Soil is a major building block for healthy forest ecosystems. Water, in addition to being a limiting resource determining forest type and vitality in many areas, often constitutes a valuable forest output for downstream users. These two substances, although perhaps not as visible as the trees, plants, and animals considered in Criteria 1, 2, and 3, are nonetheless crucial components in understanding forest ecosystems and their sustainability.
Soil and water are closely linked through the processes of erosion and sediment transfer. As a result, indicators of watershed condition often treat the two simultaneously, and forest management activities aimed at water quality and flow regulation usually have a strong soil conservation component. This linkage is clearly evident in our reporting for the indicators in this criterion.
The five indicators in Criterion 4 measure the current condition of soil and water resources in our forested ecosystems on the one hand, and our management actions designed to conserve these resources on the other. As such, they draw on qualitatively different data sources and analysis techniques. Indicators 4.19 and 4.21, which respectively measure soil degradation and physical changes in forest streams, rivers, and lakes, rely on direct observations of biophysical conditions or inferred measurements modeled on these direct observations. Indicators 4.17, 4.18, and 4.20, on the other hand, measure forest areas subject to certain land use designations or management practices. The first set of indicators provides a direct measurement of actual conditions––the second a measure of our efforts preserve and enhance these conditions.
A recent expansion of the Forest Service’s Forest Inventory and Analysis program (FIA) to include certain types of soils information has allowed us to more fully report on forest soils conditions for Indicator 4.19 in this report. We cannot yet determine trends over time, but we can point to regional differences and areas of concern. In this regard, the Northern and Southern Regions both contain substantial areas of degraded or otherwise suboptimal soils, to a degree that substantial negative impacts to certain forest ecosystems may result. Acid rain from airborne pollutants is cited as a factor underlying this degradation. Whether these conditions mark a deterioration or improvement relative to the past is not yet clear, but we will be able to determine this in the future with continued reporting for this indicator.
Indicator 4.21, which measures water conditions in forested ecosystems, does not benefit from the same systematic sampling that provides the soils information in Indicator 4.19. Instead, we have used State-level water quality reports that are reported biennially to the U.S. Environmental Protection Agency (EPA) by the States. This information does not allow for a direct measurement of water conditions, but it does identify the sources the water degradation as perceived by State reporting agencies. The indicator finds that municipal and industrial development is the largest cause of water degradation in the United States. Forestry activities, on the other hand, account for the least amount of damage of all sources identified—about one-tenth of the impairment attributed to development activities. These results, however, do not shed much light on conditions and trends in water quality in forest streams and lakes, the intended focus of the indicator. Here, as in many other cases, we are limited by the data on hand, and significant improvements in reporting can be hoped for in the future if water quality monitoring in forest areas can be expanded and improved.
Indicators 4.17, 4.18, and 4.20 focus on management practices and land-use designations designed to protect soil and water resources. Because a strong biophysical linkage exists between soils and hydrological functions, conservation land-use designations and best practices for forest management usually combine soil and water conservation objectives. For data, these indicators rely largely on State level reports of management activity and land-use designations. The lack of consistency in these reports presents considerable challenges in addressing the indicators. None of these three indicators were included in the 2003 report, and relevant comparisons could not be drawn with past activities to determine significant trends. We hope to improve on this situation in future reports, but the lack of consistency in the underlying data streams will continue to present challenges. In any case, the importance of intact forest ecosystems in conserving soil and water resources is widely recognized, as evidenced in forest practice regulations and watershed rehabilitation efforts across the United States.