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Harvard Forest Symposium Abstract 2005
- Title: The parcelization of forests and timber harvest
- Primary Author: David Kittredge (University of Massachusetts - Amherst )
- Additional Authors: Kelly Grogan (Dartmouth College)
- Abstract:
Expansion of the urban-rural interface, decline in average parcel size, shifts in owner attitudes with more emphasis on privacy and aesthetics, creation of unfavorable local bylaws that limit harvesting, and the absolute loss of forestland potentially combine to create circumstances that are not favorable to commercial timber harvesting, in spite of a predominantly forested landscape. The specific objectives of this study are to focus on parcelization in Massachusetts communities, and to identify: an expression or index to describe the extent to which it is occurring; any socioeconomic or demographic variables that are related to parcelization; and the extent to which harvesting may be influenced by parcelization. Although we use data from Massachusetts, this central question has national relevance. In the US, non-industrial private families and individuals own much commercial forestland. Results of this work will better define the extent of commercially productive forestland.
Massachusetts towns were stratified into five classes by population density, and 9 were randomly selected within each stratum. Property assessment lists were acquired from selected towns. Tax assessment parcel records are not spatially explicit, and only include a list of properties with their estimated area and assessed real estate value. We conclude that the following two simple metrics are good indicators of the extent of parcelization in a Massachusetts community: % of parcels > 20 hectares, and parcels/hectare of land in a community. Based on our description of parcelization, we find it most closely related to the following sociodemographic variables that are available for all communities, thereby allowing for potential modeling or estimation: population density, median land values, road density, % developed, and % forest.
For our 46 towns for which we have hard “parcelization” data, we studied harvest activity on private land, since that is potentially subject to parcelization. We used regulatory timber harvest data assembled at Harvard Forest by J. Burk, et al.. As parcelization increases, timber harvest on private land decreases. However, other variables that we examined can better explain the variation in the private timber harvest data. The percent of a town’s area that is covered by forest explains almost half of the variation in harvest area and about 43% of the variation in the volume of harvest, at the private level. This suggests that harvesting is an agglomeration economy. It works most efficiently when there is a critical mass of harvest activity occurring within a given area, and this critical mass is most likely only achieved in towns with a large portion of forest. Using the linear regression models created relating the area and volume of harvest to the % forest variable for sample towns with harvest indicates that towns with forest covering less that 40.9% of their area have a small probability of harvest. Using the logistic model to relate presence or absence of private harvest to the % of forest in our 46 sample towns, and then applying this model to the rest of the state provides an indication of the probability of harvest across the state (Figure 2). MassGIS identifies 915,200 hectares of privately owned forest. This is based on air photo interpretation with a minimum mapping unit of 0.4 hectare. Likewise, USDA Forest Service Forest Inventory and Analysis (FIA) estimates of commercially viable timberland in Massachusetts are based on a definition of forest minimally being 0.4 hectares that is at least 10 % stocked in trees. However, since private harvest is unlikely in towns with less than 40.9% forest cover, we estimate that only 841,353 hectares, or about 92% of private forest is actually located in towns where private timber harvest is viable.
Our results suggest that although Massachusetts is nationally the 8th most forested state in terms of land use, and trees dominate much of the landscape, commercially viable forest area is functionally limited in areas defined by both a critical mass of forest area and parcelization. All private and public forests provide a wealth of social benefits regardless of their commercial timber viability, but our results suggest that potential timber supply may be smaller than some estimates imply, and this phenomenon may be relevant in other populated landscapes beyond Massachusetts, both now and in the future.
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