Vulnerable rich fen in the Naardermeer thrives thanks to restoration measures

Rich fen species, many of them threatened in the Netherlands, are doing well in the Naardermeer nature reserve, reveals an assessment of vegetation and hydrology that spans almost 30 years.

In 1987, Utrecht University’s Prof. Martin Wassen surveyed vegetation and hydrology of the Netherlands' first nature reserve as part of his PhD. The Naardermeer nature reserve was established in 1905 by the founder of Dutch Society for the Preservation of Nature (Natuurmonumenten), Jac P. Thijsse and his colleagues, who saved the wetland area from being turned into a waste dump for Amsterdam.

Increasing protection from 1990s

Despite this long status of protection, Wassen’s research discovered that the rich fen vegetation in the east side of the nature reservation was under threat of disappearing, and recommended shutting down drinking water extraction in the nearby region ‘het Gooi’ to prevent the vulnerable rich fen from drying out and acidifying.

This advice was followed up in the 1990s. On top of that Natuurmonumenten enacted local restoration measures, including the removal of dense moss layers in parts of the fen.

Restoration measures successful, but not in the entire fen

Almost 30 years later, Wassen’s detailed survey was repeated by Annegreet Veeken as part of Utrecht University’s MSc Sustainable Development. From this, Veeken could conclude that the combination of local and regional restoration measures have been successful in increasing the abundance of rich fen species like Carex diandra and Liparis loeselii in the greater part of the fen.

Unfortunately, restoration has not been successful in the entire fen. The study observed an increase in a species poor vegetation type that is dominated by dense Polytrichum moss in patches that are only in limited contact with the fresh groundwater that is feeding the rest of the fen.

"Our analysis demonstrates that threatened wetland species can be preserved," explains Wassen, "But only by fine-tuned local nature management in combination with restoring the regional hydrology outside the boundaries of the nature reserve itself."

Publication

Annegreet Veeken & Martin J. Wassen, ‘Impact of local- and regional-scale restoration measures on a vulnerable rich fen in the Naardermeer nature reserve (the Netherlands)’, Plant Ecology (2020), https://doi.org/10.1007/s11258-020-01049-6