Rewilding the seas with seagrass, by Marieke van Katwijk, senior scientist, Radboud University Nijmegen, The Netherlands

Seagrass ecology and restoration have been my blue-green world for over 3 decades now. Their unique niche and impressive ecosystem services fascinate me. While initially focusing on seagrass basic needs such as nutrients (not too high!) and water dynamics (not too low AND not too high!), in the second decade of my career I became intrigued by the reverse: how do seagrasses change their environment. They feedback on the physical, chemical and biological surroundings. This shapes their ecosystem services. For example, their sediment stabilizing capacity is the basis for the services of coastal protection, carbon sequestration and water purification. Sediment stabilization is also a self-facilitating property and consequently population dynamics are not simply linearly related to environmental factors, but can have tipping points. For restoration success this implies that a critical mass of plants (or mimics) may be needed! While we made important scientific progress during this period, I was annoyed but also challenged by low success rates and huge unpredictability of restoration results. Fortunately, I discovered that everybody worldwide had this problem. Apparently, we have to deal with this! Enlarging the restoration scale is definitely one of the key solutions1.

Seagrass meadows provide many ecosystem services, such as carbon sequestration to mitigate climate change. It is at the base of important food webs. Restoration at a large scale is required. We could speak of rewilding the sea with seagrass.

Further broadening my scope during the third decade of my career gave me more perspective on the land-ocean interface including ecosystems like mangroves, corals, saltmarshes and shellfish reefs. We dove into the far past when we developed a dynamic view on ‘the pristine’ when seagrass landscapes were frequented by megaherbivores and megapredators2. Joining forces with social scientists deepened my view on coastal management and so-called ‘wicked problems’. From them I learned that interaction with stakeholders should be based on transaction rather than transmission3, and tools to realize that. Moreover, I feel that I can now better distinguish between realistic and unrealistic solutions. However, seemingly unrealistic solutions, or at least non-conventional measures may be needed for the future era. In 2021, we published a roadmap for “Rewilding the sea with domesticated seagrass”, where we advocate seagrass mariculture to prevent damage to donor beds4.

van Katwijk et al. 2021 Bioscience

At the interface between domestication (mariculture) and rewilding, novel land use transitions may lead to enhanced sustainability. Exciting challenges exist to optimize between ecosystem goods and services, between human use and biodiversity. Rewilding may help to make these optimizations. I am happy to help define and understand the concept of rewilding, as well as help developing principles, parameters and guidelines for applying rewilding approaches, by joining the IUCN Rewilding Working Group.


1van Katwijk MM, Thorhaug A, Marbà N, Orth RJ, Duarte CM, Kendrick GA, Althuizen IHJ, Balestri E, Bernard G, Cambridge ML, Cunha A, Durance C, Giesen W, Han Q, Hosokawa S, Kiswara W, Komatsu T, Lardicci C, Lee KS, Meinesz A, Nakaoka M, O’Brien KR, Paling EI, Pickerell C, Ransijn AMA, Verduin JJ (2016) Global analysis of seagrass restoration: the importance of large-scale planting. Journal of Applied Ecology 53: 567-578

2Christianen MJA, van Katwijk MM, van Tussenbroek BI, Pagès JF, Ballorain K, Kelkar N, Arthur R, Alcoverro T (2021) A dynamic view of seagrass meadows in the wake of successful green turtle conservation. Nature Ecology & Evolution 5:553-555 Open access

3Hanssen L., Rouwette E, van Katwijk MM (2009) The role of ecological science in environmental policy making: from a pacification toward a facilitation strategy. Ecology and Society 14 (1): 43. Open access

4van Katwijk MM, van Tussenbroek BI, Hanssen SV, Hendriks AJ, Hanssen L (2021) Rewilding the sea with domesticated seagrass. Bioscience 71:1171-1178 Open access

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