Abstract |
- In recent years the conversion of agricultural lands to more
intensive non-rural land uses has become a focus of increasing public
awareness and concern. The growing attention to farmland conversion
is manifested in increasing public policies and legilsation to protect
agricultural and forestry land uses. Nevertheless, our understanding
of the farmland conversion process is restricted. Although agricultural
land conversion has been descriptively addressed, little consideration
has been given to defining and analyzing the factors affecting the spatial
pattern of rural land conversion.
The purpose of this investigation was to analyze the impact of
selected variables on agricultural land transition to more intensive
non-agricultural uses. The research tested the reliability of a composite
site characteristic model, and individual submodels for explaining
land conversion patterns in Washington County, Oregon. Within the framework of the site characteristic model, specific objectives were:
(1) to determine those site factors which exhibited a significant
influence on agricultural land conversion,
(2) to estimate empirically the influence of each factor on agricultural
land conversion, and
(3) to determine differences in the effect of individual factors and
composite models on agricultural land conversion in areas with
varying stages of urbanization.
The site characteristic model examined in the investigation
included twenty-three predictor variables drawn from four sets of
site factors. These four broad categories of site characteristics are
accessibility indices, infrastructural-policy factors, social factors,
and environmental factors. Individual regression models were
developed for each set of site characteristic variables, as well as,
for the composite site characteristic model. Published government
documents, planning reports, and manually calculated information
from aerial photographs provided the primary sources of these data.
Following the collection of farmland conversion data from 1963
and 1973 aerial photography for Washington County, a series of multiple
regression analyses were undertaken. The results of these analyses
showed that the hypothesized site characteristics proved important
factors in explaining farmland conversion patterns. The composite
site characteristic model, with fourteen predictor variables, accounted for 78 percent of the variation in farmland conversion for
the county. Geographically, the composite model was most effective
in explaining land conversion in urban sections of the county
(R² = . 676), while achieving its lowest precision in urban-rural
fringe areas (R2 = . 627).
As expected, the effectiveness of individual submodels varied
extensively with respect to explaining land conversion. Several of
the hypothesized variables were consistently strong performers
accounting for much of the variation in farmland transition. Conversely,
numerous variables proved of only peripheral value during the
modeling. The modeling results showed the most powerful set of
variables to be the infrastructural-policy factors. This submodel,
with four significant variables, was able to explain 70.7 percent of
the variation in farmland transition for the entire county. Conversely,
the weakest set of site characteristics were the environmental factors.
With five significant variables the environment submodel accounted for
49.2 percent of the farmland conversion in the study area. As in the
case of the composite model, the relative effectiveness of the submodels
varied extensively between urban, urban-rural fringe, and
rural portions of Washington County.
The research results of the investigation found that the site
characteristic model provided a consistently powerful tool for understanding
farmland transition in all sections of Washington County, Oregon. The strong measure of reliability associated with the site
characteristic methodology, viewed within the framework of concern
for farmland conversion, suggests that the conclusions of this investigation
may have broad policy implications. The linkage between
farmland development and site characteristics provide insight regarding
the operation of agricultural land conversion process. Drawing
on the relationships pointed out in the investigation, Washington
County and other governmental units may find that the study findings
can assist in improving mechanisms for controlling land conversion.
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