Grantee Research Project Results
Final Report: Integrating Economic and Ecological Models Across Spatial Scales to Assess Aquatic Species Vulnerability to Timber Harvest and Land Use Change in Freshwater Streams of the Southeastern U.S.
EPA Grant Number: R828784Title: Integrating Economic and Ecological Models Across Spatial Scales to Assess Aquatic Species Vulnerability to Timber Harvest and Land Use Change in Freshwater Streams of the Southeastern U.S.
Investigators: Schaberg, Rex , Hershey, Anne , Cubbage, Fred , Halpin, Pat , Abt, Robert
Institution: Duke University , North Carolina State University , University of North Carolina at Greensboro
EPA Project Officer: Packard, Benjamin H
Project Period: May 1, 2001 through April 30, 2003 (Extended to March 31, 2004)
Project Amount: $399,658
RFA: Futures Research in Socio-Economics (2001) RFA Text | Recipients Lists
Research Category: Environmental Justice
Objective:
The objectives of this research project were to: (1) develop integrated ecological-economic models of potential imperilment for selected aquatic ecosystems in the Southeastern United States at multiple spatial scales; (2) evaluate the role of forest extent, forest harvest, and forest management practices in the sustenance of selected aquatic ecosystems; (3) identify case study watersheds and consider the relationship among timber market dynamics, harvest levels and locations, and potential stresses on aquatic communities; and (4) create tools that will be of subsequent use to policymakers and analysts in conservation planning and watershed management.
Summary/Accomplishments (Outputs/Outcomes):
In aggregate, landowner decisions to harvest timber can significantly affect the characteristics of forested watersheds. The economic factors that determine such market decisions operate at multi-state or regional scales. Markets determined at these regional scales are manifest in small-scale environmental outcomes. Forestry economic models routinely consider timber growth and timber removal volumes using administrative (e.g., state) rather than natural boundaries. We converted U.S. Forest Service (USFS) Forest Inventory and Analysis county data to a watershed base using geographic information system (GIS) software. We redesigned the frequently used Subregional Timber Supply (SRTS) model to run on watershed units at the USGS HUC6 level of scale, using acres (rather than timber volume) as an output metric. This provided an economically determined model of watershed disturbance in acres resulting from projected timber harvests. We simulated present and projected forest harvests by HUC6 for a 13-state southeastern region until 2020. Watersheds in northern and central Georgia and Alabama currently experience greatest harvest pressures, followed by watersheds in the southern Arkansas-northern Louisiana area and in the Piedmont and Coastal Plains regions of North and South Carolina. The simulation indicates that by 2020 Southcentral watersheds will experience relatively less intensive harvests. Watersheds in Alabama and throughout Georgia will continue to experience substantial harvest but at generally less than present levels. The areas of greatest increase will be in the southeastern Coastal region. The simulation indicates substantial increases throughout South Carolina and in the Piedmont and Southern Coastal Plain of North Carolina.
Based on econometric output from the SRTS model and the availability of additional water quality data, we subsequently focused on the State of North Carolina and developed vulnerability models for aquatic communities at several scales, using both statistical regression and geographical analysis. For the State of North Carolina, we found that 56.3 percent of the variability in macrobenthic indicators North Carolina Index of Biotic Integrity (NCIBI) of water quality could be accounted for by a regression analysis of landscape variables. The percent of the watershed in forest land cover and the topographical complexity of watershed terrain were most highly correlated with favorable index scores (NCIBI, EPTBI). Overall watershed size was less strongly correlated with favorable scores, and percent agricultural use was negatively correlated with favorable scores. Elongated watersheds with relatively longer run-off cycles were more likely to have high index values than more circular watersheds with more rapid run off.
We selected the Tar-Pamlico watershed in North Carolina as a case study as it was known to contain aquatic communities of global conservation significance, and our prior analysis had revealed high levels of timber harvest in recent decades. We conducted small-scale aquatic field studies and watershed landscape analysis at several scales. We used change vector analysis (CVA) of remotely sensed satellite data to physically locate and characterize 137,748 acres of forest harvests occurring in the study area between 1985 and 1990. Roughly 60 percent of the almost 6,000 harvests were under 10 acres in size, and although less than 5 percent were greater than 100 acres, these accounted for 40 percent of the total acres harvested. Scale was important to the interpretation of findings. Differences among watershed impacts appear modest at the HUC8 (n=10) level of aggregation; however, at the HUC14 level of scale (n=217), much more variability was evident. The average harvest extent was 9.2 percent, but in roughly 25 percent of the watersheds, harvests represented less than 5 percent of total forest area, although 12 HUC14 sub-basins had harvests of more than 20 percent of their existing forest area. Using digital elevation models (GIS), we calculated flow distances from the boundary of harvests sites to nearest stream. Almost one-half of the harvests were adjacent to streams or had a stream flowing through the harvest site. A total of 61 percent of the identified forest harvests were within 100 meters of a stream.
We conducted an aquatic field study and examined the impact of small-scale commercial forestry on the structure and function of six headwater streams in the North Carolina Piedmont portion of the study area. Despite differences in watershed land-use, there were no significant differences in the organic matter supply or temperature between streams in clear-cut and 30 managed pine stands when 50-foot hardwood buffers were maintained and when compared to reference hardwood forests. Pine sites had similar food webs to natural hardwood sites.
Algal biomass was significantly higher in clear-cut sites than forested sites and also was higher in hardwood sites than pine sites. Streams draining the clear-cut sites contained lower macroinvertebrate richness and diversity and fewer intolerant species than streams draining pine and hardwood stands; however, despite the differences in macroinvertebrates community composition, there was no difference among forest types in leaf-pack breakdown rates. Almost all timber harvest effects on streams resulted in corresponding changes to macroinvertebrate community structure. As a result, any biomonitoring method that detects changes to stream macroinvertebrate community structure should be useful for the detection of timber harvest effects on sensitive stream habitat.
We considered silvicultural Best Management Practices (BMPs) from economic and ecological perspectives. In our field study, we found that clear-cutting changes both the trophic dynamics and macroinvertebrate composition of low-order Piedmont streams in North Carolina despite the presence of hardwood buffers. Large differences were not found, however, between older pine and hardwood stands, indicating rapid recovery following regrowth of forest vegetation when hardwood buffer strips were present. This is consistent with other studies indicating that effectively implemented silvicultural BMPs and well-maintained stream management zones (SMZs) reduce harvest impacts to streams and hasten subsequent stream recovery. BMPs focus primarily on avoiding stream sediment and secondarily on maintaining stream temperature regimes. Although all states in our 13-state southeastern region except Oklahoma addressed forest canopy shading to regulate stream temperature, only 5 states (GA, KY, NC, SC, and VA) specifically addressed cold water aquatic habitat. In the 13 southeastern states surveyed, only Kentucky and North Carolina took a regulatory approach to control of nonpoint pollution from forestry operations, and in North Carolina the required Forest Practice Guidelines are implemented using voluntary BMPs. A 3-year study of active harvest sites at 200 locations in North Carolina was conducted by the state to ascertain the effectiveness of BMPs. Our analysis of these state data showed that 42 percent of harvest sites in the Mountain Region and 20 percent of the harvest sites in the Piedmont had BMP deficiencies that posed water quality risks. BMP deficiencies were more likely to occur in regions of greater topographic variability (Mountains, Piedmont). Implementation costs of BMPs also are greater in these regions. We conducted a review of forestry BMP costs within the region and found estimates ranging from $12.45 to $41.65 per acre. BMP implementation costs are higher for private individuals than for forest industry and higher for small harvest tracts than for extensive areas. BMP costs and benefits are asymmetrical as BMP costs are borne by the individual landowner as part of the timber sale whereas the benefits of improved environmental conditions are broadly shared by society.
Many benefits associated with forested landscapes are best considered in the context of watersheds. Our ability to now model timber inventory and harvests using the SRTS model at the large watershed scale (HUC6) provides an important planning tool to manage this resource in the Southeast. Greater integration across scales from regional economic models to much smaller scale ecological studies continues to be a challenge. This can be facilitated to some degree by techniques developed in this study to locate harvests on the landscape and to combine spatial and nonspatial data to rate watersheds according to selected vulnerability criteria. Such tools are critical to the evaluation of potential cumulative effects from extensive harvests and necessary to identify the occurrence of harvests in high-priority conservation areas, particularly given the decentralized and unregulated context of the many small tracts that characterize private forest ownership in the Southeast. Analysis at the HUC14 scale reveals wide variability in both resource endowments and in harvest impacts among sub-basins. Using these tools, a relatively small area of the total landscape can be prioritized using an aquatic vulnerability index (AVI) and characterized as either critically imperilled or uncommonly pristine. Such areas may become the focus for policy action. BMPs can avoid many undesirable impacts but are inconsistently implemented, creating potential for adverse effects. A macrobenthic monitoring protocol could be utilized as part of BMPs to test for possible timber harvest impacts on vulnerable aquatic communities. This could be a useful step, but further research using a controlled field trial to establish relevant biological endpoints for assessing impacts and to further refine the accuracy of our GIS methods to identify harvest locations are needed to improve scientific understanding of these complex forest stream dynamics. BMP efficacy may be reduced because BMPs are most expensive to implement where most badly needed. A policy review of options to balance private costs with public benefits may suggest ways to encourage more effective implementation.
Journal Articles on this Report : 8 Displayed | Download in RIS Format
Other project views: | All 26 publications | 9 publications in selected types | All 8 journal articles |
---|
Type | Citation | ||
---|---|---|---|
|
Cubbage FW. Costs of forestry best management practices in the south: a review. Water, Air, & Soil Pollution: Focus 2004;4(1):131-142. |
R828784 (Final) |
Exit |
|
Fortino K, Hershey AE, Goodman KJ. Utility of biological monitoring for detection of timber harvest effects on streams and evaluation of Best Management Practices: a review. Journal of the North American Benthological Society 2004;23(3):634-646. |
R828784 (Final) |
Exit |
|
Goodman KJ. The effect of forest type on benthic macroinvertebrate and trophic dynamics in the Southeastern United States. Bulletin of the North American Benthological Society 2003;20(1):232. |
R828784 (Final) |
Exit |
|
Goodman KJ, Hershey AE, Fortino K. The effect of forest type on benthic macroinvertebrate structure and ecological function in a pine plantation in the North Carolina Piedmont. Hydrobiologia 2006;559(1):305-318. |
R828784 (Final) |
Exit |
|
Potter KM, Cubbage FW, Blank GB. Schaberg RH. A watershed-scale model for predicting nonpoint pollution risk in North Carolina. Environment Management 2004;34(1):62-74. |
R828784 (Final) |
|
|
Potter KM, Cubbage FW, Schaberg RH. Multiple-scale landscape predictors of benthic macroinvertebrate community structure in North Carolina. Landscape and Urban Planning 2005;71(2-4):77-90. |
R828784 (Final) |
Exit Exit Exit |
|
Schaberg RH, Abt RC. Vulnerability of Mid-Atlantic forested watersheds to timber harvest disturbance. Environmental Monitoring and Assessment 2004;94(1-3):101-113. |
R828784 (Final) |
Exit |
|
Wear DN, Greis JG. Southern forest resource assessment: summary of findings. Journal of Forestry 2002;100(7):6-14. |
R828784 (Final) |
Exit |
Supplemental Keywords:
algal biomass, aquatic, aquatic biodiversity, aquatic ecology, aquatic ecosystem, aquatic species vulnerability, aquatic vulnerability index, assessing ecosystem vulnerability, best management practices, BMPs, biomonitoring, change vector analysis, clear-cut, EPT, ecological effects, ecological models, ecological risk assessment, ecosystem, economic analysis, economic assessment, economic models, environmental modeling, food-web, forestry, forestry BMPs, forest cover, forest landscape modeling, forest management practices, forest sustainability, geographic information system, GIS, GIS model, habitat, index of biological integrity, IBI, indicators, integrated assessment, integrated ecological assessment, interdisciplinary environmental modeling, intolerant aquatic species, landscape models, landscape patterns, landscape scale, land use, land use change, land use planning, leaf-pack, leaf processing, macrobenthic monitoring, macroinvertebrate community structure, Mid-Atlantic, multidisciplinary approach, multiscale assessment, predictive modeling, non-point source pollution, North Carolina, NCIBI, regional vulnerability assessment, regression, remote sensing, riparian forests, silviculture, simulation model, Southeast, spatial scale, stable isotopes, stream ecology, stream trophic dynamics, stream management zone, Tar-Pamlico watershed, timber, timber harvest, timber harvest costs, timber harvest patterns, timber harvest locations, timber inventory projection, water quality, watershed, watershed modeling, watershed management, woody debris recruitment., RFA, Scientific Discipline, Ecosystem Protection/Environmental Exposure & Risk, Ecosystem/Assessment/Indicators, Ecosystem Protection, Economics, Forestry, Monitoring/Modeling, Ecological Effects - Environmental Exposure & Risk, Regional/Scaling, Ecological Risk Assessment, model ecosystem effects, ecological effects, ecological exposure, habitat, ecosystem assessment, aquatic species vulnerability, foest management practices, timber harevsting, watersheds, biodiversity, spatial scale, economic assessment, economic models, land use models, multidisciplinary approach, integrated assessment, land use change, GIS, water quality, integrated ecological assessment, landscape patterns, multiscale assessment, ecological models, aquatic ecologyRelevant Websites:
http://www.env.duke.edu/scsf/ Exit
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.