Pioneer salt marsh restoration for coastal protection – Eastern Scheldt

Lessons Learned

  • Pre-growing Spartina plants in coconut fibre mats is technically possible. The growth is best done under environmental conditions similar to those where the mats will be deployed. In the current pilot, cord grass was grown in freshwater basins, due to logistic constraints. This is probably one of the reasons for the lesser growth performance after installation in the field.
  • All mats were installed in very hot weather. There was significant heat stress during transport and before the mats were inundated by the sea. This may also have contributed to the mortality observed after installation in the field. Installation of the mats would therefore better be planned earlier in the growing season (e.g. in June).
  • After installation, cord grass rooting formed a problem. This problem was possibly due to the overall condition of the plants. After 1.5 year in the fresh-water basins, all plants contained a highly dense and mature root system. Using mats with younger plants with a less developed root system would probably increase rooting after installation. Also clipping of the roots might help.
  • New pilots are needed to see if cord grass mats can be used as a means of sustainable salt marsh restoration in estuarine systems such as the Eastern Scheldt and Western Scheldt.
  • As sediment availability in the Eastern Scheldt is very low (suspended sediment concentrations in the channels on average below 20 mg/l), the outgrow of the plants in larger tussocks is expected to be slow. In more turbid estuaries with a higher sediment availability, such as the Western Scheldt, outgrow is expected to be faster, especially at less exposed sites.