"Ecosystem recovery" will occur after an oil spill but understanding when an ecosystem has recovered sufficiently has serious gaps of knowledge.  There are no papers that deal with ecosystem recovery after an oil spill in the high Arctic and only a few experimental studies in the Arctic that provide limited information to evaluate an oil spill (e.g. BIOS experiments). The studies in Prince William Sound intertidal rocky/cobble substrates suggest that there are ongoing ‘lingering’ effects of the Exxon Valdez spill that occurred more than 20 years ago while other assessment indicate the functional aspects have recovered.  These weaknesses highlight the need for a fundamental understanding of ecosystems with a focus on oil toxicity studies at the population and community/ecosystem level.  The review of ecosystem recovery in the Arctic described by the authors in this section led to suggestions of further research which can reduce remaining uncertainties.  The more generic suggestions compiled from this review are summarized below while recommendations that are important for improving Arctic NEBA are listed separately.

1. Ecosystem recovery.  New effort needs to focus on appropriate information collected throughout the Arctic and sub-arctic for decades as well as experimental studies to demonstrate rates of recovery under controlled conditions.  Expand on the conceptual basis of this section to develop an assessment of the physical and chemical attributes that influence environmental compartment resiliency and ultimately, recovery potential.
2. Utilize baseline studies.  Environmental baseline studies are conducted at exploration/production sites.  Collect, review, coordinate consistency among biological data sets, and archive the validated information on communities of organisms living in different environmental compartments.  Establish baseline conditions throughout the Arctic regions anticipated to undergo oil exploration in order to provide the natural range in those characteristics so that the state of recovery can be evaluated.
   1. Population parameters to be collated or obtained include: overall population estimates for the species abundance, variations in daily mortality rate coefficients, fecundity measures, age structure of populations, frequency of spawning, local broadcast larval distribution, and regions of special biological significance for key species.
   2. These population characteristics for each species need to be placed into a species resiliency database to provide more accurate estimates of the ability for a species to recover from a stressor. 
   3. The effects of non-dispersed oil on organisms utilizing the sea surface such as seabirds and marine mammals, as well as intertidal and shallow subtidal communities are subjects needing further study.  These investigations need to include impacts due to physical fouling and an examination of toxicity caused by various modes of action.

The recommendations presented below indicate where increased knowledge of oil transport and fate processes would result in reducing existing uncertainties in NEBA assessments.  No prioritization has been made to the list; for some of the recommendations, surrogate data may be already available.

1. Continue ecosystem-level investigations.  Conduct mesocosm experiments that focus on biological interactions of several ecosystem elements instead of single species responses, such as the BIOS experiments.
2. Compile data on resiliency metrics of VECs and ECs.  Assign semi-quantitative score to species/populations that are considered VECs to Arctic ECs. 
3. Provide a GIS mapping of seasonal and spatial VEC population use of EC and their resiliency scores.
   1. Recovery potentials
   2. Vulnerabilities
   3. Seasonal weathering/biodegradation and toxicity of OSR residuals
4. Introduce recovery metrics.  How much change is beyond natural variation?  What ecosystem-level attributes should be assessed?  Develop exemplary scenarios.  Implement full-scale ecosystem consequence analysis.