Tipping points in ecosystem structure, function and services

Fieldwork at a Tipping points workshop

Tipping points are a rapid transformation that happens when an ecosystem loses its capacity to cope with change. To understand how they manifest in New Zealand waters, we are doing the first national marine experiment in estuaries, harbours and rocky reefs, to identify tipping points, risks and how systems respond to change.

Project leader: Simon Thrush, University of Auckland

What causes tipping points?

We are investigating how ecosystems respond to change, especially the insidious effects of multiple stressors and cumulative impacts that can lead to a ‘tipping point’. Tipping points are a rapid transformation that happens when an ecosystem loses its capacity to cope with change. They usually involve the loss of valuable resources such as fish and biodiversity, or ecosystem services such as protection from coastal erosion.

Within seafloor sediments, shellfish interact with microbes, sediments and water flow to affect primary productivity, water clarity and the risk of eutrophication (excessive nutrients) in harbours. These animals are the heart of hidden infrastructure supporting many ecosystem services. They help process waste – but only up to a limit, and that limit is affected by many factors, such as climate change, ocean acidification, fishing pressure, sedimentation, nutrient runoff, and pollution. Without a better understanding of how these processes work and respond to change, we risk losing these services.

We are doing the first national marine experiment, in estuaries, harbours and rocky reefs from Northland to Southland, to identify tipping points, risks, and how systems respond to change.

We are also working with other Challenge projects to design tests for current management approaches, to reduce the risk of reaching tipping points and mitigating adverse effects. Understanding the capacity of our marine ecosystems to adapt, and the nature of changes that are happening, are essential for EBM and sustainability.

Tipping points happen when subtle but cumulative effects suddenly and drastically alter the way an ecosystem functions, and its ability to cope with changing conditions. They are almost always negative – for example the loss of environmental resources such as biodiversity and kai moana, or ecosystem services such as water purification.

Presentation to the NZ Coastal Society Conference about tipping points in NZ coastal ecosystems


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