Assessing the Hydrochemical Response of High Elevation Forest Watersheds to Climate Change and Atmospheric Deposition Using a Biogeochemical Model (PnET- BGC)
Climate is an important regulator of the hydrology and biogeochemistry of forest watersheds. To assess the potential impacts of climate change, a multi-faceted approach is required that is capable of resolving multiple climatic and other anthropogenic stressors likely to simultaneously affect ecosystems over the coming decades. The ecological responses to climate change have been assessed by observational, gradient, laboratory and field studies; however, models are the only practical approach to investigate how future changes in climate are likely to interact with other drivers of global change such as atmospheric deposition and land disturbance over broad regions. Biogeochemical watershed models are an important tool to help to understand the long-term effects of climate change on ecosystems. In this study, we are using the biogeochemical model (PnET-BGC) coupled with long-term measurements to evaluate the effects of potential future changes in temperature, precipitation, solar radiation and atmospheric CO2 on pools and fluxes of major elements at 14 diverse, intensively studied, high-elevation watersheds. Future emissions scenarios were developed from monthly output from three atmosphere-ocean general circulation models (AOGCMs; HadCM3, PCM, GFDL) in conjunction with potential lower and upper bounds of projected atmospheric CO2 (550 and 970 ppm by 2099, respectively). Here we report on long-term site measurements and PnET-BGC predictions for the Hubbard Brook Experimental Forest (HBR) in the White Mountains, New Hampshire, and Huntington Wildlife Forest (HWF) in the Adirondack Mountains, New York (two of the 14 sites), indicating a broad range of hydrologic and biogeochemical responses to changing climate. AOGCM results over the 21st century indicate an average increase in temperature ranging from 1.9 to 6.9°C and 1.9 to 7.0°C with simultaneous increases in precipitation ranging from 12.5 to 13.9% and 11.9 to 12.2% above the long term mean (1970-1999) for HBR and HWF, respectively. The increases in temperature are greater at higher latitudes, and precipitation patterns are changing. Long-term measurements and watershed modeling results show a significant shift in hydrology with earlier spring discharge (snowmelt), greater evapotranspiration, and later snowpack development. Model results also show an increase in NO3- leaching due to large increases in net mineralization and nitrification. The extent of this response is dependent on the fertilization effect that increasing atmospheric CO2 has on forest vegetation. The watershed responses of other major elements such as SO42- and Ca2+, and chemical characteristics such as pH and ANC to changes in climate varied due to site characteristics. Model predictions of dissolved organic carbon (DOC) concentrations showed increases at both sites. Model projections also suggest marked decreases in soil exchangeable calcium, magnesium and potassium with simultaneous decline in soil base saturation and Al/Ca ratio over the next century. These changes are mainly attributed to elevated leaching losses of nitrate. A sensitivity analysis showed that the temperature is the key driver of watershed responses to future climate change resulting in the greatest response of the simulated changes.
Assessing the Impacts of Climate Change on Species Habitats and Distributions in the Southeastern U.S.
Adapting to and mitigating for the impacts of climate change on wildlife will require scale and resource specific
analyses. In the Southeastern U.S. a variety of disturbances (e.g. urbanization, plant succession) including
those affected by climate change (e.g. sea level rise, fire frequency) impact the suitability of habitat through
time. In order to adapt their management strategies, resource managers and policy makers will need tools to
understand the full range of possible future conditions. Here we describe and offer preliminary results on two
studies designed to project the future range of conditions for wildlife habitat in the southeast. In the first project
we use Monte Carlo simulations to project landscape dynamics and subsequent availability of habitats for
priority species in the Southern Atlantic Migratory Bird Initiative (SAMBI) region. In that study, the indirect
impacts of climate change are incorporated through the influence of temperature and convective precipitation
on fire potential. Fires influences the landscape dynamics through state transitions (e.g., late open canopy,
early closed canopy), that are determined probabilistically. Initially the relationship between the climate
variables and fire potential were projected out to 2100 using twelve of the Global Climate Models. Currently, we
are working with Texas Technological University to refine predictions of fire potential using regionally-scaled
climate models. A variety of management and climate scenarios are being run to allow decision makers to
make direct comparisons between predictions based on those scenarios (i.e., acres of habitat, connectivity of
habitat). Results are supplied to resource managers in the form a decision support tools based on the priority
species guilds in the region. A second more extensive effort, the Southeastern Pilot, will use occupancy
models to assess range dynamics of North American land birds. Local probabilities of extinction and
colonization are viewed as the vital rates responsible for range dynamics. Competing hypotheses about
variation in these vital rates across time and space in response to changes in climate and land cover over the
past 30 years will be incorporated into spatially referenced occupancy models and tested using data from the
North American Breeding Bird Survey. The Southeast Project will identify which species are at higher risk of
range contraction and which invasive species are likely to become problematic in the region. Future work calls
for expanding the scope of the analyses to include probabilistic projections of climate change through
collaboration with Penn State and Texas Tech University. That work will provide a more complete
understanding of the uncertainty in the projections. Finally, we suggest that by integrating the approaches
adopted in these two studies, specifically regionally-scaled climate models, dynamic modeling of landscape
change, and avian range dynamics that a framework for regional assessments of the impact of climate change
on wildlife exists.
Vulnerability of High-Quality Winegrowing to Climate Change in California
We took an interdisciplinary approach to examine the climate sensitivity and adaptive capacity of both the ecological and social systems of winegrowing. In a three-year study, we used field, laboratory, modeling, and anthropological approaches to examine the vulnerability of the wine industry to climate change. We developed models of winegrape yields based on the effects of historical temperature and precipitation in California, and used these findings to project future yields under climate change. We examined the concentrations of phenolic compounds important to wine quality (anthocyanins and tannins) in Pinot noir grapes from across a range of mesoclimates. We found that increased concentrations of these phenolic compounds were correlated with cool temperatures in the fall the year before harvest, warm temperatures from budburst to bloom, and cool temperatures from bloom to veraison, and with lower light intensities in these highly sun-exposed vines. We also conducted interviews to examine the adaptation responses of winegrowers to environmental stresses. We found that growers undertake a wide variety of environmental management strategies in the vineyard, most of which are individual in nature, and either in response to an existing stress, or in anticipation of an imminent stress. Finally, we examined the potential adaptive capacity of the wine industry to climate change, based on its awareness of climate change, ability to react, and actual actions and barriers to action. We conclude that winegrowers have a fairly high adaptive capacity, but that successful adaptation in practice depends on including proactive and coordinated community responses, which are beginning to develop.
Yukon Tree Rings and Climate Change: Effect of increased freeze-thaw events on white spruce and lodgepole pine growth
Northern environments are experiencing dramatic changes in local climate, including prolonged spring and fall freeze-thaw cycles. Our research examines whether increased frequency of freeze-thaw events is linked to growth reductions in lodgepole pine (Pinus contorta) and white spruce (Picea glauca) in the Yukon Territory, Canada. Tree core samples were collected from 11 sites across the Yukon, covering a range of ecoregions, climate zones, and fire history, sampling all major forest communities accessible by road and located near the network of long-term weather stations. Over 50 tree cores from each site were sampled, analysed for ring- width, cross-dated and averaged to generate yearly ring growth at each site for each species. Ring growth was then compared against yearly freeze-thaw events at each site, defined as total days with daily temperature ranges which crossed the freezing threshold. Preliminary results indicate a negative relationship between ring growth and number of freeze-thaw events (p<0.05), suggesting that northern forests will experience growth declines in response to prolonged spring and fall freeze-thaw conditions.
An Integrated Modeling Approach to Evaluate Potential Effects of Climate Change on the Water Supply for New York City
New York City Department of Environmental Protection (DEP) is developing an integrated modeling system to further understand the implications of potential future climate changes on the quantity and quality of the New York City (NYC) Water Supply. This modeling project utilizes climate change projections as input to an integrated suite of models including watershed hydrology and water quality models, a water system operations model, and reservoir hydrothermal and water quality models. Recent predictions of future climate for the northeast U.S. generally indicate greater annual precipitation and increased temperatures compared to current climate conditions. These climate changes could potentially produce longer growing seasons, increased evapotranspiration, earlier snowpack melting, changes in the magnitude streamflow events, differences in proportion of streamflow due to overland flow, shifts in the timing of sediment and nutrient delivery to the reservoirs, and changes in the timing and intensity of reservoir thermal stratification. The integrated modeling system can be used to better understand how the interplay of these potential changes will affect the NYC Water Supply System. Utilizing the watershed, reservoir and water system models together provides a framework for evaluating feedbacks between flows and loads entering the reservoir, reservoir water quality, water demand and water system operations. Scenarios incorporated within the integrated modeling framework provide a greater understanding of the combined impacts of climate change on the water supply quantity and quality. Preliminary model simulations are presented that demonstrate how the integrated models are used to investigate climate change effects. Various statistical measures of water system quantity and quality including drought indicators, frequency of occurrence of turbidity limits and frequency of exceeding threshold chlorophyll and phosphorus concentrations are examined in order to place the results in the context of DEP's water supply concerns.
Impacts of Climate Change at Watershed Scale: Creating an Ecological Basis for "Smart Growth" and Economic Development in the Post-industrial Lehigh Valley of Eastern PA
As modeling of global climate change matures and regional projections regarding regional variability become viable, the scales of climate impact analysis and regional decision-making begin to converge. This convergence provides a critical new challenge for both the climate modeling and policy communities- "How can projected climate change insights at watershed scale most effectively inform decisions regarding land use, zoning, and growth management?" This issue is particularly critical in regions that were formerly heavily industrialized and developed, and that are now finding new avenues for economic growth in the wake of massive clear-cutting, mining, and heavy industry of the 19th and 20th centuries. The Lehigh Valley is a watershed defining a single ecosystem that contains 800,000 people, 321 square miles of croplands and 95 square miles of urban areas, with the remainder of the watershed at various successional stages after massive forest clear-cutting of the last two centuries. Many of the industries that fueled the industrial revolution were based in the Lehigh Valley, and their development came at an environmental cost that was not then recognized, but that left a legacy of mine-scarred lands, acid mine drained streams, soil and water contamination, and a derelict industrial infrastructure that state and local governments have only recently begun to address. Before these institutions can plan for redevelopment of brownfields, regional planning for housing and commercial development, and preservation of forested and agricultural lands, it is first necessary to understand the impacts of climate change on watershed hydrology, productivity, and other ecosystems functions, and to provide this information to decision-makers responsible for environmentally sustainable development and regional planning. "Smart Growth" has become a catch phrase for regional development that is sensitive to social, economic, political, and historical goals, as well as ecological constraints and climatic considerations. As such, planning for future urban development and ecosystem preservation depends on reliable downscaled global or regional climate models for a range of scenarios that can inform decision makers about how to ensure provision of ecosystem goods and services such as water quality and availability, contaminant filtration/decomposition, fish and game habitats, flood control, soil fertility (and preservation) for agriculture, sediment stability, migratory pathways, recreational resources, aesthetics, species diversity and resistance to invasives, and provision of an attractive regional setting that attracts and retains the workforce necessary for economic recovery and redevelopment in the 21st century. With this information, it will be more possible for regional planners to justify developing land in ways that meet the "police power" responsibilities of local governments to protect public health and welfare. It is yet to be tested whether a regional plan based on state-of-the-art climate and ecosystem modeling will provide a legal basis for upholding plans for "smart growth" at the regional scale in Pennsylvania. Consequently we hope that information provided by regional downscaling will yield information that helps municipalities to plan in ways that minimize their exposure to curative amendments and other legal disputes that currently force them to engage in environmentally unsound planning.