Ecosystems on the Edge: the science and management of ocean tipping points (Part 1)

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The Ocean Tipping Points project is a collaboration of natural and social scientists, lawyers, environmental managers, and stakeholders working to understand what drives abrupt ecological shifts, and how they might be prevented or reversed. In this initial blog, we introduce the concept of tipping points and highlight our latest research. In upcoming blogs, some of our researchers will present their work in more detail and discuss the implications for our case study regions and for the science and management community more widely.

Reaching a tipping point

Sea otters were once a common sight in kelp forests along vast expanses of the west coast of North America, until fur traders decimated nearly every otter population in the 1800s.  Without otters, the kelp forests began to disappear. Sea urchin populations exploded in the absence of their main predators—otters—and started grazing down the kelp forests, creating a patchwork of ‘urchin barrens’ where kelp forests were once prolific. Without the complex habitat provided by kelp, numerous marine species, including commercially important fish, can lose their main source of food and shelter.

These kelp forests underwent a dramatic shift, from a productive system with high biodiversity to a much simpler system dominated by a single species.  Beyond certain environmental thresholds, ecosystems like these can suddenly reach a ‘tipping point’ where they shift to an entirely different type of ecosystem, with different ecosystem functions and services, and often a different distribution of benefits to people. In some cases the shift results in a net loss to society, in other cases, there may be new winners and losers as a result of the shift. Shellfish fishermen, for example, may prefer the urchin barren state because it supports a valuable urchin fishery, while conservationists and those who depend on recreation and tourism industries may prefer the kelp forest state.

New research on tipping points science and management

Understanding which environmental changes lead to tipping points, how to mitigate them, and what diverse stakeholders value from the system will be key to maintaining or restoring healthy ecosystems. Three studies by Ocean Tipping Points researchers, published in the Nov. 24 special issue of Philosophical Transactions of the Royal Society—Biological Science, hold the promise of helping resource managers predict, avoid, and reverse the tipping points that lead to degraded habitats, economic losses, and social upheaval. The special issue, entitled “Marine regime shifts around the globe: theory, drivers, and impacts”, highlights 18 studies that explore the science behind ecosystem shifts, and how they can be managed.

Proactively identifying a tipping point before it is too late is not an easy task—marine and coastal ecosystems are highly complex with many interacting factors at play under the water and at the surface: nutrient cycles, climate patterns, species interactions, human pressures, and more. However, the benefit of identifying potential tipping points can provide a huge payoff if managers can respond by changing course or adapting before the environment tips into a less desirable state. Understanding what pressures can drive ecosystems over thresholds and what processes may keep certain ecosystems in tipped states can also provide insight into how to restore ecosystems back to desired states.

Scientists from Stanford University’s Center for Ocean Solutions and Environmental Defense Fund teamed up in the first study to evaluate case studies involving ecological tipping points across the globe. They found that successful management of threshold-based ecosystems depends strongly on three key factors: frequent monitoring of important environmental variables, explicit incorporation of threshold data into management actions, and managing at small geographic scales. This last factor suggests that smaller systems of approximately 6,500 mi2 (17,000 km2) or less are easier to understand, monitor, and manage at local scales.

The second study, authored by researchers from NOAA and the University of Hamburg, provides additional guidance for marine managers on how to incorporate the risk of reaching a tipping point into current ecosystem-based management frameworks. The authors demonstrate how to adapt NOAA’s widely used Integrated Ecosystem Assessment (IEA) framework for marine ecosystems where tipping points are a concern. This risk-analysis based approach helps managers determine the likelihood that an ecosystem will cross a threshold, and what the resulting socio-economic and environmental impacts might be.

In the third study, researchers from the Center for Ocean Solutions, Stockholm Resilience Center, University of Hawaii, NOAA, and the Scripps Institute of Oceanography used a comprehensive spatial dataset to identify three distinct regimes of Hawaiian Archipelago reef ecosystems: hard corals, turf algae, or macroalgae. Though some algal cover is natural in the Hawaiian Archipelago, algae-dominated reefs are often the degraded remains of once-diverse coral communities. More than half of Hawai`i’s reefs are currently in the algae-dominated regimes, thanks to multiple stressors including overfishing and nutrient pollution.

Photo credit: Laura R. CC BY-NC 2.0.

The resulting loss of coral habitat impacts biodiversity, the chance of survival for fish and invertebrates, and the way humans interact with the coastal environment—from subsistence and commercial fishing to tourism and recreation. Knowing how close a coral reef is to a tipping point could help prevent unwanted changes that affect livelihoods and result in higher management costs.

Ocean tipping points into the future

Equipped with foundational knowledge about the science and management of tipping points globally, Ocean Tipping Points researchers are currently developing two case studies with partners in Haida Gwaii, British Columbia and the Hawaiian Islands, to explore the causes and consequences of tipping points using a place-based approach. Project researchers are working with managers and community representatives on the ground to characterize past ecosystem shifts, look for early warning indicators of those shifts that could be used in monitoring, and develop practical tools and approaches for applying this knowledge in future management decisions to prevent additional ecosystem shifts or to restore degraded conditions.

In this blog series, members of the Ocean Tipping Points team will introduce their research in more detail, and discuss some of the preliminary results that are already impacting how scientists and managers frame marine management decisions. We look forward to sharing our work with you and catalyzing a wider conversation about how we can continue to improve ocean management in the face of ecosystem complexity and natural and human-driven environmental change.