Spring 2014 Vol. 13 Number 2
The Lay of the Land
Satellite Data and Computer Models Provide an Invaluable Understanding of Earth's Surface
For more than 40 years, the series of satellites known as Landsat has provided a continuous record of changes taking place on Earth's surface. As the record lengthens, researchers are able to document effects of climate variability, invasive species, and land use over time. The data and imagery have contributed substantially to the management of key national interests such as agriculture, forestry, hydrology, urbanization, homeland security, disaster mitigation, and climate change.
The future of Landsat data collection is at risk, however, according to a recent National Research Council report. The latest satellite, Landsat 8, was launched in February 2013 with only a five-year design life. Its predecessor, Landsat 7, was launched in 1999 and is operating in a degraded mode. At the time of the report's completion, Landsat 9 was under discussion but its program missions remained unclear, management responsibilities had not been articulated, and no budget had been appropriated for the program.
Through most of its history, Landsat has been fraught with inconsistent management, ad-hoc designs and implementation of the spacecraft, and reliance on sheer luck over careful planning. Typically, the satellites have been justified, planned, and executed individually or at most in pairs.
The report concludes that a continued program will not be viable under the current mission development and management practices. It recommends that the U.S. government establish a sustained and enhanced land imaging program with an overarching national strategy and long-term commitment, including clearly defined program requirements, management responsibilities, and consistent funding.
Modeling Land Change. The record of data from Landsat has provided input into land-change models, a key means for understanding how humans are reshaping the Earth's surface through agriculture, construction, energy production, and other activities, for forecasting future landscape conditions, and for developing policies to manage the use of resources and the environment from the local scale to large expanses of forest around the world.
The varieties of land-change models have different strengths, weaknesses, and applications. Some approaches use land-cover information from satellite imagery and past observed relationships to project changes a short period into the future. Others make use of social science information about land-change processes that can be used to evaluate a wider range of alternative futures.
A second Research Council report identifies opportunities to advance modeling approaches that would further our understanding of human interactions with the environment and improve decision making about land-related management and policy. These advancements could be realized in the models themselves, in land observation strategies, in cyber infrastructure, and in developing best practices in model evaluation.
A Path Forward. The Research Council's Landsat report does not recommend who should oversee the satellite program -- currently managed jointly by the U.S. Geological Survey and NASA -- but it does outline key elements of a successful program regardless of where the federal government decides it should reside. The core scientific and operation requirement for a future program is the capture and distribution of global data that is calibrated to allow the comparison of future land images with previous collections, easily accessible by all users, and free.
The report also describes top priorities for a future program that include technical capabilities, data systems, and opportunities for integration between government, private, and foreign-based entities.
-- Lauren Rugani
Advancing Land Change Modeling: Opportunities and Research Requirements. Committee on Needs and Research Requirements for Land Change Modeling, Board on Earth Sciences and Resources, Division on Earth and Life Studies (2014, 152 pp.; ISBN 978-0-309-28833-0). The study was chaired by Daniel G. Brown, professor of natural resources and environment at the University of Michigan. The study was funded by the U.S. Geological Survey and NASA.
Both reports are available from National Academies Press, tel. 1-800-624-6242.