This article was written by Professor David Smith, Chief Marine Scientist, Mars Inc.
Over the last 15 years Mars Sustainable Solutions (MSS), part of Mars Incorporated has been actively engaged in identifying solutions to reverse the long-term degradation of coral reefs. Mars is also working hard to reduce its environmental footprint and meaningfully improve the lives of people in its supply chain through their ‘Sustainable In A Generation’ plan launched in 2017. However, there is much more to be done and Mars recognises the urgent need to identify and critically examine innovative solutions aimed at restoring the regenerative capacity of our critical ecosystems. Mars has been based in Indonesia since 1992 and its employees and the many communities it sources raw materials from depending heavily on coastal fisheries for their food security and welfare. In response, MSS set up the Mars Coral Reef Restoration Program in 2006 in the centre of the world’s most biodiverse marine system within the Spermonde Archipelago, off the coast of Makassar, Sulawesi, Indonesia.
Since 2006 a relatively small team from MSS have been working closely with research teams from regional universities, an international team of scientists and the local island community to trial and optimize coral reef restoration techniques. The coral reefs of Spermonde are extensive and extremely biodiverse but large areas have been devastated by destructive fishing and some coral mining activity. The result has been the functional loss of several reefs in the region and vast areas of mobile coral rubble that have shown no natural recovery. This absence of recovery is not due to a lack of larval availability; the 150 plus islands in the Spermonde are generally well connected and some outer reefs maintain a mixed coral community at over 60% cover. Rather recovery is limited by the mobility of the substratum that inhibits the establishment of coral colonies. Anecdotal evidence suggested that these rubble beds have not recovered over a period of several decades causing long-standing consequences for biodiversity, fish biomass and island stability. Without direct intervention, it seems unlikely that there will be meaningful ecological recovery despite the fact that the general environmental conditions within this mid-section of the Spermonde (see Figure 1) are otherwise perfect for coral growth and the area has not experienced mass mortality driven by marine heatwaves. Most importantly extensive discussions with the local community facilitated by the local university teams clearly concluded that restoration was both needed and wanted.
Working alongside local and international collaborators the MSS team developed a promising reef restoration system that uses locally available material to rebuild coral reefs, literally, from the bottom up. In approaching the problem of implementing restoration at ecologically relevant scales, Mars applied supply chain thinking when scrutinising the different steps and requirements of a restoration programme. Every step in the restoration process akin to links in the chain, were examined and processes refined resulting in a rapid and cost-effective process capable of restoring the regenerative capacity of these human-induced coral rubble beds.
The approach, termed the Mars Assisted Reef Restoration System or MARRS, utilises locally fabricated steel structures to which locally sourced coral fragments are attached. These structures, called Reef Stars, are not placed in isolation on the reef, but are anchored together to form a web-like structure across the rubble beds and around existing coral bommies (see Figure 2). The web provides weight and stability and is further anchored securely into the substrata using long steel stakes hammered into the reef. The process of building has been refined over more than a decade of learning and an experienced team of trained divers are able to deploy over 300 Reef Stars in a single day which equates to 4500 coral fragments covering an approximate area of 400m2 of reef in a single day. To date over 19,000 Reef Stars have been deployed across two islands covering 4ha.
The newly established web formed by inter-connected Reef Stars is strong and highly resistant to wave energy when installed correctly. The site at Spermonde has experienced several high energy storms with no damage. In fact, the largest of storms that hit the site led to infilling of Reef Stars by rubble from adjacent reefs. These trapped rubble fragments quickly consolidated and new coral recruits were seen within a single year. Under normal conditions the establishment of the web reduces wave energy hitting the bare rubble leading to more rapid consolidation and fresh recruitment of native corals within a year. The interaction between Reef Stars, rubble and hydrodynamic forces is the topic within our current research programme.
Corals attached to the Reef Stars grow up, out and down on to the substratum, in 3 dimensions. Growth of coral in Spermonde is extremely rapid which is partly due to the suitability of the environment but also possibly due to the elevated location of corals on the Reef Stars. Growth traits of corals on Reef Stars as compared to native conspecifics is also the topic within our research programme. Within a year depending on the time of deployment relative to spawning season, new corals recruit to the underlying coral rubble and on to the Reef Stars themselves. Native settlement of corals and rapid coral growth aid the process of integration of the stars into the reef and in the Spermonde they virtually disappear within a 4-year period (see Figure 3 and Figure 4).
The reef restoration programme at the second island site in Spermonde has used a standardised science block design. Reef Stars have been deployed within a set period of time in 50 x 20m blocks (n = 10), each block consisting of around 600 Reef Stars and 9000 coral fragments. The area of reef to be restored are monitored using standard techniques before any intervention occurs (pre-build), within three months of the completion of the build (time zero) and then every six months thereafter. Both positive and negative control blocks have also been established (n = 3 in both cases). This science-led restoration build aimed at fully assessing the ecological performance of the restoration technique is now three years in. However, for a full understanding of its performance, the restoration plots will be monitored for at least five years as is recommended in recent publications.
The MARRS in Spermonde appears to kick start natural ecological process and drive rapid community recovery through promoting reef development. The complex architecture produced by Reef Stars and rapidly growing corals lead to the remarkably quick establishment of a healthy diverse and productive system. These corals are predominantly introduced into the site but also include newly recruited corals and together their growth locks the stars into the reef matrix (see Figure 4). Maintenance is required during the first three months of restoration but is reduced by rapid occupation of the web by herbivorous fish and key taxonomic groups such as parrotfish play an extremely important role in driving restoration success. As would be expected the fish community changes over time but is indistinguishable from positive controls in under three years. After three years the cover of coral reaches around 60% on average but is more like 90% in places (see Figure 3 and 4). Although the science builds are still in the process of being rigorously assessed some clear responses have been recorded. Fish assemblages go through a successional process but within just over a year total fish biomass increased 3-fold as compared to pre-build conditions and negative controls.
Mortality of coral fragments attached to Reef Stars does occur but within the Spermonde has never exceeded more than 5% across the 4 ha of reef now restored. Fish species diversity increases as does biomass and there has been no measurable reduction in fish abundance or biomass at adjacent controls sites suggesting that the restored reef promotes new fish biomass rather than simply attracting fish from adjacent reefs. Numerous pockets of fish fry have been observed across the restoration sites again suggesting that the site is functioning ecologically to increase local biomass with potential spillover benefits. Although yet to be rigorously tested observations and estimates of colony size suggest that corals rapidly reach sexual maturity and that the system may act as a source of new coral recruits to adjacent reefs which although not locally important within the Spermonde, does point to a potential use of the MARRS system in degraded areas which are recruitment limited.
Clearly, Reef Star use is most effective in rubble beds that are showing no signs of recovery and are formed by destructive human activity which has since ceased. In such systems, large areas can be rebuilt. However, Reef Stars can be used on a smaller scale in sea-scaping programmes, to compliment other restoration techniques that are more focused on repopulating hard surfaces. They are also convenient structures to deploy corals that may be better suited to survive future climate events. There are not many places in the world which only require a single technique – Reef Stars are another tool in the restoration toolbox that can be applied where it is most appropriate to do so. There are risks associated with their inappropriate use, but these risks are mitigated by a training and development programme that provides individuals with the knowledge of when they should be used and in what environmental setting. This training programme also develops the skills required to design a restoration build using MARRS and importantly how it should be maintained and monitored effectively. It is highly recommended that MARRS is not used without such training.
One of the other benefits of using Reef Stars is the potential to engage a diverse range of stakeholders in the different steps many of which would never otherwise have the opportunity to actively participate in a coral reef restoration programme (see Figure 5). Reef Stars are made of standard rebar which are coated with a coral sand or quarried limestone. Fabrication is simple but a baseline level of skill, and training, is required. Coating has been tried and tested and refined to be fast and efficient but benefits from a dedicated team. Collection of corals of opportunity need to be carefully managed to ensure diversity of both species and individuals, and that collection does not damage natural systems. But collection can be carried out by trained individuals and supplies of nursery-grown fragments can also be used if local biomass does not allow for local collection. A team dedicated to the attachment of corals increases the speed of the build as does a dedicated team of snorkellers who are trained to place the Reef Stars in situ. A trained team of divers then build the web and maintain it. These different steps in the chain allow for the participation of a diverse range of stakeholders in the restoration process. It provides a potential immediate income stream to different parts of the local community and overall greater engagement and ownership of the entire process. Ownership and participation increase awareness and recognition of conservation values all of which lead to a much more successful programme.
The programme at Spermonde involved a detailed socialisation component and continued social monitoring. Some hard lessons have been learnt about the complexity of island communities, how best to engage all members of the community and the implications of not reaching every part of the community when socialising an active conservation programme. Social science is and should be considered a core component of any restoration programme and a dedicated team of experts is required to ensure appropriate and continued engagement and understanding.
Although the MARRS programme has focused mostly in Spermonde, it is now employed across different parts of Indonesia through a dedicated National Parks programme. Key partnerships have also been formed with critical industries who value restoration. Reef Stars have been deployed in small pilot studies on the Great Barrier Reef in collaboration with tour operators and they have been employed alongside other restoration techniques is the Maldives and on the Mexican Meso-American reef system. The MARRS system is an adaptable approach to reef restoration that can be rapidly deployed and involve different members of the community. MARRS is not a panacea or a silver bullet and should be considered alongside other restoration and conservation initiatives. Of extreme importance is the fact that the success of restoration programmes cannot be used as an excuse for further damaging natural systems and any initiative must be considered along with the broader issues resulting in the demise of coral reefs globally such as overexploitation and of course climate change.
MSS are now working with numerous scientific collaborators to address key questions regarding the best use of MARRS and where it fits in the wider restoration field. MARRS continues to be used across a wide range of geographic sites within different environmental conditions to meet varied restoration objectives where it has the potential to maximise ecological value. The majority effort is focused on sites which are least-at-risk of being decimated by climate change and where restoration is needed and asked for. Restoration of least climate-vulnerable environments, at locations that can also accommodate regional training in wider restoration techniques, remains a focus of the teams’ efforts. However, the team is also working with scientific colleagues to identify and evaluate restoration solutions in climate-vulnerable locations. These activities include utilising resilient coral species or genotypes and identifying and restoring local refuge environments which have a proven capability of withstanding climatic events such as marine heatwaves. Clearly, the answer to saving the worlds coral reefs is to reverse climate change and to prevent the further degradation of ocean health through non-sustainable exploitation and development, but restoration done properly and responsibly can be an effective and highly engaging strategy that deserves a place within the conservation toolbox.