These urchin barrens likely formed over many decades — possibly due to overfishing of urchin predators such as eastern rock lobster Sagmariasus verreauxi and eastern blue groper Achoerodus viridis Ling et al.
Urban development on the coasts of metropolitan Sydney, and in particular untreated sewage outfalls, were implicated in the local extinction of P. Following improvements in wastewater infrastructure and water quality, these forests are now being restored under the aegis of Operation Crayweed see below.
Losses of E. Indeed, it seems that increasing ocean temperatures — especially in southeast and southwest Australia, which represent global hotspots of ocean warming Hobday and Pecl, — are likely to cause continued poleward range contractions of Australian kelp, to be replaced by smaller subtropical macroalgae Wernberg et al.
Work has demonstrated that following urchin removal, small areas of recovered E. On artificial reefs in Tasmania, transplanting of adult E. Whilst restoration of P. Coastal macroalgal beds — of which kelp are the largest component by biomass — have also been identified as potentially important sinks of marine carbon so called blue carbon Krause-Jensen and Duarte, ; Macreadie et al. Recent work suggests that a significant portion of kelp forest biomass can be transported to coastal sediments and the deep ocean Filbee-Dexter et al.
High biomass and fast growth rates ensure kelp forests also have critical roles in coastal nutrient-cycling Smale et al. Integrated multi-trophic aquaculture is a rapidly emerging field that might be able to utilize kelp to absorb excess nutrients associated with shellfish or finfish aquaculture Buschmann et al. Other emerging technologies and investments are also positioning kelp and macroalgae as a cornerstone of future blue economy applications, including as food for human consumption, livestock feed, biofuel, nutraceuticals, and pharmaceuticals Buschmann et al.
This service should be given special consideration with regards to forecast increases in sea level and storm activity due to climate change IPCC, Kelp and associated macroalgae also play an important role in Indigenous Australian culture and tradition reviewed by Thurstan et al. Uses include ceremonial activities, medicinal practices, clothing, food, shelter, and as domestic devices. Archival records of the use of bull kelp i.
Durvillaea spp. Additionally, the culturing, outplanting and monitoring that large-scale kelp forest restoration efforts require, provides ideal opportunities for Indigenous employment, management and custodianship also see McLeod et al. The restoration of kelp forests globally has typically followed two broad strategies: assisted recovery and active restoration. Assisted recovery — where natural kelp recovery is facilitated by either the removal of the agent of decline e. Results are nonetheless highly variable and site-dependent, and projects involving removal of the agents of decline have seemingly had greater success than those that only provide novel substratum.
Critically, assisted recovery approaches are often hindered by resource constraints and by hysteresis and feedbacks in the ecological dynamic see Scheffer et al.
We are aware of only one example where assisted recovery in isolation has resulted in the long-term restoration of kelp forests giant kelp in California, see Reed et al. The long-term success of this approach is reliant on either continued transplantation of kelp — which can be cost-prohibitive and dependent on a healthy donor population North, ; Devinny and Leventhal, — or adequate natural recruitment of juvenile kelp.
Notably, the planting of juvenile kelp whether lab-cultured or otherwise has had little success but see Perkol-Finkel et al. Within Australia there have been few attempts to restore kelp forests. The earliest reported work comes from the Seacare community group Sanderson, who attempted to restore areas of giant kelp M.
Multiple techniques were used, including transplanting juvenile kelp from donor populations; transplanting artificial substrata on which juvenile giant kelp were growing following natural recruitment; transplanting sporophylls i. Centrostephanus rodgersii urchins were also removed at some restoration sites and improved the likelihood of positive outcomes.
A single patch of giant kelp was established at one site but subsequently disappeared, in keeping with the ongoing decline of giant kelp in southeast Australia. The methods employed at the site of success did not differ from those at other sites i. Operation Crayweed is the only other reported example of targeted kelp forest restoration in Australia of which we are aware although there are several projects currently underway, as discussed below.
This ongoing project began in and aims to restore crayweed P. Adult crayweed are transplanted from donor populations outside of metropolitan Sydney to restoration sites, with the primary aim to establish sufficient adult individuals to promote recruitment of juvenile crayweed. Despite high variability among sites, survival of transplanted crayweed is typically comparable to natural mortality Campbell et al.
These restored crayweed forests have become self-sustaining without the need for additional cost or maintenance, which is a rare result in marine restoration. Additional work has employed aspects of active restoration and assisted recovery to improve understanding of kelp forests and ecological restoration. Work by Valentine and Johnson found that even after the removal of urchins, heavy inoculation with E. However, Gorman and Connell showed that recovery of E.
Others have illustrated that urchin removal can facilitate natural recovery of kelp and other macroalgae on Australian temperate reefs when healthy kelp forests are nearby the denuded areas Fletcher, ; Ling, Layton et al. Crucially however, it was only patches above a certain size and density of adult kelp that facilitated adequate recruitment to maintain the kelp canopy; illustrating the importance of minimum patch sizes and densities when transplanting E.
Given the rate of environmental change that is influencing coastlines worldwide, and that some drivers of kelp decline cannot be easily ameliorated e. While we are aware of no published work implementing these strategies for kelp restoration, research in Australia is currently pioneering the identification of warm water-tolerant seaweed genotypes as the basis of future restoration efforts IMAS, ; Gurgel et al.
Estimating the costs of implementing effective kelp forest restoration in Australia is difficult given the few examples to date. For Operation Crayweed, workers initially transplanted six 2 m 2 patches of P. Note that these costs do not include the science necessary to underpin decisions such as choice of donor site, size of patch, etc. Active restoration efforts typically occur at small to medium scales, and not the seascape scale at which kelp forest loss can occur.
And so, while Operation Crayweed has demonstrated the translation of small-scale efforts into large-scale outcomes, efficient up-scaling of active restoration remains as a key ongoing consideration. Economic projections indicate that culling of C. Novel technology is promising to improve the scalability and cost-effectiveness of urchin culling, and trials of autonomous underwater vehicles designed to locate and kill urchins are in planning.
Overall, the impetus to consider kelp forest restoration would benefit greatly from environmental accounting to ascertain the currently unknown value of kelp forests to human society, and which could underpin rigorous benefit-cost analysis e. Rogers et al. The loss of kelp forests in Australia, and indeed the world, is complex due to high levels of geographic variation and the multitude of different stressors present in any given location.
Accordingly, it is useful to apply a workflow and decision framework when approaching restoration Figure 3 , especially where this can also provide an indicator of potential local outcomes.
Development and preliminary-testing of this workflow utilized examples of kelp loss from Tasmania, where local restoration interventions must consider two species of dominant kelp i. Ecklonia radiata and Macrocystis pyrifera and multiple drivers of kelp forest decline e. Our novel workflow and decision support system illustrates multiple alternative pathways and endpoints of restoration, and critically, helps to identify circumstances where restoration is not possible or advisable also see Johnson et al.
This diversity of pathways and endpoints exists because of environmental factors that are beyond the control of practitioners, such as whether hysteresis is present in the system e. Gorman and Connell, ; Johnson et al.
The multiple pathways of kelp forest restoration are also reflective of the diversity of drivers of decline, variability in the resources available for restoration efforts, and scalability of the intervention. For example, the efficacy of assisted recovery techniques is often hindered by resource constraints e. Tracey et al. The workflow highlights that at each node, research is needed to inform decision making and progression to the next stage, and thus may also help identify knowledge gaps in baseline ecosystem knowledge.
Using this workflow to plan restoration efforts should also help practitioners and managers to ensure that interventions are considered within resource constraints and that the driver s of kelp forest decline has been addressed.
Progressing through the workflow toward the point of successful kelp restoration incorporates several key questions as decision points. Firstly, is it possible to return the environment to its pre-loss state, such as the improvements in water quality that preceded Operation Crayweed?
If not, it will be essential to select and facilitate kelp to survive in the new environmental state, for example, the selection for thermally tolerant kelp from remaining healthy individuals see IMAS However, if it is not possible to ameliorate or adapt to the novel ecosystem state, restoration efforts will be, at best, limited to the local scale Figure 3. Secondly, is there hysteresis present in the dynamics of the system? Knowledge of the capacity for hysteresis is critical since it can prove one of the biggest challenges to kelp forest restoration see Gorman and Connell, ; Marzloff et al.
Overall, ensuring natural recruitment of juvenile kelp and the continuation of self-sustaining generations is critical to long-term restoration success. Thus, it is important that kelp forest restoration focus on restoring the positive feedbacks that initiate recruitment and facilitation cascades and which promote ecosystem stability Halpern et al.
However, in some instances reference ecosystems may not be identifiable or available, for example, when there are shifting baselines and poor understanding of ecosystem dynamics Dayton et al. These diverse circumstances are acknowledged by the Society for Ecological Restoration SER who recognize that a reference ecosystem may instead be a conceptual model synthesized from numerous locations, indicators, and historical and predictive records McDonald et al.
This tool provides a consistent set of criteria against which key ecosystem attributes can be assessed, and acts as a conceptual framework for restoration practitioners, managers, and regulators. The 5-star system also provides a framework for habitat-specific indicators and metrics to be developed.
Such indicators for kelp forest restoration might include transplant survival, growth rates, and condition e. Certainly, recruitment of juvenile kelp is one of the greatest indicators of ongoing success and kelp forest resilience.
In most cases, the ideal goal, as demonstrated by Operation Crayweed, is kelp forest recovery and reestablishment beyond the restoration footprint due to spill-over of natural recruitment.
Operation Crayweed has been the most successful kelp restoration program in Australia to date. It provides an ideal opportunity to apply the 5-star recovery system to a kelp restoration project, especially since science was used to rigorously design and test restoration approaches, thus allowing objective assessment of some recovery attributes. Figure 4. Average overall score is 3. Individual attribute scores can range from 1 e. Ratings are based on both monitoring and scientific publications, as well as expert opinion of the scientists and practitioners involved in restoration.
First, we know that some key aspects of ecosystem function i. Moreover, species composition of some associated organisms in restored crayweed forests is approaching that of natural forests Marzinelli et al. Whilst the physical conditions that likely precipitated the initial decline i. Moreover, these external attributes cannot be controlled within the restoration framework, but are managed and regulated by government.
Targets for other ecosystem attributes are less well defined, have not been measured, or cannot be measured within the temporal scale defined here due to prolonged response times. The collective scientific knowledge of these systems suggests however that restoration of external connections is occurring, since crayweed cover and extent is expanding at some sites without additional intervention hence the 2—3 star rating.
While recovery across multiple trophic levels is being monitored, it is possible that recovery of higher trophic levels may take decades e. Babcock et al. The long timescales over which some attributes respond to restoration may therefore be reflected as a low rating, but can still be indicative of an appropriate trajectory of recovery.
However, depending on project and ecosystem-specific requirements, certain criteria could be weighted to provide a more subtle assessment. For Operation Crayweed, the mean attribute score was 3. While the mean score and individual recovery attributes could be used as a tool to identify areas requiring ongoing active restoration to accelerate recovery, we believe that it is sufficient to restore populations to a point whereby they can continue on a recovery trajectory naturally, without additional intervention.
This is not only cost effective but ensures that limited resources can be strategically directed to maximize restoration efforts across species and ecosystems in need.
Regardless, recovery of restored crayweed populations will continue to be measured and assessment of the need for additional interventions will be re-examined on an ongoing basis.
The SER recovery system provides assessment of the trajectory of ecosystem recovery but also identifies research gaps. For Operation Crayweed, areas that would benefit from future research include assessing whether crayweed restoration has resulted in recovery of broader ecosystem functions and services e.
While kelp forest restoration is not achievable or feasible in all situations, use of a decision framework and consideration of the initial drivers of decline should increase the likelihood of success and the appropriate use of resources. And while past examples of kelp forest restoration are as notable for the failures as the successes, it seems that under many circumstances, small to medium scale restoration is achievable.
For example, Operation Crayweed has demonstrated positive ecological outcomes at a scale beyond their initial restoration intervention. However, increasing the scalability of kelp forest restoration to the seascape-scale remains a considerable challenge, as does restoration in response to climate change where drivers of decline cannot be readily ameliorated e.
Optimal results will be achieved via thorough planning of restoration interventions and where positive feedbacks in the dynamics of kelp forests can be harnessed to promote habitat resilience and recruitment of juvenile kelp. It follows however that the challenges and costs inherent in restoring kelp forests ecosystems places a great emphasis on the importance of maintaining and conserving kelp habitats.
CL and CJ conceived the initial idea for the review. CL prepared the manuscript with input from all other authors. All authors contributed to manuscript revision. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.
We also thank our colleagues and the workers who contributed the research that forms the basis of this review, and the Australian Research Council, state governments, universities, and private foundations and donors who supported the research described here.
Agricultural commodities: March , Annual Fisheries Outlook. Google Scholar. Ambrose, R. Mitigating the effects of a coastal power plant on a kelp forest community: rational and requirements for an artificial reef. Bulletin of Marine Science 55, — Andrew, N. Spatial heterogeneity, sea urchin grazing, and habitat structure on reefs in temperate Australia. Ecology 74, — Large-scale patterns in habitat structure on subtidal rocky reefs in New South Wales.
Marine and Freshwater Research 51, — Babcock, R. Decadal trends in marine reserves reveal differential rates of change in direct and indirect effects. PNAS , — BenDor, T. Estimating the size and impact of the ecological restoration economy. Bennett, S. Marine and Freshwater Research 67, 47— Bishop, M. Cross-habitat impacts of species decline: response of estaurine sediment communities to changing detrital resources. Oecologia , — Buschmann, A. Seaweed production: overview of the global state of exploitation, farming and emerging research activity.
European Journal of Phycology 52, — Bustamente, R. Maintenance of an exceptional intertidal grazer biomass in South Africa: subsidy by subtidal kelps. Ecology 76, — Alaska is home to three types of kelp: Macrocystis two kinds, one of which is giant kelp , Nereocystis luetkeana bull kelp and Alaria fistulosa. Kelp forests grow best in nutrient-rich, clear waters whose temperatures are between 42—72 degrees F 5—20 degrees C. The water must be clear so that sunlight can reach the ocean floor where the kelp life begins.
If the water is too warm warmer than 20 degrees , the kelp does not thrive as well. Its most successful growth is in geographic areas of upwelling and where the waters are always high in nutrients and always cold. For kelp to survive, it must be anchored to strong substrate, otherwise it will be yanked loose during storms. But, it also needs a moderate current. Their life cycle varies, depending on the species. Some live for one year only; others have a longer lifespan.
Kelp forests are home to many different species, including fish, sea urchins and other marine animals, invertebrates, such as snails, and sea otters. For part of their lifetime, kelp forests in Alaska are home to 20 or more species of fish, who are attracted to the kelp by the food supply. Some fish, such as herring and Atka mackerel, spawn in kelp beds. Mammals, such as sea lions and whales, are also likely to take up residence. Each part of the kelp - at the ocean floor, in the middle and above the water in the canopy formed by the fronds - provides a home to other species.
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What is kelp? Why are kelp forests important?
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