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Ecological and Agricultural Consequences of Climatic Extremes and Variability

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Session Description: 

Climatic extremes and variability refer to the tails and spread of the distributions of climatic quantities such as temperature (e.g., heat waves, cold waves, early frosts), precipitation (e.g., droughts, floods, hail), and winds (e.g., extratropical storms, hurricanes, tornadoes). Ecosystems refer not only to the mixtures of species and age cohorts covering specific areas, but also to the populations of single species growing throughout their geographic ranges. In this context, we are viewing agricultural systems as intensely managed, monospecific populations.

The objectives of the proposed 10-day session are to: (1) review and synthesize the available information on the nature of impacts on ecosystems and agriculture produced by past and present climatic extremes and variability; (2) present the current research on projecting impacts on ecosystems and agriculture of possible future anthropogenically induced changes in climatic extremes and variability; (3) identify weaknesses in current data and research efforts needed to support decision-making, and develop recommendations for ameliorating them; and (4) publicize the meeting results by publishing them as papers in a special issue of a broadly read, refereed journal such as Climatic Change that documents items (1)–(3).
The session will be organized into three parts following items (1)–(3) above. Parts I and II of the session will each consist of approximately 3 days. Part III will be Working Group meetings on the ecological and agricultural impacts. The two Working Groups will draft a report summarizing and synthesizing the material presented during Parts I and II of the session.

Analyses of the impacts on market sectors, such as agriculture and forestry, of future changes in average temperature and precipitation induced by human activities suggest relatively minor impacts on gross world productivity, and perhaps even enhanced productivity. In contrast, the potential impacts of changes in climatic extremes and variability on market sectors and ecosystems may be severely debilitating, even as changes in climatic averages may demonstrate no cause for concern. Should impact analyses project large damages to natural systems, the timing and magnitude of appropriate climate-change abatement actions would be quite different from that needed if such damages were small. At the present time, however, too little scientific information exists to permit reliable impact analysis or risk assessment. The purpose of the proposed session is to reduce this uncertainty by bringing together experts in climatology, ecological response and agricultural impacts to review, synthesize and integrate available knowledge in these fields. The review and synthesis should expose the scientific research that is needed to resolve uncertainties that now preclude assessing the risks from changing climatic extremes and variability. The integration of knowledge about the “So what if climate changes?” will help policymakers to formulate more robust policies of climatic change abatement, mitigation and adaptation.


Part I: The Impacts on Ecology and Agriculture of Past and Present Climatic Extremes and Variability

1. Tutorial on the nature of climatic extremes and variability

2. Past ecosystem response to climate extremes and variability: some potential topics

a. Past 600 years of tree rings and summer warmth in the circumpolar Boreal Forest
b. Droughts of past 400 years in SW U.S. piñon juniper woodlands
c. Vegetation productivity response to little ice age cooling in the upper Midwest
d. Tree population spread in response to Holocene climate variation

3. Past agriculture response to climate extremes and variability: Some of the potential topics

a. Tewas Pueblos NM loss of corn, bean production for several decades following the 1919-1929 Rio Grande floods
b. Viking colonies in Greenland in 12-14th centuries
c. Decline of the Lost Colony of Roanoke Island, Virginia
d. Many studies of European agriculture during middle ages, little ice age

4. Present ecosystem response to climate extremes

a. Direct effects of extremes on populations and ecosystems

i. Hurricanes, windstorms on ecosystem structure and composition; e.g., loss of old-growth in 1938 New England hurricane, southern Atlantic states, Puerto Rico forests from Hurricane Hugo;
ii. Floods on specialized species and communities; e.g., floodplain communities and fish below Glen Canyon;
iii. Droughts on plant mortality; e.g., seedling, mature tree mortality
iv. Low temperatures on plant mortality and regeneration; e.g., Douglas Fir cold hardening, subtropical tree seedling mortality; late-spring frosts leading to mortality of Siberian larch in Iceland.

b. Indirect effects of extremes on populations and ecosystems

i. Insect outbreaks in drought-stressed populations; spruce budworm in Blue Mountains, Oregon
ii. Exotic species invasions borne on extreme winds, carried into stressed ecosystems; Kudzu vine in southeast U.S., conifer gypsy moth in the Pacific Northwest
iii. Wildfire area, intensity, frequency from wet/drought oscillations; Sequoia in California
iv. Regeneration periodicities at ecosystem boundaries; ponderosa pine in 1921 along Colorado Rim, piñon pine and juniper in arid southwestern U.S. in the 1600’s, 1800’s

5. Present agricultural response to climate extremes

a. Texas drought of 1998
b. Chinese floods of 1998
c. El Niño patterns in temperate grain belts
d. Sahel drought of the 1990s

Part II: The Impacts on Ecology and Agriculture of Possible Future Anthropogenically Induced Changes in Climatic Extremes and Variability

1. Methods for and results of projecting future climatic extremes and variability

a. Extremes and variability simulated by AGCMs
b. Extremes and variability estimated from historical data

2. Methods for projecting ecological and agricultural responses to climatic extremes and variability

a. Dynamic stand and ecosystem models
b. Landscape GIS models
c. Climate envelopes and land suitability for agriculture
d. Agricultural productivity models

3. Results of projecting effects of future extremes and variability on populations and ecosystems: Some of the potential topics

a. Migration of forest trees in the temperate and boreal zones; role of extreme winds
b. Growth of Douglas fir in the Rocky Mountains: effects of warming winter low temperature extremes.
c. Drought in continental temperate areas as determinant of tree life forms

4. Results of projecting effects of future extremes and variability on agriculture: Some of the potential topics

a. Integrated assessment of agricultural area and productivity in a warmed world
b. Summer drought and grain crops in Canada and Siberia
c. Monsoon variation and rice crops in Asia

Climatologists, both observationalists and modelers
Ecological impact analysts, both observationalists and modelers
Agricultural impact analysts, both observationalists and modelers

Workshop Topic (s): 
  • Climate Variability and Change (including Climate Modeling)
  • Human Contributions & Responses
  • Land-Use/Land-Cover Change
  • Water Cycle