Recommendations for Continuous Development and Implementation of Measurements to Determine Status and Trends in Ecosystem Exposure and Condition
RESEARCH AND DEVELOPMENT RECOMMENDATIONS
1. Develop a comprehensive understanding of chronic effects of multiple air pollutants on ecosystems at ecologically relevant temporal and spatial scales.
This includes feedbacks and interactions among the atmosphere, plants, soil, and animals in terrestrial ecosystems, and interactions of organisms, habitat, and water quality in interconnected aquatic ecosystems. Because different species and different developmental stages of these species respond differently to air pollutants, integrated field studies of air pollutant and climatic effects should cover a range of vegetation types and a range of age classes. Integrated in situ experiments should link co-located ambient air pollution measurements with observations of ecosystem response.
Specific Improvements Needed:
Field observations and experiments on interactive effects of ozone, reactive nitrogen deposition, atmospheric carbon dioxide, and climatic stress (for example, water availability) on responses of different terrestrial ecosystems (including forests at different developmental stages)
Studies on ecological consequences of depletion of nutrient cations from soil and enrichment of nitrogen and sulfur in soil
Long-term mechanistic studies to evaluate the consequences for plant physiological processes, of changes in soil chemistry that occur as a result of
air pollution, taking into account other factors such as reduced resistance to disease and climate extremes
Develop methods to combine data from various sampling designs (for example, data assimilation and meta-analysis)
Technological improvements in ozone measurement for biologically relevant ozone data (for example, appropriate temporal and spatial resolution)
Modeling of the spatial distribution of dry deposition and ozone concentrations as a function of source, terrain, and meteorology. Mesoscale meteorological models require improved treatments of surface-atmosphere interactions, simulations in complex terrain, and simulation of flows under stagnating conditions often associated with ozone episodes.
Develop coupled ecological process modeling and air quality modeling for evaluating responses spatially and temporally, and for scenario testing. The atmospheric modeling can provide spatial information on air quality to the ecosystem process models, which provide estimates of response to air pollution.
Monitoring data are needed for verification of model predictions of exposure, particularly in rural areas.
Continued studies on bioaccumulation of pollutants in aquatic and terrestrial ecosystems, and terrestrial/aquatic interactions.
Exposure, transfer, and bioaccumulation of mercury in terrestrial and aquatic ecosystems. Studies on the effects of mercury on soil microbial processes and subsequent effects on plant processes in terrestrial ecosystems, including deposition in forests, terrestrial accumulation, transport to aquatic ecosystems and conversion of inorganic mercury to methyl mercury.
2. Improve process-based models of ecosystem response to pollutants for regional assessments.
Development and testing of spatially-explicit ecosystem models need to be accelerated for determining response at scales of air pollutant exposure. In terrestrial ecosystems, field studies should be linked with improved modeling of ecosystem exposure and responses to multiple controlling factors, cumulative stress, and plant community dynamics. This includes interaction of multiple cumulative effects of air pollutants and climatic factors on physiology of receptor plants (e.g., photosynthate allocation) and below-ground processes, differential sensitivities of species, and linking shifts in biogeochemical processes to changes in community dynamics and species composition.
3. Develop and test tools for assessing impacts of pollutants on biological species, populations, and ecosystems.
As new technologies—such as stable isotope analysis and remote sensing from aircraft and satellites—develop, continued studies are needed to identify biological indicators for detecting responses to pollutants at various levels of biological organization. This understanding is particularly important for terrestrial ecosystems, as relatively little progress has been made in this area compared to that in aquatic ecosystems.
4. Improve methods for monitoring ambient air quality in ecosystems, and ecosystem response.
Continue to conduct studies to determine appropriate suites of measurements, sample design, and sampling intensity to detect changes in ecosystem condition in response to pollutants. This is particularly important for terrestrial ecosystems, where little progress has been made. Biogeochemistry, habitat and biodiversity, and the linkage between diversity and productivity, are important factors for which a comprehensive suite of indicators should be developed. Indicators should include intermediate variables (for example, leaf area index and the foliar chemistry used to model productivity) as well as final variables (for example, mortality). Examine the possibility of using critical loads to quantify impacts on terrestrial ecosystems.
5. Conduct risk assessment research.
Develop methods for quantifying susceptibility of ecosystems to multiple stressors at multiple scales. See for example Linthurst et al. (2000).
There has been a lack of coordination in research on measuring the responses of ecosystems to pollutants, and in implementation of monitoring programs that use the new knowledge gained. Likewise, responsibility for monitoring of ecosystem conditions has been divided among agencies, and offices within agencies, so that a cohesive long-term program on monitoring terrestrial and aquatic ecosystem conditions does not exist. Analysis and reporting of results have been spotty, and very much delayed (for example, U.S. Department of Agriculture Forest Service Forest Health Monitoring), and data and reports are not easily located.
Key elements for implementation of measurements to determine status and trends in air pollution exposure and ecosystem condition are:
1. The institutional framework for monitoring exposure and ecosystem response.
True coordination between federal and state agencies is necessary to implement a unified cohesive program for monitoring air quality and ter-
restrial and aquatic ecosystems, including planning, implementation, analysis, and reporting of results.
2. Transfer of knowledge gained in research and development to monitoring programs.
There should be a process for moving models and measurements from research and development to implementation in monitoring—requiring coordination between responsible agencies.
3. Establish baselines of ecosystem condition.
Baseline ecosystem condition can be identified as the initial condition for establishing trends and detecting changes. Reliable baseline conditions have not been identified and reported for terrestrial, aquatic, and coastal ecosystems across the United States. Reports to date on conditions have not been based on representative surveys of ecosystem condition, nor have they incorporated meaningful biological measures of ecosystem condition.
4. A comprehensive suite of indicators should be measured consistently in terrestrial and aquatic ecosystems with appropriate coverage across the United States, and baseline conditions of ecosystems should be established in one widely distributed consolidated report.
An ecosystem perspective is essential in monitoring at all sites, including ecological structure and function, such as soil condition in terrestrial ecosystems and habitat condition in aquatic ecosystems. Ecosystem characteristics that are important process model input variables (for example, foliar and soil carbon and nitrogen, leaf area index, and tree heights), or are important for testing or constraining models (for example, productivity) should be monitored. Soil samples from terrestrial ecosystems and sediment or tissue samples from aquatic systems should be archived for analyses in the future, when new approaches or techniques become available.
5. Co-locate long-term measurements of air quality, meteorology, and ecosystem responses (e.g., along pollution gradients).
The density and distribution of air quality monitoring stations in rural, agricultural, and remote forest areas should be increased, aided by a statistical design that will improve spatial and temporal estimates of exposure. Measurement locations should maximize coverage along gradients from urban to remote areas, and encompass a range of topographic and microclimate conditions. For ozone effects on terrestrial ecosystems, sampling should be conducted on plants with multiple years of foliage to determine cumulative effects over several years; on deciduous species, sampling should be conducted at the end of the summer, to allow summer-long cumulative effects to be determined (U.S. Forest Service Forest Inventory and Analysis [FIA] sampling actually occurs all summer) (Campbell et al. 2000). The
sampling intensity for ozone injury should be increased, and foliar sampling should be co-located with active ozone monitors.
6. Probability sample designs for monitoring will ensure coverage within a domain of existing populations.
For example, sampling can be proportional to the area coverage of different forest types or the number of first order streams (Olsen et al. 1999). The plot design and the survey design need to be sufficient to determine differences between sites.
7. Conduct intensive ecosystem studies at a subset of representative plots.
Such studies will increase the understanding of mechanisms of response to multiple factors, including air quality and climate.
8. Improve National Weather Service meteorological data by adding measurement of incident total solar radiation.
Incident radiation strongly influences ozone formation. It is a key variable used in environmental analysis, and is critical for spatial modeling of meteorology, ozone distribution, and ecosystem effects.
9. Release for regional analysis the exact locations of forest survey plots on public lands.
An amendment to the Food Security Act (2001) prohibits release of exact locations of Forest Inventory and Analysis and Forest Health Monitoring (FIA/FHM) plots, including those on public lands. The release of exact plot locations will allow scientists outside FIA/FHM to investigate air pollution effects on forest ecosystems in a spatial context. Currently, investigators who are collaborating with FIA personnel may make complicated arrangements with some regions to allow FIA personnel to run specific analyses for them, but the practice is inconsistent among regions, it is usually impractical because of the complexity of the analyses, and because there are extremely long delays in data processing (processing often delayed for years or never accomplished).
10. Expand the EPA Temporally Integrated Monitoring of Ecosystems/Long-Term Monitoring (TIME/LTM) program for monitoring surface waters to include sites from regions sensitive to atmospheric deposition (for example, Southeast, Upper Midwest, West).
Measurements should be long-term to ensure continuity for trends detection. The TIME/LTM program should be integrated with national networks to quantify atmospheric deposition and watershed information on soil, forest vegetation, and other attributes. Measurements should be linked with biogeochemistry modeling to predict both effects of acidic deposition
and response to proposed air quality controls. EPA should also consider expanding TIME/LTM to include monitoring of acid-sensitive biological indicators at a subset of sites. This would allow managers to assess linkages between changes in the acid-base status of surface waters and biological responses to changing chemical conditions.
11. Improve methods and facilities on regional scales to evaluate the status, trends and response to controls on atmospheric sources of nitrogen (see, for example, ESA [1997b]).
There is a need for basic estimates of organic nitrogen deposition rates and loadings, and for linking delivered atmospheric loads to sources. For example, the effects of forest management and agricultural practices on delivery of nitrogen to coastal waters should be examined. Assessments of atmospheric deposition profiles are needed for all key estuarine/coastal systems along the Atlantic and Gulf coasts. These profiles should be developed using a consistent set of methodologies or tailored to specific regions using a common base of information.
12. Expand the existing estuarine monitoring programs (National Estuaries Program and National Estuarine Standards Reserve System) to address existing gaps in knowledge of effects of atmospherically deposited chemicals in the coastal zone.
Where atmospheric deposition data are lacking in some systems, expansion would have to include wet and dry deposition measurements (requiring significant funding and technical expertise). Monitoring at these sites should be expanded to quantify mass inflow of reactive nitrogen and other pollutants (for example, mercury) that are derived from atmospheric sources. The monitoring program should be coordinated with measurements of estuarine conditions, including nitrogen species, dissolved oxygen, chlorophyll, and sea grass biomass. A second option is to foster the formation of integrated estuarine studies (for example, MODMON, the Neuse River Estuary Modeling and Monitoring program at the University of North Carolina (at MODMON 2001). Using either approach, the monitoring program should be linked to modeling efforts to simulate emissions and atmospheric deposition and the transport and fate of atmospherically derived pollutants within watersheds and estuarine ecosystems.