Extreme Drought: Weather Variance or Climate Change?
external image 32959423.jpgSituation
The San Antonio Missions National Historic Park is located in a unique ecological area that includes three types of ecosystems. The Edwards Plateau, Oak Woods and Tallgrass Prairie, and Tamaulipan Thornscrub ecosystems meet in the city. The conjunction of this variety of ecosystems plus the presence of numerous streams and associated riparian vegetation offer support for a diversity of plants, animals, and ecological environments that characterize the San Antonio River Valley.

Much of the land in and around the San Antonio National Park is referred to as "disturbed lands," or areas that have been engineered for human habitat. The process of human engineering of the land and water in the San Antonio River Valley dates back to two Spanish missionary settlements between 1718 and 1720 and another three Spanish missions in 1731. Human reconfiguring of the land continued through the 1950s when, for example, the San Antonio River was channelized near the park to assist with flood protection.

Today, human engineering of the San Antonio River Valley continues and is necessary to provide water to support San Antonio's growing population. Human changes to the historic San Antonio missions area has been ongoing since the creation of the national park in 1978 to support historic preservation of the area. The park has acquired many acres of property to restore the landscape and protect cultural resources. Much of this land was occupied by modern homesteads in various stages of use and was heavily disturbed. The park has restored most of the areas by removing buildings and debris in an attempt to recreate the landscape of the Spanish colonial period and also to meet modern health and safety standards.

Carbon credits

Before the introduction of sheep, goats, and cattle, the upland areas of the Lower Pecos Canyonlands had extensive grasslands like this restored area. During wet climatic intervals the grasslands flourished, and herds of buffalo migrated into the area. Photo by Phil Dering.
Before the introduction of sheep, goats, and cattle, the upland areas of the Lower Pecos Canyonlands had extensive grasslands like this restored area. During wet climatic intervals the grasslands flourished, and herds of buffalo migrated into the area. Photo by Phil Dering.



Many of today's plowed fields and old fields (succeeding to huisache tree uplands) are located where historic labores (fields) were tended during Spanish colonial times. Areas with the historic acequias were at one time dry scrublands. Because of water provided by acequias irrigation systems (historically engineered canals that carry snow runoff or river water to distant fields), thick riparian vegetation with tall trees have replaced scrublands in some areas. However, drought conditions in 2011 have turned Texas and parts of the Plains into a parched moonscape of cracked earth. According to an Aug. 5, 2011, Associated Press story, the drought "could persist into next year, prolonging the misery of farmers and ranchers who have endured a dry spell that is now expected to be the state's worst since the 1950s."
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(Above) This color-coded interactive map shows a progression of changing global surface temperatures from 1885 to 2007. Dark blue indicates areas cooler than average. Dark red indicates areas warmer than average. (Credit: NASA/Goddard Scientific Visualization Studio). What does the Climate Time Machine tell you about your state's temperatures during this 122-year period?

The U.S. Drought Monitor shows that conditions in the summer of 2011 are among the worst on record. View (YouTube movie): Severe Texas Drought – Takes Toll on Rivers - Drying Up! Then use the TX Water Development Board Drought Information Summary to view Drought Severity for Texas.

How do you interpret the cause and effect of having less moisture in the air leading to higher temperatures?

Use the Frayer Modelto investigate whether there is a connection between the excessively high temperature and rising greenhouse gas levels in the atmosphere. Modify the Frayer Model structure to include your analysis of climate indicators versus weather conditions for the San Antonio River Valley. Based on the data you collect and your analysis, would you predict that severe drought and record heat waves will be more common in the Central Plains in the future decades?
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Use the TX Water Development Board Drought Information Summary to view drought severity for each of the regions shown.
Image (above) shows the latest three-month average temperature and precipitation anomalies for the United States. Image Credit: NOAA.
Image (above) shows the latest three-month average temperature and precipitation anomalies for the United States. Image Credit: NOAA.


Task
During the summer of 2011, higher than normal temperatures and dry vegetation mixed with high winds and low humidity to create extreme drought conditions in Texas. Your task is to determine whether the drought is a consequence of global climate change, or are these conditions more likely normal seasonal weather patterns for this area? Should Texas and other states in the Great Plains plan for long term drier weather and higher temperatures? Or will the weather return to more temperate conditions with varying higher and lower seasonal temperatures and precipitation levels?

In carrying out your task, consider whether human interventions to the waterways and landscape play a role in exaggerating ecology changes.

The Parks Service is interested in your analysis of this situation because your research results (causes and consequences) might apply to other ecological areas across the country.
Engage
  • Use the Natural Resources Water Simulation to investigate the concepts of sustainability and carrying capacity. See how variations in the environment cause variations in carrying capacity.
Explore
Resources

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Use Google Earth to explore the San Antonio River Valley.


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Vegetation Map of San Antonio Missions National Historical Park, National Park Service, U.S. Department of the Interior, produced by USGS.



Use the Vegetation Classification and Mapping Project Report, San Antonio Missions National History Park: Natural Resource Technical Report NPS/GULN/NRTR-2007/074R
(sample below) to review and access recent analysis of species range and distribution, representative ground photos, and aerial photo signatures from the USGS-NPS Vegetation Mapping Program for each type of plant classification
Explain
Use this web resource from NOAA to provide evidence of
historical perspectives to global climate change research.
North American Drought: A Paleo Perspective and guided access to Instrumental Records of Drought for the United States go back more than 10,000 years.

Elaborate
Use mathematical procedures such as algebra, statistics, scientific notation, and significant figures to analyze data using the International System (SI) units. Communicate valid conclusions supported by data using several formats, such as technical reports, lab reports, labeled drawings, graphic organizers, journals, presentations, and technical posters. Use analytical tools such as the following: Crop Moisture Index (CMI), Palmer Drought Severity Index (PDSI), Standardized Precipitation Index (SPI), Keetch-Byram Drought Index (KBDI), Reservoir Storage (RS), Streamflow Index (SFI). http://www.twdb.state.tx.us/apps/droughtinfo/default.aspx

Evaluate
Student work will be evaluated based on an agreed-upon rubric or other rating system that can be applied to papers, projects, presentations, or project development activities.