The Science of LCLUC

Key Science Questions

The LCLUC research program addresses the following key land-use science questions:

  • Where are land-cover and land-use changing, what is the extent and over what time scale and how do the changes vary from year to year? (Measurement, Variability)
  • What changes are occurring in global land-cover and land-use, and what are their causes? (Forcing)
  • What are the impacts of climate variability and changes on LCLUC and what is the potential feedback? (Impacts, Responses)
  • What are the consequences of changing land-use activities for ecosystems and how do they respond to and affect global environmental change? (Consequences, Responses, Adaptation)
  • What are the consequences of land-cover and land-use change for human societies and the sustainability of ecosystems? (Consequences, Vulnerability, Resilience)
  • How will land-cover change on time scales from years to centuries? (Modeling, Prediction)
  • What are the projected changes in land-cover and their potential impacts? (Modeling, Prediction)

LCLUC Science Components

The focus of LCLUC research is on quantifying the location, extent and variability of change, the causes or forcing factors of change, for example, climatic, ecological and socioeconomic drivers, the processes of change and the responses and consequences of change. NASA LCLUC research projects use a combination of space observations, in situ measurements, process studies and numerical modelling. As an interdisciplinary research program, LCLUC fosters strong partnerships between physical and social scientists to develop the integrated science necessary to understand why and how patterns of land-use and land-cover are changing, how they will change in the future and the implications of these changes. LCLUC research crosscuts several other research areas, e.g. climate change and variability, water cycle, carbon cycle, ecosystems and biodiversity, and human contributions and responses to environmental change.

Variability: The current spatial pattern of land-cover is a result of previous and current land-use. Quantifying the location, extent and trends of recent land-cover and land-use change is an important component of land-change science. Satellite systems often provide the only means to inventory land-cover and monitor land-cover change in a timely fashion. NASA has developed procedures for wall-to-wall mapping of land-cover and spatially explicit monitoring of land-cover change. Systematic long-term observations of land-cover are essential to enable scientists to quantify the rates of change and their variability over time. Establishing consistent long-term data records of land-cover is an important objective for the LCLUC Program.

Forcing: To make a projection of how land-cover will change in the future and to be able to better manage land-use it is important to understand the drivers of change. These include the local and proximate physical, socioeconomic and demographic causes of change, as well as the broader global and regional climatic or macroeconomic forces of change. Quantifying processes of land-use change is undertaken by combining in-situ measurements and ground surveys with satellite data. This is often done through regional case studies.

Responses and Impacts: The impacts of land-use change can be biophysical and socioeconomic and they can be positive and negative. Changes in forest cover can affect carbon sources and sinks, local water resources and biodiversity through landscape fragmentation. Changes in fire regimes can affect ecosystem structure, trace gasses, aerosol emissions and water quality. Overuse of marginal lands leads to degradation and impoverishment affecting human livelihood. Agricultural intensification through the use of fertilizers can improve crop production but may degrade water quality. Changes in land-use can affect human health by changing insect habitat or disease vectors. Agricultural abandonment leads to changes in land-cover, for example, by increasing woody vegetation. Urban expansion and suburban development can result in a loss of agricultural lands or wetlands. Changes in land-use can affect local and regional climate.

Prediction and Feedbacks: Modelling of land-use change provides a means to understand the consequences of different land management options and study the feedbacks. For example, coupled land-use and dynamic vegetation models are needed to understand the impacts of future land management on carbon budgets. Recent trends in land-use change and an understanding of the processes of change provide a point of departure for predictive modelling. Spatially explicit modelling of land-use is needed to study scenarios of land change under different land-uses for a large number of science applications. There are a number of approaches for modelling land-use that are currently being investigated, including statistical empirical models, cellular automata and agent-based modelling. Better understanding the impacts of land-use change on climate and the impacts of climate change on land-use is also needed.  

Underpinning the Earth Science research paradigm (variability-forcing-response-consequences-prediction) is an ongoing program of LCLUC research, which includes the development of new algorithms and data sets, methods and techniques for characterizing, monitoring and modelling land-cover and land-use change and validating derived products. This is achieved by combining the new methods and land-use models with remote sensing and GIS. Development of techniques for data management and analyses are needed to handle the large volumes of data needed for global and regional monitoring and analysis. Global and regional data sets of land-cover characteristics developed within this program support the NASA modelling activities and provide the long-term data records needed to study trends. 

Forcing Factors 

 

  • Climatic and ecological drivers: The NASA Land-Cover and Land-Use Change program will rely primarily on existing components of Earth Science and national and international science agencies for the development of historical and climatic data sets.

  • Socioeconomic drivers: The NASA program will investigate the human dimension processes directly when they are coupled to observed recent changes in the landscape or regional predictive models.

Responses and Consequences

  • Land-cover conversion: The primary NASA interest is to identify the current distribution of land-cover types and land use, and to track their conversion to other types. The LCLUC program has a particular interest in the impacts of land cover and land use change on biogeochemical cycles (e.g. carbon and nitrogen) and the hydrological cycle.

  • Land-use intensification: To understand the consequences of intensified management of agricultural, agroforestry, and grazing systems, particularly in the tropics and subtropics. To measure the longer-term degradation of forested ecosystems that occurs.

  • Land degradation in arid and semiarid environments: To define, develop, and evaluate improved remote sensing measurement techniques and data integration methods for characterizing land degradation. The objective of the research is to provide scientific understanding and observational techniques required for improved efficiency in the management of both managed and unmanaged land resources.

LCLUC researchers are encouraged to use both remote sensing and in-situ data, integrated with geographic information system (GIS) techniques, in a manner which enables improved assessments of the extent and causes of land use change and degradation, vulnerability to further degradation, and the development of options for more sustainable land uses.

Modelling and Implications 

 

It is important to develop, parameterize, and evaluate models that couple the physical and social aspect of land use change as well as the biogeochemical and biophysical dynamics of the land surface and atmosphere. The program will emphasize the development of data sets and techniques that use representations of the actual land cover present and changes in land cover, rather than potential natural vegetation. Links to other process studies in hydrometerology, tropospheric chemistry, and aerosol radiative forcing will be explored to gain a better understanding of the relationship between changes in land cover, the processes that drive those changes, and biogeochemical and physical changes in the Earth's atmosphere and climate system. In addition to incorporating actual land cover and land cover change in ecosystem process models it is important to develop models of land use change. Prediction of land use change based on an understanding of the processes involved will provide an important tool for framing land management questions.

Ultimately, it will be the ability to model systems undergoing land-use change that will provide tools for both scientists and decision-makers to evaluate the potential consequences of different management practices, and to assess the consequences of policies that affect land cover conversion.

Techniques and Methods 

 

Coordination is sought between the LCLUC Program and the algorithm development and testing within the NASA Terrestrial Ecology Program, the EOS Interdisciplinary Science and Instrument Science Teams. Of particular relevance to this program are the algorithms used to generate higher products from the systematic MODIS VIIRS, Landsat and Sentinel observations, as LCLUC scientist often use the land cover and change related products from these sensors. The program makes use of the global archives of coarse and moderate resolution satellite data, acquired over the last twenty or more years for addressing land-cover and land-use change. With the technical problems encountered by the Landsat 7 instrument in 2003, emphasis was given within the LCLUC program to utilizing data from other U.S. and international moderate resolution sensors previously involving ASTER, EO1, CBERS, IRS and SPOT but more recently the European Sentinels. Attention within the LCLUC program continues to  be given to research on fusion and inter-use of data products (MuSLI). It is hoped that these activities help pave the way for an international constellation of moderate resolution sensors (CEOS Land Surface Imaging Constellation). Similarly research is encouraged in the use of fine spatial resolution data (1m-3m) for the study of land use in the context of answering scientific questions. These data are available to NASA investigators through the NASA Commercial Archive. With NASA focusing on the Decadal Survey Missions, the LCLUC program is interested in the development of new techniques that prepare for the use of new and soon-to-be-available remotely sensed data. In particular the program is interested in LCLUC science applications using thermal, microwave systems and hyperspectral data. With respect to technique development, the LCLUC program continues to be interested in technical research oriented towards automated land classification and change detection at regional to global scales, parameterization or validation of land use models using remotely sensed data and data services to improve the state of the art with respect to documenting land-cover and land-use change. 

 

Data Systems for LCLUC Research 

 

The unprecedented large volumes of data for land use research have necessitated the development of innovative data processing, delivery and analysis systems. The evolving EOS Data and Information System and a number of competed research opportunities such as MEASURES, have provided support for data systems research and development. The MODIS Advanced Data Processing System (MODAPS) at the Goddard Space Flight Center (GSFC) continues to generate land-cover related products from the daily MODIS instruments on board the Terra and Aqua platforms. Data products at 250m -1km are being reprocessed as the algorithms are improved to provide consistent data records. The long term continuity of MODIS-like data is now ensured by the VIIRS instrument on SNPP and more recently on JPSS-1 (NOAA-20). The NASA land data sets generated for the VIIRS systems are generated at the LAND SIPS and as with MODIS are distributed by the NASA Distributed Active Archive Center at the Eros Data Center (EDC) and in near real time through LANCE, to meet the needs of the science community. Landsat time series data are used widely by the LCLUC Science community and are also available from the EDC DAAC.

 

Harmonized Landsat and Sentinel (HLS) Data 

 

The Landsat and European Sentinel products represent the most accessible moderate spatial resolution multispectral satellite data. Following the recent launch of the first out of two Sentinel-2a and 2b satellites, the potential for synergistic the data has created unprecedented opportunities for developing time-series of moderate resolution data. Thus, harmonization of the data is a high priority for the scientific community, removing the burden of pre-processing from individual investigators. Coordination with ESA is on-going.  LCLUC recently initiated an activity to support the use of multi-source data for LCLUC science. The MuSLI program is exploring the combination of different types of data to better characterize lands cover change.

 

Global Land Survey 

 

In partnership with the private sector, NASA purchased a global data set of cloud-free Landsat imagery for 1990 and 2000. These data were orthorectified and are easily accessible and freely available. They have increased the use of Landsat data for LCLUC studies worldwide. In May 2003 the Landsat 7 scan line corrector failed and although the instrument continues to receive data, the imagery are of limited use. With no Landsat instrument ready to immediately replace Landsat 7, there was an increasing data gap, posing a critical impediment to LCLUC science. The LCLUC program, worked with the USGS is developing a mid-decadal (2004-2006) high resolution global cloud-free data set to extend the previous global data sets. The data set included data from Landsat 5, ASTER, EO1 and Landsat 7 temporal composites. This data set included data provided by foreign ground stations. 

 

Global Geo-Referenced Field Photo Library 

 

Land use and land cover change studies at regional to global scales require large numbers of field sites for algorithm development and accuracy evaluation. Rapid development in integration of digital camera, hand-held GPS device, computer and internet make it possible for both scientific communities and citizens to collect and share geo-referenced field photos. The Global Geo-Referenced Field Photo Library, developed at the Earth Observation and Modelling Facility of University of Oklahoma, offers the capacity for users to upload, query (by themes and geographically), and download geo-referenced field photos in the library. It offers interactive capacity for users to interpret and classify field photos into relevant land cover types and builds photo-based land cover database.  The users can use both photos and associated databases to carry out land use and land cover analysis in a geographical information system. The users who provide field photos can decide whether individual photos are to be shared or not. This tool and the resultant photo library will enable our NASA LCLUC communities to share their field photos, and promote the NASA LCLUC effort in remote sensing.