Meeting Summary
THE STATE OF THE ART OF LAND USE MODELING

I. Current State of the Art in Land Transformation Modeling

  • Models are either stochastic (logit, markov, cellular automata, etc.) or processed based (dynamic ecosystem model).

  • Models are developed independently by various teams with essentially no reuse or interoperability components.

  • Models are linked to a heterogeneous group of external applications, such as GIS, statistical packages, and visualization packages.

  • A few models exist which utilize distributed computing, but are application or model specific.
II. Projected State of the Art in Land Transformation Modeling
  • Models are linked stochastic, process based, and other (fuzzy expert system, individual based, etc.).

  • Integrated Problem Solving Environment (PSE) will be widely used.

  • The PSE will incorporate a uniform interface to external applications.

  • Transparent distributed computing will be widely available.

  • Data interoperability is widely supported.

  • Uniform GUI - Learning environment and modeling interface.

COMPARATIVE MODELING

Land use transition models, while reflecting a varied heritage and disciplinary background, share many commonalities. Common approaches are the use of transition probabilities in a class transition matrix, the use of multinominal logit methods, cellular modeling, and the use of the GIS weighted overlay approach. Emerging models that show potential are object oriented, expert system assisted, and use cells as their spatial unit rather than parcels.

Model choice issues related to source data include the choice of data model (features, cells or objects), and the comparability of multitemporal land use maps. Also important is the spatial aggregate structure of the modeling unit, be it watershed, county, metropolitan area, etc. Of almost unanimous concern in land transition modeling are the stability, estimation of, and autocorrelation in the transition probabilities.

Research on comparisons between models, such as that conducted on global climate models, is important to evaluate model performance, and to assist in validation.


DATA ISSUES AND NEEDS

Land Use and Land cover information is essential for the calibration, baseline, and testing of land use models. The information needs to be continuously updated, at spatial and temporal resolutions that are compatible with the models and have appropriate thematic content and detail.

Issues:

Are discrete categories appropriate? Spatial boundaries are occasionally more appropriately represented as fuzzy gradations. However, land use boundaries are typically fairly crisp because they are based on ownership. However, probabilistic models might benefit by maintaining probabilities as more continuous representations of land cover/use. Further, because aerial and satellite image processing provides much of the data, probabilistic or fuzzy approaches might be used. More continuous data might also be used and represent land use intensity, and changes in intensity.

Time and space scales are co-dependent and critical. Higher spatial resolution data are typically constrained to less frequent updates. For example, land use/cover information from Landsat TM might be updated over a large area every 5 years or decade (e.g. MRLC) whereas data at a resolution of AVHRR might be updatable monthly. Generally, detail as well as quality decreases with age of data.

Remote sensing provides raster data. Is that appropriate or sufficient? What land use modeling approaches use grids vs. networks vs. objects as data models? These issues may be spatial and process-scale dependent. For example, very detailed models often work with individual entities (plants, people), whereas more aggregate models work better with a grid framework.

Use vs. Cover. Some of the models predict land use change based on economics, some predict land cover based on biophysical processes. Yet, the difference between use and cover are often not distinct for the purposes of data collection. Anderson's classification attempts to combine use and cover. Satellite remotely sensed data provide land cover information well, but land use information requires more spatial detail and interpretations.

Needs:

Rethink Anderson - Do we need a new classification system? In what way? Can Anderson be improved? Do land use and land cover need separate systems? Can they be amalgamated?

Landsat is critical - provide support for program.

There are more data choices coming online with new private and public sector satellites. Modelers should be aware and flexible to make use of the most appropriate resolution data.

Monitoring and Rapid Assessment Protocols. We need to develop methods to quickly monitor and observe changes on large scales.

Is MRLC model appropriate?


APPLICATIONS

Applications are problem specific, tied to a geographic hierarchy. The spectrum of analysis ranges from global to local issues and areas of interests. Land use analysis models need to operate at the different geographic levels. The resolution of the data should be transparent to the model.

A land use model is applied to generate the results of a proposed scenario. A scenario usually has a focus which has either an urban or ecological driver(s). A focus or driver is comprised of factors, parameters or criteria that the user of the model can alter, prioritize, or weight to serve alternative scenarios. The land use model should allow the user to vary the time frame for each scenario being generated. The results of the scenario or application can be used as output to launch another model, to calibrate the land use model, and to assist in the decision making process.


POLICY/SOCIAL/ECONOMIC FACTORS

This is a very complex subject area so no single consensus can be reached in a short session. A list of topics/concerns emerged. This is a summary of some of the elements under ten of these.
  1. Policy, social and economic (human dimension factors) are indispensible to models of land use change and, therefore, land cover.

  2. The indicators that are used to record or measure the factors to be entered influence very much how many converging (confounded) factors are or are not included.

  3. The united variables that are selected often shapes (or reshapes) the way the system is understood.

  4. The assumptions about human behavior, human choice, and system stability and predictability determine the degree to which the model is simple and manageable but removed from reality or complex and unwieldy but approximating reality. The assumptions must be stated clearly and challenged regularly.

  5. The incorporation of human dimension factors means necessarily that other disciplines are involved. They bring both different assumptions (different indicators) and different methodologies. These complicate interaction but open doors for enhancing model performance (for example should multinominal logit be used where probit analysis can be used?)

  6. In the system we wish to model, experimentation is not possible and much of the bases of reductionist science is challenged.

  7. Scales of space and time: The processes of human activities operate at very different time scales from ecological processes with which they are linked. The local spatial scale of landscape units are affected by social, economic and policy factors at smaller scales (larger area).

  8. Surprise in the system is inevitable and all systems are ultimately idiosyncratic. This raises the question of the value of models that purport to be general. At one scale, individual decisions are determined by very personal circumstances and quality of life considerations that are hard to measure. At another scale, things like earthquakes, fires, war, economics cycles, are unpredictable but leave indelible marks in land use processes.

  9. Therefore, for all of these reasons it seems as though it might be futile to attempt to model. But such models are necessary because they (1) consolidate data, (2) make assumptions explicit, (3) permit testing of hypotheses, and (4) allow a basis for prediction about change.

  10. But to the extent that the resultant information becomes a part of the decision making process, the model is a part of the process it is modeling and so the role of modeling as a means of shaping the future (rather than just predicting it) needs to be considered.

RESEARCH NEEDS

What are the big science, blue sky questions (requiring the expenditure of tens of millions of dollars) regarding land use and land cover modeling that can be answered through an organized research effort?
  1. Are there a common (and limited) set of factors (variables) which explain (across a sample of the largest urban areas):
    • the extent and rate of urbanization/land cover change
    • composition of urbanization/land cover change.
    Can we identify them?
    Does data and modeling scale matter to the identification of these factors?
    How do we validate these factors (predictive validation, cross-validation)?

  2. Which dimensions of scalability matter the most?
    • grid size
    • polygon grain
    • grid shape
    • temporal scale (noise vs. signal)

  3. Across a sample of representative urban regions, does the extent and composition of urban land use forms really affect the differential production of:
    • ozone and greenhouse gases (vs. meteorological conditions)
    • particulate (vs. Greenhouse gases)
    • watershed nitrogen and nutrient loadings (vs. hydrology) Are there critical periods that deviate from the typical?

  4. What land use/land cover/landscape ecology primitives/objects would be most appropriate for a next-generation object-oriented land use/land cover modeling system. How do these differ from current conceptualizations of time, space, and scale in GIS?

  5. What are the key public policy issues that land use/land cover modeling can usefully inform (i.e., shape appropriate interventions). At what scale? Can we develop some useful heuristics/screening criteria for answering this question?

FUTURE COLLABORATION AND INTERACTION

Multiple pathways should be used to collaborate and interact within and without the group represented here.

INTERNAL

Internal communication can be sustained most easily and consistently using a common web site. The site begun for this meeting could be continued for the purpose, perhaps using "forum" software so that all participants can post messages/information directly and immediately to the site. The contents of this user-maintained web site could then periodically be edited or distilled.

A follow-up to this meeting could be convened in a year or two. Timing could capitalize on reconvening of this group under current sponsorship, other joint funding opportunities, and the International GIS/Modeling Conference.


EXTERNAL

The above web page will be useful outside the group as well but any directly interactive function will probably be less important. Links to related pages will perhaps be more important.

A paper collection could be completed either as an NCGIA in-house report or a special issue of a journal. The first would not be peer-reviewed. Papers from this meeting could be used in either case with moderate adaptations.

A review paper could be done by joint authors as an article, a USGS open file report, or the front piece to a book which would give a systematic treatment, perhaps with case studies. A book could indicate the state of the art most comprehensively, particularly at this "moment of reinvigoration" and expansion.


SPECIAL

A "working group on land use modeling" could be formed as a virtual entity with the advantage that the burden of participation could be limited by individual desires yet its existence can be cited to endorse or sanction collective actions.


NOTES

Gray literature and intensive web page development are methods which do not have strong incentives attaching.

A writing project was begun at Santa Fe by Pijanowski, Parks, and Maxwell. A potential framework has been discussed and participation is invited.

A fourth GIS/Modeling Conference (following Santa Fe) is under consideration using a modified approach. Time, place and form are undecided.


OPTIONS

(previously listed in charge to group):

Web page
Review papers
Paper collection
Special issues
NCGIA Report
Open file report