How Does Sea Grass Conservation And Restoration Help Fight Climate Changes?

May 3, 2019 - Scubareefing

^{Common on-site approaches to seagrass conservation and restoration}

The most common approach to conserving seagrass ecosystems is to reduce common threats to them (e.g. pollution, damage by boats), for example through new regulations. Restoring seagrass ecosystems can include harvesting and transplanting seagrass plants and subsequent management and monitoring of restored sites. 

Seagrasses provide coastal protection

A review on seagrasses in Europe found that these ecosystems can reduce current velocity, dissipate wave energy and stabilize the sediment, most reliably in shallow waters with low wave energy environments, and where biomass does not fluctuate through time. Reducing wave energy can contribute to reducing flooding and erosion in coastal areas and settlements, two hazards that may increase in severity with a changing climate.

©Vilainecrevette / Shutterstock.com

Seagrass beds may keep pace with sea level rise 

Seagrass beds can trap sediment and thus raise their surface elevation. Where sedimentation and accretion rates keep pace with sea level rise, there is more chance that seagrass beds will maintain their coastal protection services in the face of climate change.

Seagrass beds serve as a habitat and nursery ground for fish, supporting fisheries and livelihoods

Seagrass beds provide habitat for fish and other commercially relevant marine animal stocks . Supporting seagrass ecosystems through conservation or restoration can help with the continued provision of food and income, and therefore contribute to maintaining people’s resilience and capacity to adapt to climate change.

Seagrass beds may support diversified livelihoods

The contribution of seagrass beds to stable fisheries may mean that communities that do not presently rely on fisheries as a source of livelihood could benefit from this source of livelihood in the future, if other livelihoods come under threat. 

Additional benefits

There may be additional benefits for biodiversity

Seagrass habitat is important for a wide range of species that may spend all or part of their life cycle within the seagrass ecosystem, and conservation efforts are likely to be key for biodiversity protection. Seagrasses also provide key feeding grounds for endangered species such as turtles, and have been shown in some locations to have a buffering effect on pH, modifying it through photosynthetic activity.

There are additional benefits for carbon storage

Seagrass beds also provide carbon storage capacity in their own biomass but also through their ability to trap organic sediments, thus contributing to climate change mitigation. This is why seagrasses are among the systems referred to as ‘blue carbon’ sinks. 

Key issues that can affect success 

Anthropogenic pressures

Seagrass beds are highly sensitive ecosystems, threatened by anthropogenic factors such as physical damage by boats, poor water quality, pollution, dredging and dumping. For seagrass conservation and restoration to be an effective EBA measure, efforts need to be made to mitigate and manage these local, human-induced pressures.

Site and ecosystem characteristics 

Seagrass beds reduce waves and currents in shallow areas more effectively when they occupy a higher proportion of the water column. Since some species are naturally taller and therefore occupy a greater proportion of the water column than others, it may be important to take this into account when selecting species for restoration efforts, or when prioritising management efforts for existing seagrass beds. Stiffness, biomass, density, leaf length and morphology are other species-specific characteristics that influence the coastal protection value of seagrass beds. These characteristics should also be considered when making decisions about seagrass conservation and restoration for EBA.

Seagrass beds are most reliably effective at providing coastal protection services in shallow waters with low wave energies and low seasonality. In other circumstances, seagrass beds may less reliably provide coastal protection services.

Since different species show different sea temperature tolerances, mixed species meadows may have a better chance of survival and resilience in the face of increasing sea temperatures as a result of climate change.

Critical environmental parameters which impact on the integrity and presence of seagrass beds include wave energy, salinity, temperature, water clarity and nutrient concentrations. Optimal conditions (e.g. for temperature) depend on the species used, so there is a need to consider the species’ ecological requirements in comparison to the local marine conditions.

©Ethan Daniels / Shutterstock.com

Ability to protect commercially and subsistence relevant fish species

The significance of seagrass beds for commercial fish species production and/or subsistence purposes is likely to be species-specific and may vary geographically and over time. Some fish species may require other habitats such as mangroves or mudflats at certain stages of their life cycle. Thus, solely focussing conservation or restoration efforts on seagrass beds may not have the desired effect for these species. Therefore, if the focus is on protecting fisheries, it is important to identify the specific fish species involved and their habitat requirements.

Recovery after disturbance

Natural recolonisation following disturbance may occur in some cases, though the recovery of disturbed seagrass beds varies and is likely to be greatly assisted by the removal of human stressors. Reducing the time that areas are bare following disturbance is important to prevent erosion of the substrate.

Relevant policy context and developments

Common policy approaches for seagrass conservation and restoration include legal designation (e.g. establishing general protection for seagrass ecosystems, or specific protection in the form of marine protected areas as well as establishing codes of practice, planning and zoning, stakeholder education and capacity building. The appropriate mix of these strategies is likely to depend on national circumstances and site location.

Ongoing management

For seagrass restoration, since implementation success predominately depends on trial and error, employing adaptive management using native species is strongly recommended.

©think4photop / Shutterstock.com

Monitoring programmes should be set up with a time horizon of 5 years (or 10+ in more wave exposed sites) to document the effectiveness of the intervention (see the document by the US National Oceanic and Atmospheric Administration in the Useful resources and materials section at the bottom of this page).

On the ground implementation

Seagrass transplanting is labour intensive, and can require the use of divers in deeper water, which can result in considerable financial expenditure where volunteers are not available. Transplanting also has an ecological cost, as inappropriate harvesting can damage the source ecosystem. The recovery time depends on the species harvested.

The effectiveness of a particular seagrass restoration method is very site specific and may require the use of different species at different stages to replicate natural succession processes. Also, the parameters of the transplant site must closely match those of the source or reference site (i.e. through the selection of similar ecotypes). Many efforts at transplantation have failed because of unsuitability of site conditions