Stabilising tropical beaches with seagrass

Stabilising tropical beaches with seagrass

Rebecca James

Natural vegetated bays have a complex bathymetry

Introduction – Ecological processes – Real-world examples - Application

0.1 m

-9 m Elevation

© IGN

Galion Bay, St Maarten

Introduction – Ecological processes –Real-world examples - Application

Built by seagrass and coral reefs

Introduction – Ecological processes –Real-world examples - Summary

Wave attenuation by the natural ecosystem

Normal conditions Hurricane conditions

Wave height, Hrms (m)

0 0.5 1.0 1.5

Introduction – Ecological processes –Real-world examples - Summary

Wave attenuation by a defoliated meadow

Normal conditions Hurricane conditions

Wave height, Hrms (m)

0 0.5 1.0 1.5

Introduction – Ecological processes –Real-world examples - Summary

Wave attenuation by only the reef

Normal conditions Hurricane conditions

Wave height, Hrms (m)

0 0.5 1.0 1.5

Real world example: Mirador Nizuc, Mexico

Introduction – Ecological processes –Real-world examples - Application

Tussenbroek et al. 2017

No seagrass vs. seagrass

Introduction – Ecological processes –Real-world examples - Application

Eroding vs. stable beach

Erosion and

beach retreatment Stable

Introduction – Ecological processes –Real-world examples - Application

Introduction – Ecological processes –Real-world examples - Application

Upscaling seagrass-based climate adaption

Disturbed-unstable beach

Seagrass capture and stabilize sediment

Promotion of seagrass colonization

Natural self-sustaining beach

Difficult to colonize

Unstable sediment surface Sand nourishment

required Stable beach

Reduced erosion, raised bed level

Wave-induced erosion Calcifying algae

produce sand

Reduced sand production

Wave energy Wave energy

Introduction – Ecological processes –Real-world examples - Application

Methods of restoring seagrass meadows

Mei Tan Y. et al. (2020) Frontiers in Marine Science

Introduction – Ecological processes –Real-world examples - Application

Success of seagrass restoration

Mei Tan Y. et al. (2020) Frontiers in Marine Science Initial no. seagrass shoots

van Katwijk et al. (2015). Journal of Applied Ecology

53: 567-578

Introduction – Ecological processes –Real-world examples - Application

Identifying suitable habitat

Mei Tan Y. et al. (2020) Frontiers in Marine Science Staehr et al (2019). Frontiers in

Marine Science 6: 175

Need long-term monitoring of

environmental conditions

Introduction – Ecological processes –Real-world examples - Application

Upscaling seagrass-based adaption

Identifying suitable habitat

• Long-term monitoring

• Sufficient windows of opportunity

Enhancing conditions

• Good water quality

• Reef protection

Planting seagrass Meadows

• Sustainable

plant/seed source

• Protection from

disturbance

Acknowledgments

• Collaborators: Tjeerd Bouma, Peter Herman, Marieke van Katwijk, Aaron Lynch, Brigit van Tussenbroek, Marjolijn Christianen

• SCENES project group

• Réserve Naturelle Nationale de Saint-Martin

• Nature Foundation St Maarten