Unnatural History
of Foothill Yellow-Legged Frogs


Ryan Peek | 2023-05-09

Changed Landscapes

“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

CA Mines

  • Legacy remains
  • Thousands of mines / tailings in CA
  • Active panning & sluicing in many rivers


Unnatural History: Mining

And they persisted…

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

Dammed Rivers

  • Over 1,400 large dams (NID 2007)
  • CA hydropower is ~15% of energy supply (Hall 2006)
  • Residential energy demands expected to increase by 24% by 2035 (US EIA 2010)
  • Majority of dams are for irrigation (47%), water supply (23%), and hydroelectric (14%)

Unnatural History: Regulation

Flow modification

Major threat to freshwater biodiversity and is widespread in CA

Depleted
(87%)

Inflated
(81%)

No Alteration
(5%)

Zimmerman et al. 2018

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

Flow Regimes





Unregulated flow patterns have high seasonality & predictability







Regulated flow patterns disrupt predictability

Flow Predictability vs. Seasonality

Flow Predictability vs. Seasonality

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

And still…
persisted?

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 can limit oviposition surfaces!

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

Questions?