Engineering Marine Habitats from Oil Rigs
Mankind’s search for fuel led to the exploration and discovery of deep reserves of oil and natural gas underwater. Since then, the offshore oil and natural gas drilling industry has boomed into a massive economic and energy source with over 12000 rigs currently active across the world. Over time, technological advancements and innovations have allowed the industry to venture further and further away from the shore while increasing the complexity of the structure and function of their offshore oil platforms. But what happens to these structures above when the seabeds underneath run out of oil?
2000 oil platforms are to be decommissioned by 2040.
Historically, end-of-life processes for old oil rigs involve the complete removal of structures from underwater. This is carried out via non-explosive removal, for instance, by using diamond saws to cut off structures, or explosive demolition. Both processes are energy and labour-intensive, not to mention the destruction of the marine habitats that colonise these platforms over the years. With increasing global interest in clean energy technology, the offshore oil and natural gas industry is now headed towards its eventual decline. An estimated 600 platforms are to be decommissioned between 2017 and 2021, with a further 2000 projects to be decommissioned by 2040. As such, an environmentally-friendly alternative for the removal of these defunct structures is the need of the hour.
From oil rigs to artificial reefs
The Rigs-to-reef initiative (R2R) started in Louisiana, USA in the late 1980s as an environmentally-friendly alternative to end-of-life destruction, reusing offshore structures as functional reefs. The process involves toppling the defunct structure in place and partially removing or relocating the structure to a designated site to stimulate habitat growth for marine life. Today, these artificial reefs, located in the Gulf of Mexico and Gulf of California, represent one of the first-ever man-made natural habitats to potentially function better than their natural counterparts.
There are several reasons why. Out beyond the coastline, much of the extended high seas function as marine deserts due to lack of nutrient intermixing. The establishment of R2R structures away from the coast provides a hard substrate of ‘jacketed’ platforms on which diverse marine communities develop, enabling nutrient supply and increasing availability of food along different heights for a diverse range of marine species. As a result, these oil rigs function as excellent nurseries for fish growth from larval to adult stages, mimicking the rich ecosystem of coastal reef habitats. In fact, a 2014 study found that fish production per unit area in artificial reefs is higher than in natural systems. Chris Lowe, from the University of California, tracked the movements of marine species and found that a majority of fish had a preference for artificial reefs. The reason for this affinity could be the ease of finding prey without having to leave their habitat.
In other areas such as the north-west shelf of Australia, the Adriatic Sea, and parts of the North Sea, R2R platforms offer the only protection against trawling, a highly destructive fishing technique that employs weighted nets dragged along the seabed to catch fish, inevitably destroying fragile seabed ecosystems in the process. In California, fishing around reefs is prohibited, thus making the regions surrounding the platforms unofficial marine protected areas. Consequently, these areas have seen the revival of several overfished species (for example, the rockfish population of the US West Coast) and have provided a source of connectivity between natural reef structures (such as for cold-water corals in the North Atlantic) which is important for species intermingling and maintaining genetic exchange.
Cost-saving has played a huge role in making the R2R initiative a lucrative investment for big oil companies. Decommissioning platforms cost billions of dollars, so this modern restoration strategy provides a financial incentive for oil companies to do their part for marine conservation. Along with the newfound interest in offshore wind and wave energy technology, these structures could be another great way of increasing marine biodiversity while meeting global energy demands. Not surprisingly, the R2R strategy is now being seriously considered for implementation in several countries, including the UK, EU, Malaysia, China and Australia.
A safe harbour?
Despite promising headway, there are concerns surrounding the efficacy of R2R and potential drawbacks. Marine experts have questioned whether the increased biological productivity in artificial reefs is due to an increased concentration of fish stocks or whether it is simply due to the aggregation of fish species from nearby natural reef systems. If the latter is true, R2R could have unintended consequences and create an imbalance in the natural marine environment. The notion that these artificial structures exactly mimic the trophic structures of natural systems has been contested by a recent 2020 study which found that artificial structures promote the establishment of non-indigenous and sometimes potentially invasive species (e.g. orange cup corals) onto the oil platforms.
The development of assisted reefing programs is crucial to supplement the so-called ‘rainforests of the ocean’ as they adapt to changing conditions.
While no doubt successful conservation stories have been heard, the claim that artificial reefs are a safe harbour for endangered fish species is also questionable. Fishing and diving around offshore rigs, in regions where it is allowed, is a major component of local tourism industries. In Louisiana, recreational fishing is centred around offshore platforms – over 70% of recreational fishing trips within national fishing zones are in direct association with offshore platforms, where fish densities are 20–50 times higher than surrounding areas. In the absence of proper monitoring and regulation regimes, these reef platforms could very well act as concentrated sites for the removal of fish stocks in the marine environment.
An adaptive strategy
The debate over the overall effectiveness of R2R is relevant, particularly for the UK and EU, given the backdrop of heavy decommissioning plans underway in the North Sea. Extensive scientific research on ecosystem impacts from artificial habitats, effective governance and monitoring regimes, community sensitisation in protecting these areas, and multi-stakeholder involvement will all be key in ensuring the enhanced fitness and functionality of these neo-reef ecologies. While assisted reef development has been a boon for marine communities in the Gulf of Mexico, further research will demonstrate whether this is a one-size-fits-all solution for decommissioning plans globally.
With increasing global warming and ocean acidification, there is no doubt regarding the urgent crisis that global natural reef ecosystems face. Even in good-governance scenarios (i.e. restricting global temperature incline within 1.5 °C above pre-industrial levels), studies have predicted that shallow tropical coastlines will experience an increase in warming of at least 0.4 °C in the coming decades, thus guaranteeing frequent mass bleaching events in highly sensitive coral species.
Increasing sea levels, physical events like storms and hurricanes, and the peak vulnerability of habitat-forming corals to ocean acidification make the development of assisted reefing programs crucial to supplement the so-called ‘rainforests of the ocean’ as they adapt to changing conditions. There is a need, however, to be cognizant that artificial reefing is ultimately an adaptive strategy and not a root solution to the overarching problem of global warming. Shifting from an oil and gas based economy to a renewable one is the only way forward, and to do so while adding to the biodiversity of the marine ecosystem is a bold and novel vision for deep-sea marine conservation.
Banashree Thapa is a Commonwealth Masters scholar from India attending the Biodiversity Conservation and Management program at the University of Oxford. Her previous work experience has revolved around campaign management on energy conservation, environment education and climate justice in iNGOs and grassroot youth movements. She is interested in seascape ecosystem research and conservation and is currently working on investigating the drivers of inter-decadal mangrove forest change for Indonesia.
Art by Josie Illingworth-Law.