Forests and Changing Climate

“Mitigation deals mostly with carbon,adaptation deals with water”

John Hoklren, OSTP

“Of all the outputs of forests, water may be the most important”

National Academy of Sciences 2008

Expected Climate Change Effects

Precipitation: more rain & less snow 33% snowpack loss 1.6 °C increase by 2060 (Knowles 2002)

Earlier snowmelt Faster snowmelt

Predicted Loss of Snowpack(Knowles 2002)

°C Increase % Snowpack Loss

Year

0.6 5 2030

1.6 33 2060

2.1 50(43 to 66)*

2090

*Effect greater in northern Sierra and Cascades

3 °C increase by 2070-2099 (Bureau of Reclamation 2011)

Modeled Mean Annual Flow& Percent Decrease (Null et al. 2010)

Watershed Basecase Percent decrease from Basecase

2° C increase 6° C increase

Feather 5776 2.2 8.8Yuba 3020 2.0 7.1Bear 492 3.6 9.6American 3556 3.1 9.5Cosumnes 603 5.2 14.0Mokelumne 979 3.4 9.4Calaveras 330 3.3 8.9Stanislaus 1561 2.4 8.1Tuolumne 2445 1.8 5.8Merced 1348 3.0 8.2San Joaquin 2294 1.3 4.1Kings 2117 1.1 3.6Kaweah 586 3.8 11.5Tule 199 4.6 14.3Kern 926 4.2 12.2

AnimalsVegetation

Soil Water

Bacteria &

Fungus

Nutrients & Carbon

Pacific Southwest Research Station, Fresno, CA

Kings River Experimental WatershedsKREW

KREW Study: Paired Watershed Experiment

Annual Stream Discharge

Climate Change

& Water Yield

Bull 203Size: 342 acresElevation: 7170-8170

ftMean Temp: 6.9°C

Providence 303Size: 327 acresElevation: 5670-6530

ftMean Temp: 8.8°C

Water Cycle or Budget

Atmosphere Transpirationby Vegetation

Soil Streams& Lakes

Evaporation

Oceans

Percent of Precipitation to Become Runoff

0

10

20

30

40

50

60

70

WY 2004 WY 2005 WY 2006

% o

f Pre

cip

Providence

Bull

Findings: Water Yield & Climate

Precipitation amount (30-80 in/year) Reaches maximum at 3,940 ft

Runoff ratio (discharge / precipitation) 10% increase per 1,000 ft

Snow-dominated 2 to 3 times discharge

Trees at rain-snow using more water in winter (evapotranspirtation 30 in)

Upper Kings River BasinGoulden et al. 2012

Measured evapotranspiration 10,000 ft 18 in/yr 6,600 ft 30 in/yr (60% higher)

Due to winter dormancy at cold, snow dominated

Both are mixed-conifer forest

Atmospheric lapse is -5.3 °C per 3,300 ft 3 °C warming shift vegetation upslope ET increase of up to 60%

Climate Change& Water Quality

Erosion: Roads & Wildfire Increased sediment yield because

Climate change = vegetation disturbance

Road maintenance and decommissioning effective but will not mitigate increase in sediment from increased wildfire

Goode et al. (2012) Idaho case study

Findings: Flow Pathways Determined using water chemistry

Primary: Subsurface flow ~ 60% Soil-bedrock interface

Snowmelt runoff < 40% Fall storm runoff < 7%

Adaptation: Multiple Stressors

Air pollution Increased wildfire Insect outbreaks Climate change

“I would feel more optimistic about a bright future for man if he spent less time proving that he can outwit Nature and more time tasting her sweetness and respecting her seniority.”

E.B. White