“We acted upon the western landscape with the force of a geological agent”
(Wallace Stegner)

Unnatural History: Mining

Mining

  • Hydraulic mining removes 8x as much sediment as was excavated from Panama Canal
  • First used by Edward Matteson near Nevada City, California in 1853
  • Sawyer Decision in 1884, enjoined operation in tributaries to navigable waters.

Unnatural History: Mining

Mining

  • 1893: small-scale mining recommences (Camminetti Act)
  • The legacy of ~40 years transformed the landscape permanently

Unnatural History: Mining

Landscapes Transformed

1876

1996

Malakoff Diggins State Park

Unnatural History: Mining

Failing Freshwaters

  • Half the world’s population lives within 20km of a permanent river (Small and Cohen 1999)
  • Projected mean extinction rates in freshwater organisms 5x greater than terrestrial (Ricciardi & Rasmussen 1999)

Unnatural History: Freshwaters

Flow modification

Flow Seasonality

Species life histories are finely tuned to capitalize on specialized temporal niches associated with climatic variability (Chesson 2000, Chase 2011)

  • Seasonality is measure of occurrence of distinct within-year conditions or events

  • Predictability is the regularity of recurrence annually

Unnatural History: Regulation

Functional Flows Concept

  • idea that there are aspects of a flow regime that directly link to ecological, geomorphic, or biogeochemical processes in riverine systems

  • these in turn are foundational to supporting processes that sustain biological communities

Conservation Management

Perils of Unpalatable Periphyton

  • “Rock Snot” (Didymo) is spreading in rivers with flucuating flows and cold water releases (MFA, SFY)
  • impacts tadpole growth and survival
  • impacts egg deposition sites!

Didymo periphyton limited tadpole growth

Drought & Harmful Algal B︎looms

Bouma-Gregson et al 2017
  • Climate change “whiplash” will ⬆ winter floods and drought periods, which can favor cyanobacteria proliferations
  • Water withdrawal/diversion ⬇ summer river flow and ⬆ likelihood of cyanotoxin production.

Disease

Summary

  • High variability (i.e., climate/flow) is combined with sparse density, trends may not be detectable until populations decline below critical thresholds

  • Background variation in population size and shifts in spatial distribution makes it difficult to detect effects even with years of data

  • Encroachment by riparian vegetation and trespass cultivation exacerbate local decline

  • Climate uncertainty (more extreme droughts and floods) likely to increase risk of extirpation