Overview & Relevance:
As the concentration of carbon dioxide in the atmosphere rises, there is increasing interest in trying to manage the biosphere in such a way as to increase the amount of carbon retained in the biosphere. There are a variety of reasons, in addition to the greenhouse effect of atmospheric carbon dioxide, for wanting to manage the amount of carbon in the biosphere. These reasons include concerns about biodiversity, the well-being of watersheds, the fertility of soils, and the long-term health of ecosystems generally. In terms of the greenhouse effect, the Kyoto Protocol suggests that, at some level, measures to increase biospheric carbon have the same benefit as measures to decrease emissions of carbon dioxide from fossil-fuel burning.
One important distinction between measures that reduce carbon flows from fossil fuels to the atmosphere and those that increase carbon flows from the atmosphere to the biosphere has to do with permanence. Reducing emissions from fossil fuels to the atmosphere can yield an essentially permanent decrease in the amount of carbon in the atmosphere, at least up to the scale of global fossil fuel resources. Increasing flows of carbon from the atmosphere to the biosphere (or decreasing flows of carbon from the biosphere to the atmosphere) on the other hand, can be reversed on a very short time scale if, for example, the forest is subsequently burned or the soil plowed.
In fact, in the face of changing climate and increasing social pressures, there may be increasing forces that operate against protecting carbon in the biosphere or accumulating additional carbon in the biosphere over the long term, i.e. over 50 to 100 years or more. Regardless of human efforts to mitigate climate change, increasing atmospheric CO2, increasing temperature, changes in the hydrologic balance, increasing human population, changes in land use, and other environmental changes, will exert increasing stress on current forests and other carbon-rich ecosystems.
Recognizing the stresses on forests and that change is an essential feature of terrestrial ecosystems, how then should present day investments in forest protection or forest expansion, or carbon accounting under an instrument like the Kyoto Protocol, be tempered by the potential for change over the long term? What spectrum of change can be realistically expected in the long term and should near-term commitments be influenced by long-term uncertainties? How might climate mitigation policies interact with the other stressors affecting terrestrial ecosystems?
Trying to mitigate climate change through management of the biosphere may differ from reducing emissions in one other important way. Large-scale changes in the biosphere may feed back into the climate system by altering the albedo of the Earth, the hydrologic balance at the Earth’s surface, and the surface roughness. Thus these efforts to mitigate climate change may, in fact, have significant climate consequences.
Trying to make present day investments in the long-term health of ecosystems, and trying to make the Kyoto Protocol (or some successor international accord) operational and consistent with its stated objectives, thus confronts a variety of long-term questions. Few would argue that there are many benefits in the near term in trying to protect the health of present ecosystems and to minimize the rate of growth of the concentration of carbon dioxide in the atmosphere. How, though, should our longer-term vision play a role in our current decisions?
This AGCI workshop explored the long-term outlook for management of forests and other ecosystems and how this outlook might be incorporated in current planning and accounting. The workshop included four major elements:
1. What is the sensitivity of forests to changes in climate, including atmospheric CO2?
2. What other stresses (such as tropospheric ozone, nitrogen deposition, land-use change, and the interaction of multiple stresses) can be expected to affect the extent and health of forests over the next century?
3. How might changes in the extent and health of forests and other ecosystems feed back within the global climate system?
4. How might current investments in forest management and protection and carbon accounting under an international climate accord be influenced by our long-term vision of the inherent stresses and how are present forest management strategies and practices matched to the set of factors interacting with forests?
Our organizing question was the extent to which concerns about long-term changes in climate can motivate long-term changes in forest management that actually help mitigate climate change and insure the health and diversity of terrestrial ecosystems.
Workshop Topic (s):
- Carbon Cycle
- Human Contributions & Responses
- Land-Use/Land-Cover Change