Yosemite National Park

Historical trends and future scenarios

It is a challenge to manage National Parks in the face of a changing climate. A multi-institutional research team recently provided Yosemite National Park resource managers with an analysis to help prepare for upcoming changes. This study is particularly important because prior to having this downscaled climate data, resource managers did not have information at a fine enough resolution to support decision making.

The team ran MC1, a widely used, dynamic global vegetation model (DGVM) using future climate scenarios downscaled to a 800 meter spatial resolution. The model projects vegetation shifts, associated carbon and nutrient cycling, and fire occurrence and impacts.

We do not know how humans will behave over the next hundred years, nor is it possible to predict vegetation and fire dynamics with absolute accuracy. However, by focusing on similarities among the set of model projections, managers get powerful and robust results that point to a likely future outcome.

Click here to see a summary of likely outcomes for Yosemite National Park during the 21st century under various future climate scenarios.

In this study, the Yosemite National Park research team addressed several questions:

How have average temperatures of the coldest month
changed between 1900 and 2000?

1900 to 1950: The actual decrease from 1900 to 1950 is about 1 degree C. The rate of decrease is about 2 degrees C per century.

1950 to 2000: The actual change from 1950 to 2000 is an increase of about 1.5 degrees C.

Between the period of two field surveys (1930s and 1997) large changes in vegetation cover have occurred that the DGVM did not simulate well. The legacy of human land use combined with fire suppression, increased visitor use, changes in herbivory-predator relations, have likely driven actual vegetation cover away from areas of potential or appropriate growing conditions simulated by the model. Actual vegetation changes during the 20th century may also be a reflection of climate changes during the 19th century which were not simulated.

How might Yosemite's vegetation change or shift in the future
under three climate scenarios?

In the latter part of this century, a combination of projected rising temperatures and declining precipitation, associated with extensive wildfires will cause vegetation shifts in much of Yosemite National Park. Mediterranean type ecosystems are predicted to expand into areas currently occupied by montane forest and valley bottom vegetation.

If drought conditions worsen as climate models scenarios show they will, the landscape will exhibit obvious signs of ecosystem stress: drought-stressed remnant forests sensitive to insect infestation and wildfires, large areas of fire scars and early post-disturbance vegetation. Newly established forests will likely include many more broadleaf trees than middle and high elevation Yosemite forests do now.

Overview of Predictions:

A summary of projections for Yosemite National Park during the 21st century under various emissions scenarios:

Climate and Hydrology

Carbon Cycle

Fire

Montane Chaparral and Hardwoods

Montane Ecosystems

Subalpine Ecosystems

Alpine Vegetation Communities

Desert

Related Work:

Shaw R. et al. (2008). The impact of climate change on Califorrnia's ecosystem services. Report to California Energy Commission and California Environmental Protection Agency. (pdf)

References:

Aerial Information Systems (1997). Yose_1997veg_final_poly [computer map, Arc coverage] 1997. Yosemite National Park: National Park Service.

"Conklin DR (2009).  Simulating Vegetation Shifts and Carbon Cycling in Yosemite National Park.  PhD dissertation, Oregon State University. 134 pages.

Gordon C. et al. (2000). The simulation of SST, sea ice extents and ocean heat transports in a version of the Hadley Centre coupled model without flux adjustments. Climate Dynamics 16: 147-168.

Gordon HB et al. (2002). The CSIRO Mk3 Climate System Model Aspendale: CSIRO Atmospheric Research. CSIRO Atm. Res. tech. paper no. 60.

IPCC (2007).  Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment. Report of the Intergovernmental Panel on Climate Change, Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K 280 .B. Averyt, M. Tignor and H.L. Miller (eds.). Cambridge University Press, Cambridge, UK and New York, NY, USA.

Panek, J., D. Conklin, B. Kuhn, D. Bachelet, and J. van Wagtendonk. Projected Vegetation Changes Over the 21st Century in Yosemite National Park Under Three Climate Change and CO2 Emission Scenario. (2009). Report to the National Park Service under task agreement #J8R07070021. (pdf)

Wieslander AE (1935). First steps of the forest survey in California. Journal of Forestry 33: 877-884

Photo Credit: Wayne Spencer (Conservation Biology Institute)