Risk assessments of future changes to ecosystem dynamics and risk of tipping points

 First, the approach semi-quantitatively scored the “Likelihood” of a significant change happening in three Essential Ocean Variables (EOVs) by 2070. This was based on forecasts for all 12 iAtlantic study regions and included Atlantic Meridional Overturning Circulation (AMOC) strength, conservative seawater temperature (T), and absolute salinity (S). Second, the approach semi-quantitatively scored the “Consequences” of those changes for the ecosystem compartments studied in Deliverable 3.2. After careful integration across defined water masses and EOVs, a combined score for each study region was obtained. Higher scores indicated more confidence that forecasted changes would bring about ecosystem changes by 2070.

Summary Assessment Reports were produced for each study region. These overwhelmingly showed high confidence that future sea temperatures are going to have consequences for the ecosystem compartments that we studied. Moderate to high scores due to temperature change alone were identified in 9 out of 12 study regions. When averaged across all 3 EOVs, we have the highest confidence that the ecosystems we studied around Iceland (capelin, groundfish including monkfish, humpbacks) and in the Malvinas Current (cold-water coral mounds, billfish, tuna, and pelagic sharks) are going to change by 2070. We do not imply whether an ecosystem change leads to positive or negative outcomes, just that the delivery of ecosystem services arising from those ecosystem compartments is likely to change, which should put managers and their authorities on alert. For study regions and ecosystems where we were less confident about ecosystem change, our approach presents a simple integrated assessment framework to update these scores once more ecosystem time series are added or new analyses of their drivers of change become available.

Our semi-quantitative assessments provided the opportunity for managers to reflect on how to integrate ecosystem changes into their own decision-making powers at local, regional and international levels through a series of recommendations:

• Ramp up investments in monitoring and mitigating change in certain regions, especially at high latitudes where we are confident that multiple ecosystem compartments will change by 2070;
• Ensure adequate investment and resourcing to collect and share ocean observations across the Atlantic, particularly in Study Regions where ocean temperatures are likely to warm and where a marine “tropicalisation” has already been apparent the last two decades;
• Build and maintain public-private partnerships, industry collaborations, and data-sharing mechanisms across diverse knowledge systems to enable similar or repeat assessments;
• Deliver on commitments to slow the pace of global climate change, and use a portfolio of ABMTs to increase resilience.

Caveats and uncertainties in both oceanographic and ecosystems inputs to iAtlantic’s semi-quantitative assessments were reported in Deliverables 1.2 and 3.2, but the present assessment still provides decision-makers with a better place-based understanding of whether future oceanographic conditions could alter living marine resources important to the Atlantic socioeconomy. Should human activities continue at current rates and blue growth be permitted in regions scored at “High confidence” then impacts of additional human activities could further compound these changes and push or ‘tip’ ecosystems into alternate states or regimes that may be less desirable. To avoid this, managers and their authorities need to develop policies to ensure effective monitoring and mitigation measures can be implemented to maintain ecosystem function.