Barotrauma injury has historically been a concern for fish exposed to underwater explosions and passage through hydroturbines. Recently this concern has been extended to include underwater sound generated by pile driving, particularly that generated during impact driving of larger-diameter steel casing. Description of the characteristics of sound impulses generated by impact pile driving that are a threat to fish is lacking and current protective criteria that rely on simple peak overpressure do not have a clear scientific basis and appear too restrictive. This paper considers the mechanisms for barotrauma injury to both physostomous and physoclistous fish as a function of acclimation depth and the criteria developed for protection of fish from barotrauma pressures generated by explosions and passage through hydroturbines. These mechanisms and criteria are discussed within the context of observations of impact pile driving generated pressure time histories and observations of barotrauma injury to fish made during pile driving projects on the West Coast of the United States. Also considered are the results of recent sound-mitigation efforts, including driving of steel casing pile in the dry, the use of both confined and unconfined bubble curtains, and the success of these mitigation efforts as measured by comparison with fish-protection criteria.

The targeted application of prescribed fire has long been used by Native Californian peoples to manage plant resources of cultural value. Their ability to employ this management tool has been increasingly restricted by local, state and federal agencies in response to recent drought conditions and the highly flammable state of most western U.S. forests, where, for decades, fires of any magnitude have been suppressed as a matter of policy. This diminished access to cultural prescribed fire has impacted tribal access to many of the plant resources and cultural activities upon which Karuk and Yurok cultures are based. The research presented in this dissertation: 1) uses historical and modern references to describe fire management practices of tribes throughout California, specifically targeting acorns as food resource, 2) investigates the effect of non-traditional spring burns on rates of tanoak (Notholithocarpus densiflorus, Fagaceae) acorn infestation by frugivorous Filbertworms (Cydia latiferreana, Tortricidae) and Filbert weevil larvae (Curculio occidentalis, Curculionidae), 3) evaluates the effectiveness of indigenous acorn collection criteria in correctly assessing the consumption quality of acorns, and 4) examines the responses of culturally significant plant species found in tanoak gathering areas to prescribed fire applied non-traditionally in spring. Assessed metrics were species diversity, species richness, and vegetative cover.

Traditionally, fires used to maintain productive heritage tanoak stands were set in late summer and fall. However, prescribed burns at this time of year have become very difficult to implement, so this study focused on the responses of the assemblages to a more easily executed, spring burn. During the two year study of acorn infestation rates in response to fire, I found that spring prescribed fire reduced acorn infestation in both the year of the fire and one year post-fire. Indigenous acorn collection criteria were very effective in distinguishing edible acorns from both inedible and insect-infested acorns. However, the traditional method of acorn evaluation did misclassify a sizeable proportion of the acorns as inedible, when they were actually of good food quality. Intended or not, this conservative misidentification provides added insurance that insect-infected acorns are not added to those stored within a household for future use. Over the three years that the responses of culturally valuable understory taxa to fire were monitored, all three metrics (species diversity, species richness, and vegetative cover) were sharply reduced by fire. Species diversity and richness showed substantial recovery by the second post-fire year, but neither had fully recovered. Understory plant cover showed very little, in any, recovery two years after the experimental fires. In particular, the percent cover of tanoak seedlings and lignotuber sprouts were greatly reduced, which may increase visibility of abscised acorns to tribal gatherers. As a single cultural fire targets multiple resource goals, these results indicate that some, but not all, resource goals traditionally achieved with fall fire were met with spring prescribed fire.

Significance

Foraged leafy greens are consumed around the globe, including in urban areas, and may play a larger role when food is scarce or expensive. It is thus important to assess the safety and nutritional value of wild greens foraged in urban environments.

Methods

Field observations, soil tests, and nutritional and toxicology tests on plant tissue were conducted for three sites, each roughly 9 square blocks, in disadvantaged neighborhoods in the East San Francisco Bay Area in 2014–2015. The sites included mixed-use areas and areas with high vehicle traffic.

Results

Edible wild greens were abundant, even during record droughts. Soil at some survey sites had elevated concentrations of lead and cadmium, but tissue tests suggest that rinsed greens of the tested species are safe to eat. Daily consumption of standard servings comprise less than the EPA reference doses of lead, cadmium, and other heavy metals. Pesticides, glyphosate, and PCBs were below detection limits. The nutrient density of 6 abundant species compared favorably to that of the most nutritious domesticated leafy greens.

Conclusions

Wild edible greens harvested in industrial, mixed-use, and high-traffic urban areas in the San Francisco East Bay area are abundant and highly nutritious. Even grown in soils with elevated levels of heavy metals, tested species were safe to eat after rinsing in tap water. This does not mean that all edible greens growing in contaminated soil are safe to eat—tests on more species, in more locations, and over a broader range of soil chemistry are needed to determine what is generally safe and what is not. But it does suggest that wild greens could contribute to nutrition, food security, and sustainability in urban ecosystems. Current laws, regulations, and public-health guidance that forbid or discourage foraging on public lands, including urban areas, should be revisited.