Modeling Land Use Changes in the Palouse Region of the Northwestern United States

Transcription

1 Modeling Land Use Changes in the Palouse Region of the Northwestern United States Toru OTAWA 1 Introduction Modeling regional land-use change is nothing new. Many regional modeling studies were conducted in North America, when an access to mainframe computers became readily available to researchers in the late 1960 s. (For example, Steinitz and Rogers, 1970; Zube, Fabos and Brush, 1975). They were carried out to help manage urban growth in metropolitan regions such the Boston-New York-Washington, D.C. corridor. Researchers relied on crudely generalized, low-resolution geographic data for the analyses of the regional land uses. This reliance was unavoidable because the computing power available to researchers several decades ago was extremely limited and is unimaginable if compared with today s computing standards. Not only the computing power has increased but also the quality and availability of geographic data have immensely improved. These computing trends, along with the increasing societal needs for more sustainable regional land and resource uses, call for the shift of research paradigm from the metropolitan to suburban and rural regions of North America. This study was driven by such a shift of societal norm. Black, et al. (1998) began to address bio-diversity issues in a rural region called the Palouse but focused little on regional land-uses issues. Similar studies have been listed comprehensively in Land Use History of North America (USGS, 2000). Another case study in Asia is also reported (Kaga, et. al., 2001). A more elaborate land use model was created and applied to a region in eastern Canada (Merem, 2005). The Palouse region is located in the inland Northwest of the United States and is characterized by rolling landforms mainly due to their aeolian geologic origins. Like other regional studies of similar nature, the present study was hindered by the lack of accurate and reliable spatial-temporal data in digital format. This is particularly true for the years preceding World War II and during the early post-war period. Not only the geographic data from the early settlement period was lacking, but also few standardized and thoroughly tested methodologies existed to measure spatial-temporal patterns of regional land uses. In addition, similar issues existed for simulation models that are used to predict future regional land-use changes. 2 Objectives The primary objectives of this research are (1) to identify a temporal pattern of land-use changes in the Palouse region of the Northwestern U.S. by analyzing land-use data from historical aerial photographs and (2) to help make recommendations for better and sound planning of the Palouse region. Understanding the temporal land-use patterns since the early settlement by European immigrants in the region would provide regional researchers

2 T. Otawa with a useful departure point to help define future research needs. Once a spatial-temporal land-use model has been established and validated, it may be used to help guide regional policy makers make sound and better decisions for the Palouse region. 3 Temporal Land-use Data Collection and Analyses First, an extensive effort was made to identify historical aerial photographs that share the same geographic extent in the Palouse region. Very few sets of aerial photographs were found that date back to the 1930 s in the University of Idaho library and in other libraries in the region. The rigorous search effort resulted in a series of aerial photographs taken in 1933, 1965, 1970, 1981, and 1992, which covered approximately 20 km 2 of the areas adjacent to the City of Potlatch, Idaho. Additionally, Inside Idaho, the official GIS data server in the state of Idaho, collected a 1997 digital orthophoto image of the area that was also used in this research. Most of these aerial photographs were taken in the early summer season. Both historical and current census data, such as population and housing units in the area, were available from the U.S. Census Bureau. Second, all five aerial photographs identified in the search process were scanned at the resolution of 600 dot-per-inch (dpi) and saved in the TIFF format. Next, they were georeferenced to UTM (Zone 11-North American Datum of 1983 or NAD83) using a module in ArcGIS Version 9. Several major intersections of roads common to all five of the aerial photographs were used to rubber-sheet or warp as reference ground controls for geo-spatial rectification. For this task, the 1:24,000-scale, TIGER data from the 2000 census was used. The 1997 orthophoto image had already been converted to the digital format and been projected to UTM (Zone 11-NAD83). 3.1 Land-use Classification and Coding Generally, forests, built-up areas, and rivers are easily discernible on the aerial photographs due to their distinctive characteristics. Other land uses such as agricultural areas, rangelands, and riparian zones are often ambiguous to distinguish primarily due to the resolution and scale of the historical aerial photographs. This is also true for the supervised digital image analyses of land cover types pending the resolution of the image data and atmospheric factors. Parcel data from a tax assessor s office could help identify the specific land use on land; however, the data is limited to detecting land-use attributes in recent years only and may not be applicable prior to the 1960 s. Therefore, Anderson s land-use and land-cover coding scheme was re-introduced in this study (Anderson, 1969). The classification of land-use on aerial photographs is represented by different colors (Tab. 1). Using the land-use color code allows researchers to classify land uses relatively easily. The use of this classification scheme helps ensure compatibility with other studies and land use projects in the national system (Anderson, Hardy, Roach and Witmer, 1976). A change detection technique to reveal new urban growth areas is demonstrated (Hitt, 1994).

3 Modeling Land Use Changes in the Palouse Region of the Northwestern United States Tab. 1: Remote Sensing Land-use Color Code (Anderson, Hardy, Roach and Witmer, 1976). Classification Color Munsell Forest Land Green 10GY 8/5 Tundra Green-Gray 10G 8.5/1.5 Water Dark Blue 10B 7/7 Wetland Light Blue 7.5B 8.5/3 Rangeland Light Orange 10YR 9/4 Agricultural Land Light Brown 5YR 7/4 Urban or Built-up Land Red 5R 6/ On-screen Digitizing of Land Use Polygons Next, land use polygons were digitized on-screen by applying the above scheme and were saved in the ArcGIS Shapefile format. This process of on-screen digitizing was repeated for each of the scanned digital aerial photographs. In total, six digital map layers were created. 3.3 Land-use Pattern of 1933 Fig. 1: Land-use Map of In 1933, forestlands totaled 24% of the entire study area, and built-up area accounted for 11%. As for the natural structure observed in the year, North Fork of Palouse River ran through the city of Potlatch and served as the background landscape for the built-up area. The expanding rural settlements and the old built-up area were both located in between the range and agricultural lands. The latter totaled 35% of the study area and the patched forestlands surrounded these land uses. The results from the analyses of the 1933 land-use patterns show that the river and forests remained as a natural structural base, and the surrounding agricultural land uses supported the city economy.

4 T. Otawa Tab. 2: Land-use Classification of LAND-USES CODE ATTRIBUTE AREA (Sq. M.) 100 FORESTED 2,540, , RIPARIAN 323, RANGELAND 2,559, AGRICULTURA L 3,720, BUILT-UP 1,277,992 TOTA L 10,775,025 BUILT-UP 11% AGRICULTURE 35% FOREST 24% RIPARIAN 3% 3% RANGELAN D 24% 3.4 Land-use Pattern of 1965 In 1965, forestland totaled 22% of the area, and 2% of the forestlands contained within the previously cultivated agricultural lands changed to agriculture land-use. The built-up area increased to 13%. The river and forestlands served as the hinterland of the built-up area, as in A large portion of the river corridor changed to the riparian land-cover type, while the built-up area expanded in every direction in this period. In a way, urban sprawl occurred around this small city, and the built-up area spread in a disorderly fashion in every direction. The patched forestlands that existed within larger agricultural areas amalgamated into the single agriculture land-use. The surface water areas were reduced and in some instances diminished into a wide riparian corridor. However, the area did not experience a dramatic change in land use from 1933 as will occur in later periods. 3.5 Land-use Pattern of 1970 In 1970, forestlands, which accounted for 20% of the total area, had been on decline steadily, while agricultural lands expanded significantly. The built-up area also expanded to 14%. The agricultural lands had increased since 1965 presumably into steeper ground and further into the rangeland, which clearly explains the reduction of the rangeland acreage during this period. The riparian areas continue to expand, which may be explained by the accelerated surface water uses by humans. Areas along highways and roads began to develop into urban land uses, a good indication of improvements made to the regional transportation infrastructure in the U.S. at the time.

5 Modeling Land Use Changes in the Palouse Region of the Northwestern United States 3.6 Land-use Pattern of 1981 As we entered in the 1980 s, forestlands and the river corridor continued to decline as did in the previous period between 1933 and The riparian areas were slowly increasing, but this variation may have been a seasonal factor. However, the agricultural lands and built-up areas had considerably expanded since 1970, while the rangeland largely decreased to 12%. The introduction of heavy machineries, along with the shift of population toward western states, may have contributed to the decline of forested and range lands in this period. 3.7 Land-use Pattern of 1992 Forestlands had slightly increased since 1981, while the agricultural land had somewhat decreased. This may reflect some positive change in land management policies and approaches such as the Conservation Reserve Program (CRP) of the U.S. Department of Agriculture at that time. For many years, forestlands, along with surface water and the rangeland, had consistently been on decline up to this point. The river corridor, riparian areas, rangelands and built-up areas changed very little during the decade. 3.8 Land-use Pattern of 1997 As before, forestland, river corridor, riparian areas, and the rangeland slightly decreased again, while agricultural lands and built-up areas continued to increase. A notable change occurred between 1992 and 1997 is that the agricultural lands expanded into riparian areas, leading to the further reduction of riparian areas. This aerial photograph indicates that there is very little room left for expansion. The study area has been fully developed into agricultural and urban land uses. Fig. 2: Land-use Map of 1997.

6 T. Otawa Tab. 3: Land-use Classification of LAND-USE CODE ATTRIBUTE AREA (Sq. M.) 100 FORESTED 1,779, , RIPARIAN 517, RANGELAND 1,104, AGRICULTURA L 5,320, BUILT-UP 1,957,044 TOTAL 10,775,025 BUILT-UP 18% AGRICULTURAL 49% FORESTED 17% RIPARIAN 1% 5% RANGELAND 10% 4 Temporal Analysis of Land Use in Study Area From the analyses of land-use change within the study area over the period of 65 years, it is apparent that urbanization, agricultural expansion and the riparian corridor had steadily increased for this period of observation, while forestlands, surface water, and rangeland had diminished significantly. Thirty percent of the forestlands in the area had been converted to agricultural production and urbanization, while 73% of the river corridor had predominantly been changed into riparian zones. The latter may be an indication of the increased peak-time flow due to urbanization and/or the expansion of agricultural fields. To a lesser extent, it may also be attributed to the increased use of surface water for home and other uses commonly found in rural areas. Both agricultural expansion and urbanization occurred primarily in the rangelands leading to the massive loss of rangelands during the period (Tabs. 2 and 3). Major changes in land use during the study period largely resulted from the intensification of agriculture (Fig. 4). Development of an extensive railroad network just after the turn of the century opened markets outside of the Palouse region. Farming became commercialized. Wheat and other cereals were well adapted to the hillsides and climate of the Palouse region and they emerged as the dominant agricultural crops in the region (Grimes, 1991). The era between 1931 and 1970 was one of continued mechanization, and especially industrialization (Grimes, 1991). With the development of the new technology, farming became less labor intensive, allowing fewer people to farm larger areas (Fig. 4). By 1970, most farm workers used motorized equipment, which removed the need for pasturelands and provided equipment that could till even the steepest slopes. Fertilizers, introduced after World War II, increased crop production by 200% to 400%. With the advent of industrial agriculture, the last significant refugia for native communities were plowed (Grimes, 1991). The introduction of farm animals into the region also triggered the loss of native vegetation during the same period (Tisdale, 1961). The

7 Modeling Land Use Changes in the Palouse Region of the Northwestern United States expansion of agriculture not only lead to the loss of native plant communities but also induced massive soil erosion at the regional scale (Kaiser, 1961) FORESTED Area (m 2 ) RIPARIAN Year RANGELAND AGRICULTUR AL Fig. 3: Temporal Analyses of Land-uses in Study Area (1933~1997). Since the 1970 s, the compositions of the rural population and land use have changed. Rural population began to rise as more urban residents sought rural suburban sites for their homes (Tab. 4). Ironically, many yesterday's farmers and their children who still own farmland in the study area have moved to towns and cities further away from their farms (unpublished data from Latah County Records). The influx to the area outweighed the exodus from it, and population in rural areas is still growing albeit curtailing the ratio. However, the impact of urban growth is not as severe as the environmental impact caused by the expansion of modern agriculture into forests and rangelands that has occurred for the last several decades due to differences in their spatial magnitude. Fig. 4: Rural population and average farm size through time for Whitman County, Washington (U.S. Department of Commerce, 1900, 1930, 1970 and 1992).

8 T. Otawa Tab. 4: Residential Units Built within the City of Potlatch during Study Period (U.S. Census Bureau, 2000). Year Housin g Unit Cumulative Number of Units 1939 or earlier to to to to to to to Housing Unit Year to Land Use Model Fig. 5: Land Use Model of the Study Area.

9 Modeling Land Use Changes in the Palouse Region of the Northwestern United States Derived from the temporal land-use data collected over several decades, the dispersion and gradients were calculated by SPSS. Consequently, a land-use model for the selected study area of the Palouse region was formulated (Fig. 5). Referring to the R 2 values in Fig. 5, albeit insufficient data observations, each of the land use formulae fits one of the four common types of mathematical functions very well. The future land-use pattern of the study area may be projected by applying the formulae. To demonstrate the projection capability of the model, the year 2010 was chosen (Fig. 6). The direction of change can be determined by tracking the locations of the polygon centroids, i.e., calculating the vector from each period in which the land use data was collected. The result of the land-use projection is astounding. Forestlands, surface water, and rangeland will diminish to the minimum level, if the current rate of change continues. The river flowing through the study area may become merely a small stream by the year PROJECTED LAND- USE ATTRIBUTE AREA (Sq. M.) FORESTED 1,772,765 13,566 RIPARIAN 525,724 RANGELAND 959,134 AGRICULTURAL 5,452,825 BUILT-UP 2,051,011 1 Mile TOTAL 10,775,025 Fig. 6: Projected Land Uses of the Study Area in Conclusions A land-use model was successfully created from the temporal analyses of several historical aerial photographs for the study area. In this research project, the study area was limited to several square miles due to the availability of historical aerial photographs. The lack of historical geospatial data will continue to plague land use modelers, if similar efforts are to prolong. One of the main questions that has to be answered is whether the selected study area clearly represents the landscapes of the entire Palouse region. Is the rate of change in inner areas of the region any different from what has been identified in this present study? Is the rate of change identical in similar landscapes in the region? An attempt will be made to answer these questions in the next phase of the research project.

10 T. Otawa If it proves that similar trends are occurring in land-uses throughout the Palouse region, there is urgency for policy change for regional planners and land managers. One of the major policy implications is that the agricultural lands are no longer expandable to the outer areas of the region. To maintain the landscape health of the region, farmers must address sustainability of their production within the existing land areas. They have to be less resource-dependent, e.g., surface and groundwater. The precision-farming technology research in the region is a step in the right direction to help minimize the dependency (Yang, et. al., 1998). Some may have to choose crops more profitable than wheat and similar types of grain that depend on extensive area coverage for production. Additionally, they are facing pressure from urbanization if the farmland is located in close proximity to urban fringes. Another use of the model may be to guide urban growth to less environmentally sensitive landscapes. It may be particularly useful to help preserve and create landscape corridors for a regional park system and/or wildlife resources in the areas much growth is anticipated. The GIS-based land-use projection model, albeit relatively simple, has proven its usefulness. With more historical aerial images throughout the Palouse region, recommendations that are more conclusive may be made in the future. 7 Acknowledgments Seung Kyum Kim, a former Master s student in Landscape Architecture at the University of Idaho, now of Design Workshop, Inc., assisted the author in data collection and analysis for which he is so grateful. All of the digital maps and tables presented herein were generated by Mr. Kim under the direction of the author in References Anderson, J.R. (1969): USGS Land Use and Land Cover Classification. Anderson, J.R., E.E. Hardy, J.T. Roach, & R.E. Witmer (1976): A Land Use and Land Cover Classification System for Use with Remote Sensor Data. Grimes, W. (1991): Learning from I-90: The North-South Freeways Implications for Urban Form. U.S. Department of Commerce, Washington, D.C. Hitt, K.J. (1994): Refining 1970's Land-Use Data With 1990 Population Data to Indicate New Residential Development. U.S. Geological Survey, Reston, Virginia Kaga, H., N. Izaki, Y. Shimomura, & N. Masuda (2001): Study on Change in Landscape Structure over Time in Suburban Area by Using GIS. Korean Institute of Landscape Architecture International Edition, 1: Kaiser, V.G. (1961): Historical Land Use and Erosion in the Palouse: a Reappraisal. Northwest Science, 35(4): Merem, E.C. (2005): Environmental Accounting for Changes in Farm Land Use: A Canadian Case Study. Mellen, Lewiston, New York

11 Modeling Land Use Changes in the Palouse Region of the Northwestern United States Steinitz, C. and P. Rogers (1970): Systems Analysis Model of Urbanization and Change. MIT Press, Cambridge, Massachusetts Tisdale, E.W. (1961): Ecologic Changes in the Palouse. Northwest Science, 35 (4): U.S. Census Bureau (2000): Profile of General Demographic Characteristics: 2000, Geographic Area: Potlatch City, Idaho. U.S. Department of Commerce (1900): Twelfth Census of the United States. Census Bureau, Washington, D.C. U.S. Department of Commerce (1930): Fifteenth Census of the United States. Census Bureau, Washington, D.C. U.S. Department of Commerce (1970): Census of Population. Census Bureau, Washington, D.C. U.S. Department of Commerce (1992): Census of Agriculture. Census Bureau, Washington, D.C. U.S. Geological Survey (2000): Land Use History of North America. Yang, C., C.L. Peterson, G.J. Shropshire, & T. Otawa (1998): Spatial Variability of Field Topography and Wheat Yield in the Palouse Region of the Pacific Northwest. Transactions of the American Society of Agricultural Engineers, 41 (1): Zube, E.H., J.G. Fabos, & R.O. Brush (1975): Landscape Assessment: Values, Perceptions and Resources. Van Nostrand Rainhold, New York