Detecting resilience loss in ecosystems



Juan C. Rocha

slides: juanrocha.se/presentations/IAS_resilience_loss

Outline

  1. Jargon check: resilience & regime shifts [5]

  2. Detecting resilience loss in global ecosystems [20]

  3. How people behave when confronted with thresholds? [15]

resilience | rɪˈzɪlɪəns | (also resiliency)


noun [mass noun]

1 the capacity to recover quickly from difficulties; toughness: the often remarkable resilience of so many British institutions.
2 the ability of a substance or object to spring back into shape; elasticity: nylon is excellent in wearability, abrasion resistance and resilience.

The Oxford Dictionary

Resilience

The capacity of any system to absorb disturbance and reorganise while undergoing change so as to still retain essentially the same function, structure, feedbacks, and therefore identity

Folke, C. 2016. “Resilience (Republished).” Ecology and Society doi:10.5751/ES-09088-210444.

Resilience

  • Henri Poincaré discovered bifurcations in 1886
  • Bifucations (non-linear dynamics) are foundational to studies across natural, social sciences and humanities.
    E.g poverty traps, segregation, evolution of cooperation, cancer, language, finance, climate, the states of matter, among many others.
  • In 1960-70s ecology: related to the meaning of stability and catastrophe theory
    (Lewontin, MacArthur, Holling, Ludwig, Walters, Noy-Meir, May)

Forest to savanna

Regime shifts are large, abrupt and persistence critical transitions in the function and structure of (eco)systems

Coral transitions

Regime shifts are large, abrupt and persistence critical transitions in the function and structure of (eco)systems

Fisheries collapse

Regime shifts are large, abrupt and persistence critical transitions in the function and structure of (eco)systems

Regime shifts and resilience

Scheffer at al 2001 Nature

Why are regime shifts important?

RS

Where are regime shifts likely to happen?

Detecting resilience loss in ecosystems

Resilience indicators

Scheffer et al. 2009. Nature

Critical slowing down


Verbesselt J, et al. Remotely sensed resilience of tropical forests. 2016.

Limitations: fail when dynamics are driven by stochastic processes or when signals have too much noise

Hastings & Wysham. 2010. Ecology Letters

Resilience indicators

Resilience indicators

West, Geoffrey. 2017. Scale

Data

Earth System DataLab

  • Terrestrial:
    • Gross primary productivity (2001:2018)
    • Ecosystem respiration (2001:2018)
    • Leaf area index (1994:2017)
  • Marine:
    • Chlorophyll A (1998:2018)

Analysis: one pixel



Muggeo VMR. Estimating regression models with unknown break-points. Stat Med. 2003;22(19):3055–71.

Gross primary productivity Terrestrial ecosystem respiration

Gross primary productivity

~30% of ecosystem show symptoms of resilience loss, boreal forest and tundra particularly strong signals

Terrestrial ecosystem respiration

~30% of ecosystem show symptoms of resilience loss, boreal forest and tundra particularly strong signals

Chlorophyll A

~25% of ecosystem show symptoms of resilience loss, Indo-Pacific oceans particularly strong signals

Break points not only cluster in space, also in time!

Next steps


How do people behave when confronted with situations pervaded by thresholds?

  • Regime shifts in marine environments
    • Fisheries collapse
    • Mangroves collapse
    • Coral transitions
    • Coastal eutrophication
    • Hypoxia
  • Potential impacts on society
    • ~50M people depend on small-scale fisheries
    • Mostly in developing countries

Method: Framed field experiment

History of regime shifts

  • 256 fishers groups of 4 players
  • Communication allowed
  • Threshod: 100% probability of climate event
  • Risk: 50% probability
  • Uncertainty: 10-90% probability

Treatment effects

  • Individual extraction: \[x_{i,t}\]

  • Proportion of extraction: \[x_{i,t}/S_t\]

  • Cooperation: \[C_{i,t} = \frac{x_{i,t}}{\frac{S_t - \theta}{N}}\]

  • Diff-in-diff regression: \[\hat{Y_i} = \hat{\mu} + \hat{\gamma}G_i + \hat{\delta}T_i + \hat{\tau}G_iT_i\]

It’s harder to coordinate under treatments, but agreements increase the probability to coordinate and react to lower stock sizes by reducing fishing preasure. Agreements also reduce the variance of extraction and the variance of cooperation. Changes in fishing effort depends on treatments while changes in cooperation depends on context.

Lessons

  • Fishermen facing thresholds fish less – they take care of the resources
  • By reducing fishing effort or keeping close to the social optimal people do cooperate. However, cooperation by itself is not affected by our treatments, it seems to be driven more by personal and group dynamics.
  • If the existence of threshold effects already triggers cooperative behavior in natural resource users, then communicating their potential effects on ecosystems and society is more important that quantifying the precise point at which ecosystems tip over. Specially because such thresholds are hard to observe, measure, and they change over time.

Conclusions

  1. Ecosystems around the world are showing symptoms of resilience loss
    Up to ~30% as proportion of area

  2. Boreal forest and tundra showing particularly strong early warning signals

  3. While elusive, resilience can be approximated from data
    Critical slowing down | slow forcing: basin wider and less depth
    Critical speeding up | stochastic forcing: basin narrows
    Fractal dimension | loss of adaptive capacity

  4. When facing thresholds, cooperation does not necessarily breaks down
    Rocha et al 2020. PlosONE

Tack | Gracias

Questions?


email: juan.rocha@su.se
twitter: @juanrocha
slides: juanrocha.se/presentations/IAS_resilience_loss
preprint: coming soon!

Stockholm Resilience Centre
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