Step 5: Identifying probable causes

2 What’s going on at Pretend Creek? TYPE OF EVIDENCE↑ metals↑ temp↓ DO Data from the case Spatial co-occurrenceYESNO Stressor-response relationships from the field YES (Zn) ? (Cu) Causal pathwayYES Manipulation of exposureYES Data from elsewhere Stressor-response relationships from other field sites YES

3 Define the Case List Candidate Causes Evaluate Data from the Case Detect or Suspect Biological Impairment As Necessary: Acquire Data and Iterate Process Identify and Apportion Sources Management Action: Eliminate or Control Sources, Monitor Results Biological Condition Restored or Protected Decision-maker and Stakeholder Involvement Stressor Identification Step 5: Identify Probable Cause Evaluate Data from Elsewhere

4 How we identify probable causes Eliminate when you can Diagnose when you can Otherwise, analyze strength of evidence Apply a scoring system to the available evidence under each type of evidence HOW?

5 The scoring system R refutes D diagnoses +++convincingly supports (or weakens - - -) ++strongly supports (or weakens - -) + somewhat supports (or weakens - ) 0 neither supports nor weakens NEno evidence

6 Scoring of spatial/temporal co-occurrence + The effect occurs where or when the candidate cause occurs, OR the effect does not occur where or when the candidate cause does not occur. 0 It is uncertain whether the candidate cause and the effect co-occur The effect does not occur where or when the candidate cause occurs, OR the effect occurs where or when the candidate cause does not occur. R The effect does not occur where or when the candidate cause occurs, OR the effect occurs where or when the candidate cause does not occur, AND the evidence is indisputable.

7 +++ Laboratory tests with site media show clear biological effects that are closely related to the observed impairment. + Laboratory tests with site media show ambiguous effects, OR clear effects that are not closely related to the observed impairment. 0Laboratory tests with site media show uncertain effects. - Laboratory tests with site media show no toxic effects that can be related to the observed impairment. Scoring of laboratory tests of site media

8 Scoring of stressor-response from other field studies ++ The stressor-response relationship in the case agrees quantitatively with stressor-response relationships from other field studies. + The stressor-response relationship in the case agrees qualitatively with stressor-response relationships from other field studies. 0 Agreement between the stressor-response relationship in the case and stressor-response relationships from other field studies is ambiguous. - The stressor-response relationship in the case does not agree with stressor-response relationships from other field studies. -- There are large quantitative differences or clear qualitative differences between the stressor-response relationship in the case and the stressor-response relationships from other field studies.

9 Willimantic case study MetalsNH 3 FlowSilt Low DO TempFood Episodic Mix Types of Evidence that Use Data from the Case Spatial/Temporal Co-Occurrence Evidence of Biological Mechanism Causal Pathway Stressor-Response from the Field Manipulation of Exposure Verified Predictions Types of Evidence that Use Data from Elsewhere Stressor-Response from Other Field - + Stressor-Response from Laboratory Example: strength of evidence analysis

10 Weighing the evidence for each candidate cause Evaluate the quantity & quality of evidence Evaluate consistency & credibility Summarize the compelling evidence

11 Evaluate quantity & quality of evidence Quality & quantity of data influence scores Lots of consistent evidence reduces quality concerns for any 1 type of evidence Poor quality data may be discounted Consider study designs, methods, relevance, variability, & other QA issues

12 Evaluate consistency & credibility Prepare summary table of scores Do not add up scores! Evaluate consistency of evidence Look for compelling evidence If evidence is inconsistent, consider mechanistic explanations – e.g., lab data not consistent with field conditions due to differing bioavailability

13 Scoring consistency & credibility Consistency of Evidence All available types of evidence support the case for the candidate cause All available types of evidence weaken the case for the candidate cause All available types of evidence support the case for the candidate cause, but few types are available. + All available types of evidence weaken the case for the candidate cause, but few types are available. - The evidence is ambiguous or inadequate.0 Some available types of evidence support and some weaken the case for the candidate cause. - Explanation of the Evidence There is a credible explanation for any negative inconsistencies or ambiguities in an otherwise positive body of evidence that could make the body of evidence consistently supporting. + There is no explanation for the inconsistencies or ambiguities in the evidence. 0 There is a credible explanation for any positive inconsistencies or ambiguities in an otherwise negative body of evidence that could make the body of evidence consistently weakening. -

14 Willimantic case study MetalsNH 3 FlowSiltLow DO TempFoodEpisodic Mix Types of Evidence that Use Data from the Case Spatial/Temporal Co-Occurrence Evidence of Biological Mechanism Causal Pathway Stressor-Response from the Field Manipulation of Exposure Verified Predictions Types of Evidence that Use Data from Elsewhere Stressor-Response from Other Field - + Stressor-Response from Laboratory Evaluating Multiple Types of Evidence Consistency of Evidence

15 Summarize compelling evidence Make an overall evaluation of strength of evidence for each candidate cause – what evidence compels belief that candidate cause induced effect? – what evidence strongly casts doubt? Consider the principle characteristics of causal relationships – these are what you’re trying to show – they summarize the 15 types of evidence

16 There is no magic formula… All candidate causes must be compared to determine: – if there is more than 1 probable cause – your level of confidence in the results

17 Comparing evidence among causes: best-case scenario You have compelling evidence for 1 candidate cause; others are weak or refuted... TYPE OF EVIDENCE CANDIDATE CAUSE 123 A++-R B+-- C+- Consistency+- …celebrate, then remediate for Candidate Cause 1

18 Comparing evidence among causes: more (likely) scenarios You have uneven evidence across candidate causes... TYPE OF EVIDENCE CANDIDATE CAUSE 123 A++– B+– C++ Consistency+ – Strong evidence for one candidate cause may be sufficient Consider if weakness is due to lack of data – and try to fill holes

19 You have unsatisfying evidence across all candidate causes… TYPE OF EVIDENCE CANDIDATE CAUSE 123 A+– B–– C+ Consistency– – – Reconsider the impairment Consider additional candidate causes Consider episodic events Consider gathering more data

20 You have evidence suggesting multiple causes… TYPE OF EVIDENCE CANDIDATE CAUSE 123 A+++ + B+ + C + Consistency+ + + Consider disaggregating indices or metrics Combine causes if they share causal pathways, modes of action, sources and routes of exposure, or if they interact Remediate dominant cause Design remediation to address multiple causes

21 You have insufficient data… TYPE OF EVIDENCE CANDIDATE CAUSE 123 ANE – B+ C Consistency000 Gather data if possible Consider other bases for remediation (e.g., BMPs, chemical criteria) and monitor biological responses Use professional judgment as last resort

22 Next: let’s try it out! Scoring the evidence exercise

23 What’s going on at Pretend Creek? TYPE OF EVIDENCE↑ metals↑ temp↓ DO Spatial co-occurrenceNE Stressor-response relationships from the field (data from case) NE Stressor-response relationships from other field sites (data from elsewhere) NE Causal pathwayNE Manipulation of exposureNE Consistency of evidence Explanation of evidence

24 Things to keep in mind when scoring… Be consistent across candidate causes Don’t double-count data Think about the quality & quantity of the data you’re using Document your thought process

25 How do I communicate results? Make your logic clear Present the critical evidence Reveal uncertainties Fit communication to your audience For technical reviewers, include text & tables For decision makers, may be helpful to use annotated conceptual model

26 Using models for communication: Pretend Creek ↓ dissolved oxygen ↑ metals↑ temperature ↓ EPT richness urbanization industrial facility damsubdivisiondairy farm

27 Using models for communication: Pretend Creek ↓ dissolved oxygen ↑ metals↑ temperature ↓ EPT richness urbanization industrial facility damsubdivisiondairy farm DO higher at impaired site vs. reference

28 Using models for communication: Pretend Creek ↓ dissolved oxygen ↑ metals ↑ temperature ↓ EPT richness urbanization industrial facility damsubdivisiondairy farm after rerouting industrial discharge had decreased metal concentrations & increased EPT taxa richness DO higher at impaired site vs. reference

29 Using models for communication: Pretend Creek ↓ dissolved oxygen ↑ metals ↑ temperature ↓ EPT richness urbanization industrial facility damsubdivisiondairy farm after rerouting industrial discharge had decreased metal concentrations & increased EPT taxa richness DO higher at impaired site vs. reference temperature higher at impaired site vs. reference; negatively correlated with EPT taxa richness

30 What comes after causal analysis? If confidence in results is low… – plan studies to obtain critical evidence – experimental studies most likely to be convincing If confidence in results is high… – identify sources – take action – monitor results

31 Example: fish kills in Virginia & West Virginia 1. Low dissolved oxygen in water 2. Gill damage from ammonia, high pH, or other mechanism prevents uptake of oxygen 3. Altered blood chemistry from nitrite exposure prevents fish from using oxygen 4. Viral, bacterial, parasitic, or fungal infections 5. Mortality from high pH 6. Mortality from pH fluctuations 7. Mortality from ammonia toxicity 8. Toxicity of unspecified substances 9. Starvation due to inadequate food resources Causal analysis resulted in: Narrowed list of candidate causes List of priority data needs There was no “smoking fish”…