(The primary intent of these questions is to help focus the development of priorities for TOPC activities.)
Policy makers have been informed that the global climate system is changing as a result of human activities. They now require information on the implications of such changes on terrestrial natural and managed ecosystems. Specifically, they need answers to four broad questions.
1. Are the changes to terrestrial ecosystems, which may be beneficial or detrimental, attributable to climate change? If so, what is the rate and magnitude of the change, and is there any change in the frequency of extreme events? To address these questions, several sub-questions must be addressed, including the following:
a. Are there changes in snow cover, glacier dimensions and the area or depth of permafrost?
b. Are there changes in the quantity, timing or location of runoff, especially in catchments not exposed directly to land use change?
c. Has there been a change in the frequency of floods or droughts?
d. Has there been a change in the frequency or extent of vegetation fires, insect outbreaks, windthrow or other major ecosystem disturbances?
e. Are there changes in the length of the growing season, either through changes in the frost-free period or the duration of soil moisture?
f. To what degree are changes in runoff and ice melt contributing to sea level rise?
g. To what degree has climate change contributed to changes in the volume of groundwater in aquifers?
2. Are the changes in terrestrial ecosystems affecting, or likely to affect, their ability to sustain food and fibre production to meet human needs, economic activities associated with terrestrial ecosystems, such as forestry and tourism, and suitable habitats for the full diversity of plants and animals? For example:
a. What is the impact of climate change and rising carbon dioxide on plant growth (net primary productivity) in terrestrial ecosystems?
b. Has the extent or location of land suitable for particular forms of agriculture or forestry altered?
c. What is the impact of climate change on the structure and composition of the land cover (including issues such as the location and extent of forests and wetlands), particularly in combination with direct human alteration of land cover?
d. What is the impact of climate change, the rate of climate change and the frequency of extremes on species near their climatic limits, particularly for isolated populations of rare organisms?
3. Are changes in terrestrial ecosystems acting to enhance or moderate climate change? For example:
a. How is the ability of terrestrial ecosystems to act as sinks or sources of radiatively-active gases, aerosols or the precursors, in particular carbon dioxide, methane, nitrous oxide and tropospheric ozone, modified?
b. Is the fraction of solar energy absorbed by the surface altered?
c. Is the partitioning of absorbed energy between latent and sensible energy changed?
d. Has the aerodynamic roughness of the land surface altered?
- Are elevated carbon dioxide and nitrogen deposition altering altering the processes which control carbon pools in live and plants and the soil?
4. How can information from the study of terrestrial ecosystems be applied to improve the tools used to assess and predict climate change and its impacts? For example:
a. How can the data be assimilated in a form which improves the accuracy and resolution of the land surface-atmosphere interactions in general circulation models?
b. How accurate are the climate and terrestrial ecosystem models in mimicking existing conditions, and how sensitive are they to changes in their parameters within the range of natural variability plus measurement uncertainty?
c. Are there sensitive ‘early warning’ indicators of change in terrestrial ecosystems, or easily-measured and broadly distributed integrators of complex, slow or intermittent change processes?
