Hydrological Threats to Ecosystem Services Provided by USDA Forest Service

Transcription

1 Hydrological Threats to Ecosystem Services Provided by USDA Forest Service Yongqiang Liu Center for Forest Disturbance Science USDA Forest Service, Athens, GA, USA International Symposium on Synergistic Approaches to Food and Water Security George Mason University. October 17-19, 2012

2 USDA Forest Service The U.S. Forest Service is one of the U.S. federal land management agencies. FS manages 155 national forests and grasslands with 193 million acres, about onefourth of total forested land of about 747 million acres, about one-third of nation s land. It is dedicated to the improvement of water resources, development of climate change resiliency, creation of jobs that will sustain communities and restoration and enhancement of landscapes.

3 Water related forest ecosystem services (Millennium Ecosystem Assessment, 2005) Regulating Provisioning Regulating services are benefits obtained from the regulation of ecosystem processes flow and ground water, soil erosion, water purification and water temperature. Supporting Cultural Provisioning services include products obtained from ecosystems conserve water resources. Supporting services include the ecological elements and processes to sustain ecosystems soil-vegetationatmosphere water cycling. Cultural services benefit people through water related recreation About 80 percent of the Nation s scarce freshwater resources originate on forests, 25~1000 mm per unit area of land per year (Brown et al. 2008).

4 Hydrological threats Hydrological threats to forest ecosystem services - stressed or degraded forest water conditions due to natural or human factors. Natural contributors -climate variability (droughts) and climate change (global warming) -climate can affect the hydrologic cycle and thus water quality and quantity from forests. Critical forest ecosystem services can be threatened or compromised. Issues -Current hydrological threats to U.S. forest ecosystem -Future trends in the hydrological threats Objectives -Hydrological conditions in the U.S. through analyzing water indices (Liu 2011, Liu et al. 2012) -Hydrological conditions in the South from water research, part of Southern Climate Change Adaptation and Mitigation Management Option project (Marion et al. 2012)

5 Threat Indicator (soil) Keetch-Byram Drought Index (KBDI) - Soil moisture deficit, measuring the amount of precipitation necessary to return the soil to full saturation - Determined by maximum temperature, daily rainfall, average annual rainfall. Forest drought classification Low (0-200) Soil moisture and large class fuel moistures are high. Typical of spring dormant season following winter precipitation. Moderate ( ) Lower litter and duff layers are drying. Typical of late spring, early growing season. High ( ) Extreme ( ) Lower litter and duff layers are dry. Typical of late summer, early fall. Lower litter and duff layers are very dry. Live fuels can also be dry at these levels. Often associated with more severe drought.

6 Threat Indicator (vegetation) - Ratio of water and dry weights of dead or live fuels. - Dead fuel moisture responds solely to ambient environmental conditions Dead fuel moisture classification 1-h, <1/4" diameter 10-h 1/4 to 1" 100-h 1 to 3" 1000-h 3 to 8" Fine flashy fuels that respond quickly to weather changes. Computed from observation time temperature, humidity, and cloudiness. Computed from observed temperature, humidity, and cloudiness, or can be an observed value, from a standard set of "10-Hr Fuel Sticks". Computed from 24-hour average boundary condition composed of day length, hours of rain, and daily temperature/humidity ranges. Computed from a 7-day average boundary condition composed of day length, hours of rain, and daily temperature/humidity ranges

7 Current and future climate - From the North America Regional climate change assessment program (NARCCAP), an international program to produce high resolution climate change simulations to investigate uncertainties in regional scale projections of future climate and generate climate change scenarios for use in impacts research. - Run a set of regional climate models (RCMs) driven by a set of GCMs over North America. - Simulations for the current period and for the future period at a spatial resolution of 50 km with the IPCC SRES A2 emissions scenario for the 21st century. - Simulations with HRM3 driven by HadCM3 were used for the results presented and compared with other simulations for specific regions.

8 Present (top) and future change (bottom) seasonal precipitation (mm)

9 Present (top) and future change (bottom) temperature (max. o C)

10 Present (top) and future change (bottom) KBDI

11 Degraded hydrological conditions

12 Present (top) and future change (bottom) fuel moisture (%)

13 Trends of U.S. summer KBDI (top) and seasonal fuel moisture (bottom) over 30-year period The red and green curves represent the present period of and future period of The red line is slope of present variations.

14 Increasing wildfire trends resulted partially from drying forest hydrological conditions

15 Inner (left) and inter (right) year variability

16 Comparison with other models

17 Water Yield (mm) Future trends in southern water yield Mean trends predicted for in mean annual water yield, normalized by mean annual water yield. Hatched area represents locations where the predicted trend in water yield is statistically significant (p < 0.05) (b) Predicted South-wide 10-yr moving-mean annual water yield. The green area represents the range in predicted water yield over the four climate projections.

18 Mean annual Water Supply Stress Index (a ratio of water demand/water supply) based on four climate projections for (a) Baseline ( ), and (b) Future ( ) (a) Baseline (b) Future

19 Conclusions Current threats of hydrological conditions are high in the inter-mountains all seasons and the South in summer. The drying trend is happening and is expected to continue in this century. Larger variability is expected for the costal regions. Increasing water shortage is expected for many southern areas.

20 Thanks!