Better protection for mangroves with models for successful seedling establishment

Dec 12, 2013
The wave tanks in Singapore Credit: Thorsten Balke

Seedlings of mangroves do not have an easy time to get established. Many forces of nature work against their anchorage in the soil. Human intervention in coastal areas and climate change also make life difficult for mangrove seedlings. Thorsten Balke studied the conditions that enable mangrove seedlings to be successful. On 18 December he will defend his PhD thesis at Radboud University.

Mangrove forests protect coastlines and are important for biodiversity; they are a nursery ground for many fish species and host a variety of plants that have adapted to grow in salt water. For successful management and restoration of mangrove forests, good understanding of the interaction between vegetation, and the forces of nature is required. Geographer Thorsten Balke studied the establishment of mangroves: how do the seedlings get to the tidal flat and what factors ensure their growth to become a successful mangrove forest? To answer these questions, he carried out experiments in Singapore and New Zealand.

The dangers of high tide

What is the biggest danger for mangrove seedlings? High tide. Due to the currents and waves that accompany high tide, sedimentation and erosion can prevent seedlings from becoming established on the bare tidal flat. During sedimentation, material carried by the water sinks to the l bed and accumulates there, essentially burying the seedlings. Erosion is another factor, whereby soil particles are removed from the bed by water currents.

Many limiting factors

However, the seedlings also work against themselves. Due to their own buoyancy, it takes some time before they become firmly anchored in the soil and can no longer be dislodged. Under ideal conditions, relatively short roots are sufficient, but only longer roots can withstand the currents and waves that accompany high tide. And after the seedlings are anchored in the soil, their growth process can still fail because they become buried by sediments, or they topple due to .

This video is not supported by your browser at this time.

Experiments in wave tanks

To study all these aspects in detail, Balke set up an experiment in Singapore to simulate the various rates of sedimentation and erosion at high tide. He did this in nine large water basins, 3 m x 1 m, with wave generators, in which he could manually push the silt up and down. In combination with wind data and tidal time series, Balke developed models for the establishment of young by predicting windows of opportunity: tidal periods in which the conditions are ideal for the establishment and further development of mangrove seedlings.

Models in practice

Mangrove seedlings at high tide. Credit: Thorsten Balke

What can we do with these models? 'We now understand both the optimal conditions for successful establishment of a mangrove forest and the optimal location and optimal time to sow mangroves', explains Balke. 'Policymakers can take these factors into account when restoring mangroves. Moreover, with this information we can create scenarios to predict the consequences of on .' The results of Balke's models emphasise that the most important factor for successful restoration is not planting seedlings, but improving the growing conditions for the seedlings. For example, in Indonesia mangrove rehabilitation projects are being developed using brushwood groynes to counteract erosion and enable mangrove to develop. Balke: 'All my publications are open source, so that everyone in the world can use this information freely.'

Explore further: Philippines to plant more mangroves in wake of Typhoon Haiyan

add to favorites email to friend print save as pdf

Related Stories

Mangroves could survive sea-level rise if protected

Jul 31, 2013

Human activity is currently a bigger threat to mangroves, and the natural defences they provide against storm surges and other coastal disasters, than rising sea levels, according to a new study.

Bengali forests are fading away

Jan 10, 2013

Rapid deterioration in mangrove health is occurring in the Sundarbans, resulting in as much as 200m of coast disappearing in a single year.

Research finds mangroves being fed to death

May 19, 2009

(PhysOrg.com) -- New UQ Science research has found the increase in nutrients coming out of our river systems is putting pressure on our mangrove forests and making them far more susceptible to environmental ...

Constructed ecosystems reduce risk of flooding

Dec 09, 2013

In many locations throughout the world, protection against increasingly severe flooding can be improved by the construction of large ecosystems (e.g. tidal marshes and mangroves). In comparison with conventional flood-prevention ...

Recommended for you

Nestling birds struggle in noisy environments

23 hours ago

Unable to fly, nestling birds depend on their parents for both food and protection: vocal communication between parents and offspring helps young birds to determine when they should beg for food and when they should crouch ...

The secret life of the sea trout

Oct 29, 2014

Jan G. Davidsen and his graduate students are spies. They use listening stations and special tags they attach to their subjects to track their movements. They follow their subjects winter and summer, day ...

Giant tortoises gain a foothold on a Galapagos Island

Oct 28, 2014

A population of endangered giant tortoises, which once dwindled to just over a dozen, has recovered on the Galapagos island of EspaƱola, a finding described as "a true story of success and hope in conservation" ...

Fish "personality" linked to vulnerability to angling

Oct 28, 2014

Individual differences in moving activity in a novel environment are linked to individual differences in vulnerability to angling, according to an experimental study completed at the University of Eastern Finland and the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.