Offshore decommissioning is the comprehensive process undertaken when offshore energy platforms reach their end of productive life. This complex engineering task is essential to ensure that the surrounding marine environment is restored as closely as possible to its pre-lease condition, minimizing environmental impact and protecting ocean ecosystems and nearby communities. The process typically involves multiple stages, including project management, engineering and planning, regulatory compliance, platform preparation, well plugging and abandonment—where applicable, removal of structures such as platforms and pipelines, and site clearance.
With the majority of offshore installations constructed during the oil and gas boom now approaching the end of their lifespans, decommissioning has become a rapidly growing sector within the energy industry. The scale of the challenge is significant: With over 1,500 offshore oil and gas platforms in the North Sea alone. Globally, annual spending on decommissioning is projected to reach $13 billion within the next 25 years, reflect- ing both the technical complexity and the increasing regulatory and environmental expectations associated with these projects.
Sparking Debate
Decommissioning activities of offshore energy structures have long sparked debate on the best course of action for ocean ecosystems. Some argue that through the platform’s lifetime, the artificial habitat created carries significant value to the marine ecosystem with the potential for increasing biodiversity and fish populations. Alongside this argument, researchers have suggested there might be ecological roles that these offshore artificial structures carry that need to be considered during decommissioning assessments.
Dr. James described marine connectivity as “the movement of animals, plants, nutrients, and genetic material between patches of habitat or populations. It is essentially the roads that connect spaces and ensure our biodiversity is healthy, resilient, and persistent.”
Dr. James is a research collaborator for the Decommissioning Relative Effects of Alternative Management Strategies (DREAMS) project. As part of this endeavor, she led a study titled “The ‘everything is everywhere’ framework: Holistic network analysis as a marine spatial management tool,” which was published in Ecological Informatics and detailed how artificial structures, such as wind turbines or oil and gas platforms, could influence the connectivity and dispersal of marine species.
“While DREAMS broadly aimed to assess the environmental impacts of various decommissioning strategies, this research centered on larval dispersal and how man-made structures—whether retained, removed, or relocated—affect marine connectivity,” Dr. James shared.
The study introduces the ‘everything is everywhere’ framework, a method that combines hydrodynamic modeling, particle tracking, and graph network analysis to evaluate marine connectivity. By applying a newly developed Connectivity Importance Index (CII), the research identifies key connectivity hotspots—areas where ecological connections are strongest, providing crucial information for future sustainable marine spatial management.
Leveraging Modeling
One of the most powerful things modeling has to offer is its ability to generate data without field sampling. Unlike field-only approaches, modeling can integrate diverse datasets, simulate future conditions, and reveal emergent patterns such as ecosystem-wide connectivity. It enables scenario testing that supports better-informed policy decisions and helps us anticipate the ecological outcomes of human actions before they occur.
When discussing the methods involved in the research study, Dr. James explained, “This study was entirely computational, and as such did not use any direct in-field methods. Instead, it relied on modeled environmental data to simulate connectivity patterns. Ground-truthed and validated tools, like FVCOM (Finite Volume Community Ocean Model) and ERSEM (European Regional Seas Ecosystem Model), enabled us to explore ecological processes at scale without requiring new field observations.
“We use a suite of modeling tools that work together to simulate physical and ecological processes. For this project, we used the FVCOM hydrodynamic model to simulate ocean currents, PyLag for particle tracking to mimic larval dispersal, and ERSEM to estimate primary productivity, which helps us gauge food availability for larvae. These were combined with graph network theory to assess connectivity patterns. The data we used included oceanographic conditions, infrastructure locations, bathymetry, and biological parameters like planktonic larval duration.”
Informing the Future
When asked how modeling studies could inform future decision-making, Dr. James pointed out that “these findings offer a science-based framework for decommissioning decisions by showing which structures contribute most to connectivity and where new infrastructure could strengthen ecosystem resilience.
“Our findings show that some high-connectivity regions extend beyond existing infrastructure. This suggests that future offshore developments, such as renewable energy installations, could be strategically positioned to support ecosystem resilience. It also highlights areas where repurposing existing structures—rather than removing them entirely—may offer greater ecological benefits.”
When pushed on suggestions for future research, Dr. James was clear on the need: “We’re interested in refining the models by incorporating species-specific traits, such as larval behavior and spawning timing, and in evaluating how ecosystem connectivity changes after actual decommissioning events.
“We’d also like to understand more about how these networks support genetic flow between populations and contribute to overall ecosystem resilience. In addition, we’re keen to explore how offshore structures influence species interactions—particularly competition—and how they may facilitate the spread of invasive or non-native species through enhanced connectivity.”
To find out more about Plymouth Marine Laboratory, visit: https://pml.ac.uk
This “topside talks” appeared in eco magazine’s 2025 Summer Edition—Rethinking Offshore Operations. Read more of the magazine here.
