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Open Access Publications from the University of California

Institute of the Environment

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The Institute of the Environment supports innovative interdisciplinary research, teaching and outreach activities which respond to problems in the environment and strengthen the scientific foundation for environmental decision making.

The Institute of the Environment champions research and service at the University of California, Davis which benefits the biological, physical and human environment. The institute provides campus-wide leadership, hosts centers and projects, and seeds research and educational initiatives to solve environmental problems. Their activities link traditional academic and administrative units by providing the intellectual setting for interaction between researchers, regulatory agencies, policy-makers and the public to find solutions to complex environmental problems.

Institute of the Environment

There are 52 publications in this collection, published between 2003 and 2024.
Ecotoxicology Lead Campus Program Publications (2)


Habitat and population fragmentation as a result of human disturbance in the form of human transportation and settlement corridors is affecting the viability of wildlife populations worldwide. I studied dispersal, inter-population movement and population fragmentation of grizzly bears near the southern extent of their North American range in southwestern Canada and northwestern U.S.A. This area represents the interior portion of the southern edge of grizzly bear distribution following 100 years of range contraction. I address whether anthropogenic fragmentation has affected grizzly bear populations in this vulnerable area. Human attitudes toward grizzly bears, and large carnivores in general, have experienced a paradigm shift from active persecution towards tolerance and respect. However, major forces underpinning range contraction, including human-caused mortality and fragmentation, may be still operating, albeit, more subtly and less intentionally. Checking further range contraction requires specific knowledge of the processes at work. Improvements have been made in managing and monitoring human-caused mortality; however, besides the obviously isolated populations (e.g., Yellowstone National Park), the status of fragmentation in this region was largely unknown. My goals were to use genetic analyses to explore bear movement and dispersal within and between the relictually inhabited mountain ranges in southwestern Canada and test whether or not the human environment associated with linear transportation and settlement corridors is fragmenting grizzly bear populations. I genetically sampled and generated 15-locus microsatellite genotypes for 835 bears across approximately 100,000 km2 in immediately adjacent geographic areas separated by various levels of human disturbance associated with highways and associated human development. I used population assignment techniques, parentage analysis, cluster analysis, multiple linear regression and several matrices of population genetics. I found evidence of natural and human-caused fragmentation, identified fragmenting forces, established population and sub-population boundaries in the region, identified small vulnerable sub-populations, and discussed these in relation to factors that make bears susceptible to fragmentation. Female movement was restricted by human transportation and settlement corridors, and male movement appeared to be reduced in some areas. Fragmentation by north/south-oriented human-settled valleys and by major east/west transportation corridors has resulted in a partially fragmented set of local sub-populations varying in size and intensity of fragmentation. I found one small isolated population (n 300). Through multiple linear regression, I implicated human settlement patterns, human-caused mortality, and highway traffic volume as inhibiting inter-population movement. Because several fragmented sub-units are small, maintaining regional connectivity may be necessary to ensure long-term persistence. Despite grizzly bear vagility, their conservative dispersal behaviour and difficulty in living close to humans makes maintenance of regional connectivity challenging. This work demonstrates, at a regional scale, the impact that transportation corridors and their associated settlements can have on movements of animals, and highlights the ultimate effect this may have on populations. The historical mechanisms of range contraction (fragmentation and human-caused mortality) appear to still be operating and require mitigating management strategies. My results suggest that these strategies must focus on linkage zone development and highway crossing structures, as well as mortality management beyond the roadway and within adjacent populations.


Studies from different continents have proved amphibians to be the most frequently killed vertebrates on roads. In Central-Europe their ratio is between 70 and 88 percent. Local populations are known to become extinct or genetically isolated, and avoidance is also recognised, especially where the road network is dense and the traffi c is intensive. Besides ecological and conservation considerations, amphibian road kills also present a hazard for motorists when amphibians migrate in large numbers. Mitigation measures for amphibians have been applied since the 1960s. In Central-Europe the fi rst amphibianrelated culvert modifi cation occurred at Parassapuszta, Hungary, in 1986. A number of amphibian-oriented mitigation measures have been made in the region under roads and motorways since then, especially after 1995. The aim of this paper is to describe the main features of these constructions, overview the different designs, and make suggestions for their improvement as well as for future amphibian-oriented mitigation measures in general. A total of 31 road sections was monitored. Besides amphibian tunnels, game passages and game bridges were also investigated. Both the detailed characterisation of the technical solutions and the survey of amphibian populations and habitats were included in the methodology. The investigation of the tunnel systems showed a great diversity, e.g., in tunnel and fence material, their position in relation to the road, and connections between them. For economical reasons concrete tunnels were the most common. Both circular and square cross-section tunnels were in place. The accessibility of the entrance was a possible problem, especially in areas where erosion is considerable. Plastic mesh and concrete fences were both applied with a height fl uctuating between 45 and 70cm. Plastic fences are usually fi xed to wooden poles, which need to be checked before the migration period starts. However, the advantage of such fencing is fl exibility, which makes possible, e.g., the turning back of its ends to prevent amphibians from getting on the road. Some systems did not work because certain elements (usually fences) were in bad condition. Elsewhere lack of maintenance reduced the effi ciency of mitigation measures. Missing elements should be replaced immediately, even if the amphibian migration period is over, because other animals, e.g., small mammals, also use these systems. The lowest distance between tunnels in amphibian mitigation systems is 40m in the region (Kudowa Zdrój, Poland). Usually, amphibian tunnels were placed 50-100m from each other, which is an acceptable distance. In case of adequate fencing, game passages and game bridges would also be appropriate for the crossing of amphibians as well as reptiles and small mammals, similar to slightly modifi ed existing culverts under high road mortality sections, and there would be a need for such conservation improvements at several sites. As a result of this work, several recommendations on the maintenance of amphibian tunnels and fences were also developed. Further cooperation among different agencies and organisations was urged, nationally as well as internationally. The improvement of public relation activities on fauna passages also seems to be needed for the effective protection of wildlife on roads.

Environmental Policy and Management (1)
Tahoe Research Group/Tahoe Environmental Research Center Publications (19)


The New York State Department of Transportation operates and maintains approximately 16,500 miles of highway that occupies approximately 1 percent of the state’s land area. Due to the tendency of the highway system to follow streams, coastlines and other natural landscape features, this 1% of land is located within, over and adjacent to many very sensitive and important environmental areas. Considering that NYSDOT, like most transportation departments, is now shifting its efforts more and more towards improving, operating and maintaining the existing transportation infrastructure, as opposed to building large-scale new alignment projects, the role of incorporating environmental improvements into maintenance and operational programs is increasing in importance. The project objective was to Proactively reach out to internal and external partners to identify priorities anddevelop multi-agency strategies and projects that improve environmental conditions along NYSDOT’s rights-of-way and roadsides. The approach required thorough internal teamwork involving many regional groups and external partnering with resource agencies and environmental organizations in order identify, develop and coordinate prioritized environmental stewardship projects. These “best practices” are then implemented during highway maintenance activities. NYSDOT has 11 regional offices with each region having a Landscape Architecture/Environmental Services unit located within the Regional Design Group. Although, located within the Design Group, these Units provide environmental services to all regional groups - including maintenance. In addition, in 2001, a senior environmental specialist (a.k.a. maintenance environmental coordinator or MEC) was assigned to each regional maintenance group to supplement existing programs by dedicating full-time effort coordinating environmental issues in the maintenance group. One aspect of this effort has been a focus on incorporating environmental right-of-way and roadside “Best Practices” into regional maintenance programs. Critical elements of this strategy include fostering internal teamwork within the region and developing partnerships with external groups. By using internal knowledge and resources and external expertise and assistance, the Department’s organizational strengths can be efficiently and effectively managed to expand right-of-way roadside environmental stewardship programs. Examples of 2002 “best practices” to be discussed include: (1.) control methods for invasive plants; (2.) installation of water level control structures at chronic nuisance beaver locations; (3.) installation of water quality improvement structures near drinking water supplies; (4.) turtle mortality abatement efforts; (5.) alternative mowing strategies to enhance grassland songbird nesting habitat; (6.) establishment of living snow fences; (7.) osprey nesting enhancements; (8.) methods to reduce deer vehicle collisions; (9.) migratory bird protection on bridges; (10.) herbicide education programs; and (11.) small petroleum spill abatement measures. These strategies and Best Practices are applicable to any national, provincial, state or local transportation department with an interest in incorporating environmental improvements into daily maintenance activities.


Congress is in the process of reauthorizing TEA-21, the six-year, $300 billion transportation bill, providing an excellent opportunity to integrate many of the ideals brought forth in ICOET into transportation policy. With appropriate federal guidance, such best practices in the areas of wildlife, fisheries, wetlands, water quality, and overall ecosystems management could become the standard. Likewise, without support within the new bill, many states and practitioners will find it more difficult to continue making positive strides in stewardship and resource protection. Reauthorization issues that promise to be of interest to ICOET participants include: 1. Environmental streamlining 2. Transportation enhancements 3. Impact mitigation 4. Congestion Mitigation and Air Quality (CMAQ) 5. Continuation of University Transportation Centers (UTC) 6. Cooperative Environmental Research Program (CERP) 7. Habitat connectivity across transportation corridors (aquatic and terrestrial) 8. Transportation on Federal lands 9. Landscape level transportation planning

ENVIRONMENTAL PLANNING IN FLORIDA Florida’s ETDM Process: Efficient Transportation Decision Making While Protecting the Environment

The Florida Department of Transportation has developed a completely new process for how the State of Florida plans transportation projects and accomplishes environmental review and consideration of sociocultural effects. The new process for transportation decision making was developed by FDOT working in conjunction with federal and state agencies to develop an entirely new process that efficiently meets statutory requirements and delivers projects which respect and protect Florida’s resources. The new process is called “Efficient Transportation Decision Making” or the ETDM Process. The objectives of the multi-agency working group that developed this process were outlined by Congress in Section 1309 of the Transportation Equity Act for the 21st Century (TEA-21): • Provide early and continuous involvement of agencies and the public in the review process. • Integrate environmental review and permitting processes. • Establish coordinated time schedules for agency action. • Establish effective dispute resolution mechanisms. • Provide access to information through use of technology. FDOT assembled 23 federal and state agencies at the initial “summit” in February 2000 to ask for their support and commitment to develop this process. Summit participants developed a “vision statement” for the new process. Their agencies then participated in a series of multi-agency meetings to identify the elements of a process that would improve efficiency (early involvement, easy access to good data, continuous agency and community involvement, teamwork, a method to screen projects early, and an effective method for handling disputes). Early agency involvement is provided through two “screening” events, which occur early in project planning and before significant engineering work proceeds. These events are the “Planning Screen” and the “Programming Screen.” Agency input received early in planning may identify the need for wildlife crossings, community-expressed concerns or other needs for reconfiguration of a project to avoid or minimize adverse effects. This early awareness improves the project cost estimates, which can affect project priorities. Coordination is achieved through Environmental Technical Advisory Teams (ETATs) which are formed for each of the seven FDOT districts. ETAT members review project information and provide input about technical scopes of work required for project development. These focused scopes of work are expected to improve the quality of information considered and will allow the FDOT to address key issues of concern. All coordination is achieved using the Environmental Screening Tool (EST). This is an Internet-accessible interactive database system with GIS which allows ETAT members and the public to view project plans and the effects on resources. Stakeholder input is documented in the EST and visible to all parties involved in transportation decision making. The EST is described more fully in a companion paper. A key provision in the ETDM Process is that disputed projects do not advance to the FDOT Work Program until dispute resolution has occurred. A methodology for resolving disputes is built into the new process and focuses problem resolution at the local level where consultation among ETAT members is expected to resolve most disputes prior to elevation within agencies.

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