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Environmental legislation in the US (i.e. NEPA) requires defining baseline conditions on current rather than historical ecosystem conditions. For ecosystems with long histories of multiple environmental impacts, this baseline method can subsequently lead to a significantly altered environment; this has been termed a 'sliding baseline'. In river systems, cumulative effects caused by flow regulation, channel revetment and riparian vegetation removal significantly impact floodplain ecosystems by altering channel dynamics and precluding subsequent ecosystem processes, such as primary succession. To quantify these impacts on floodplain development processes, we used a model of river channel meander migration to illustrate the degree to which flow regulation and riprap impact migration rates, independently and synergistically, on the Sacramento River in California, USA. From pre-dam conditions, the cumulative effect of flow regulation alone on channel migration is a reduction by 38%, and 42-44% with four proposed water diversion project scenarios. In terms of depositional area, the proposed water project would reduce channel migration 51-71 ha in 130 years without current riprap in place, and 17-25 ha with riprap. Our results illustrate the utility of a modeling approach for quantifying cumulative impacts. Model-based quantification of environmental impacts allow scientists to separate cumulative and synergistic effects to analytically define mitigation measures. Additionally, by selecting an ecosystem process that is affected by multiple impacts, it is possible to consider process-based mitigation scenarios, such as the removal of riprap, to allow meander migration and create new floodplains and allow for riparian vegetation recruitment.

BackgroundTemperate fruit and nut trees require adequate winter chill to produce economically viable yields. Global warming has the potential to reduce available winter chill and greatly impact crop yields.Methodology/principal findingsWe estimated winter chill for two past (1975 and 2000) and 18 future scenarios (mid and end 21st century; 3 Global Climate Models [GCMs]; 3 greenhouse gas emissions [GHG] scenarios). For 4,293 weather stations around the world and GCM projections, Safe Winter Chill (SWC), the amount of winter chill that is exceeded in 90% of all years, was estimated for all scenarios using the "Dynamic Model" and interpolated globally. We found that SWC ranged between 0 and about 170 Chill Portions (CP) for all climate scenarios, but that the global distribution varied across scenarios. Warm regions are likely to experience severe reductions in available winter chill, potentially threatening production there. In contrast, SWC in most temperate growing regions is likely to remain relatively unchanged, and cold regions may even see an increase in SWC. Climate change impacts on SWC differed quantitatively among GCMs and GHG scenarios, with the highest GHG leading to losses up to 40 CP in warm regions, compared to 20 CP for the lowest GHG.Conclusions/significanceThe extent of projected changes in winter chill in many major growing regions of fruits and nuts indicates that growers of these commodities will likely experience problems in the future. Mitigation of climate change through reductions in greenhouse gas emissions can help reduce the impacts, however, adaption to changes will have to occur. To better prepare for likely impacts of climate change, efforts should be undertaken to breed tree cultivars for lower chilling requirements, to develop tools to cope with insufficient winter chill, and to better understand the temperature responses of tree crops.

This study presents a GIS-based database framework used to assess aggregate terrestrial habitat impacts from multiple highway construction projects in California, USA. Transportation planners need such impact assessment tools to effectively address additive biological mitigation obligations. Such assessments can reduce costly delays due to protracted environmental review. This project incorporated the best available statewide natural resource data into early project planning and preliminary environmental assessments for single and multiple highway construction projects, and provides an assessment of the 10-year state-wide mitigation obligations for the California Department of Transportation. Incorporation of these assessments will facilitate early and more strategic identification of mitigation opportunities, for single-project and regional mitigation efforts. The data architecture format uses eight spatial scales: six nested watersheds, counties, and transportation planning districts, which were intersected. This resulted in 8058 map planning units statewide, which were used to summarize all subsequent analyses. Range maps and georeferenced locations of federally and state-listed plants and animals and a 55-class landcover map were spatially intersected with the planning units and the buffered spatial footprint of 967 funded projects. Projected impacts were summarized and output to the database. Queries written in the database can sum expected impacts and provide summaries by individual construction project, or by watershed, county, transportation district or highway. The data architecture allows easy incorporation of new information and results in a tool usable without GIS by a wide variety of agency biologists and planners. The data architecture format would be useful for other types of regional planning.

Government agencies that develop infrastructure such as roads, waterworks, and energy delivery often impact natural ecosystems, but they also have unique opportunities to contribute to the conservation of regional natural resources through compensatory mitigation. Infrastructure development requires a planning, funding, and implementation cycle that can frequently take a decade or longer, but biological mitigation is often planned and implemented late in this process, in a project-by-project piecemeal manner. By adopting early regional mitigation needs assessment and planning for habitat-level impacts from multiple infrastructure projects, agencies could secure time needed to proactively integrate these obligations into regional conservation objectives. Such practice can be financially and ecologically beneficial due to economies of scale, and because earlier mitigation implementation means potentially developable critical parcels may still be available for conservation. Here, we compare the integration of regional conservation designs, termed greenprints, with early multi-project mitigation assessment for two areas in California, USA. The expected spatial extent of habitat impacts and associated mitigation requirements from multiple projects were identified for each area. We used the reserve-selection algorithm MARXAN to identify a regional greenprint for each site and to seek mitigation solutions through parcel acquisition that would contribute to the greenprint, as well as meet agency obligations. The two areas differed in the amount of input data available, the types of conservation objectives identified, and local land-management capacity. They are representative of the range of conditions that conservation practitioners may encounter, so contrasting the two illustrates how regional advanced mitigation can be generalized for use in a wide variety of settings. Environmental organizations can benefit from this approach because it provides a platform for collaboration with infrastructure agencies. Alone, infrastructure agency mitigation obligations will not satisfy all greenprint objectives, but they can be a major contributor to the ongoing process of implementing ecologically sustainable regional plans. © 2009 by the author(s).

Landscape fragmentation due to urban development, transportation infrastructure, and agriculture poses a threat to environmental integrity. There is a need to quantify the level of landscape fragmentation in an ecologically meaningful way for inclusion in planning and decision-making. Effective mesh size (meff) is an ecologically relevant metric that quantifies landscape fragmentation based on the probability that two randomly chosen points in a region are located in the same non-fragmented patch. We investigated variation in meff measured by transportation districts, municipal counties, and six spatial levels of watersheds within the state of California. Four fragmentation geometries were developed by overlaying highways, roads, urbanized areas, agricultural areas, and natural fragmenting features. Two meff calculation methods were compared: one where planning unit boundaries fragment the landscape (CUT), the other allowing for cross-boundary connections (CBC). The CUT procedure always produced lower meff values than CBC, with greater differences occurring in smaller planning units, confirming the bias introduced using boundaries with landscape metrics. Calculated meff values varied from 0 to 20 885 km2 across 6994 units in California. Roads contributed the most to fragmentation, while agriculture contributed little, as California's agricultural areas are already heavily fragmented by roads. This paper provides a systematic, quantitative, and intuitive method for transportation, land use and environmental planners to analyze cumulative impacts of multiple fragmenting features across a range of spatial scales within a variety of planning units. This approach could be used for analyzing the impact of future land development scenarios, and integrated into regional planning processes. © 2008 Elsevier B.V. All rights reserved.

Watts et al. (Reports, 6 May 2007, p. 736) introduced a metric of landscape pattern called roadless volume (RV). However, as with most previous metrics, RV does not explicitly address ecological processes. We demonstrate that RV can produce results inconsistent with the notion of landscape connectivity and contend that more ecologically relevant metrics are available.

The University of California Information Center for the Environment (ICE) and the California Department of Transportation (Caltrans) are developing a GIS-based analytical framework to improve the effectiveness of biological mitigation throughout California. Goals include incorporating the best available sets of mapped natural resource data into the early project planning and preliminary environmental assessments for single and multiple projects. Incorporation of these data will facilitate early and more strategic identification of mitigation requirements and op¬portunities, for both single-project and regional mitigation efforts.The cost of delays and over-runs due to late and fragmented project-by-project environmental planning and mitigation in California is estimated at $75 million per year. Developing systematic GIS-based decision-support tools to identify important species and habitats, both those impacted directly by Caltrans activities and those that might contribute to effective mitigation in the same locale or watershed will permit Caltrans, counties, and environmental regulators to incorporate the results of biological impact assessments earlier in the planning process, and identify opportunities mitigating the combined biological impacts of many projects in a given area. By building upon previous efforts and using tools known to be effective for integrated analyses, this project will help Caltrans improve planning results, decrease costs, improve project delivery schedules and provide greater environmental protection in the long-term.To accomplish these goals, Geographic Information Systems (GIS) analysis and conservation planning principles are being applied to develop multi-scale longrange (10-year) mitigation need forecasts for each Caltrans district, county, and watershed in the State of California. These will be used to determine the cumulative mitigation needs for early biological mitigation planning of multiple projects in a given area. Available statewide biological data have been integrated into a database that can be queried by Caltrans district, county, or any of six levels of watershed classification. For a queried geographic area, the database returns the biological resources expected to exist in the area based on the available data, as well as the potential impacts to these resources from Caltrans projects that are currently funded to be constructed in the area over the next 10 years. The type of project programmed to occur was then used to estimate the impact zone of each project (e.g. road repaving, road widening, new road, etc.). Then, by querying the database for a given geographic region, the area, habitats and species potentially affected by cumulative biological impacts from all programmed highway projects in that region can be estimated. From this, estimates of area and types of lands that would need to be acquired for mitigation can be determined.This project provides a framework for analyzing and estimating biological mitigation needs that could be generalized for use in transportation planning in other geographic areas, as well as for other types of planning. The database schema developed here could easily be adapted to analyze the potential impacts and mitigation needs for urban growth planning efforts, and other development projects with biological impacts that require biological mitigation planning. Overall, by integrating available data into a useful database format, this project has developed a system for assessing long-term biological mitigation needs that will assist in the implementation of early biological mitigation planning.

Habitat fragmentation due to transport infrastructure and other human development poses a threat to many wildlife species. This threat may differ depending on the species and types of fragmenting elements. There is a need to quantify the level of habitat fragmentation and the impact of habitat fragmentation on different wildlife species for use in transportation planning. Such measures would be useful in assessing the cumulative impacts of multiple road projects on wildlife connectivity and habitat suitability, for long-range wildlife impact mitigation planning for transportation projects, and as an indicator for the environmental monitoring of habitat fragmentation due to roads.Effective mesh size (meff) is a biologically relevant landscape metric that quantifies the degree of landscape fragmentation. The definition of the effective mesh size is based on the probability that two randomly chosen points in a region will be located in the same non-fragmented area of land. We calculated effective mesh size to assess the level of land¬scape fragmentation in the State of California, USA, based on four fragmentation geometries defined by a combination of highways, minor roads, urbanized areas, agricultural areas, and natural fragmenting features (e.g., rivers, lakes, and alpine areas). The effective mesh size for these four fragmenting geometries were calculated for the entire State of California using eight sets of planning units: 1) transportation planning districts, 2) municipal county boundaries, and 3) six levels of watersheds. To demonstrate the methodology, we examined how effective mesh size may impact two species important to transportation planning in California: mule deer (Odocoileus hemionus) and mountain lion (Puma concolor). The calculated effective mesh sizes were compared with the home range sizes and daily movement distances of the selected focal species to determine the potential impacts of habitat fragmentation and to identify areas where transportation projects will potentially impact these focal species.Based on the results of this analysis, we suggest that integrating an effective mesh size-based tool into transportation planning frameworks would be valuable to improve identification of potential landscape level impacts early in the planning process. The calculation of effective mesh size will give transportation planners a way to analyze the cumulative impacts of roads in districts, counties, and watersheds and can be used as an environmental indicator for ecological assessment of transportation system impacts.

The United States Forest Service is required to analyze road systems on each of the national forests for potential environmental impacts. We have developed a novel and inexpensive way to do this using the Ecosystem Management Decision Support program (EMDS). We used EMDS to integrate a user-developed fuzzy logic knowledge base with a grid-based geographic information system to evaluate the degree of truth for assertions about a road’s environmental impact. Using spatial data for natural and human processes in the Tahoc National Forest (TNF, California, USA), we evaluated the assertion "the road has a high potential for impacting the environment." We found a high level of agreement between the products of this evaluation and ground observations of a TNF transportation engineer, as well as occurrences of road failures. We used the modeled potential environmental impact to negatively weight roads for a least-cost path network analysis to 1573 points of interest in the forest. The network analysis showed that out of 8233 km of road analyzed in the forest, 3483 km (42%) must be kept in a modified road network to ensure access to these points. We found that the modified network had improved patch characteristics, such as significantly fewer "cherry stem" roads intruding into patches, an improved area-weighted mean shape index, and larger mean patch sizes, as compared to the original network. This analysis system could be used by any public agency to analyze infrastructure for environmental or other risk and included in other mandated analyses such as risks to watersheds.

Guidelines for protecting and managing identified wildlands in the Sierra Nevada are included in this document to assist conservation practitioners and resource managers in the maintenance of vital wildlands and wildlife. These guidelines recommend limiting habitat fragmentation by controlling road density and habitat loss in wildlands. This will directly benefit wildlife species and maintain the health of ecosystems. Other guidelines recommend the establishment of conservation easements, wildlife friendly zoning ordinances, and wildlife under-and over-passes where roads prohibit movement. These guidelines will become more specific through the site planning process, which will be encouraged at the local scale.