% of total average natural emissions into and out of the atmosphere each year. Looking at the answer to #3 what percent of human emissions can be used for net biome production? What might happen to the rest of the 8GtC?
The number of GtC/yr absorbed by natural changes from month to month and year to year. The graph below follows 40 years of carbon from fossil fuel emissions and atmospheric carbon.
Source: IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK.
ACTIVITY 5
1. Describe the trend seen? Name 10 ways to decrease fossil fuel emissions.
2. Draw a best-fit line for the atmospheric increases and determine the increase in GtC/year.
The changes in the annual uptake of CO2 by the oceans and the land depend on the changes in CO2 in the atmosphere. These changes are mainly caused by changes or variability in climate. Climate events such as El-Ninos can also influence the land processes that absorb and release carbon.
Most of this variability is observed over land in the tropics, but also occurs in all other ecosystems.
This variability is a reminder that climate change will also significantly affect the future role of the biosphere as a source or sink of carbon.
Four important factors affect future carbon exchanges on land in the biosphere are listed below:
- Carbon dioxide (CO2) and Nitrogen (N) fertilization – improves rates of growth, changes the ecosystem biodiversity, becomes saturated over time.
- Warmer temperatures – speed growth and changes the range of species in colder ecosystems, decreases growth in warmer ecosystems, increases plant and soil organisms respiration
- Changes in precipitation – changes the risk of fire, affects the growth of vegetation
- Land use changes – can be either made to increase natural carbon sources or sinks.
Without action to reduce emissions or to continue doing business as usual (BAU), the atmosphere and natural and human sources and sinks continue to increase. This means that the physical, social, economic technological and political aspects of our world do not change, but continue to cause changes in the atmospheric concentrations of greenhouse gases.
The diagram below shows how modeling Business As Usual (BAU) will cause continue to cause increases in atmospheric concentrations.
Source: IPCC 2001. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Changes [Houghton, J.T., et al. (eds.)]. Cambridge University Press, Cambridge, UK.
The diagram below estimates how forest fires in Ontario will respond to climate change by the month. It does not take other factors of possible change into account. Forest fires add particulate matter and carbon dioxide to the atmosphere. Burning or combustion is part of the natural cycle of life in a forest especially dry seasons.
Decay also adds carbon dioxide (CO2) to the atmosphere as part of the carbon cycle. This too is a natural part of the life of a forest. Decay returns trees to the soil for recycling the forest.
What is different under climate change is the rate of growth and decay. The rate of these processes increase as temperatures increase. The extent of the area of decay also increases as the area of snow cover and permafrost decrease. This melting and decay may also release methane. Methane, molecule for molecule, is a much more effective greenhouse gas effective in causing more heat to be retained in the greenhouse.
The forest fire season in Ontario is expected to begin much earlier. By May there is already significant risk of fire. Note the effect of twice or 2X the amount of CO2 below!!
Source: Stocks, B.J.; Fosberg, M.A.; Lynham, T.J.; Mearms, L.; Wotton, B.M.; Yang, Q.; Jin, J-Z.; Lawrence, K.; Hartley, G.R.; Mason, J.A.; McKenney, D.W. 1998. Climate change and forest fire potential in Russian and Canadian boreal forests. Climatic Change 38:1-13.
Source: G. Miller (2004) About Ontario Environmental Commissioner of Ontario, www.eco.on.ca
ACTIVITY 6
Check and compare the 3 ecozones of Ontario shown here and note where the greatest chance in forest fire with the previous figure.
American Inst of Biological Sciences Vo. 51, #9
“The Great Lakes Basin will experience 50-75 % decrease in leaf area and 10-25% decrease in runoff according to the average simulated change.
Ozone concentrations have been shown to reduce growth i.e. affect photosynthesis to reduce food making or carbon gain by trees. Experiments have been done with seedlings and mature trees one 160-year-old tree. All show a linear decrease in photosynthesis with an increase in exposure to ozone. Increasing temperatures and CO2 concentrations will tend to offset the effects of increasing ozone so the overall effect may be neutral.
Improved integration of forest process models is needed to better predict future conditions.
Increased temperature generally increases in productivity but there many other factors to consider. Drier conditions for forest areas mean increased frequency of fires.”
Diversity of Present Forest Families in Ontario
Don MacIver (2000) Forest Families, Forest Biodiversity Integrated Assessment Mapping Project www.utoronto/imap
ACTIVITY 7
At the bottom of the legend locate the colour for forest families at Windsor.
1. What percent of Windsor trees were considered tropical families before 2000?
2. Check the diagram below for the effect of 2X CO2 twice the carbon dioxide New percentage?
Don MacIver (2000) Forest Families, Forest Biodiversity Integrated Assessment Mapping Project www.utoronto/imap
ACTIVITY 8
1. Locate the same colour on the 2xCO2 map and name the largest city there. What % tropical are the Windsor forest families to become under these conditions?
2. Broad leaf or deciduous trees may be a bigger percentage of any forest cover.How will this effect the reduction of emissions strategy?
“The migration rates of tree species and the rate of ecosystem establishment under climate change both need long-term studies dealing with long-term monitoring of forest composition and growth. Forests will also be directly impacted by warmer temperatures as humans convert more forests to farmland. The greater number of heat days will allow farmers to grow more and different crops.
A combination of permanent ground-based forest monitoring plots and improved remote-sensing technologies could help create a baseline to better predict the future of our forests under climate change”. Source: American Inst of Biological Sciences Vo. 51, #9
The graph below relates hardwood tree families to climate.
Source: Don MacIver (2000) Forest Families, Forest Biodiversity Integrated Assessment Mapping Project www.utoronto.ca/imap/
ACTIVITY 9
The figure above shows a direct or linear relationship between the number of families and the heat units (grow degree days).
1. What change would you expect to see in Ontario as the temperature increases?
2. Check the report below and see how you might change your answer.
NEW FORESTS UP TAKE CARBON SLOWLY
The rate of CO2 uptake by trees is very dependent on the type of tree and the age of the stand.
For most species, there is very little carbon accumulation in the first decade of growth.
Fast growing species are the exception, but mature quickly, become saturated as a sink, and unless harvested become a sink again.
Growing Ontario Hybrid Poplar – A carbon sink?
AGE
Source: National Climate Change Process Sinks Table Report
ACTIVITY 10
1. Which tree acts as a carbon sink for the longest time? Why?
2. At what projected age that hybrid poplar becomes a carbon sink? Why?
American Inst of Biological Sciences Vo. 51, #9
Research for multiple environmental stress interactions at the forest level even at the tree level, is very limited. Interactions between atmospheric CO2, soil water and nutrient limitations, carbon sequestration and species composition; between CO2 and troposphere O3 on plant water-use efficiency need more research.
The diagram below represents the processes in living plants in a forest environment.
N = Nitrogen VPD = Vapour Pressure Deficit NPP = Net Primary Production
(+) = enhancement (-) = suppression of the receptor process
Source: J. Aber et al. (2001) Forest Processes and Global Environmental Change: Predicting the effects of Individual and Multiple Stressors. BioScience, 51 (9) September. Copyright, American Society of Biological Sciences
ACTIVITY 11
The rate of chemical reactions in the soil will be speeded up by temperature increases due to climate change.
1. What effect will an increase in the rate of photosynthesis have on the rate of respiration and the percentage of carbon dioxide in the atmosphere? See also carbon sequestration.
2. Why might this considered an adaptation and not a mitigation strategy for climate change?
3. What gas is missing from this diagram? Hint: Check the products of photosynthesis!