Global analysis of seagrass restoration: the importance of large-scale planting

Marieke M. van Katwijk, Anitra Thorhaug, Núria Marbà, Robert J. Orth, Carlos M. Duarte, Gary A. Kendrick, Inge H. J. Althuizen, Elena Balestri, Guillaume Bernard, Marion L. Cambridge, Alexandra Cunha, Cynthia Durance, Wim Giesen, Qiuying Han, Shinya Hosokawa, Wawan Kiswara, Teruhisa Komatsu, Claudio Lardicci, Kun-Seop Lee, Alexandre MeineszMasahiro Nakaoka, Katherine R. O'Brien, Erik I. Paling, Chris Pickerell, Aryan M. A. Ransijn, Jennifer J. Verduin

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325 Scopus citations

Abstract

In coastal and estuarine systems, foundation species like seagrasses, mangroves, saltmarshes or corals provide important ecosystem services. Seagrasses are globally declining and their reintroduction has been shown to restore ecosystem functions. However, seagrass restoration is often challenging, given the dynamic and stressful environment that seagrasses often grow in. From our world-wide meta-analysis of seagrass restoration trials (1786 trials), we describe general features and best practice for seagrass restoration. We confirm that removal of threats is important prior to replanting. Reduced water quality (mainly eutrophication), and construction activities led to poorer restoration success than, for instance, dredging, local direct impact and natural causes. Proximity to and recovery of donor beds were positively correlated with trial performance. Planting techniques can influence restoration success. The meta-analysis shows that both trial survival and seagrass population growth rate in trials that survived are positively affected by the number of plants or seeds initially transplanted. This relationship between restoration scale and restoration success was not related to trial characteristics of the initial restoration. The majority of the seagrass restoration trials have been very small, which may explain the low overall trial survival rate (i.e. estimated 37%). Successful regrowth of the foundation seagrass species appears to require crossing a minimum threshold of reintroduced individuals. Our study provides the first global field evidence for the requirement of a critical mass for recovery, which may also hold for other foundation species showing strong positive feedback to a dynamic environment. Synthesis and applications. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration. For effective restoration of seagrass foundation species in its typically dynamic, stressful environment, introduction of large numbers is seen to be beneficial and probably serves two purposes. First, a large-scale planting increases trial survival - large numbers ensure the spread of risks, which is needed to overcome high natural variability. Secondly, a large-scale trial increases population growth rate by enhancing self-sustaining feedback, which is generally found in foundation species in stressful environments such as seagrass beds. Thus, by careful site selection and applying appropriate techniques, spreading of risks and enhancing self-sustaining feedback in concert increase success of seagrass restoration. Journal of Applied Ecology © 2016 British Ecological Society.
Original languageEnglish (US)
Pages (from-to)567-578
Number of pages12
JournalJournal of Applied Ecology
Volume53
Issue number2
DOIs
StatePublished - Nov 25 2015

Bibliographical note

KAUST Repository Item: Exported on 2020-10-01
Acknowledgements: We thank Prof. dr. G. Borm, Dr. J. C. M. Hendriks and Prof. dr. P. Herman for thorough statistical advice and stimulating discussions, Dr. L. Hanssen for inspiring feedback during all phases of the research, C. Belaire, Dr. I. Yasir and R. Hudson for providing data and K. Giesen, C. Gadouillet and N. Krupski for entering data. A. T. was funded by Greater Caribbean Energy and Environment Foundation grants. N. M. was supported by a Gledden Fellowship from the Institute of Advanced Studies of the University of Western Australia. N. M. C. M. D and A. C. were supported by Biomares contract number LIFE06 NAT/PT/000192. N. M. and C. M. D. were supported by Opera (FP7, contract number 308393). C. P. and the Cornell Cooperative Extension Marine Program are funded in part by County Executive Steve Bellone and the Suffolk County Legislature, Hauppauge, New York. E. B. and C. L. were funded by University of Pisa (Lardicci 308/ex60% 2010). M. L. C and G. A. K were supported by ARC Linkage Grants (LP130100155, LP0454138). This paper is Contribution No. 3495 of the Virginia Institute of Marine Science, College of William & Mary. This is a contribution to the CSIRO Marine and Coastal Carbon Biogeochemistry Flagship Cluster.

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