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Project Topic
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Source streams, or headwaters, are often provided with the least protection from forestry and other land uses. However, the impact on ecological status of small streams from increasing water temperature, mobilising sediment, nutrients and contaminants may overwhelm the resilience of these stream ecosystems. Moreover, such changes initiate the downstream transport of these altered conditions. Protection of source streams by providing sufficient buffers is considered to be costly, but that is primarily as opportunity costs for industry. When the values of ecosystem services to downstream users is included, there is a potentially different solution. This is critical to fulfilling the Water Framework Directive 7 (and similar goals for protection of water in Canada and other countries) to ensure that anthropogenic alterations do not impair the ecological status of streams, or their inputs to downstream rivers and lakes. Source streams with small catchment areas are also prone to extreme events, both droughts and floods, relevant to the Floods Directive. Moreover, climate-proofing our stream networks through riparian area protection to reduce uncertainty about water supplies and downstream impacts may provide additional values to aid in sorting out the trade-offs among benefits (relevant to Horizon 2020). This project aims to estimate the ecological, hydrological, water quality, and economic consequences of different management scenarios (e.g., buffers), by comparing the economic and social trade-offs for different value sets and management practices, and to reduce uncertainty of how these possible impacts integrate across scales. We have three objectives. First, we will develop a model platform to explore the consequences of various forms of streamside management around source (headwater) streams. This model will use existing and new data on nutrient flows, sediment fluxes, temperature increases, and loss of productive capacity under different forest management treatments and across many landscapes. The opportunity costs of foregone timber extraction will be compared against the trade-offs to other ecosystem values (clean water, flood protection, productivity). We will generate scenarios of different management configurations to be explored by policy-makers. This will enable a discussion of the value of better protecting source streams and perhaps giving up some protection to larger streams to meet Water Framework Directive objectives. Our second objective is to augment the available data for small stream responses to forest management across our varied landscapes, using comparisons of harvested versus unharvested (no recent harvests) with and without riparian reserves, and to compare headwater versus larger streams. This will be coupled with mesocosm-scale experiments to determine mechanisms of responses by small streams to forestry impacts. Our third objective is to prepare a design and white paper for the large, distributed, landscape-scale experiment that should be done to determine the ecosystem values gained by protection of headwater streams.
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